BoP Lab / Classes / F6

F6 vs SRF vs FM vs GTX pace at every track

Lap times across years say as much about the weather as the class. % of F6 is each class's best lap as a share of F6's on the same day, so the conditions drop out: 100% is level, less is quicker, and a move in it is the class getting faster or slower against the field.

Class · click a class to switch, + to compare alongside (up to 4: remove one to add another)

ASB-SpecEPF6×FAFCFE2FFvsFM ×FPFVFXGT1GT2vsGTX ×HPPP2SMSMXvsSRF ×SRF3STLSTUT1T2T3T4Show 48 inactive classes

Series Runoffs Super Tour Both

Reference class · the yardstick the % column and chart are measured against

Tracks · untick to narrow Auto Club Speedway Barber Motorsports Park Blackhawk Farms Raceway Buttonwillow Raceway Park Circuit of St. Louis (formerly Gateway Motorsports Circuit of the Americas Daytona International Speedway Grattan Raceway Hallett Motor Racing Circuit Homestead-Miami Speedway Indianapolis Motor Speedway Laguna Seca Michelin Raceway Road Atlanta Mid-Ohio Sports Car Course New Jersey Motorsports Park NOLA Motorsports Park Pacific Raceways Pittsburgh International Race Complex Portland International Raceway Pueblo Motorsports Park Road America Sebring International Raceway Sonoma Raceway Summit Point Raceway Thunderhill Raceway Park Virginia International Raceway Watkins Glen International Willow Springs Raceway

Closest to the field: F6 100.0% of F6 Calvin Stewart, Virginia International Raceway Runoffs 2023 race

% of F6Lap times

F6SRFFMGTXsolid race · dashed qualifying · slower is lower

F6SRFFMGTXsolid race · dashed qualifying · each class's best lap as a share of F6's at the same event (the reference class, changeable above); 100% is level, less is quicker, so up the chart is quicker

