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BoP Lab / Buttonwillow Raceway Park

F6 vs SRF vs F5 vs GT2 pace at Buttonwillow Raceway Park

Class · click a class to switch, + to compare alongside (up to 4: remove one to add another)
Reference class · the others' laps as a share of this one's at the same event, so years compare despite weather; + a class above to measure against it
Track configuration

Quickest here: GT2 1:42.698 Tim Carroll, Cal Club 2026 qualifying

1:431:441:451:461:4711 rule changes between Cal Club 2025 and Cal Club 202611 ▾GT2 race best at Cal Club 2025: 1:46.926 (Brad McAllister)GT2 race best at Cal Club 2026: 1:44.128 (Tim Carroll)GT2 qualifying best at Cal Club 2025: 1:45.818 (Brad McAllister)GT2 qualifying best at Cal Club 2026: 1:42.698 (Tim Carroll)Cal Club 2025Cal Club2025Cal Club 2026Cal Club2026
F6SRFF5GT2solid race · dashed qualifying · slower is lower
EventF6SRFF5GT2
Qual bestRace bestTrapQual bestRace bestTrapvs F6Qual bestRace bestTrapvs F6Qual bestRace bestTrapvs F6
Cal Club 2026 CALCL262026-02-211:42.698Tim Carroll · fastest of 8 · top 5 within 7.4s-3.120s (-2.95%)1:44.128Tim Carroll · fastest of 8 · top 5 within 4.3s-2.798s (-2.62%)155.7Rocky Crocker+37.8 mph (+32.1%)
11 rule changes (SRF: 3, GT2: 8)5 cars added · 2 aero · 1 engine · 2 wording · 1 other · GT2 Porsche 911 SC gains 4.0L air-cooled engine option at 2275 or 2350 lbs depending on valve count. · M3 E92 classified in GT2 with 3999cc V8, 35mm restrictor, 3300 lb minimum weight. · GT2 adds Cadillac CTS, Chevrolet Impala/Malibu/Monte Carlo/SS, Dodge Intrepid, Ford Fusion/Taurus, Lincoln MKS, Pontiac G8/GTO/Grand Prix, Toyota Camry, and Gen late Model Stock Car bodies Camaro/Mustang/Camry. · GT2 Mazda BP 1839cc DOHC classified with 2250 lbs minimum weight, 46mm restrictor, EFR6258 or EFR7163 turbo allowed. · SRF3 adds HD Oil Cooler P/N G1148500 option alongside standard P/N G480503, no fan permitted. · GT2 Porsche 911, 963, 994 may use 993 3.8 RSR rear deck lid or faithful aftermarket reproductions. · SRF drivers with disabilities may modify seat and controls for safety and comfort with SCCA approval, noted in logbook, for that driver only. · SRF SADEV-SRF3 6-speed sequential transmission: effective date clarified to 1 April 2025 onward. · GT2 Pontiac Fiero drivetrain changed to RWD and hood bulge permitted for front engine relocation. · TA2 OEM wing height rule exemption removed; STO permits factory aero but bans it with aftermarket wings.showhide
  • GT2 Allow Larger Air Cooled Engines in Porsche 911 GT2 #39249cars addedaddedGT2 Porsche 911 SC gains 4.0L air-cooled engine option at 2275 or 2350 lbs depending on valve count.
  • GT2 Classify T1 BMW in GT2 #39408cars addedaddedM3 E92 classified in GT2 with 3999cc V8, 35mm restrictor, 3300 lb minimum weight.
  • GT2 Additional Body Options to Replace Older Stock Car Bodies #39086cars addedaddedGT2 adds Cadillac CTS, Chevrolet Impala/Malibu/Monte Carlo/SS, Dodge Intrepid, Ford Fusion/Taurus, Lincoln MKS, Pontiac G8/GTO/Grand Prix, Toyota Camry, and Gen late Model Stock Car bodies Camaro/Mustang/Camry.
  • GT2 GT3 Turbo to GT2? #39365cars addedaddedGT2 Mazda BP 1839cc DOHC classified with 2250 lbs minimum weight, 46mm restrictor, EFR6258 or EFR7163 turbo allowed.
  • GT2 Tech Bulletins for GT2 and GT2-ST #39537cars added -100 lbs
  • SRF Add HD Oil Cooler #38979engineadded · engineSRF3 adds HD Oil Cooler P/N G1148500 option alongside standard P/N G480503, no fan permitted.
  • GT2 Rear Deck Lid for Older Air-Cooled Porsche #38506aeroadded · aeroGT2 Porsche 911, 963, 994 may use 993 3.8 RSR rear deck lid or faithful aftermarket reproductions.
  • SRF Driver Safety & Comfort #37966otheraddedSRF drivers with disabilities may modify seat and controls for safety and comfort with SCCA approval, noted in logbook, for that driver only.
  • SRF Update SADEV transmission specs #37992wordingwordingSRF SADEV-SRF3 6-speed sequential transmission: effective date clarified to 1 April 2025 onward.
  • GT2 Hood Bulge allowed #37000wordingwordingGT2 Pontiac Fiero drivetrain changed to RWD and hood bulge permitted for front engine relocation.
  • GT2 OEM Wing Adjustment #37590aeroaeroTA2 OEM wing height rule exemption removed; STO permits factory aero but bans it with aftermarket wings.
