BoP Lab / Buttonwillow Raceway Park

F5 vs SRF vs T4 pace at Buttonwillow Raceway Park

Quickest here: T4 1:58.339 Oscar Jackson, Cal Club 2025 qualifying

F5SRFT4solid race · dashed qualifying · slower is lower

	Event	F5			SRF				T4
	Event	Qual best	Race best	Trap	Qual best	Race best	Trap	vs F5	Qual best	Race best	Trap	vs F5
	Cal Club 2026 CALCL262026-02-21								2:01.678Izzy Sanchez · fastest of 5 · top 5 within 5.9s+3.339s (+2.82%)	2:01.157Izzy Sanchez · fastest of 5 · top 5 within 7.2s+1.235s (+1.03%)	135.5Izzy Sanchez+27.2 mph (+25.1%)
22 rule changes (SRF: 3, T4: 19)3 cars added · 2 induction · 2 suspension & brakes · 2 tyres & wheels · 2 weight · 1 aero · 1 removed · 2 wording · 7 othershowhide 2026-02-01 T4 T4 and T3 Feedback #39230removed 2026-02-01 T4 T4 Mustang 4.0 #39489induction 2026-02-01 T4 Allow Alt Bushing Material in Toe Links #39607suspension & brakes 2026-01-01 T4 Alternate Placement of Fuse Panel and Electronics Request #39370other 2026-01-01 T4 Clarify T4 Brake Rotor Allowance #39503suspension & brakes 2025-12-01 T4 Classing 1995-99 Dodge Neon SOHC #39285cars added 2025-11-01 T4 02-06 Mini Cooper Gear Ratios #38966other 2025-11-01 T4 Reinstatement of the 2005-2010 Cobalt into T4 #38987cars added 2025-11-01 T4 Request to Classify Mercedes C230K #39080cars added 2025-11-01 T4 ND Gearset Request for T4 #39166other 2025-11-01 T4 E&O wheel size on ND #39168tyres & wheels 2025-11-01 T4 ND Spec Lines Wrong PT#'s #39170weight 2025-11-01 T4 Touring 4 Post-Runoffs BOP Adjustments and Changes #39251induction -100 lbs 2025-10-01 SRF Add HD Oil Cooler #38979other 2025-08-01 T4 Incorrect Touring Heading #38451wording 2025-07-01 T4 Allow B-Spec cars to run in T4 #38439other 2025-06-01 T4 T4 Mustang #38059weight -100 lbs 2025-06-01 T4 SSC tire allowance #38216tyres & wheels 2025-05-01 T4 Correct Ring and Pinion Ratio to T3, Sorry I Mean T4 3.7 V6 Stang #38041wording 2025-05-01 T4 T4 Mustang #38058aero 2025-04-01 SRF Driver Safety & Comfort #37966other 2025-04-01 SRF Update SADEV transmission specs #37992other
	Cal Club 2025 CALCL252025-02-22								1:58.339Oscar Jackson · fastest of 5 · top 5 within 8.3s	1:59.922Oscar Jackson · fastest of 4 · top 4 within 7.3s	108.4Tony Kiratsous
204 earlier rule changes on record, in force before Cal Club 2025 (from 2019)40 weight · 36 suspension & brakes · 23 tyres & wheels · 19 cars added · 12 engine · 10 induction · 3 aero · 2 removed · 20 wording · 39 other · 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. · F500 Rotax engines now permit Ingi Tech Sparker ignition DCP-CDI-P2 as alternate ECU. · 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. · F500 Majors and Runoffs cars must install AIM part #X47KPFSOLO2R0 data box mount for Solo or Solo 2. · F5 cars must install AIM part #X47KPFSOLO2R0 data box mount for Majors and Runoffs. · 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. · F500 Rotax 593 HO engine now permitted; 875 lbs minimum weight, MA0242SP1020A or MA0242SP1063A restrictor, specific intake boots and piston required. · F500 