	Event	F6			SRF					FM					GTX
	Event	Qual best	Race best	Trap	Qual best	Race best	Trap	vs F6	% of F6	Qual best	Race best	Trap	vs F6	% of F6	Qual best	Race best	Trap	vs F6	% of F6
	Road America Runoffs 20262026-09-28	2:18.489Calvin Stewart · fastest of 13 · top 5 within 4.2s-0.617s (-0.44%)	2:20.255James Weida · fastest of 13 · top 5 within 2.0s+1.415s (+1.02%)	143.0Calvin Stewart-4.5 mph (-3.1%)
11 rule changes (SRF: 5, GTX: 6)4 cars added · 3 engine · 3 wording · 1 other · SRF rain/brake light part number and GCR section reference corrected for original roll hoop mounting. · Ferrari 296 GT3 added to GTX-MISC with homologation, restrictor, and minimum weight specifications effective 2026-04-01. · GT3U class removed from GCR; GT3U cars now compete in STU. · SRF3 spark plugs limited to NGK LTR7IX-11 P/N G301041 only; washers and sealing rings prohibited. · GTX adds RCR T70 Coupe, 2200 lbs minimum weight, no restrictor. · SRF3 adds HD Oil Cooler P/N G1148500 option alongside standard P/N G480503, no fan permitted. · GTX Ligier LMP3 now allows any normally aspirated LS Chevrolet engine. · GTX adds Porsche GT2 RS Clubsport with factory specifications required at all race events. · 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. · TA2 rear wing height rule clarified: OEM aerodynamic devices exempt from peak-of-roof height limit.showhide 2026-09-01 SRF GCR Rain/Brake Light Correction #40579wordingwordingSRF rain/brake light part number and GCR section reference corrected for original roll hoop mounting. 2026-04-01 GTX Ferrari 296 GT3 Classification Request #39873cars addedaddedFerrari 296 GT3 added to GTX-MISC with homologation, restrictor, and minimum weight specifications effective 2026-04-01. 2026-03-01 GTX Remove GT3U from GCR as it is now in STU #39862cars addedremovedcars addedGT3U class removed from GCR; GT3U cars now compete in STU. 2026-03-01 SRF SRF3 Spark Plugs #39899engineengineSRF3 spark plugs limited to NGK LTR7IX-11 P/N G301041 only; washers and sealing rings prohibited. 2026-01-01 GTX Please Consider Adding a Spec Line to GTX Table 4 for the RCR T70 #39470cars addedaddedGTX adds RCR T70 Coupe, 2200 lbs minimum weight, no restrictor. 2025-10-01 SRF Add HD Oil Cooler #38979engineaddedengineSRF3 adds HD Oil Cooler P/N G1148500 option alongside standard P/N G480503, no fan permitted. 2025-06-01 GTX Ligier P3 LS Swap #38164engineaddedengineGTX Ligier LMP3 now allows any normally aspirated LS Chevrolet engine. 2025-05-01 GTX Request to Classify Porsche GT2 RS Clubsport #37972cars addedaddedGTX adds Porsche GT2 RS Clubsport with factory specifications required at all race events. 2025-04-01 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. 2025-04-01 SRF Update SADEV transmission specs #37992wordingwordingSRF SADEV-SRF3 6-speed sequential transmission: effective date clarified to 1 April 2025 onward. 2025-01-01 GTX Correct language regarding OEM Areo Devices #37137wordingwordingTA2 rear wing height rule clarified: OEM aerodynamic devices exempt from peak-of-roof height limit.
	Road America Runoffs 20242024-10-01	2:19.106Calvin Stewart · fastest of 22 · top 5 within 1.3s	2:18.840James Weida · fastest of 22 · top 5 within 1.0s	147.6Calvin Stewart
16 rule changes (SRF: 10, GTX: 6)2 engine · 2 suspension & brakes · 1 aero · 1 cars added · 1 tyres & wheels · 1 weight · 5 wording · 3 other · 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 Acura NSX minimum weight rises to 3000 lbs, restrictor increases to 45mm TIR. · 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 Nissan and GT3 Mazda, Mitsubishi 4G93, Nissan QR25DE/DD, QE25DE/DD now permit Direct Injection per 9.1.2.F.7.5.E. · GTX KTM X-Bow added to class with restrictor and weight specification for 2024. · 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. · SRF radiator options expanded: Enterprises P/N 480465 with baffle 480464, 480466, or Automotive 1R698 and CU698 allowed if cross-reference equivalent.showhide 2024-10-01 SRF Update SRF3 Air Filter Rule #36681wordingremovedSRF3 air filter rule removes K&N RC-9160 option, specifies Weems P/N WM301020 only. 2024-10-01 SRF Update SRF Brake Rotor Thickness #36687suspension & brakessuspension & brakesSRF Wilwood vented rotor minimum thickness increases to 13.25mm, 0.522 inches. 2024-10-01 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. 2024-09-01 SRF Protest Fee Clarification #36540wordingwordingFE and SRF protest fee rules redirected to GCR section 8.3.1.D for fees and procedure. 