Cal Club 2025 CALCL252025-02-221:45.818Brad McAllister · fastest of 6 · top 5 within 14.6s1:46.926Brad McAllister · fastest of 6 · top 5 within 13.3s117.9Guy Laidig
157 earlier rule changes on record, in force before Cal Club 2025 (from 2019)37 cars added · 28 engine · 23 weight · 6 aero · 6 tyres & wheels · 4 induction · 2 suspension & brakes · 35 wording · 16 other · GT2 STO aftermarket ABS weight penalty reduced from 100 lbs to 50 lbs. · GT2 Panoz Esperante GTS adds 2013-2016 Ford EcoBoost Twin Turbo V-6, 3496 cc, 2600 lbs, twin turbo induction. · TA2 rear wing height rule clarified: OEM aerodynamic devices exempt from peak-of-roof height limit. · GT2 Sunbeam Tiger gains Holly 650 cfm carburetors PN #80541-1 and PN #80541-2 as alternate options. · SRF3 air filter rule removes K&N RC-9160 option, specifies Weems P/N WM301020 only. · SRF Wilwood vented rotor minimum thickness increases to 13.25mm, 0.522 inches. · SRF3 Hoosier decal placement changed from four logos on nose and tail to three logos on sides and center front. · FE and SRF protest fee rules redirected to GCR section 8.3.1.D for fees and procedure. · SRF Hoosier contingency decal requirement reduced from four decals in specific locations to three decals with simplified placement. · SRF wet tyres: front P185/60R13 H20 or W2 and rear P205/60R13 H20 or W2 removed; front P185/65R13 W2 and rear P205/60R13 W2 now required. Hoosier decal placement specified. · GT2-ST: aftermarket replacement differential housings permitted if exact equivalent. · GT4 cars now permitted in GT2-ST with factory power stick or Pro Series restrictor, 100-pound weight penalty for slicks. · GT2-ST Acura NSX minimum weight rises to 3000 lbs, restrictor increases to 45mm TIR. · GT2-ST Spec Corvette (14-19) LS2 restrictor increases from 78mm to 80mm flat plate. · Chevrolet Corvette C8 (2020–) classified in GT2-ST: 6162 cc, 3300 lbs minimum, 71 mm restrictor, flat plate. · Mitjet ST 2015 added to GT2, must run per VTS specs with FIA form CdM008. · GT1-GTX rear blade spoiler: angle 50–75°, max 59.0 wide by 5.0 high inches; total area limit removed. · GT1, GT2, GT3, GTL, GTX Direct Injection now permitted if original equipment. · GT2 Chevrolet Corvette 7011 OEM 7-liter minimum weight reduces to 3125 lbs, down 150 lbs. · GT2 Nissan and GT3 Mazda, Mitsubishi 4G93, Nissan QR25DE/DD, QE25DE/DD now permit Direct Injection per 9.1.2.F.7.5.E. · GT2 Dodge Viper Gen 3 hybrid kit restrictor reduced from 50mm to 45mm flat plates in 8300 class. · SRF rain/brake light must be Super Bright LEDs Inc. P/N PT-STRB-R24; secondary filament must connect to rain light switch. · SRF brake light must be Super Bright LEDs Inc. P/N PT-STRB-R24, with SCCA Enterprises P/N 180427A pigtail and strobing rain light kit. · SRF adds mandatory front brake ducts 12–36 inches, throttle pedal heel-toe extension, braided stainless flex lines, camber limit 5.0 degrees, radiator opening height 3½ ± ½ inches, rear shift cable clamp P/N WM302007A. · GTL spec lines moved contiguous with GT2 and GT3; GTA category and specs renumbered behind GTL; P2 engine tables reorganised with restrictor and weight specifications clarified. · GT2-ST Dodge Viper including Comp Coupe, ACR/ACR-X adds VRL front fascia, 100 lbs weight reduction. · SRF radiator options expanded: Enterprises P/N 480465 with baffle 480464, 480466, or Automotive 1R698 and CU698 allowed if cross-reference equivalent. · GT2 Mazda 20B rotary minimum weight reduced to 2280 lbs, with 100-lb penalty for Grand Am transaxle and independent rear suspension. · GT2 BMW E46 M3, E36, Z3, 5000cc V8: 3.4L at 2575 lbs, 4.0L at 2900 lbs, 4.5L at 2950 lbs, 5.0L at 3000 lbs; S54 97mm stroke permitted at 2800 lbs. · GT2 Corvette C7 restrictor increases from 73mm to 77mm flat plate. · SRF wet front tyre changes to Hoosier P/N 46100 P185/60R13 H20 or W2 with 2.5" ground clearance. · GT2 adds 2009-2012 Porsche Cayman S, 3.4L, RWD, no PDK transmission. · Fields Cardinal V8 added to GT1 with Ford V8 engine, 4.9L, 2100 lbs, fuel injection. · SRF front W2 rain tyre Hoosier part number changes from 46100 to 46101 P185/65R13. · GT2 Ginetta G56 GTA may use Factory installed ProMap ECU Map. · SRF removes 1985 Renault Alliance solid front rotor option; restrictor sizes decrease 1mm for newer Kawasaki and multi-brand engines; minimum weights increase to 1100 lbs. · GT2 Mazda 13B Street Port turbo changes from EFR 76/70 to BW7670 or Garrett G30-660 with 46mm TIR at 2280 lbs. · GT2 Porsche SOHC 2478/2681/2992 turbos: EFR 76/70 compressor 42mm to 44mm, SIR to TIR designation. · GT2-ST Chevrolet Corvette 14-19 restrictor increases from 70 to 73 mm. · GT2 and GTL add Toyota 4A-F and 4A-FE 1.6L DOHC 16V engines as permitted options. · GT2 Mazda 13B turbocharger part number changed from EFR 70/76 to 76/70, compressor 42mm to 46mm. · GT2-ST BMW E36/46 spec line adds MA Shaw carbon/composite door and body kit options to notes. · GT3 normally aspirated cars may now use chokes instead of SIRs, same size as listed SIR, one per carburetor barrel. · GT3 2.0L 4-valve non-turbo engines may run unrestricted at 2060 lbs minimum weight. · GT2 TA2 and GTA throttle body part numbers updated to GM 12570790 or Edelbrock 33869/3870. · GT2 Ginetta G56 GTA may now use optional 18" x 9" and 18" x 10" wheels. · GT2/ST BMW E36/E46 Z3 5000cc V8 now permits MAShaw body kit: wide body, M3 front bumper with splitter, fenders, rockers, flairs, rear bumper. · GT2 Chevrolet Corvette L76 5967 restrictor increases from 73 mm to 74 mm. · F500 Rotax 493 and 593 intake boots: removed Moto Tassinari V3124-873B-2 from 493/593 non-HO allowance, added Moto Tassinari V3120-794A-2 option for non-HO. · GT1, GT2, GT3, GTL, GTX tail lights may now be original style or custom panel graphic with functioning red LED brake lamps. · Ginetta GTA G56 added to GT2 as spec car, 2600 lbs, 3.7L Ford V6 sealed, 6-speed Quaife sequential. · F500 Rotax engines now permit Ingi Tech Sparker ignition DCP-CDI-P2 as alternate ECU. · GT2 adds approved carbon roof suppliers and part numbers for BMW E36 and E46 models to Notes. · GT2 BMW E46 M3, E36, Z3, and 5000cc V8 may use 95mm S54 crankshaft at +150 lbs. · Audi R8 GT4 added to GT2 at 5.2L, 3000 lbs minimum weight, factory restrictor. · F500 clarifies stepped diameter exhaust headers prohibited except at cylinder head flange area. · F500 Rotax 593 intake boot options clarified; oil injection pump removal now permitted. · SRF tire rule wording clarified: tires must be run as delivered. · SRF brake rotor minimum thickness