Suzuki GSXR600 engine years extended from 2003-2013 to 2003-2019. · F5 request to adjust external jetting device cockpit control denied; no rule change made. · F5 cockpit adjustment request response published in Fastrack letter 28359. · F500 Honda CBR600RR, Suzuki GSXR600, Yamaha R6 restrictor reduced to 28mm from 29mm. · F500 Honda CBR600RR, Suzuki GSXR600, and Yamaha R6 minimum weights increase to 900 lbs.showhide 2025-02-01 T4 Ford Mustang V6 (05-14) #37516other 2025-02-01 T4 Request to Classify Club Spec in Appropriate Touring Classes #37523cars added 2025-01-01 T4 Remove spec lines that have expired #37269induction 2025-01-01 T4 2016-2018 Mazda Miata MX5 #37085weight -75 lbs 2024-12-01 T4 Redundant Verbiage Regarding Mustang Spec Lines for Driveshaft #36484suspension & brakes 2024-12-01 T4 R53 Mini Cooper S Weight Reduction Request #36612weight 2024-12-01 T4 Allowable Wheel Offset #36855tyres & wheels 2024-12-01 T4 Fuel Emissions Components #37076engine 2024-12-01 T4 2019-2024 Mazda 3 for T4 #37077cars added 2024-12-01 T4 fix brake wording #37129suspension & brakes 2024-12-01 T4 Evaporative emissions systems #37130engine 2024-12-01 T4 Allow Spec MX5 upgrade kit for 2009-11 RX8 S2 Transmision #37140other 2024-12-01 T4 Move Spec Boxster to T4 #37158cars added 2024-12-01 T4 3.7 Mustangs to T4 #37188cars added 2024-12-01 T4 BMW 320i Spec Line #37204other 2024-12-01 T4 MX5 2006-2015 NC Help #37221other 2024-12-01 T4 Classification for a 2005 Cadillac CTS 3.6 liter 6 speed manual #37224cars added 2024-12-01 T4 Civic SI in T4 #37248weight -50 lbs 2024-12-01 T4 2006-2015 T4 NC Mx5 spec line #37278weight 2024-12-01 T4 ND MX-5 wheel allowance #37279tyres & wheels 2024-12-01 T4 T4 BOP #37281weight +75 lbs 2024-12-01 T4 Allow 7.5 #37286tyres & wheels 2024-11-01 T4 Bop Request 06-11 Honda Civic Si #37013other 2024-10-01 SRF Update SRF3 Air Filter Rule #36681other 2024-10-01 SRF Update SRF Brake Rotor Thickness #36687suspension & brakes 2024-10-01 SRF Hoosier Tire Decal Placement #36739tyres & wheels 2024-09-01 SRF Protest Fee Clarification #36540wording 2024-09-01 SRF Update to Letter 36619 with new Hoosier Contingency Decal Info #36624tyres & wheels 2024-08-01 SRF Update Rain Tire Rule and Hoosier Decal Placement #36436tyres & wheels 2024-08-01 T4 T4 Camaro V6 weight reduction #36232weight 2024-08-01 T4 BOP adjustment for ND MX5s #36345weight -50 lbs 2024-07-01 T4 Mustang T2/T3 #35877other 2024-07-01 T4 Homologation of car to T4 #36030cars added 2024-07-01 T4 T2-T4 Driveshaft Mistake...? #36050weight 2024-07-01 T4 MINI Cooper S Spec Lines Corrections. #36086removed 2024-07-01 T4 Allow Removal of Sound Tubes #36130induction 2024-07-01 T4 B8/8.5 Audi S4 T3 and T2 #36195cars added 2024-06-01 T4 Allow OEM Front Spoiler 06-08 Miata in T4 #35941aero 2024-06-01 T4 T4 Mustang Weight Reduction In T4 Spec #36051weight -50 lbs 2024-06-01 T4 R53 Mini Cooper S spec line request In #36056suspension & brakes 2024-05-01 T4 Allow T4 and T3 RX8 to Disable/Remove Factory Oil Inj. #35761engine 2024-05-01 T4 2023 ND2 Miata