BoP Lab / Buttonwillow Raceway Park

F5 vs SRF vs FB vs STU pace at Buttonwillow Raceway Park

Quickest here: STU 1:50.913 Tony Rivera, Cal Club 2026 qualifying

F5SRFFBSTUsolid race · dashed qualifying · slower is lower

	Event	F5			SRF				FB				STU
	Event	Qual best	Race best	Trap	Qual best	Race best	Trap	vs F5	Qual best	Race best	Trap	vs F5	Qual best	Race best	Trap	vs F5
	Cal Club 2026 CALCL262026-02-21												1:50.913Tony Rivera · fastest of 6 · top 5 within 14.1s-4.488s (-3.89%)	1:52.737Tony Rivera · fastest of 7 · top 5 within 7.7s-0.903s (-0.79%)	135.2Tony Rivera+21.8 mph (+19.3%)
20 rule changes (SRF: 3, STU: 17)8 weight · 3 induction · 2 engine · 2 tyres & wheels · 1 cars added · 1 wording · 3 othershowhide 2026-01-01 STU Request for Permission on Aftermarket Turbo Kit and Intake #39529induction 2025-12-01 STU Turbo Inlet Restrictor Table #38961induction 2025-12-01 STU 275 Tire Rule #38983tyres & wheels 2025-12-01 STU STU Honda Engine weight penalty #39375weight 2025-11-01 STU Non-Homologated Engine Swaps - Specifically K24A2 w/ Honda CRZ #38746weight 2025-10-01 SRF Add HD Oil Cooler #38979other 2025-09-01 STU Lotus Weight Reduction E&O #38919weight 2025-08-01 STU STU-TCR Adjustments #38723weight 2025-08-01 STU Lotus Weight Reduction #38772weight -50 lbs 2025-07-01 STU 2.8-3.2L N/A Engine Allowances #38007engine 2025-07-01 STU 2006-2015 Mazda Miata Intake Manifold #38422induction 2025-07-01 STU Requesting Approval of the JDM Honda h23a #38489cars added 2025-05-01 STU Wheel Size Inconsistency #38018tyres & wheels 2025-05-01 STU Table C: STU-GT3U Clarification #38268weight 2025-04-01 SRF Driver Safety & Comfort #37966other 2025-04-01 SRF Update SADEV transmission specs #37992other 2025-03-01 STU BMW N54/N55 Engine Allowance Follow Up #37447engine 2025-03-01 STU STU Mini Cooper pulley size clarification re: letter #36980 #37717wording 2025-03-01 STU Question About a Weight Modifier #37782weight 2025-03-01 STU Increase Minimum Weight #37919weight +100 lbs
	Cal Club 2025 CALCL252025-02-22												1:55.401Wilson Powell · fastest of 4 · top 4 within 8.7s	1:53.640Rylan Hazelton · fastest of 5 · top 5 within 8.0s	113.3Rylan Hazelton
129 earlier rule changes on record, in force before Cal Club 2025 (from 2019)30 weight · 17 induction · 15 engine · 14 tyres & wheels · 11 suspension & brakes · 8 cars added · 7 aero · 10 wording · 17 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 2025-01-01 STU Audi 1.8t Wagon STU Table B #36685weight 2025-01-01 STU Merger GT3 to STU #37486other 2025-01-01 STU GT3 TCR Tire allowance #37494tyres & wheels 2024-12-01 STU Request to Remove Miata Hubs from General category #37138tyres & wheels 2024-12-01 STU BMW N54/N55 Engine Allowance #37146engine 2024-11-01 STU R53 15% Pulley Request #36980other 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 STU RWD Turbo Disadvantage #36255induction 2024-03-01 STU Letter #35397 addendum #35453weight 2024-03-01 STU S54 Drysump #35464other 2024-02-01 STU ST Electric-Assisted Steering Systems #35066other 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 2023-10-01 SRF SRF Radiator Rule Update #34805other 2023-07-01 STU 2022 Toyota GR Cup for STU #34449cars added 2023-06-01 SRF Hoosier SRF Wet Front Tire Rule Update #34189tyres & wheels 2023-05-01 SRF Update SRF Front W2 Rain Tire Part Number #34118tyres & wheels 2023-04-01 STU Alternate OEM Miata Intake Manifold #33827induction 2023-03-01 SRF Update SRF Brake Rule #33469suspension & brakes 2023-03-01 STU E&O STU NA Weight Chart. #33737weight 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 STU Request Mazda 13 B turbo #32668induction 2022-08-01 STU Hood Vents and Intercooler Scoops #32733other 2022-08-01 STU Non 4 valve weight reduction removed #32808weight 2022-07-01 F5 Clarify stepped exhaust header references #32743wordingwordingF500 clarifies stepped diameter exhaust headers prohibited except at cylinder head flange area. 2022-07-01 STU Error in new minimum weight table when combined with other text #32711weight 2022-07-01 STU Redundant Language in May GCR #32713engine 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 2022-05-01 STU Opposed to the Proposed STU Weight Chart #32381weight 2022-05-01 STU Clarification request for GCR 9.1.4.D.3.a Splitter Definition #32414aero 2022-04-01 STU Request Adjustment to Min Weight for STU BMW E36 M3 (95-99) #31535weight -90 lbs 2022-04-01 STU BMW E36 M3 Canadian (North American) S50B32 engine #31866engine 2022-04-01 STU Engine Swap Origin Country #32209engine 2022-04-01 STU CRX/Civic Del Sol #32214cars added 2022-04-01 STU Error correction #32383weight 2022-04-01 STU Single TB Weight Modifiers Add to Chart #32393weight 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 STU Single TB Weight