reduced from 13.25 mm to 12.20 mm; seals and air filter specs clarified. · GT2 shock absorber attachment points clarified as movable; wording correction only. · GT2 Porsche 104.0 x 88.0 SOHC minimum weight increases to 2090 lbs; EFR 76/70 turbo allowances added for three Porsche engines at specific weights. · F500 Majors and Runoffs cars must install AIM part #X47KPFSOLO2R0 data box mount for Solo or Solo 2. · Ginetta G40 added to GT2 with Mazda MZR/L5-VE engine, 2488cc or 2399cc, 1950 lbs base weight. · Toyota Supra GT4 added to GT2-ST with 3000cc displacement, 3000 lb minimum weight, factory restrictor. · GT2 Porsche 944/924 may use ERC 76/70 Turbo instead of Jayco super 50. · GT2-ST Porsche Cayman 05-15 throttle body restrictor increased from 70mm to 75mm. · F5 cars must install AIM part #X47KPFSOLO2R0 data box mount for Majors and Runoffs. · GT2 Porsche Cayman 05-15 4.0L and 4.2L swap flat plate restrictor for throttle body restrictor at 2700 lbs. · SRF wet tyres front P185/65R13 W2 option added; air box clarified as-delivered; SRF3 restrictor plate G301048 mandatory Jan 1 2022; P2 motorcycle engines up to 1005cc with 35mm restrictor, 2009+ stock 1075 lbs, 2008 stock 1025 lbs, modifie… · GT2 Mazda 13B street port gains EFR 70/76 turbocharger with 42mm inlet restrictor at 2280 lbs minimum. · GT3 Volkswagen Fun Cup Beetle EVO3 classified, sealed SOHC 1984cc engine, 2060 lbs minimum weight. · GT2 Dodge Viper ACR/ACR-X8300 front fascia loses 100 lbs, to 3175 VRL. · F5 clarifies mechanical shifting only; throttle-cut and flat-shifter devices permitted if driver retains full control. · F5 single-seat open-wheel cars: rigid suspension becomes limited suspension in class definition. · GT2 adds 04-06 World Challenge Pontiac GTO, 6062 cc, 3000 lbs minimum, World Challenge rules. · GTA part numbers updated: 0-80541-1 to 0-80541-2 in two locations and 6010 to 6014X in TA2 Appendix. · Grullon GT 2.0L Acura K20 moved from GTX to GT2-ST class at 2350 lbs unrestricted. · SRF wet tyres add Hoosier W2 option alongside existing H20 from October 4, 2021. · SRF adds SADEV-SRF3 6-speed sequential transmission option with ratios 3.0–0.92:1 and 3.20 final drive. · SRF seal requirements clarified: seals now must be on driveline components in designated locations; unsealed components removed and inspected by CSR or Enterprises rather than engine shipped for testing. · GT2-ST Porsche Cayman restrictor increases from 65mm to 75mm flat plate at 2700 lbs. · GT2 Dodge Viper VRL Spec minimum weight reduced 100 lbs to 3275. · TA2 cars may run prior generation rules or current Trans Am rules at 2930 lbs minimum weight with free tire make and size. · F500 Rotax 593 HO engine now permitted; 875 lbs minimum weight, MA0242SP1020A or MA0242SP1063A restrictor, specific intake boots and piston required. · SRF3 alternator pulley specified as P/N G902130 or G902130A, minimum 12oz. · GT2 Sunbeam SBF engine firing order 1,3,7,2,6,5,4,8 now available for Boss 302 variants. · GT2-ST Corvette (-2019) LS2 and L76 5967 gain 100 lbs minimum weight to 3100; 6162 and 7011 variants gain 50–100 lbs; L76 restrictor opens 70 to 73 mm. · GT2 rear engine opening position requirement removed. · GT2 Ford Mustang/Thunderbird Boss 302 firing order changes from unrestricted to optional later SBF 302 order 1,3,7,2,6,5,4,8. · SRF and SRF3 mandatory identification revised: removed Ford Performance and Blue Oval decals, added Hoosier logo placement. · GT2 allows ABS braking systems if shown on the individual Spec Line. · GT2 Corvette C6 and C7 spec lines split for clarification; C7 LS2, L76, LS3, LT1, LS7 weights raised 100–150 lbs effective 3/1/2021. · GT2 Ford Mustang/Thunderbird Boss 302 firing order becomes unrestricted. · GT2 BMW E46 M3 and E36, Z3, and 5000cc V8 minimum weight reduced to 2500 lbs. · GT2 Chrysler/Dodge/Plymouth DOHC 2429cc engine classified, 1950 lbs minimum weight. · SRF rear springs limited to P/N 280390 only, previous part numbers no longer allowed; ground clearance wording clarified. · F500 Suzuki GSXR600 engine years extended from 2003-2013 to 2003-2019. · GT2 stock car bodies removal rescinded; 1997-current year commercially available stock car bodywork allowed. · GT2 Appendix L section 4.8.4.2.10.3.6 renumbered, eliminating subsections .17–.19. · GT2 TA2 wing width maximum clarified to 65 -5/16 inches, including end plates. · GT1/GT2/GT3/GTL/GTX turbocharging and supercharging now permitted if listed on spec line. · Chevrolet Corvette (-2019) GT2-ST permitted LS1/LS6 alternate intake manifold, DORMAN part # 615-900. · GT2 997.2 GT3 Cup minimum weight reduced from 3000 to 2900 lbs. · GT2 BMW E46 M3, E36, Z3, and 5000cc V8 gain Trans Am SGT option: regular shifter 3000 lbs., paddle shifter plus 150 lbs. · GT2 allows up to four hood/fender louvered panels, max 600 sq inches total, min five slots each, ahead of windscreen. · F5 request to adjust external jetting device cockpit control denied; no rule change made. · F5 driver adjustable carburettor mixture: refer to separate Fastrack letter #28359 for ruling. · F5 cockpit adjustment request response published in Fastrack letter 28359. · TA2 Gurney flap wording clarified: replace 'wicker bill' and 'wicker' with 'Gurney flap' throughout wing specifications. · STO rear wing rules clarify that wicker is called Gurney flap in two places; no performance change. · GT Gurney flap wording clarified: wickerbill and tab terminology replaced with Gurney flap throughout sections 9.1.2.F.7.b. · GT2 Dodge Viper 8.4 OEM minimum weight reduced to 3275 lbs. · GT2 Chevrolet Corvette -2019 OEM minimum weight reduced to 3275 lbs. · GT2 Corvette -2019 LS6 allowed to reduce weight by 50 lbs. · SRF Penske shock P/N 280396 bump stop P/N 280407 becomes mandatory, maximum one per shock, effective 05/01/2020. · GT2 Panoz GT-S may use TA2 Choice Engine with any 5-speed H-shift transmission. · GT2-ST Corvette LS2 restrictor increases from 70mm to 75mm flat plate; LSX block option added. · GT2-ST Corvette L76 added: 5967cc displacement, 3000 lb minimum weight, 70mm flat plate restrictor. · GT2 Porsche 991.2 GT3 Cup Car engine displacement corrected to 4.0L from 3.8L. · GT1, GT2, GT3, GTL, GTX may use bonded-glass factory windshields without clips or straps if attached per original specifications. · GT2 Chevrolet SS replaces Dodge Charger; all stock car bodies removed from GT2 in 2021. · F500 Honda CBR600RR, Suzuki GSXR600, Yamaha R6 restrictor reduced to 28mm from 29mm. · GTX Misc. adds Factory Five Type 65 Coupe R Ford 