Classification and Allowances #35837weight 2024-05-01 T4 Errors and Omissions for 06-09 VW Rabbit Rotor #35851suspension & brakes 2024-05-01 T4 Driveshafts #35916weight 2024-05-01 T4 GCR ERROR - letter not properly applied to GCR #35999weight 2024-04-01 T4 Corrections to T4 RX8 Spec line #35767aero 2024-03-01 T4 Reorganize Spec Lines #35375induction 2024-03-01 T4 Allow any 400lb rear spring in the RX8 #35433suspension & brakes 2024-03-01 T4 370Z Brake Rotor Size Correction #35487suspension & brakes 2024-02-01 T4 More Car Lightening Stuff #35319weight 2024-02-01 T4 ND Missed Items #35352other 2024-02-01 T4 Inclusion of B-C spec cars in T4 #35374other 2024-02-01 T4 T2-T4 Set expiration dates on spec lines #35378induction 2024-01-01 SRF Update SRF Rain / Brake Rule #34706suspension & brakes 2024-01-01 SRF Update SRF Brake Light Rule v1 #34853suspension & brakes 2024-01-01 SRF SRF / SRF3 Rule Updates #35268weight 2024-01-01 T4 Mazda MX-5 ND1 Spec Line Request #34232weight +50 lbs 2024-01-01 T4 BRZ/FRS/86 Spring Allowance #35038suspension & brakes 2024-01-01 T4 TSX Allowance #35219other 2024-01-01 T4 Requested Update of Model Years of 370Z #35231other 2023-10-01 SRF SRF Radiator Rule Update #34805other 2023-09-01 T4 Inclusion of similar car. (CLK 320) #34626other 2023-08-01 T4 Rules Clarification for Mazda RX8 Spec Line #34395weight 2023-08-01 T4 rule book corrections #34437wording 2023-08-01 T4 Ride Height Correction for the T3 Solstice. #34615suspension & brakes 2023-07-01 T4 2002-2006 Mini Cooper S R53 Spec Line Request #34336weight -50 lbs 2023-06-01 SRF Hoosier SRF Wet Front Tire Rule Update #34189tyres & wheels 2023-06-01 T4 05-06 Mini Wheel Weight #34112weight 2023-06-01 T4 06-09 VW Rabbit #34153induction 2023-06-01 T4 96-01 Audi a4 2.8 Spring Rate #34217suspension & brakes 2023-05-01 SRF Update SRF Front W2 Rain Tire Part Number #34118tyres & wheels 2023-04-01 T4 Request to Classify 2004-2008 Acura TSX in T4 #33590cars added 2023-04-01 T4 T4 Mustang Brakes/Swaybar #34036suspension & brakes 2023-03-01 SRF Update SRF Brake Rule #33469suspension & brakes 2023-03-01 T4 BMW 320I intercooler #33762other 2023-02-01 T4 2019-2021 Mazda MX5 ND2 #32027cars added 2023-02-01 T4 Mustang OEM Grill Request #33333other 2023-02-01 T4 Mazda OEM LSD was letter 32655 typo #33666wording 2023-01-01 T4 Allowable Springs and Sway Bars for 06-11 Civic si Spec Line #33294suspension & brakes 2023-01-01 T4 Touring (T2-T5) Category #33617tyres & wheels 2023-01-01 T4 ENO 9.1.9.2.D.1.e.1.a. #33651other 2022-12-01 T4 T4 mustang #32789weight -25 lbs 2022-12-01 T4 Mazda OEM LSD was letter 32655 #32933weight -25 lbs 2022-10-01 T4 Another 2022 BRZ/86 T3 request #32945weight +225 lbs 2022-09-01 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. 2022-08-01 F5 Ensure availability of ECU for Rotax engines #32695engineadded · engineF500 Rotax engines now permit Ingi Tech Sparker ignition DCP-CDI-P2 as alternate ECU. 2022-08-01 T4 04-09 Mazda3 Balance Shaft Delete Kit #32795other 2022-07-01 F5 Clarify stepped exhaust header references #32743wordingwordingF500 clarifies stepped diameter exhaust headers prohibited except at cylinder head flange area. 2022-06-01 F5 593 carb boot availability and oil pump clarification #32527wordingwordingF500 Rotax 593 intake boot options clarified; oil injection pump removal now permitted. 