2024-09-01 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. 2024-08-01 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. 2024-05-01 GTX Request for Spec Line 1010 Reconsideration #35009weight +300 lbsslowerweightGT2-ST Acura NSX minimum weight rises to 3000 lbs, restrictor increases to 45mm TIR. 2024-02-01 GTX 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. 2024-02-01 GTX GT Direct Injection allowance and rules #35437engineaddedengineGT1, GT2, GT3, GTL, GTX Direct Injection now permitted if original equipment. 2024-02-01 GTX GT2/3 remove Direction Injection not allowed in Spec line notes #35439engineaddedengineGT2 Nissan and GT3 Mazda, Mitsubishi 4G93, Nissan QR25DE/DD, QE25DE/DD now permit Direct Injection per 9.1.2.F.7.5.E. 2024-01-01 GTX KTM X Bow GTX #34956cars addedaddedGTX KTM X-Bow added to class with restrictor and weight specification for 2024. 2024-01-01 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. 2024-01-01 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. 2024-01-01 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. 2023-12-01 GTX 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. 2023-10-01 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.
	Virginia International Raceway Runoffs 20232023-09-23	1:57.437Calvin Stewart · fastest of 9 · top 5 within 4.7s	1:58.816Calvin Stewart · fastest of 9 · top 5 within 3.6s	144.0Calvin Stewart
43 rule changes (SRF: 17, GTX: 26)18 cars added · 4 tyres & wheels · 3 engine · 1 weight · 13 wording · 4 other · GTX adds Ligier LMP3 with 3.7L NA engine, 22 mm restrictor, 2203 lbs minimum weight. · GTX adds Ligier JSP4 to MISC class; restrictor, weight and notes to be determined by SCCA. · SRF wet front tyre changes to Hoosier P/N 46100 P185/60R13 H20 or W2 with 2.5" ground clearance. · 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. · 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 TA2 and GTA throttle body part numbers updated to GM 12570790 or Edelbrock 33869/3870. · GT1, GT2, GT3, GTL, GTX tail lights may now be original style or custom panel graphic with functioning red LED brake lamps. · GTX adds Porsche 992 GT3 Cup Car; restrictor and specifications not stated in provided text. · 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. · GTX adds Wolf GB08 F1 Ford 52XS V8 NA at 1725 lbs minimum weight. · C7 Corvette Grand Sport added to GTX Misc with 3200 lbs minimum weight, displacement on demand valve train removable. · GTX eligible prototypes: IMSA GTP years changed to 1981-1993, plus five prototype categories newly allowed. · GTX McLaren 720s GT3 added to class with 30 mm restrictor and 3000 lbs minimum weight. · GTX-FIA GT3 all models lose intake restrictor requirements; McLaren name corrected. · 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… · GT3 Volkswagen Fun Cup Beetle EVO3 classified, sealed SOHC 1984cc engine, 2060 lbs minimum weight. · GTX SRO-GT4: Porsche 718 Club Sport MR GT4 classified, unrestricted, 2900 lbs minimum weight. · 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. · GTX adds Grullon GT unrestricted with 2350 lbs minimum weight, factory spec required. · SRF3 alternator pulley specified as P/N G902130 or G902130A, minimum 12oz. · SRF and SRF3 mandatory identification revised: removed Ford Performance and Blue Oval decals, added Hoosier logo placement. · SRF rear springs limited to P/N 280390 only, previous part numbers no longer allowed; ground clearance wording clarified. · GT1/GT2/GT3/GTL/GTX turbocharging and supercharging now permitted if listed on spec line. · GTX adds Chevrolet Camaro ZL1 with LT4 supercharged engine at 3400 lbs minimum weight. · GTX adds KTM X-Bow GT4, turbocharged 2.5L Audi TFSI I5, 2000 lbs minimum weight. · 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. · GTX tube frame cars now permit stock car bodies; minimum weight 2780 pounds. · GTX Lotus Evora GTS added with 3.5L 2GR-FE engine, 2950 lbs minimum weight, OEM supercharger pulleys. · SRF Penske shock P/N 280396 bump stop P/N 280407 becomes mandatory, maximum one per shock, effective 05/01/2020. · GT1, GT2, GT3, GTL, GTX may use bonded-glass factory windshields without clips or straps if attached per original specifications. · 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. · 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.showhide 2023-07-01 GTX Request Ligier LMP3 Classification #34043cars addedaddedGTX adds Ligier LMP3 with 3.7L NA engine, 22 mm restrictor, 2203 lbs minimum weight. 