302/351 and 5.0/5.2L NA at 2600 lbs, plus Ferrari 458/488 Challenge, Ford FP350S, Chevrolet C6, Lamborghini Super Trofeo. · 991.2 GT3 Cup Car added to GT2 at 3100 lbs with 63mm throttle body restrictor. · GT2 Acura NSX minimum weight cut from 3000 lbs to 2700 lbs. · GT2 Porsche 991.1 GT3 Cup restrictor size increases from 67 mm to 70 mm. · GT2 Porsche 996/997.1 GT3 Cup minimum weight drops to 2800 lbs. · GT2 Corvette -2019 restrictor reduced from 75 mm to 70 mm. · SRF rain and brake rule supersedes GCR 9.3.32.B.2 effective 1/1/2024 through 12/31/2024. · SRF adds tire warmer prohibition and specifies Hoosier dry and wet tire part numbers. · SRF front nose weight minimum reduced from 35 to 32 lbs. · SRF2 becomes Regional Only; SRF3 nomenclature changed from GEN3 to Ford 1.6L conversion; SRF and SRF3 no longer compete together for points. · F500 Honda CBR600RR, Suzuki GSXR600, and Yamaha R6 minimum weights increase to 900 lbs. · GT2 TA2 cars must meet 2930 lbs minimum weight per current Trans Am rules or Appendix L. · SRF drivers may now use Dash Windscreen Kit P/N 1180103 or P/N 180102. · GT2-ST Toyota Supra 3SGTE added: 2.0L, 2900 lbs minimum weight, 43mm restrictor. · Acura NSX all years classified to GT2-ST: 3.5L turbocharged, 3000 lbs minimum, 43mm restrictor, specific aero and turbo required. · GT2 TA2 minimum weight increases 100 lbs to 2930 pounds. · GT2 BMW E36/E46 M3 and Z3: 4.5L V8 permitted at 2950 lbs, 5.0L V8 at 3000 lbs, plus Flossman body kit allowed. · GTX tube frame cars now allowed fuel injection with maximum 90mm throttle body. · GTX adds Ligier JS2 R classification with restrictor and minimum weight. · GT2 Ford Mustang 5.2L classified at 3300 lbs minimum weight, 82mm single throttle body, carbon fiber body parts allowed. · GT1 and GT2/3/Lite remove ride height ground clearance rules; cars may now touch ground when tires deflate. · GT2/ST Porsche Cayman eligible model years extended from 2005–2011 to 2005–2015. · GT2 Porsche Cayman adds 4.0L with 65mm flat plate restrictor at 2700 lbs minimum weight. · GT2 BMW E46 M3, E36, Z3, and 5000cc V8 may now use Flossman body kit. · GT2 TA2 clarifies rules; shock caps to $850, brake calipers to $550, pads to $250/axle, wheels to $175 each; allows carbon fiber rear wing; engine setback 21.75 inches max (A–F) or 24 inches (G); carbureted engine displacement 366 cubic in… · GT2 adds BMW 1 Series E82 2008–2012 with N52B30 engine, 2996 cc, 2140 lbs minimum weight. · GT2 Porsche Cayman 05-11 minimum weight drops to 2800 lbs; STO and X51 motor variants noted at 2950 and 2850 lbs. · GT2 Ford Mustang 05- with Ford Racing 5.2l Aluminator engine classified: 5200cc displacement, 3400 lbs minimum weight, 2×41mm flat plate restrictor. · GT2 Porsche 996/997.1 GT3 Cup: add 3.6L displacement and 2900 lbs minimum weight; remove aftermarket exhaust header allowance for 996. · GT2 Ford Mustang FP350S minimum weight reduced 100 lbs to 3400. · GT2 Ford Mustang 05- EcoBoost added: 3500 cc, 3200 lbs minimum, 41 mm restrictor. · GT2 Mazda RX7 Downing GTS body kit allowed without 75 lbs. weight penalty. · GTX FIA GT3: Audi R8 now 40 mm restrictor and 2900 lbs; BMW Z4 now 70 mm restrictor and 2800 lbs; Ferrari 488 now 35 mm restrictor, TIR, and 3025 lbs.showhide
  • GT2 GT2/ST - Remove Aftermarket/Racing ABS penalty #36538weightfaster · weightGT2 STO aftermarket ABS weight penalty reduced from 100 lbs to 50 lbs.
  • GT2 Panoz Esperante GTS BOP #36686cars addedaddedGT2 Panoz Esperante GTS adds 2013-2016 Ford EcoBoost Twin Turbo V-6, 3496 cc, 2600 lbs, twin turbo induction.
  • GT2 Correct language regarding OEM Areo Devices #37137wordingwordingTA2 rear wing height rule clarified: OEM aerodynamic devices exempt from peak-of-roof height limit.
  • GT2 GT2 Sunbeam Tiger Alternate Carburetor #37198inductionadded · inductionGT2 Sunbeam Tiger gains Holly 650 cfm carburetors PN #80541-1 and PN #80541-2 as alternate options.
  • SRF Update SRF3 Air Filter Rule #36681wordingremovedSRF3 air filter rule removes K&N RC-9160 option, specifies Weems P/N WM301020 only.
  • SRF Update SRF Brake Rotor Thickness #36687suspension & brakessuspension & brakesSRF Wilwood vented rotor minimum thickness increases to 13.25mm, 0.522 inches.
  • SRF Hoosier Tire Decal Placement #36739wordingwordingSRF3 Hoosier decal placement changed from four logos on nose and tail to three logos on sides and center front.
  • SRF Protest Fee Clarification #36540wordingwordingFE and SRF protest fee rules redirected to GCR section 8.3.1.D for fees and procedure.
  • SRF Update to Letter 36619 with new Hoosier Contingency Decal Info #36624wordingwordingSRF Hoosier contingency decal requirement reduced from four decals in specific locations to three decals with simplified placement.
  • SRF Update Rain Tire Rule and Hoosier Decal Placement #36436tyres & wheelstyres & wheelsSRF wet tyres: front P185/60R13 H20 or W2 and rear P205/60R13 H20 or W2 removed; front P185/65R13 W2 and rear P205/60R13 W2 now required. Hoosier decal placement specified.
  • GT2 GT2-ST Rule Clarification #36093otheraddedGT2-ST: aftermarket replacement differential housings permitted if exact equivalent.
  • GT2 GT4 cars may run in GT2-ST #36235cars addedaddedGT4 cars now permitted in GT2-ST with factory power stick or Pro Series restrictor, 100-pound weight penalty for slicks.
  • GT2 Request for Spec Line 1010 Reconsideration #35009weight +300 lbsslower · weightGT2-ST Acura NSX minimum weight rises to 3000 lbs, restrictor increases to 45mm TIR.
  • GT2 Request to Eliminate the FPR from the Corvette (-2013) with LS2 #35878enginefaster · engineGT2-ST Spec Corvette (14-19) LS2 restrictor increases from 78mm to 80mm flat plate.
  • GT2 Classify Corvette C8 (2020- ) into GT2/ST #33759cars addedaddedChevrolet Corvette C8 (2020–) classified in GT2-ST: 6162 cc, 3300 lbs minimum, 71 mm restrictor, flat plate.
  • GT2 Requesting classification for a 2015 Mitjet ST in GT2 #35408cars addedaddedMitjet ST 2015 added to GT2, must run per VTS specs with FIA form CdM008.
  • GT2 Rear Blade Spoiler Clarification #35261aeroaeroGT1-GTX rear blade spoiler: angle 50–75°, max 59.0 wide by 5.0 high inches; total area limit removed.
  • GT2 GT Direct Injection allowance and rules #35437engineadded · engineGT1, GT2, GT3, GTL, GTX Direct Injection now permitted if original equipment.
  • GT2 REDUCE C6 CORVETTE WEIGHT WITH OEM 7 LITER ENGINE REDUCE BY 150LB #35385weight -150 lbsfaster · weightGT2 Chevrolet Corvette 7011 OEM 7-liter minimum weight reduces to 3125 lbs, down 150 lbs.
