BoP Lab / Classes / STU

STU vs FX pace at every track

Lap times across years say as much about the weather as the class. % of STU is each class's best lap as a share of STU'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.

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AS +B-Spec +EP +FA +FC +FE2 +FF +FP +FV +vsFX ×GT1 +GT2 +GTX +HP +P +P2 +SM +SMX +SRF3 +STL +STU×T1 +T2 +T3 +T4 +Show 51 inactive classes

Series Runoffs Super Tour Both

Reference · what % is measured against

Tracks · untick to narrow Auto Club Speedway Barber Motorsports Park Blackhawk Farms Raceway Buttonwillow Raceway Park 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 World Wide Technology Raceway

Closest to the field: STU 100.0% of STU Eric Heinrich, Daytona International Speedway Runoffs 2015 race · FX 84.5% of STU Dimitrios Tsesmetzis, Virginia International Raceway Runoffs 2022 race

% of STULap times

STUFXsolid race · dashed qualifying · slower is lower

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

	Event	STU			FX
	Event	Qual best	Race best	Trap	Qual best	Race best	Trap	vs STU	% of STU
	Road America Runoffs 20262026-09-28	2:24.912Richard Astacio · fastest of 17 · top 5 within 2.6s+1.829s (+1.28%)	2:26.416Richard Astacio · fastest of 16 · top 5 within 1.5s+1.919s (+1.33%)	145.1Hugh Stewart+0.8 mph (+0.5%)
16 rule changes (STU: 15, FX: 1)7 weight · 4 induction · 3 tyres & wheels · 2 engineshowhide 2026-09-01 STU Wheel and tire requirements for GT3U #40679tyres & wheels 2026-08-01 FX Update sealed engine teardown section #40622engine 2026-07-01 STU 9” Wheels #40433tyres & wheels 2026-07-01 STU Weight adjustment to former GT3U cars #40474weight 2026-06-01 STU Request to allow BMW M50B20TU engine in STU #40202engine 2026-06-01 STU Calculating Weight #40224weight 2026-05-01 STU Turbo Restrictor Size Increase Request #40008induction 2026-05-01 STU GT86 Cups Car in STU #40028weight 2026-04-01 STU Mazda Rx-8 Renesis - Streetported Variant & Added Weight #39785weight 2026-04-01 STU Eliminate 33 and 34 mm TIRs #39872weight 2026-03-01 STU Fab 9 Racing Intake Manifold in STU #39767induction 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
	Road America Runoffs 20252025-09-29	2:23.083Peter Cunningham · fastest of 16 · top 5 within 2.6s-3.144s (-2.15%)	2:24.497Chip Herr · fastest of 15 · top 5 within 3.8s-1.327s (-0.91%)	144.3Chip Herr-1.0 mph (-0.7%)
19 rule changes (STU: 18, FX: 1)8 weight · 3 engine · 3 tyres & wheels · 1 cars added · 1 induction · 1 wording · 2 othershowhide 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 2025-03-01 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 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 FX Request to Change to Weight for Ligier JS F422 #37124weight -15 lbs 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
	Road America Runoffs 20242024-10-01	2:26.227Thomas Noble · fastest of 18 · top 5 within 2.3s-1.656s (-1.12%)	2:25.824Thomas Noble · fastest of 17 · top 5 within 2.4s-2.586s (-1.74%)	145.3Thomas Noble+1.1 mph (+0.8%)
8 rule changes (STU: 4, FX: 4)2 weight · 1 induction · 1 tyres & wheels · 4 othershowhide 2024-08-01 STU RWD Turbo Disadvantage #36255induction 2024-07-01 FX Adjust minimum weights to align with pro F4 rules #36221weight -15 lbs 2024-04-01 FX Add Classification for 2nd Gen Ligier JS F422 #35844other 2024-03-01 FX Clarify Formula 4 Rules in FX #35700tyres & wheels 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 2023-11-01 FX FM Rules Update #34841other
	Virginia International Raceway Runoffs 20232023-09-23	2:00.389Johan Schwartz · fastest of 13 · top 5 within 2.3s-0.226s (-0.19%)	2:02.302Mark Liller · fastest of 14 · top 5 within 1.6s-30.055s (-19.73%)	144.0Mark Liller+0.1 mph (+0.1%)
6 rule changes (STU: 3, FX: 3)3 weight · 1 cars added · 1 induction · 1 othershowhide 2023-07-01 STU 2022 Toyota GR Cup for STU #34449cars added 2023-06-01 FX USF2000 Van Diemen with Mazda MZR LF-DE 2.0L in FC #34329weight 2023-04-01 STU Alternate OEM Miata Intake Manifold #33827induction 2023-03-01 STU E&O STU NA Weight Chart. #33737weight 2023-02-01 FX E&O - Remove references to FB and FM in GCR section 1.4.2.D #33725other 2022-12-01 FX Reclassify 2010-2017 Formula Renault 2.0 as a spec line car in FA #33395weight
	Virginia International Raceway Runoffs 20222022-09-24	2:00.615Johan Schwartz · fastest of 21 · top 5 within 2.6s+0.667s (+0.56%)	2:32.357Mark Liller · fastest of 19 · top 5 within 4.3s+31.874s (+26.46%)	143.9Johan Schwartz+0.1 mph (+0.1%)	1:51.480Trevor A Russell · fastest of 5 · top 5 within 9.7s	2:08.711Dimitrios Tsesmetzis · fastest of 4 · top 4 within 6.8s	137.2Trevor A Russell	-23.646squal -9.135s	84.5%qual 92.4%