2023-07-01 GTX Ligier JSP4 Request #34173cars addedaddedGTX adds Ligier JSP4 to MISC class; restrictor, weight and notes to be determined by SCCA. 2023-06-01 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. 2023-05-01 GTX Please classify Fields Cardinal V8 #33784cars addedaddedFields Cardinal V8 added to GT1 with Ford V8 engine, 4.9L, 2100 lbs, fuel injection. 2023-05-01 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. 2023-03-01 SRF Update SRF Brake Rule #33469enginefasterengineSRF 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. 2022-12-01 GTX GT2 (TA2)/GTA Part Number Update #33315wordingwordingGT2 TA2 and GTA throttle body part numbers updated to GM 12570790 or Edelbrock 33869/3870. 2022-09-01 GTX 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. 2022-06-01 GTX Classify 992 GT3 Cup #32649cars addedaddedGTX adds Porsche 992 GT3 Cup Car; restrictor and specifications not stated in provided text. 2022-06-01 SRF SRF Tire Rule Update #32614wordingwordingSRF tire rule wording clarified: tires must be run as delivered. 2022-06-01 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. 2022-05-01 GTX Add Classification to the accepted Model Table #31981cars addedaddedGTX adds Wolf GB08 F1 Ford 52XS V8 NA at 1725 lbs minimum weight. 2022-05-01 GTX Request to classify C7 Corvette Grand Sport IN GTX Misc #32254cars addedaddedC7 Corvette Grand Sport added to GTX Misc with 3200 lbs minimum weight, displacement on demand valve train removable. 2022-05-01 GTX E&O list of eligible prototypes #32511cars addedaddedGTX eligible prototypes: IMSA GTP years changed to 1981-1993, plus five prototype categories newly allowed. 2022-03-01 GTX McLaren 720s GT3 #31955cars addedaddedGTX McLaren 720s GT3 added to class with 30 mm restrictor and 3000 lbs minimum weight. 2022-02-01 GTX Remove restrictions from GTX-FIA GT3 #32039enginefasterengineGTX-FIA GT3 all models lose intake restrictor requirements; McLaren name corrected. 2021-12-01 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… 2021-10-01 GTX Request car classification #31032cars addedaddedGT3 Volkswagen Fun Cup Beetle EVO3 classified, sealed SOHC 1984cc engine, 2060 lbs minimum weight. 2021-09-01 GTX Request to classify 2020 Porsche 718 GT4 Clubsport MR #30956cars addedaddedGTX SRO-GT4: Porsche 718 Club Sport MR GT4 classified, unrestricted, 2900 lbs minimum weight. 2021-08-01 GTX 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. 2021-08-01 GTX GTX class correction to GT2/ST #30973cars addedaddedGrullon GT 2.0L Acura K20 moved from GTX to GT2-ST class at 2350 lbs unrestricted. 2021-08-01 SRF SRF Wet Tires #30849tyres & wheelsaddedtyres & wheelsSRF wet tyres add Hoosier W2 option alongside existing H20 from October 4, 2021. 2021-08-01 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. 2021-08-01 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. 2021-07-01 GTX Request classification of Grullon #30481cars addedaddedGTX adds Grullon GT unrestricted with 2350 lbs minimum weight, factory spec required. 2021-06-01 SRF SRF3 Alternator Pulley #30684engineaddedengineSRF3 alternator pulley specified as P/N G902130 or G902130A, minimum 12oz. 2021-03-01 SRF Mandatory identification: #30223wordingwordingSRF and SRF3 mandatory identification revised: removed Ford Performance and Blue Oval decals, added Hoosier logo placement. 2020-12-01 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. 2020-09-01 GTX GT Category Wording #29193wordingaddedGT1/GT2/GT3/GTL/GTX turbocharging and supercharging now permitted if listed on spec line. 2020-08-01 GTX Request Car classification #28935cars addedaddedGTX adds Chevrolet Camaro ZL1 with LT4 supercharged engine at 3400 lbs minimum weight. 2020-08-01 GTX X-Bow GT4 #29088cars addedaddedGTX adds KTM X-Bow GT4, turbocharged 2.5L Audi TFSI I5, 2000 lbs minimum weight. 2020-07-01 GTX TA2 Gurney flap wicker clarification #28874wordingwordingTA2 Gurney flap wording clarified: replace 'wicker bill' and 'wicker' with 'Gurney flap' throughout wing specifications. 2020-07-01 GTX STO Gurney flap wicker clarification #28883wordingwordingSTO rear wing rules clarify that wicker is called Gurney flap in two places; no performance change. 2020-07-01 GTX 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. 2020-06-01 GTX Request to Re-classify SP Stock car to GTX #28333cars addedaddedGTX tube frame cars now permit stock car bodies; minimum weight 2780 pounds. 2020-05-01 GTX Request to Classify Lotus Evora GTS #27057cars addedaddedGTX Lotus Evora GTS added with 3.5L 2GR-FE engine, 2950 lbs minimum weight, OEM supercharger pulleys. 