  • GT2 GT2/3 remove Direction Injection not allowed in Spec line notes #35439engineadded · engineGT2 Nissan and GT3 Mazda, Mitsubishi 4G93, Nissan QR25DE/DD, QE25DE/DD now permit Direct Injection per 9.1.2.F.7.5.E.
  • GT2 Dodge Viper Gen 3 hybrid Kit Update Request #35200engineslower · engineGT2 Dodge Viper Gen 3 hybrid kit restrictor reduced from 50mm to 45mm flat plates in 8300 class.
  • SRF Update SRF Rain / Brake Rule #34706otherotherSRF rain/brake light must be Super Bright LEDs Inc. P/N PT-STRB-R24; secondary filament must connect to rain light switch.
  • SRF Update SRF Brake Light Rule v1 #34853otherotherSRF brake light must be Super Bright LEDs Inc. P/N PT-STRB-R24, with SCCA Enterprises P/N 180427A pigtail and strobing rain light kit.
  • SRF SRF / SRF3 Rule Updates #35268suspension & brakessuspension & brakesSRF adds mandatory front brake ducts 12–36 inches, throttle pedal heel-toe extension, braided stainless flex lines, camber limit 5.0 degrees, radiator opening height 3½ ± ½ inches, rear shift cable clamp P/N WM302007A.
  • GT2 Errors in GTCS Headings and Use of the Terms Category and ClassChange existing GTL and GTA Rules #34453wordingwordingGTL spec lines moved contiguous with GT2 and GT3; GTA category and specs renumbered behind GTL; P2 engine tables reorganised with restrictor and weight specifications clarified.
  • GT2 Late E & O #34966weightfaster · weightGT2-ST Dodge Viper including Comp Coupe, ACR/ACR-X adds VRL front fascia, 100 lbs weight reduction.
  • SRF SRF Radiator Rule Update #34805otheraddedSRF radiator options expanded: Enterprises P/N 480465 with baffle 480464, 480466, or Automotive 1R698 and CU698 allowed if cross-reference equivalent.
  • GT2 GT2 Mazda 20B 3 rotor ENO #34765weight -220 lbsfaster · weightGT2 Mazda 20B rotary minimum weight reduced to 2280 lbs, with 100-lb penalty for Grand Am transaxle and independent rear suspension.
  • GT2 appendix letter #33635 #34206cars addedaddedGT2 BMW E46 M3, E36, Z3, 5000cc V8: 3.4L at 2575 lbs, 4.0L at 2900 lbs, 4.5L at 2950 lbs, 5.0L at 3000 lbs; S54 97mm stroke permitted at 2800 lbs.
  • GT2 Remove Weight and Restrictor Penalty for Corvette C7 Body #34342enginefaster · engineGT2 Corvette C7 restrictor increases from 73mm to 77mm flat plate.
  • SRF Hoosier SRF Wet Front Tire Rule Update #34189tyres & wheelstyres & wheelsSRF wet front tyre changes to Hoosier P/N 46100 P185/60R13 H20 or W2 with 2.5" ground clearance.
  • GT2 Request to class 2011 Porsche Cayman S #33771cars addedaddedGT2 adds 2009-2012 Porsche Cayman S, 3.4L, RWD, no PDK transmission.
  • GT2 Please classify Fields Cardinal V8 #33784cars addedaddedFields Cardinal V8 added to GT1 with Ford V8 engine, 4.9L, 2100 lbs, fuel injection.
  • SRF Update SRF Front W2 Rain Tire Part Number #34118tyres & wheelstyres & wheelsSRF front W2 rain tyre Hoosier part number changes from 46100 to 46101 P185/65R13.
  • GT2 Adding Ginetta G56 GTA Factory ProTune for GT2 Class #33825engineadded · engineGT2 Ginetta G56 GTA may use Factory installed ProMap ECU Map.
  • SRF Update SRF Brake Rule #33469enginefaster · engineSRF removes 1985 Renault Alliance solid front rotor option; restrictor sizes decrease 1mm for newer Kawasaki and multi-brand engines; minimum weights increase to 1100 lbs.
  • GT2 GT2 Mazda 13B Turbo #33729engineengineGT2 Mazda 13B Street Port turbo changes from EFR 76/70 to BW7670 or Garrett G30-660 with 46mm TIR at 2280 lbs.
  • GT2 Request Permission to Use a Substitute Turbo #33337engineengineGT2 Porsche SOHC 2478/2681/2992 turbos: EFR 76/70 compressor 42mm to 44mm, SIR to TIR designation.
  • GT2 Request to Reduce Restriction on C7 GT2 Corvette #33342enginefaster · engineGT2-ST Chevrolet Corvette 14-19 restrictor increases from 70 to 73 mm.
  • GT2 Toyota 4A-F and 4A-FE 1.6L DOHC 16V Engine Request #33415cars addedaddedGT2 and GTL add Toyota 4A-F and 4A-FE 1.6L DOHC 16V engines as permitted options.
  • GT2 GT2 Mazda 13b turbocharger part # update #33437enginefaster · engineGT2 Mazda 13B turbocharger part number changed from EFR 70/76 to 76/70, compressor 42mm to 46mm.
  • GT2 GT2-ST BMW E36/46 spec line remove #33610otheraddedGT2-ST BMW E36/46 spec line adds MA Shaw carbon/composite door and body kit options to notes.
  • GT2 GT3 Choke option effective 1-01-2023 #33669inductionadded · inductionGT3 normally aspirated cars may now use chokes instead of SIRs, same size as listed SIR, one per carburetor barrel.
  • GT2 GT3 2.0L choke/weight option #33670otheraddedGT3 2.0L 4-valve non-turbo engines may run unrestricted at 2060 lbs minimum weight.
  • GT2 BOP adjustment for GT2 & GT2-ST #33681induction
  • GT2 GT2 (TA2)/GTA Part Number Update #33315wordingwordingGT2 TA2 and GTA throttle body part numbers updated to GM 12570790 or Edelbrock 33869/3870.
  • GT2 Ginetta G56 GTA - Optional Wheels #33357tyres & wheelsadded · tyres & wheelsGT2 Ginetta G56 GTA may now use optional 18" x 9" and 18" x 10" wheels.
  • GT2 Allow the MAShaw Body Kit on the GT2/ST Spec Line for BMW E36/E46 #32447aeroadded · aeroGT2/ST BMW E36/E46 Z3 5000cc V8 now permits MAShaw body kit: wide body, M3 front bumper with splitter, fenders, rockers, flairs, rear bumper.
  • GT2 Request for C5/C6 Corvette Restrictor Size Review #32982enginefaster · engineGT2 Chevrolet Corvette L76 5967 restrictor increases from 73 mm to 74 mm.
  • F5 Intake Boots Correction #33028wordingwordingF500 Rotax 493 and 593 intake boots: removed Moto Tassinari V3124-873B-2 from 493/593 non-HO allowance, added Moto Tassinari V3120-794A-2 option for non-HO.
  • GT2 Tail lights on all GT category race cars. #32799wordingwordingGT1, GT2, GT3, GTL, GTX tail lights may now be original style or custom panel graphic with functioning red LED brake lamps.