Modifiers #31449weight 2022-03-01 STU Request to Remove A4 1.8t from STU Spec Line Tables #31465weight 2022-03-01 STU Improved Touring Tires #32063tyres & wheels 2022-02-01 STU Request Allowance for Balance Shaft Delete in STU #31434engine 2022-02-01 STU Request Louvers in hood vents #31916other 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 STU Request to Add Honda K23 Spec Line #30682cars added 2022-01-01 STU RE: Aug FT letter 30682 #31060other 2022-01-01 STU Throttling Device Clarification #31323induction 2021-12-01 SRF Three Updates to SRF Rules #31523weight 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 STU STU Fender flares #30696tyres & wheels 2021-07-01 STU Request weight reduction for 12A bridgeport motor in Miata #30751weight -200 lbs 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 2021-05-01 STU Request for Fender Flare Clarification #30375weight 2021-04-01 STU Provision for Interchangeable Engine Components Already Allowed #30342engine 2021-04-01 STU ST Oil Coolers E&O Correction to 9.1.4.2.H #30388wording 2021-03-01 SRF Mandatory identification: #30223engine 2021-03-01 STU Super Touring Alternate Miata Hubs #30345tyres & wheels 2021-02-01 STU Brake Component Relocation #29990suspension & brakes 2021-02-01 STU Porsche PDK #30081weight 2021-02-01 STU Reference Letter #29333 Proposed STU 13B Spec Line Changes #30086weight 2021-02-01 STU Drive Shaft Request #30087other 2021-01-01 STU 13B Rules Adjustment #29333cars added 2020-12-01 SRF SRF Shocks, Springs and Ride Height. #29688suspension & brakes 2020-12-01 STU Request clarification on wing measurement #29640aero 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. 2020-09-01 STU Request for Advanced Aero Rule Wording Clarification. #29124aero 2020-08-01 STU Minimum Weight Determination #27695weight 2020-08-01 STU ST Gurney flap Wicker clarification #29012aero 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 STU Request for Alternate Intake Manifold #26514induction 2020-07-01 STU Request for Addition to GT3 Approved Turbo List #27576induction 2020-07-01 STU Request BoP for my Car #29004induction 2020-07-01 STU Sequential Shifters in STU #29031other 2020-06-01 STU Rotary Help #27833weight 2020-05-01 SRF SRF Bump Stop Correction #27019suspension & brakes 2020-04-01 STU Request to approve Honda S2000 HKS supercharger #27281engine 2020-04-01 STU Request BoP on the Lotus #27637weight +100 lbs 2020-04-01 STU Turbo Inlet Restrictor On MK5 Volkswagen #27704induction 2020-04-01 STU Honda K20C1 removal #27732induction 2020-04-01 STU Change GM LNF 2.0 Allowance to LSJ Engine for Viable STL 2.0 #27884engine 2020-04-01 STU Alternate Engine for Porsche 944 #28259engine 2020-03-01 STU Please Modify the STU Wheel Size Rule for Clarity #27694weight 2020-03-01 STU Turbo Engine Cars Base Weight #28032weight 2020-01-01 F5 Change 600cc restrictor size #27883inductionslower · inductionF500 Honda CBR600RR, Suzuki GSXR600, Yamaha R6 restrictor reduced to 28mm from 29mm. 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 2019-12-01 STU Request for an electronic throttle body #27342induction 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 STU Request to correct E&O advanced aerodynamics #27290aero 2019-07-01 SRF SRF Dash Windscreen Kit #27028other 2019-07-01 STU Remove -2mm penalty from SR20DET Nissan #26982weight 2019-07-01 STU Request clarification for manifold and throttle in STU #27004induction 2019-05-31 STU Request to clarify afterrmarket side skirts exhaust exit #26814suspension & brakes 2019-05-31 STU Wheel Flare wording #26872tyres & wheels 2019-05-01 STU Request Ride Height Clarification #26597suspension & brakes 2019-04-01 STU Request to Use Japanese Mazda 13b Intake Manifold #25790induction 2019-04-01 STU Request Alternate Intake for Mazda MZR In a Rear Wheel Drive App. #26352induction 2019-04-01 STU E&O Suspension #26424wording 2019-04-01 STU Revisit B20 VTEC #26530cars added 2019-04-01 STU Move Flared Fenders to STU Advanced Aero #26564aero 2019-04-01 STU TCA Civic SI E&O #26606induction 2019-04-01 STU S54 Spec line #26620weight 2019-03-01 STU Request to Class Assignment for 2017 Civic #24287cars added 2019-03-01 STU Request to run E46 3246cc in STU #25126weight 2019-03-01 STU Engine Classification for Rotary #25564engine 2019-03-01 STU K24/K20 Head Swap Clarification/Amendment #25899induction 2019-03-01 STU Request to Classify 12a Bridge Ported Rotary Engine #25985cars added 2019-03-01 STU World Challenge Car Eligibility #26387weight 2019-03-01 STU Request a phone call for discussion regarding weight #26398weight 2019-03-01 STU Advanced Aero E&O #26413aero 2019-01-01 STU Request to Equalize Direct Injected Turbo Cars #24890induction

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.