2020-05-01 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. 2020-02-01 GTX Windshield Clips #27323otheraddedGT1, GT2, GT3, GTL, GTX may use bonded-glass factory windshields without clips or straps if attached per original specifications. 2020-01-01 GTX 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. 202-01-01 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. 2019-12-01 SRF SRF Tire Warmer Rule #27622tyres & wheelstyres & wheelsSRF adds tire warmer prohibition and specifies Hoosier dry and wet tire part numbers. 2019-12-01 SRF SRF / SRF3 Nose Weight Reduction #27706weightfasterweightSRF front nose weight minimum reduced from 35 to 32 lbs. 2019-12-01 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.
	Virginia International Raceway Runoffs 20192019-10-05									1:55.124Bryce Cornet · fastest of 8 · top 5 within 2.3s	2:15.816Bryce Cornet · fastest of 8 · top 5 within 4.9s	135.7Bryce Cornet
6 rule changes (SRF: 1, GTX: 5)1 aero · 1 cars added · 1 engine · 2 wording · 1 other · SRF drivers may now use Dash Windscreen Kit P/N 1180103 or P/N 180102. · GTX tube frame cars now allowed fuel injection with maximum 90mm throttle body. · GTX adds Ligier JS2 R classification with restrictor and minimum weight. · GT1 and GT2/3/Lite remove ride height ground clearance rules; cars may now touch ground when tires deflate. · GTX strikes FIA GT4 references and replaces with SRO GT4. · 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 2019-07-01 SRF SRF Dash Windscreen Kit #27028aeroaddedaeroSRF drivers may now use Dash Windscreen Kit P/N 1180103 or P/N 180102. 2019-05-01 GTX Request GTX Fuel injection for previous GT-1 tube frame cars #26141engineaddedengineGTX tube frame cars now allowed fuel injection with maximum 90mm throttle body. 2019-05-01 GTX Request to Classify Ligier JS2 R #26535cars addedaddedGTX adds Ligier JS2 R classification with restrictor and minimum weight. 2019-04-01 GTX Request Ride Height Clarification #26600wordingfasterGT1 and GT2/3/Lite remove ride height ground clearance rules; cars may now touch ground when tires deflate. 2019-03-01 GTX Replace FIA references with SRO #26427wordingwordingGTX strikes FIA GT4 references and replaces with SRO GT4. 2019-01-01 GTX 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.
	Sonoma Raceway Runoffs 20182018-10-10									1:37.598Bryce Cornet · fastest of 13 · top 5 within 0.9s	1:37.909Bryce Cornet · fastest of 12 · top 5 within 1.3s	124.1Melvin David Kemper Jr
No rule changes on record between these events
	Indianapolis Motor Speedway Runoffs 20172017-09-25				1:51.573Thomas Kirchman · fastest of 50 · top 5 within 2.8s	1:53.769Todd Harris · fastest of 45 · top 5 within 0.2s				1:41.231Jarret Voorhies · fastest of 16 · top 5 within 1.7s	1:41.146Jarret Voorhies · fastest of 16 · top 5 within 1.2s
No rule changes on record between these events
	Mid-Ohio Sports Car Course Runoffs 20162016-09-19				1:37.344Mike Miserendino · fastest of 27 · top 5 within 0.8s	1:37.621Todd Harris · fastest of 27 · top 5 within 0.6s				1:26.043Jacob Loomis · fastest of 8 · top 5 within 3.1s	1:27.922Jacob Loomis · fastest of 8 · top 5 within 2.7s
No rule changes on record between these events
	Daytona International Speedway Runoffs 20152015-09-21				2:14.306Cliff White · fastest of 39 · top 5 within 1.2s	2:16.700Cliff White · fastest of 38 · top 5 within 0.5s				1:57.804Joseph Burton-Harris · fastest of 10 · top 5 within 2.3s	1:58.029Joseph Burton-Harris · fastest of 10 · top 5 within 1.7s

By track

Track	Events	Typical % of F6	Best	Latest
Road America	2	100.0%	100.0%Runoffs 2024	100.0%Runoffs 2026
Virginia International Raceway	2	100.0%1 of 2 with F6	100.0%Runoffs 2023	100.0%Runoffs 2023
Daytona International Speedway	1	0 of 1 with F6
Indianapolis Motor Speedway	1	0 of 1 with F6
Mid-Ohio Sports Car Course	1	0 of 1 with F6
Sonoma Raceway	1	0 of 1 with F6

About this data

Every event the class ran, at any track, oldest to newest on the chart and newest first in the table. Each point is the class's best lap as a share of F6's best on the same day: the weather and the day cancel out, so one figure compares across years where lap times cannot; a class that suits one track more than another still reads differently there. It still moves when the yardstick's own balance changes or its field thins, and an event the yardstick did not run has no point. A best from fewer than three cars is greyed. The rule changes that took effect between two events are folded between their rows.