  • GT2 Addendum to letter #32514 Ginetta GTA G56 #33076cars addedaddedGinetta GTA G56 added to GT2 as spec car, 2600 lbs, 3.7L Ford V6 sealed, 6-speed Quaife sequential.
  • F5 Ensure availability of ECU for Rotax engines #32695engineadded · engineF500 Rotax engines now permit Ingi Tech Sparker ignition DCP-CDI-P2 as alternate ECU.
  • GT2 Information requested for carbon roofs on BMW E36/E46 cars in GT2 #32682cars addedaddedGT2 adds approved carbon roof suppliers and part numbers for BMW E36 and E46 models to Notes.
  • GT2 Request to Allow the 95mm S54 BMW Crankshaft in GT2-ST #32698engineadded · engineGT2 BMW E46 M3, E36, Z3, and 5000cc V8 may use 95mm S54 crankshaft at +150 lbs.
  • GT2 Request to classify Audi R8 FIA GT4 to GT2 #32805cars addedaddedAudi R8 GT4 added to GT2 at 5.2L, 3000 lbs minimum weight, factory restrictor.
  • F5 Clarify stepped exhaust header references #32743wordingwordingF500 clarifies stepped diameter exhaust headers prohibited except at cylinder head flange area.
  • F5 593 carb boot availability and oil pump clarification #32527wordingwordingF500 Rotax 593 intake boot options clarified; oil injection pump removal now permitted.
  • SRF SRF Tire Rule Update #32614wordingwordingSRF tire rule wording clarified: tires must be run as delivered.
  • SRF Brake, seal, and air filter clarifications #32670otherfasterSRF brake rotor minimum thickness reduced from 13.25 mm to 12.20 mm; seals and air filter specs clarified.
  • GT2 Typo in rules for shocks #32308wordingwordingGT2 shock absorber attachment points clarified as movable; wording correction only.
  • GT2 additional response to letters #31898 & 32083 #32424engine +140 lbsslower · engineGT2 Porsche 104.0 x 88.0 SOHC minimum weight increases to 2090 lbs; EFR 76/70 turbo allowances added for three Porsche engines at specific weights.
  • F5 E&O class name #32194otheraddedF500 Majors and Runoffs cars must install AIM part #X47KPFSOLO2R0 data box mount for Solo or Solo 2.
  • GT2 Request to Classify Ginetta G40 in GT2 #31597cars addedaddedGinetta G40 added to GT2 with Mazda MZR/L5-VE engine, 2488cc or 2399cc, 1950 lbs base weight.
  • GT2 2021 Supra GR GT4 #31737cars addedaddedToyota Supra GT4 added to GT2-ST with 3000cc displacement, 3000 lb minimum weight, factory restrictor.
  • GT2 Proposed Technical Bulletin #31900otherunclearGT2 Porsche 944/924 may use ERC 76/70 Turbo instead of Jayco super 50.
  • GT2 GT2/ST Porsche Cayman #31451 correct TBR size error #31991enginefaster · engineGT2-ST Porsche Cayman 05-15 throttle body restrictor increased from 70mm to 75mm.
  • F5 Data Box Mounting Plate #31638otheraddedF5 cars must install AIM part #X47KPFSOLO2R0 data box mount for Majors and Runoffs.
  • GT2 Restrictor Clarification for 2015 Cayman #31451otherunclearGT2 Porsche Cayman 05-15 4.0L and 4.2L swap flat plate restrictor for throttle body restrictor at 2700 lbs.
  • SRF Three Updates to SRF Rules #31523otherotherSRF wet tyres front P185/65R13 W2 option added; air box clarified as-delivered; SRF3 restrictor plate G301048 mandatory Jan 1 2022; P2 motorcycle engines up to 1005cc with 35mm restrictor, 2009+ stock 1075 lbs, 2008 stock 1025 lbs, modifie…
  • GT2 Turbo Request for 13B Engine #30656engineadded · engineGT2 Mazda 13B street port gains EFR 70/76 turbocharger with 42mm inlet restrictor at 2280 lbs minimum.
  • GT2 Request car classification #31032cars addedaddedGT3 Volkswagen Fun Cup Beetle EVO3 classified, sealed SOHC 1984cc engine, 2060 lbs minimum weight.
  • GT2 Correct letter 30565 GT2/ST #31088weightfaster · weightGT2 Dodge Viper ACR/ACR-X8300 front fascia loses 100 lbs, to 3175 VRL.
  • F5 Clarify allowable assisted shifting systems #30871wordingwordingF5 clarifies mechanical shifting only; throttle-cut and flat-shifter devices permitted if driver retains full control.
  • F5 Request to correct terminology #30976wordingwordingF5 single-seat open-wheel cars: rigid suspension becomes limited suspension in class definition.
  • GT2 Request the 04-06 Pontiac GTO WC Car Be Added to the GT2/ST Chart #30339cars addedaddedGT2 adds 04-06 World Challenge Pontiac GTO, 6062 cc, 3000 lbs minimum, World Challenge rules.
  • GT2 Request to Update GTA Obsolete Part Numbers #30615wordingwordingGTA part numbers updated: 0-80541-1 to 0-80541-2 in two locations and 6010 to 6014X in TA2 Appendix.
  • GT2 GTX class correction to GT2/ST #30973cars addedaddedGrullon GT 2.0L Acura K20 moved from GTX to GT2-ST class at 2350 lbs unrestricted.
  • SRF SRF Wet Tires #30849tyres & wheelsadded · tyres & wheelsSRF wet tyres add Hoosier W2 option alongside existing H20 from October 4, 2021.
  • SRF SADEV-SRF3 Transmission #30926cars addedaddedSRF adds SADEV-SRF3 6-speed sequential transmission option with ratios 3.0–0.92:1 and 3.20 final drive.
  • SRF SRF Update Maintenance, Repairs and Seals #30961wordingwordingSRF seal requirements clarified: seals now must be on driveline components in designated locations; unsealed components removed and inspected by CSR or Enterprises rather than engine shipped for testing.
  • GT2 Porsche Cayman Engine Modification and Engine Request #30472enginefaster · engineGT2-ST Porsche Cayman restrictor increases from 65mm to 75mm flat plate at 2700 lbs.
  • GT2 Request weight clarification Viper CC #30565weightfaster · weightGT2 Dodge Viper VRL Spec minimum weight reduced 100 lbs to 3275.
  • GT2 Variance, 2021 TA2 Rules vs GCR Appendix L #30641cars addedaddedTA2 cars may run prior generation rules or current Trans Am rules at 2930 lbs minimum weight with free tire make and size.
  • F5 Request to Allow Rotax 593 HO Engine #30712cars addedaddedF500 Rotax 593 HO engine now permitted; 875 lbs minimum weight, MA0242SP1020A or MA0242SP1063A restrictor, specific intake boots and piston required.
  • SRF SRF3 Alternator Pulley #30684engineadded · engineSRF3 alternator pulley specified as P/N G902130 or G902130A, minimum 12oz.
  • GT2 GT2 tiger firing order #30421wordingwordingGT2 Sunbeam SBF engine firing order 1,3,7,2,6,5,4,8 now available for Boss 302 variants.
