BoP Lab / Classes / F5
F5 vs STU vs FM pace at every track
Lap times across years say as much about the weather as the class. % of F5 is each class's best lap as a share of F5'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.
Closest to the field: F5 100.0% of F5 Matthew Strand, Daytona International Speedway Runoffs 2015 race · STU 77.8% of F5 Franklin Church, Sonoma Raceway Runoffs 2018 qualifying · FM 95.5% of F5 Bryce Cornet, Sonoma Raceway Runoffs 2018 race
| Event | F5 | STU | FM | ||||||||||||
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| Qual best | Race best | Trap | Qual best | Race best | Trap | vs F5 | % of F5 | Qual best | Race best | Trap | vs F5 | % of F5 | |||
| 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%) | ||||||||||||
15 rule changes (STU: 15)4 cars added · 3 weight · 2 induction · 2 tyres & wheels · 4 wording · GT3U wheel and tyre options clarified: 15x7 with 225 section at +275 lbs; 15x9 with 245 section at +275 lbs plus 1.5%; 16–18x9 with 245 section at +275 lbs plus 3.0%. · STU cars at or under 2,825 lbs minimum weight limited to 8-inch wheels; over 2,825 lbs limited to 9-inch wheels. · STU GT3U minimum weight increases from GT3 race weight plus 225 to plus 275 pounds; 2.0L unrestricted engines add 75 lbs. · STU adds BMW M50B20TU engine, 1991 cc, minimum weight per chart, must meet all STU engine regulations. · STL, STU weight calculation procedure clarified: positive percentages added first, negative subtracted second, then fixed weights applied. · STU Honda K20C1 Turbo I4 turbo restrictor increases from 35mm to 36mm TIR. · STU GT86 Cup car must meet 2022 Toyota GR Cup rules, tires maximum 245 section width. · STU Mazda Renesis Street Port added to Table B with 2450 lbs minimum weight and 70mm throttle body options. · STU eliminates 33 and 34 mm inlet restrictor options, removing minimum weights of 2380 and 2525 lbs. · STU Mazda MZR engines may now use Fab 9 Elite NC MX5 Performance Intake manifold as alternative option. · STU Mazda MZR (LF, L3, L5) Turbo added; Goodwin intake removed, Jack Spania Racing 70 mm intake and Fab9 Tuning bottom-mount turbo kit approved. · STU 36mm restrictor revised to 2830 cc, 37mm to 2980 cc. · STU removes 275 tire option and 2% weight adder for cars over 3150 lbs; maximum section width now 245. · STU Honda K20 and K24 engines lose 2% weight penalty; minimum weight now per chart only. · STU Honda K24 engine swap weight increases by 2 percent, effective November 1, 2025.show
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| 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%) | ||||||||||||
18 rule changes (STU: 18)6 weight · 4 cars added · 3 tyres & wheels · 2 engine · 1 induction · 2 wording · STU Lotus Elise SC and Exige SC weight reduced from 2450 to 2250 lbs. · STU-TCR gains GT3 TCR spec lines; 275 tyre option now costs 150 lb adder, up from 100 lb. · Lotus Evora GT4 minimum weight drops to 2700 lbs; Elise Cup R to 2250 lbs; Elise SC and Exige SC to 2450–2550 lbs. · STU 2.8–3.2L N/A engines now permit 245 max tyre width; over 3150 lbs cars may run 275 with 2% weight penalty. · STU Mazda MZR intake manifold now allows Goodwin 61-2510 or Gato Performance 31972. · STU Honda JDM H23a added, 2259 cc, minimum weight per chart, must meet ST engine regulations. · STU wheels capped at 18 inches diameter; under 2,850 lbs max 8 inches wide, over 2,850 lbs max 9 inches wide. · STU-GT3U minimum weight reduced from plus 250 to plus 225 pounds; wheel and tyre options clarified with weight adjustments. · STU BMW N54/N55 3.0 classified at chart plus 3% minimum weight; N54 twin turbo not allowed. · STU Mini Cooper S SC pulley diameter reduced to 2.185 inches. · STU Honda K20C1 Turbo