30 rule changes (STU: 21, FX: 9)10 weight · 6 engine · 5 tyres & wheels · 3 induction · 2 cars added · 1 aero · 3 othershowhide 2022-08-01 FX Pro Formula F2000/USF2000 Transmission E&O #32823weight 2022-08-01 FX Formula Mazda Minimum Weight #33010weight 2022-08-01 FX Formula Mazda Spec Line E&O Corrections #33011engine 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 FX Formula Renault 2.0 (10-17) Intake Restrictor #32745induction 2022-07-01 FX Allow Performance Electronics PE3-8400 for USF2000 MZR #32767engine 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 2022-05-01 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 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 FX FM Rule Set Clarification #31881tyres & wheels 2022-02-01 FX E&O F4 Tires #31940tyres & wheels 2022-02-01 FX E&O USF2000 Tube Frame #31951tyres & wheels 2022-02-01 FX URGENT - FX- Formula Renault Tire #32058tyres & 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 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
	Indianapolis Motor Speedway Runoffs 20212021-09-25	1:47.078Joe Moser · fastest of 30 · top 5 within 2.0s-1.843s (-1.69%)	1:47.441Joe Moser · fastest of 28 · top 5 within 1.8s-1.946s (-1.78%)	146.9Kip VanSteenburg	1:38.596Vaughn Glace · fastest of 15 · top 5 within 4.1s	1:38.833Vaughn Glace · fastest of 15 · top 5 within 4.3s	138.6Vaughn Glace	-8.608squal -8.482s	92.0%qual 92.1%
17 rule changes (STU: 12, FX: 5)4 tyres & wheels · 4 weight · 3 cars added · 1 aero · 1 engine · 1 induction · 1 suspension & brakes · 1 wording · 1 othershowhide 2021-08-01 FX Rules Adjustment #30950tyres & wheels 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 FX FX/FRP Tire Rule #30723tyres & wheels 2021-05-01 FX Classify the 2000-2009 Formula Renault 2.0 / Fran-Am 2000 #30460cars added 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 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 FX Request for Car Classification to Compete in Formula X #29933cars added 2021-01-01 STU 13B Rules Adjustment #29333cars added 2020-12-01 FX Update specifications for FormulaSPEED cars #29674induction 2020-12-01 STU Request clarification on wing measurement #29640aero
	Road America Runoffs 20202020-10-02	2:27.883David Fiorelli · fastest of 14 · top 5 within 4.1s	2:28.410Anthony Geraci · fastest of 14 · top 5 within 3.1s	144.2David Fiorelli	2:16.968Jacob Loomis · fastest of 12 · top 5 within 2.7s	2:17.553Jacob Loomis · fastest of 11 · top 5 within 3.5s	139.3Brad Drew	-10.857squal -10.915s	92.7%qual 92.6%
23 rule changes (STU: 17, FX: 6)7 induction · 5 weight · 3 cars added · 3 engine · 2 aero · 1 tyres & wheels · 2 othershowhide 2020-09-01 FX Follow up to to Letter#28991 Request for FX classification #29281cars added 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 FX Request to be added to FX group #28991other 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 2020-04-01 FX Request to classify FSV in FX #28057cars added 2020-04-01 FX Classify FormulaSPEED in FX #28715cars added 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 FX Request to remove tire marking language from FM #28415tyres & wheels 2020-03-01 STU Please Modify the STU Wheel Size Rule for Clarity #27694weight 2020-03-01 STU Turbo Engine Cars Base Weight #28032weight 2020-02-01 FX Change to FX Table 1 #28322induction 2019-12-01 STU Request for an electronic throttle body #27342induction
	Virginia International Raceway Runoffs 20192019-10-05	1:59.948Kevin Boehm · fastest of 25 · top 5 within 3.5s	2:00.483Kevin Boehm · fastest of 25 · top 5 within 2.5s	143.8Kevin Boehm
22 rule changes (STU: 22)6 induction · 5 weight · 3 aero · 3 cars added · 2 suspension & brakes · 1 engine · 1 tyres & wheels · 1 wordingshowhide 2019-08-31 STU Request to correct E&O advanced aerodynamics #27290aero 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
	Sonoma Raceway Runoffs 20182018-10-10	1:19.234Franklin Church · fastest of 10 · top 5 within 21.5s	1:46.514Kevin Boehm · fastest of 9 · top 5 within 7.4s	103.0Franklin Church
No rule changes on record between these events
	Indianapolis Motor Speedway Runoffs 20172017-09-25	1:48.921Rob Huffmaster · fastest of 34 · top 5 within 2.0s	1:49.387Rob Huffmaster · fastest of 31 · top 5 within 2.4s
No rule changes on record between these events
	Mid-Ohio Sports Car Course Runoffs 20162016-09-19	1:32.738Joe Moser · fastest of 16 · top 5 within 2.5s	1:34.597Cameron Maugeri · fastest of 16 · top 5 within 0.8s
No rule changes on record between these events
	Daytona International Speedway Runoffs 20152015-09-21	2:05.494Eric Heinrich · fastest of 18 · top 5 within 4.6s	2:06.756Eric Heinrich · fastest of 17 · top 5 within 3.5s

By track

Track	Events	Typical % of STU	Best	Latest
Road America	4	100.0%	100.0%Runoffs 2020	100.0%Runoffs 2026
Virginia International Raceway	3	100.0%	100.0%Runoffs 2019	100.0%Runoffs 2023
Indianapolis Motor Speedway	2	100.0%	100.0%Runoffs 2017	100.0%Runoffs 2021
Daytona International Speedway	1	100.0%	100.0%Runoffs 2015	100.0%Runoffs 2015
Mid-Ohio Sports Car Course	1	100.0%	100.0%Runoffs 2016	100.0%Runoffs 2016
Sonoma Raceway	1	100.0%	100.0%Runoffs 2018	100.0%Runoffs 2018

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 STU'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.