  • GT2 GT2-ST CORVETTE CHANGES #30029weight +100 lbsslower · weightGT2-ST Corvette (-2019) LS2 and L76 5967 gain 100 lbs minimum weight to 3100; 6162 and 7011 variants gain 50–100 lbs; L76 restrictor opens 70 to 73 mm.
  • GT2 Request underfloor clarification #30121aeroremoved · aeroGT2 rear engine opening position requirement removed.
  • GT2 29742 Change new wording to read as: #30329wordingwordingGT2 Ford Mustang/Thunderbird Boss 302 firing order changes from unrestricted to optional later SBF 302 order 1,3,7,2,6,5,4,8.
  • SRF Mandatory identification: #30223wordingwordingSRF and SRF3 mandatory identification revised: removed Ford Performance and Blue Oval decals, added Hoosier logo placement.
  • GT2 ABS Restrictions #30064otheraddedGT2 allows ABS braking systems if shown on the individual Spec Line.
  • GT2 RM 21-01 C6 & C7 clarification #30192weightslower · weightGT2 Corvette C6 and C7 spec lines split for clarification; C7 LS2, L76, LS3, LT1, LS7 weights raised 100–150 lbs effective 3/1/2021.
  • GT2 Request change to engine firing order rule #29742engineadded · engineGT2 Ford Mustang/Thunderbird Boss 302 firing order becomes unrestricted.
  • GT2 Request E-46 BMW M3 balance of performance #29833weight -100 lbsfaster · weightGT2 BMW E46 M3 and E36, Z3, and 5000cc V8 minimum weight reduced to 2500 lbs.
  • GT2 Request for Bigger Engine in Plymouth Breeze #29380cars addedaddedGT2 Chrysler/Dodge/Plymouth DOHC 2429cc engine classified, 1950 lbs minimum weight.
  • SRF SRF Shocks, Springs and Ride Height. #29688otherotherSRF rear springs limited to P/N 280390 only, previous part numbers no longer allowed; ground clearance wording clarified.
  • F5 Request to Update Suzuki Engine Years for F500 #29453engineadded · engineF500 Suzuki GSXR600 engine years extended from 2003-2013 to 2003-2019.
  • GT2 rescind GT2 stock car bodies removal #29219cars addedaddedGT2 stock car bodies removal rescinded; 1997-current year commercially available stock car bodywork allowed.
  • GT2 E&O Typos in Appendix L #29447wordingwordingGT2 Appendix L section 4.8.4.2.10.3.6 renumbered, eliminating subsections .17–.19.
  • GT2 GT2 wing width wording correction #29469wordingwordingGT2 TA2 wing width maximum clarified to 65 -5/16 inches, including end plates.
  • GT2 GT Category Wording #29193wordingaddedGT1/GT2/GT3/GTL/GTX turbocharging and supercharging now permitted if listed on spec line.
  • GT2 Corvette GT2-ST intake manifold #29221engineadded · engineChevrolet Corvette (-2019) GT2-ST permitted LS1/LS6 alternate intake manifold, DORMAN part # 615-900.
  • GT2 997.2 E&O link to 27915 #29373weightfaster · weightGT2 997.2 GT3 Cup minimum weight reduced from 3000 to 2900 lbs.
  • GT2 Request for allowance Trans Am SGT #28951cars addedaddedGT2 BMW E46 M3, E36, Z3, and 5000cc V8 gain Trans Am SGT option: regular shifter 3000 lbs., paddle shifter plus 150 lbs.
  • GT2 Omitted GT2 fender/hood openings #29171aeroadded · aeroGT2 allows up to four hood/fender louvered panels, max 600 sq inches total, min five slots each, ahead of windscreen.
  • F5 Request for Cockpit Adjustment of External Jetting Devices #28359wordingunclearF5 request to adjust external jetting device cockpit control denied; no rule change made.
  • F5 Two Stroke Motors (reply to #28359 WDYT) #28816engine
  • F5 Re letter requesting driver adjustable carb mixture #28840wordingunclearF5 driver adjustable carburettor mixture: refer to separate Fastrack letter #28359 for ruling.
  • F5 #28359 WDYT Request for Cockpit Adjustment #28875wordingunclearF5 cockpit adjustment request response published in Fastrack letter 28359.
  • GT2 TA2 Gurney flap wicker clarification #28874wordingwordingTA2 Gurney flap wording clarified: replace 'wicker bill' and 'wicker' with 'Gurney flap' throughout wing specifications.
  • GT2 STO Gurney flap wicker clarification #28883wordingwordingSTO rear wing rules clarify that wicker is called Gurney flap in two places; no performance change.
  • GT2 GT Gurney flap wicker clarification #28909wordingwordingGT Gurney flap wording clarified: wickerbill and tab terminology replaced with Gurney flap throughout sections 9.1.2.F.7.b.
  • GT2 Request to Adjust Weight of OEM 8.4 Viper #28739weight -50 lbsfaster · weightGT2 Dodge Viper 8.4 OEM minimum weight reduced to 3275 lbs.
  • GT2 Request to Adjust Weight of OEM Chevrolet Corvette #28896weight -50 lbsfaster · weightGT2 Chevrolet Corvette -2019 OEM minimum weight reduced to 3275 lbs.
  • GT2 Request Corvette engine parity #28576weightfaster · weightGT2 Corvette -2019 LS6 allowed to reduce weight by 50 lbs.
  • SRF SRF Bump Stop Correction #27019wordingwordingSRF Penske shock P/N 280396 bump stop P/N 280407 becomes mandatory, maximum one per shock, effective 05/01/2020.
  • GT2 Request to revisit Panoz GT-S BoP #28280cars addedaddedGT2 Panoz GT-S may use TA2 Choice Engine with any 5-speed H-shift transmission.
  • GT2 GT2-ST Corvette LS2 & L76 #28583enginefaster · engineGT2-ST Corvette LS2 restrictor increases from 70mm to 75mm flat plate; LSX block option added.
  • GT2 GT2-ST Corvette L76 #28584cars addedaddedGT2-ST Corvette L76 added: 5967cc displacement, 3000 lb minimum weight, 70mm flat plate restrictor.
  • GT2 Request 991.2 Porsche engine displacement verify typo #28194enginefaster · engineGT2 Porsche 991.2 GT3 Cup Car engine displacement corrected to 4.0L from 3.8L.
  • GT2 Windshield Clips #27323otheraddedGT1, GT2, GT3, GTL, GTX may use bonded-glass factory windshields without clips or straps if attached per original specifications.
  • GT2 Request to Add Chevrolet SS Body to Appendix L #27898cars addedremoved · cars addedGT2 Chevrolet SS replaces Dodge Charger; all stock car bodies removed from GT2 in 2021.
  • F5 Change 600cc restrictor size #27883inductionslower · inductionF500 Honda CBR600RR, Suzuki GSXR600, Yamaha R6 restrictor reduced to 28mm from 29mm.
  • GT2 Request Factory Five Daytona coupe classification #26308cars addedaddedGTX Misc. adds Factory Five Type 65 Coupe R Ford 302/351 and 5.0/5.2L NA at 2600 lbs, plus Ferrari 458/488 Challenge, Ford FP350S, Chevrolet C6, Lamborghini Super Trofeo.