I4 exempted from 3% direct injection weight adder. · STU GT3U minimum weight increases 150 pounds to 250 pounds. · STU Audi 1.8T Wagon removed; Porsche 944 1800cc weight to Chart, turbo inlet restrictor deleted. · STU-GT3 reclassified as STU-GT3U, effective 1 January 2026. · STU GT3 TCR may run 275-wide DOT tires with 100 lb weight penalty; A compound prohibited at 275. · STL STU Mazda Miata alternate front hubs Mazda Motorsports Development Part #0000-04-5HUB-S1 approved. · STU BMW N54/N55 turbo inlet restrictors now required per GCR definition; twin turbo conversion to single turbo clarified. · STU Mini Cooper S SC: 1900 stock pulley spec to 2.565 diameter; 2100 now permits 2.285 diameter pulley.show
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| 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%) | ||||||||||||
4 rule changes (STU: 4)2 aero · 1 induction · 1 other · STU RWD turbo cars no longer required to reduce inlet restrictor by 1 mm from table minimum. · STU Mini Cooper S SC gains alternate LEAP OMICRON hood scoop part LEP-OMICRON3 as permitted option. · STU BMW S54 B32 OEM dry sump oiling system now permitted. · STL and STU now permit electric power steering pumps, OEM electric-assisted steering, or column-mounted electric steering assist systems.show
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| 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%) | ||||||||||||
3 rule changes (STU: 3)1 cars added · 1 engine · 1 weight · STU adds 2022 Toyota GR Cup and GR86 Cup, both 2387cc, 2700 lbs, 18-inch wheels, 245/620R18 slicks. · STU Mazda BP5A now classified at 1839 cc displacement, 2510 lbs minimum weight, alternate intake manifold permitted. · STU minimum weights adjusted: 2450 cc to 2595 lbs, 2600 cc to 2710 lbs.show
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| Virginia International Raceway Runoffs 20222022-09-24 | 1:57.689James Weida · fastest of 11 · top 5 within 3.9s+0.328s (+0.28%) | 2:21.862Sven de Vries · fastest of 10 · top 5 within 14.3s+24.290s (+20.66%) | 142.9Calvin Stewart+0.1 mph (+0.1%) | 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%) | +10.495squal +2.926s | 107.4%qual 102.5% | |||||||
27 rule changes (F5: 6, STU: 21)6 weight · 5 engine · 2 aero · 2 cars added · 2 tyres & wheels · 8 wording · 2 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. · STU Mazda 13B Turbo added as Chart Limited displacement, streetport only, alternative turbos only. · STU OEM louver vents no longer count against vent allowance or 200 square inch limit. · STU non-4-valve engines gain 9% base engine weight reduction allowance; 2400cc minimum weight drops 1 lb to 2595. · F500 clarifies stepped diameter exhaust headers prohibited except at cylinder head flange area. · STU normally-aspirated engines 2976cc–3200cc with single throttle body lose 10% base engine weight reduction allowance. · ST removes redundant language about engine balance shaft removal and alternate pulley installation. · F500 Rotax 593 intake boot options clarified; oil injection pump removal now permitted. · STU cars that qualified for 9 inch wheels in 2021 may continue running them through 2022 only. · STU splitter definition clarified: must attach to lowest point of front, have no vertical deviations. · STU BMW E36 M3 (95-99) S52B32 minimum weight cut to 3110 lbs from 3200, displacement to 3152 cc. · STU BMW S50B32 Euro maximum displacement 3201 cc, minimum weight 3300 lbs, permits 0.040 overbore and 0.5 compression increase. · ST engine swap origin rule narrowed: North America changed to United States only for case-by-case approval. · STU Honda CRX 84-91 and Civic Del Sol 93-97 both ineligible for front-wheel-drive weight reductions. · STU wheel