2022-06-01 SRF SRF Tire Rule Update #32614tyres & wheels 2022-06-01 SRF Brake, seal, and air filter clarifications #32670suspension & brakes 2022-06-01 T4 Request Wider Wheels for Hyundai Tiburon #32536tyres & wheels 2022-05-01 T4 Request to Add Spec Line for 2004-2009 Mazda3 i 2.0 #32395weight 2022-05-01 T4 Request Alternate Front & Rear Strut/Shock Top Hats #32452suspension & brakes 2022-04-01 T4 Request to Allow the Use of Aftermarket ECU's in Touring #31067engine 2022-04-01 T4 Request JWT BSR Kit for 02-06 Nissan Sentra SE-R/Spec V #31685other 2022-04-01 T4 Please Confirm Touring 4 (98-00) BMW 323 is E46 generation #31972other 2022-04-01 T4 RX-8 Spring Part Numbers (E&O) #32151suspension & brakes 2022-04-01 T4 04-09 Mazda3 Tire Limit Clarification #32249tyres & wheels 2022-04-01 T4 Shock Part Number Errors & Omissions #32252suspension & brakes 2022-04-01 T4 Update Solo Spec Coupe to latest '20 specs for Road Racing #32262other 2022-04-01 T4 Request 2016 Mazda MX5 springs #32265suspension & brakes 2022-03-01 F5 E&O class name #32194otheraddedF500 Majors and Runoffs cars must install AIM part #X47KPFSOLO2R0 data box mount for Solo or Solo 2. 2022-03-01 T4 Reply to letter #31486/29879 T2-T4 Grill openings #31935suspension & brakes 2022-03-01 T4 BRZ vs BRZ TS #32022tyres & wheels 2022-02-01 T4 MX-5 Durability Detailed #31102weight 2022-02-01 T4 Request Allowances for 2005 - 2010 Mustang #31624wording 2022-01-01 F5 Data Box Mounting Plate #31638otheraddedF5 cars must install AIM part #X47KPFSOLO2R0 data box mount for Majors and Runoffs. 2022-01-01 T4 Reply to letter 29879 T2-T4 Grill Openings #31486suspension & brakes 2022-01-01 T4 Please Adjust 98-00 BMW 323 Min Weight to Reflect Current Class #31595weight -200 lbs 2022-01-01 T4 Consolidate 12-13 and 14-15 Honda Civic Si spec lines for T4 #31596removed 2022-01-01 T4 Request to clarify radiator hoses #31682wording 2022-01-01 T4 Clarify Permitted/Allowed #31743suspension & brakes 2022-01-01 T4 Correct RSX wording #31746tyres & wheels 2022-01-01 T4 Camaro #31751suspension & brakes 2021-12-01 SRF Three Updates to SRF Rules #31523weight 2021-12-01 T4 Nissan Sentra SE-R Spec. V #30958cars added 2021-12-01 T4 Mazda RX-8 Spec Line Suspension Parts #31113induction 2021-12-01 T4 Diverter Valve Plunger Upgrade #31307engine 2021-12-01 T4 Adjust Honda FWD in T4 to encourage more Drivetrain Diversity #31472tyres & wheels 2021-12-01 T4 Touring 4 BOP adjustments for 2022 #31482weight -175 lbs 2021-11-01 T4 Request to Classify 2014 VW Jetta 1.8t TSI #30436cars added 2021-08-01 F5 Clarify allowable assisted shifting systems #30871wordingwordingF5 clarifies mechanical shifting only; throttle-cut and flat-shifter devices permitted if driver retains full control. 