  • GT2 Porsche 991.2 GT3 Cup GT2 Classification #27701cars addedadded991.2 GT3 Cup Car added to GT2 at 3100 lbs with 63mm throttle body restrictor.
  • GT2 Request for Acura NSX Spec Line Changes #27755weightfaster · weightGT2 Acura NSX minimum weight cut from 3000 lbs to 2700 lbs.
  • GT2 GT2 991.1 restrictor size change #27914enginefaster · engineGT2 Porsche 991.1 GT3 Cup restrictor size increases from 67 mm to 70 mm.
  • GT2 GT2 996/997.1 weight change #27915weight -100 lbsfaster · weightGT2 Porsche 996/997.1 GT3 Cup minimum weight drops to 2800 lbs.
  • GT2 GT2/ST Corvette comp adjustment #27920engineslower · engineGT2 Corvette -2019 restrictor reduced from 75 mm to 70 mm.
  • SRF SRF Rain / Brake Rule - BoD approved as follows #34958wordingwordingSRF rain and brake rule supersedes GCR 9.3.32.B.2 effective 1/1/2024 through 12/31/2024.
  • SRF SRF Tire Warmer Rule #27622tyres & wheelstyres & wheelsSRF adds tire warmer prohibition and specifies Hoosier dry and wet tire part numbers.
  • SRF SRF / SRF3 Nose Weight Reduction #27706weightfaster · weightSRF front nose weight minimum reduced from 35 to 32 lbs.
  • SRF SRF / SRF3 Majors & Regional Class Updates #27723wordingwordingSRF2 becomes Regional Only; SRF3 nomenclature changed from GEN3 to Ford 1.6L conversion; SRF and SRF3 no longer compete together for points.
  • F5 Request for Weight Increase for Motorcycle Powered Cars #27214weight +25 lbsslower · weightF500 Honda CBR600RR, Suzuki GSXR600, and Yamaha R6 minimum weights increase to 900 lbs.
  • GT2 TA2 Weight Clarification #27077weightslower · weightGT2 TA2 cars must meet 2930 lbs minimum weight per current Trans Am rules or Appendix L.
  • SRF SRF Dash Windscreen Kit #27028aeroadded · aeroSRF drivers may now use Dash Windscreen Kit P/N 1180103 or P/N 180102.
  • GT2 Request to classify Toyota Supra with 3SGTE engine #25185cars addedaddedGT2-ST Toyota Supra 3SGTE added: 2.0L, 2900 lbs minimum weight, 43mm restrictor.
  • GT2 Request to Classify Acura NSX from T1 to GT2? #26121cars addedaddedAcura NSX all years classified to GT2-ST: 3.5L turbocharged, 3000 lbs minimum, 43mm restrictor, specific aero and turbo required.
  • GT2 Request for TA2 BOP in GT2 #26509weightslower · weightGT2 TA2 minimum weight increases 100 lbs to 2930 pounds.
  • GT2 Request for e36/e46 bmw 4500 cc v8 at 2950lbs in GT2/ST #26106cars addedaddedGT2 BMW E36/E46 M3 and Z3: 4.5L V8 permitted at 2950 lbs, 5.0L V8 at 3000 lbs, plus Flossman body kit allowed.
  • GT2 Request GTX Fuel injection for previous GT-1 tube frame cars #26141engineadded · engineGTX tube frame cars now allowed fuel injection with maximum 90mm throttle body.
  • GT2 Request to Classify Ligier JS2 R #26535cars addedaddedGTX adds Ligier JS2 R classification with restrictor and minimum weight.
  • GT2 Request Ford Perfomance 5.2L crate engine FPR clarification #26159cars addedaddedGT2 Ford Mustang 5.2L classified at 3300 lbs minimum weight, 82mm single throttle body, carbon fiber body parts allowed.
  • GT2 Request Ride Height Clarification #26600wordingfasterGT1 and GT2/3/Lite remove ride height ground clearance rules; cars may now touch ground when tires deflate.
  • GT2 Request Porsche Cayman year classification #26241cars addedaddedGT2/ST Porsche Cayman eligible model years extended from 2005–2011 to 2005–2015.
  • GT2 GT2/ST Porsche Cayman engine #26250cars addedaddedGT2 Porsche Cayman adds 4.0L with 65mm flat plate restrictor at 2700 lbs minimum weight.
  • GT2 ST/GT2 BMW Flossman Kit Clarification #22138aeroadded · aeroGT2 BMW E46 M3, E36, Z3, and 5000cc V8 may now use Flossman body kit.
  • GT2 Request Clarification/Revision of Appendix L (2013 TA2 Rules) #25110wordingwordingGT2 TA2 clarifies rules; shock caps to $850, brake calipers to $550, pads to $250/axle, wheels to $175 each; allows carbon fiber rear wing; engine setback 21.75 inches max (A–F) or 24 inches (G); carbureted engine displacement 366 cubic in…
  • GT2 Request to classify BMW E82 (1 series) into GT2 #25539cars addedaddedGT2 adds BMW 1 Series E82 2008–2012 with N52B30 engine, 2996 cc, 2140 lbs minimum weight.
  • GT2 2010 Cayman Street Tuner Into an STO Car,Addendum #25545weightfaster · weightGT2 Porsche Cayman 05-11 minimum weight drops to 2800 lbs; STO and X51 motor variants noted at 2950 and 2850 lbs.
  • GT2 Request - Classify Ford Performance 5.2l #25716cars addedaddedGT2 Ford Mustang 05- with Ford Racing 5.2l Aluminator engine classified: 5200cc displacement, 3400 lbs minimum weight, 2×41mm flat plate restrictor.
  • GT2 Add missing displacement, minimum weight. Remove #25765wordingwordingGT2 Porsche 996/997.1 GT3 Cup: add 3.6L displacement and 2900 lbs minimum weight; remove aftermarket exhaust header allowance for 996.
  • GT2 Request for Ford FP 350s Weight Reduction #25806weightfaster · weightGT2 Ford Mustang FP350S minimum weight reduced 100 lbs to 3400.
  • GT2 Request to Classify EcoBoost Mustang #25842cars addedaddedGT2 Ford Mustang 05- EcoBoost added: 3500 cc, 3200 lbs minimum, 41 mm restrictor.
  • GT2 Request to Remove Mazda RX 7 Body Work Penalty #26024weightfaster · weightGT2 Mazda RX7 Downing GTS body kit allowed without 75 lbs. weight penalty.
  • GT2 GTX Homologation table update #26034otherunclearGTX FIA GT3: Audi R8 now 40 mm restrictor and 2900 lbs; BMW Z4 now 70 mm restrictor and 2800 lbs; Ferrari 488 now 35 mm restrictor, TIR, and 3025 lbs.

Best is the class's fastest lap in that event's qualifying or race sessions, with the driver who set it, how many cars set a time that session and how close the top five were; a best from fewer than three cars is greyed. With two or more classes, "vs" is the gap of each class's best to the first class's at the same event. Newest event first. The coloured figure under each value is the change from the previous event that has one (green is quicker, red slower). Whole laps only, so events with different sector layouts still compare. Weather and track condition are not accounted for.