width rule clarified: under 2950 lbs uses max 8.0 inches, 2950 lbs and over uses max 9.0 inches. · STU single-throttle body cars get lower minimum weights: 2450cc to 2596 lbs, 2500cc to 2635 lbs, 2550cc to 2675 lbs. · F500 Majors and Runoffs cars must install AIM part #X47KPFSOLO2R0 data box mount for Solo or Solo 2. · STU single throttle body weight reduction removed; minimum weights revised down to 2990 lbs at 3000cc from 3300 lbs. · STU Audi A4 1.8T minimum weight fixed to 3050 lbs, K04 turbo removed, VF30 with 35mm restrictor required; Porsche 944 1800 weight fixed to 3050 lbs, VW/Audi 1.8L engine removed, 35mm inlet restrictor required. · STL and STU Improved Touring vehicles must now conform to section 9.1.4 Tires & Wheels. · STU engines may delete balance shafts and plug openings; alternate pulleys or gears allowed only for timing belt or chain operation. · STU hood vents now allow louvers within 200 square inches. · F5 cars must install AIM part #X47KPFSOLO2R0 data box mount for Majors and Runoffs. · STU adds Honda K23 with 2354 cc displacement and chart minimum weight, K24 block allowed with K23 internals and head. · STU Honda K23 relaxes internal engine requirement, now needs only K23 crankshaft. · STL/STU intake manifold and cylinder head porting clarified as free; intake and exhaust porting wording removed.show
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| Indianapolis Motor Speedway Runoffs 20212021-09-25 | 1:42.619Ryan Mayfield · fastest of 22 · top 5 within 1.6s-0.517s (-0.50%) | 1:43.140Sven de Vries · fastest of 20 · top 5 within 1.7s+0.280s (+0.27%) | 144.4James Weida | 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 | +4.301squal +4.459s | 104.2%qual 104.3% | |||||||
15 rule changes (F5: 3, STU: 12)3 cars added · 1 aero · 1 engine · 1 suspension & brakes · 1 weight · 7 wording · 1 other · 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. · STU fender flare wording clarified: flare of exterior contour may not change wheel opening size, location or shape from side view. · STU Mazda 12A Bridgeport weight reduced from 2550 lbs to 2350 lbs. · F500 Rotax 593 HO engine now permitted; 875 lbs minimum weight, MA0242SP1020A or MA0242SP1063A restrictor, specific intake boots and piston required. · STU fender flare rules clarified: maximum 2 inches total, must cover tire contact patch from above, cannot alter body configuration or wheel opening geometry. · STU Honda S2000 now allows F20/F22 K24 crankshaft with chart weight for achieved displacement. · ST oil coolers and filters now explicitly listed as addable or substitutable parts in vents and breathers section. · ST 90-05 Mazda Miata allowed alternate front wheel hub Mazda Motorsports Development Part #0000-04-5HUB-S1. · ST cars may now relocate ABS actuation hardware and wiring anywhere in the engine compartment. · STU Porsche PDK automatic transmission limited to 8 forward speeds; sequential DCT systems require 3.5% minimum weight increase. · STU Mazda 13B Street Port 2400 removes choke location rule, allows auto-type 2bbl with any dual-Y manifold. · STU driveshaft and half-shafts now explicitly permitted in steel or aluminum, removing OEM material requirement. · STU Mazda 13B Spec and Bridge Port removed; Street Port added at 2400 lbs minimum weight. · ST aero devices and reference areas must include end plates, exclude fasteners under 1/2" protrusion.show
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| Road America Runoffs 20202020-10-02 | 2:20.954Calvin Stewart · fastest of 16 · top 5 within 1.8s | 2:21.391James Weida · fastest of 14 · top 5 within 1.5s | 143.2Aaron Ellis | 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 | +7.019squal +6.929s | 105.0%qual 104.9% | |||||||