2021-08-01 F5 Request to correct terminology #30976wordingwordingF5 single-seat open-wheel cars: rigid suspension becomes limited suspension in class definition. 2021-08-01 SRF SRF Wet Tires #30849tyres & wheels 2021-08-01 SRF SADEV-SRF3 Transmission #30926other 2021-08-01 SRF SRF Update Maintenance, Repairs and Seals #30961engine 2021-07-01 T4 Wrong Part Number on 320i Spec Line #30645wording 2021-06-01 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. 2021-06-01 SRF SRF3 Alternator Pulley #30684weight 2021-06-01 T4 Civic Type R Brake Rotors #29817suspension & brakes 2021-05-01 T4 Mini Cooper Spec Line Anomalies #30478weight 2021-05-01 T4 Request CAI Mustang in T4 #30562induction 2021-04-01 T4 Request consistency review in GCR #30263other 2021-03-01 SRF Mandatory identification: #30223engine 2021-03-01 T4 E & O T4 Mustang Wheels #30245tyres & wheels 2021-02-01 T4 2021 Toyota Supra #29567cars added 2021-02-01 T4 06-15 MX-5 Durability #29781other 2021-02-01 T4 Request for Update to T4 Spec Line for Chevrolet Sonic (2011-) #29838induction 2021-02-01 T4 NC MX-5 06-15 Part Number updates for 2021 #29921weight 2021-02-01 T4 BMW Z4 2.5L (03-05) Spec Line #30037weight -50 lbs 2021-02-01 T4 Sway Bars for T4 2016+ MX5 Mazda #30063suspension & brakes 2021-02-01 T4 Change part numbers on BRZ, FRS lines in T4 #30104wording 2021-02-01 T4 T4 Mustang Axle Ratio and Wheels #30149tyres & wheels 2021-01-01 T4 Request to Classify BMW M2 CS #29523cars added 2021-01-01 T4 Allow the SpecMX-5 Update Kit Into Touring 4 for the MX-5 #29681other 2021-01-01 T4 Request Mustang 8.8ÃƒÂ¢Ã¢â€šÂ¬Ã‚Â rear axle replacement #29860other 2021-01-01 T4 Cap year range on all 86s #29908other 2020-12-01 SRF SRF Shocks, Springs and Ride Height. #29688suspension & brakes 2020-12-01 T4 Alfa Romeo 4C Launch Edition #29531other 2020-12-01 T4 Post Runoffs Feedback for T4 #29752tyres & wheels -50 lbs 2020-10-01 F5 Request to Update Suzuki Engine Years for F500 #29453engineadded · engineF500 Suzuki GSXR600 engine years extended from 2003-2013 to 2003-2019. 2020-08-01 T4 Scion FRS Solo Spec Coupe Gear Ratio #29021other 2020-07-01 F5 Request for Cockpit Adjustment of External Jetting Devices #28359wordingunclearF5 request to adjust external jetting device cockpit control denied; no rule change made. 2020-07-01 F5 Two Stroke Motors (reply to #28359 WDYT) #28816engine 2020-07-01 F5 Re letter requesting driver adjustable carb mixture #28840other 2020-07-01 F5 #28359 WDYT Request for Cockpit Adjustment #28875wordingunclearF5 cockpit adjustment request response published in Fastrack letter 28359. 2020-07-01 T4 T4 RX8 bodywork clarification #28941aero 2020-07-01 T4 2006-2015 MX-5 Clarification #28942tyres & wheels 2020-07-01 T4 Request to Add a Vehicle to the Roster (contd.) #27698other 2020-06-01 T4 Request to Classify 2004 Mercedes Benz 320 CLK #27663cars added 2020-05-01 SRF SRF Bump Stop Correction #27019suspension & brakes 2020-05-01 T4 Request to change allowed header part # for T4 06-15 Miata #28223wording 2020-05-01 T4 Z3M Roadster Weight #28437weight 2020-03-01 T4 