23 rule changes (F5: 6, STU: 17)6 engine · 2 cars added · 2 weight · 1 induction · 10 wording · 2 other · F500 Suzuki GSXR600 engine years extended from 2003-2013 to 2003-2019. · STU fender flare rule reworded: now per-corner up to 2" total, 1% weight penalty applies to entire modification. · STL and STU clarify weight adjustment calculation order: engine adjustments first, then chassis percentage additions, subtractions, and fixed pounds. · STL STU rear wing Gurney flap terminology clarified from wicker to Gurney flap in mounting and chord rules. · 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. · STU request for alternate intake manifold denied; no change to rules. · GT3 and STU add Borg-Warner EFR6258 turbocharger to approved turbo lists. · STU large displacement turbo engines limited by GCR turbo list; no BoP change granted. · STU sequential shifters referred to Board of Directors for approval; no rule change effective. · STU Mazda 13B Bridge Port and Street Port added with 2550 lbs and 2250 lbs minimum weight respectively. · STU Honda S2000 gains HKS Supercharger kits 12001-AH006 and 12001-AH010 as allowed options. · STU Lotus Elise Cup R and SC Exige SC gain 100 lbs minimum weight to 2300, 2500. · STU Volkswagen GTI/GLI MK5 and Jetta Mk4 may now install turbo inlet restrictor in OEM housing, per TIR spec. · STU Honda K20C1 Turbo I4 restrictor reduces from 36mm to 35mm. · STU GM Ecotech LNF now permitted without turbo, with LE5 head and intake manifold, meeting STL specs. · STU Porsche 944 now permits VW/Audi 1.8L and 2.0L turbo engines as alternates to original. · STU vehicles over 2951 lbs base weight may use 9 inch wide wheels, changed from 2950 lbs. · STU turbocharged engines now use base weight instead of minimum weight; DFI cars add 3% to base weight. · F500 Honda CBR600RR, Suzuki GSXR600, Yamaha R6 restrictor reduced to 28mm from 29mm. · STU allows OEM electronic throttle bodies, manual conversion, cam changes, and manual-to-electronic conversion with same inner diameter.show
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| Virginia International Raceway Runoffs 20192019-10-05 | 1:57.361Wiley Mcmahan · fastest of 15 · top 5 within 3.8s | 1:57.572Wiley Mcmahan · fastest of 15 · top 5 within 4.0s | 142.8Eric McRee | 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 | +2.911squal +2.587s | 102.5%qual 102.2% | 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 | +18.244squal -2.237s | 115.5%qual 98.1% | ||
23 rule changes (F5: 1, STU: 22)5 cars added · 4 engine · 3 aero · 3 induction · 1 weight · 6 wording · 1 other · F500 Honda CBR600RR, Suzuki GSXR600, and Yamaha R6 minimum weights increase to 900 lbs. · STU wing assembly wording corrected: no part may be higher than roof height. · STU Nissan SR20DET removes -2mm penalty from Table B. · STU allows alternate intake manifolds on case-by-case basis; stock throttle device and manifold otherwise required. · STU aftermarket side skirts now allowed if they meet 3-inch ride height, lack ducts except jacks or exhaust, don't exceed fascia width, stay below door bottom, and don't reinforce chassis. · STU wheel flare wording clarified: each fender may be flared to 2" with 1% weight penalty, maintaining OEM profile. · STL and STU ride height measurement clarified: lowest rocker panel point without driver, excluding pinch weld. · STU Mazda 13B Bridge Port now permits ELITE ROTARY SHOP FD V2.0 intake manifold; stock throttle body requirement removed. · STU Mazda MZR gains alternate Goodwin intake manifold option with stock or Acura throttle body. · STU alternate suspension components rule moved from section E to section D. · STU Honda/Acura B20 now permits B16 or B18 VTEC cylinder