Request for 12-13 and 14-15 Honda Civic Springs #27848suspension & brakes 2020-03-01 T4 Request to Clarify T4 05-10 Mustang Spring Allowance #27899suspension & brakes 2020-02-01 T4 Request to Allow Brake Upgrade on T4 Mustang #27329suspension & brakes 2020-02-01 T4 Please Switch the Solstice GXP as Specified in T2, to T3 #27413weight -50 lbs 2020-02-01 T4 Request to Classify all Mazda RX8 Models in T3/T4 #27606cars added 2020-02-01 T4 Request for 2014-2018 Mazda 3 GT Brakes #27659suspension & brakes 2020-02-01 T4 Request to allow aftermarket OEM coolant expansion tank #27763engine 2020-02-01 T4 Request to allow aftermarket OEM power steering reservoir #27764wording 2020-02-01 T4 Request for Factory Installed Wings on Subaru BRZ #27831other 2020-02-01 T4 Request for Replacement Clutches #27892other 2020-02-01 T4 Request to Classify Chevy Sonic 1.4 In T4 #27906cars added 2020-02-01 T4 Weight Change Request for 1999 Mazda Miata #28129weight -50 lbs 2020-01-01 F5 Change 600cc restrictor size #27883inductionslower · inductionF500 Honda CBR600RR, Suzuki GSXR600, Yamaha R6 restrictor reduced to 28mm from 29mm. 2020-01-01 T4 Clarification of On-Board Fire System for T2 #27183wording 2020-01-01 T4 Mustang Ecoboost and GT Transmission #27439other 2020-01-01 T4 BRZ/FRS/86 Tire Size in T4 #27660tyres & wheels 2020-01-01 T4 NC MX5 2006-2015 Spec Adjustment Request #27739weight -75 lbs 2020-01-01 T4 T4 RX8 Classification Error #27902wording 2020-01-01 T4 Request to add Toyota 86 GT to Spec Line #27910other 202-01-01 SRF SRF Rain / Brake Rule - BoD approved as follows #34958suspension & brakes 2019-12-01 SRF SRF Tire Warmer Rule #27622tyres & wheels 2019-12-01 SRF SRF / SRF3 Nose Weight Reduction #27706weight 2019-12-01 SRF SRF / SRF3 Majors & Regional Class Updates #27723other 2019-08-31 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. 2019-08-31 T4 Request spare tire/wheel clarification #27012tyres & wheels 2019-08-31 T4 Research E&O Mazda MX5 #27112weight 2019-07-01 SRF SRF Dash Windscreen Kit #27028other 2019-07-01 T4 MR2 Spyder Year Correction #26936wording 2019-05-31 T4 Request to allow piggy back ECU on 2000 Mazda Protégé #26085engine 2019-05-31 T4 Request helper spring as optional #26678suspension & brakes 2019-04-01 T4 Request to classify 2000 - 2001 BMW 323 #25096cars added 2019-03-01 T4 Correct Mazda MX-5 Hard Top Notes #26137weight 2019-03-01 T4 Consider opening class rules to allow any thermostat #26187wording 2019-03-01 T4 Cap 2016 Mazda Miata year at 2018 #26388other 2019-02-01 T4 2012-2015 Honda Civic Si Performance Request #26129suspension & brakes 2019-01-01 T4 Errors, Omissions, and Updates (Various) #22414weight 2019-01-01 T4 Request for Adjustments to fiat 124 specline #25371induction 2019-01-01 T4 Add Clarification to Spec Car Classifications Vehicle Spec #25774weight 2019-01-01 T4 Clarify Subframe Bushings Permitted for T2-T4 #25800suspension & brakes 2019-01-01 T4 Consider Solo SSC cross over classification into T4 #25802cars added

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.