head and matching intake manifold. · STU flared fenders up to 2" with 1% weight penalty moved from base to Advanced Aero. · STU Honda Civic Si TCA 2017- requires 37mm TIR throttle as of June 1, 2019. · STU BMW S54B32 OEM classified separately from E46, displacement 3246 cc, minimum weight 3300 lbs, OEM engine mandatory. · Honda Civic Si 2017- added to STU with 1500cc displacement, 2800 lbs minimum weight, OEM engine and bodywork, specific HPD parts allowed. · STU BMW E46 S54 OEM 3246cc added at 3300 lbs minimum; no Super Touring allowances, OEM intake and cams, 1mm overbore, compression +0.5 permitted. · STU Mazda 13B and 13B Bridge Port may use 13B RE or REW housings and intake with turbo removed. · STU Honda K24 may use intake part numbers 17100-RRB-A00 or 17100-PRB-A10. · STU Mazda 12A Bridge Port added, minimum weight 2550 lbs, Nikki or Auto-type carburettor with specified modifications. · STU World Challenge car weight rule deleted; no replacement specified. · STU AWD/RWD cars no longer must reduce restrictor 1 mm from table. · STU rear wing maximum 12" cord, 72 sq in end plates each, roof height max, body width limit. · STU adds Honda K20C1 Turbo I4, 1996 cc, 3025 lbs minimum weight, 36mm TIR required.show
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| Sonoma Raceway Runoffs 20182018-10-10 | 1:41.807Jeff Jorgenson · fastest of 5 · top 5 within 6.6s | 1:42.491David Lapham · fastest of 5 · top 5 within 9.5s | 113.3David Lapham | 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 | +4.023squal -22.573s | 103.9%qual 77.8% | 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 | -4.582squal -4.209s | 95.5%qual 95.9% | ||
| No rule changes on record between these events | |||||||||||||||
| Indianapolis Motor Speedway Runoffs 20172017-09-25 | 1:43.136Wiley Clinton McMahan · fastest of 38 · top 5 within 1.4s | 1:42.860Wiley Clinton McMahan · fastest of 37 · top 5 within 1.6s | 1:48.921Rob Huffmaster · fastest of 34 · top 5 within 2.0s | 1:49.387Rob Huffmaster · fastest of 31 · top 5 within 2.4s | +6.527squal +5.785s | 106.3%qual 105.6% | 1:41.231Jarret Voorhies · fastest of 16 · top 5 within 1.7s | 1:41.146Jarret Voorhies · fastest of 16 · top 5 within 1.2s | -1.714squal -1.905s | 98.3%qual 98.2% | |||||
| No rule changes on record between these events | |||||||||||||||
| Mid-Ohio Sports Car Course Runoffs 20162016-09-19 | 1:28.528Calvin Stewart · fastest of 14 · top 5 within 3.9s | 1:29.853Steven Thompson · fastest of 12 · top 5 within 4.5s | 1:32.738Joe Moser · fastest of 16 · top 5 within 2.5s | 1:34.597Cameron Maugeri · fastest of 16 · top 5 within 0.8s | +4.744squal +4.210s | 105.3%qual 104.8% | 1:26.043Jacob Loomis · fastest of 8 · top 5 within 3.1s | 1:27.922Jacob Loomis · fastest of 8 · top 5 within 2.7s | -1.931squal -2.485s | 97.9%qual 97.2% | |||||
| No rule changes on record between these events | |||||||||||||||
| Daytona International Speedway Runoffs 20152015-09-21 | 2:01.824W. Clint McMahan · fastest of 16 · top 5 within 3.0s | 2:03.298Matthew Strand · fastest of 15 · top 5 within 4.9s | 2:05.494Eric Heinrich · fastest of 18 · top 5 within 4.6s | 2:06.756Eric Heinrich · fastest of 17 · top 5 within 3.5s | +3.458squal +3.670s | 102.8%qual 103.0% | 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 | -5.269squal -4.020s | 95.7%qual 96.7% | |||||
By track
| Track | Events | Typical % of F5 | Best | Latest |
|---|---|---|---|---|
| Road America | 4 | 100.0%1 of 4 with F5 | 100.0%Runoffs 2020 | 100.0%Runoffs 2020 |
| Virginia International Raceway | 3 | 100.0%2 of 3 with F5 | 100.0%Runoffs 2019 | 100.0%Runoffs 2022 |
| 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 F5'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.