T4 Support for Rule Changes: Camber, Shocks
#37911 from Colin Koehler · Taken care of · Minutes (2025-05 Fastrack)
Thank you for your letter. Please see letter #38077 for survey results and conclusions.
BoP Lab / Drivers / Colin Koehler
Colin Koehler 9 letters to Fastrack
Against the front of the class, by track and class
| Track | Class | Sessions | Typical gap to class best | Closest |
|---|---|---|---|---|
| Portland International Raceway (1.88 mi) | STL | 4 | +2.308s (2.67%) | +1.486s (1.72%) |
| Portland International Raceway (1.98 mi) | STL | 4 | +0.642s (0.74%) | +0.189s (0.22%) |
| Portland International Raceway (1.98 mi) | T4 | 11 | +1.083s (1.21%) | +0.391s (0.42%) |
| Indianapolis Motor Speedway (2.59 mi) | T4 | 7 | +1.618s (1.38%) | +1.069s (0.90%) |
| Portland International Raceway | T4 | 1 | ||
| Road America (4.05 mi) | T4 | 4 | +4.682s (2.97%) | +3.138s (1.99%) |
| Unknown track (4.05 mi) | T4 | 3 | +11.499s (7.22%) | +7.739s (4.86%) |
Gap is the driver's best lap in a session against the fastest lap in their class in that same session (zero is fastest in class), shown as time lost and as a share of the lap, so conditions cancel out and tracks can be compared. Typical is the median session.
Portland International Raceway (1.88 mi)
| Event | Session | Class | # | Car | Pos | Best lap | Class best | To class best | Trap | Class trap | To class trap |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Oregon 2026 | Grp 2 STL STU T3 T4 B-Spec Race 2 | STL | 10 | Scion FRS | 5/7 | 1:27.978 | 1:26.492Jared Korth | +1.486s (1.72%) | 120.41/7 | 120.4you | +0.0 mph (0.0%) |
| Oregon 2026 | Grp 2 STL STU T3 T4 B-Spec Qual 2 | STL | 10 | Scion FRS | 6/7 | 1:36.691 | 1:27.968Jared Korth | +8.723s (9.92%) | 114.24/7 | 118.8Jared Korth | -4.6 mph (-3.9%) |
| Oregon 2026 | Grp 2 STL STU T3 T4 B-Spec Race 1 | STL | 10 | Scion FRS | 6/9 | 1:28.750 | 1:26.442Jared Korth | +2.308s (2.67%) | 120.21/9 | 120.2Ryan Gutile | +0.0 mph (0.0%) |
| Oregon 2026 | Grp 2 STL STU T3 T4 Qual 1 | STL | 10 | Scion FRS | 7/9 | 1:28.977 | 1:26.145Ryan Gutile | +2.832s (3.29%) | 119.52/9 | 120.1Ryan Gutile | -0.5 mph (-0.4%) |
Portland International Raceway (1.98 mi)
| Event | Session | Class | # | Car | Pos | Best lap | Class best | To class best | Trap | Class trap | To class trap |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Oregon 2025 | Grp 5 STU GT3U T3 T4 STL Race 2 | STL | 10 | Scion FRS | 4/8 | 1:27.938 | 1:27.296Jared Korth | +0.642s (0.74%) | 118.54/8 | 120.6Roldan de Guzman | -2.1 mph (-1.7%) |
| Oregon 2025 | Grp 5 STU GT3U T3 T4 STL Qual 2 | STL | 10 | Scion FRS | 5/8 | 1:29.315 | 1:28.260Roldan de Guzman | +1.055s (1.20%) | 116.35/8 | 118.8Patrick Drinkwine | -2.5 mph (-2.1%) |
| Oregon 2025 | Grp 5 STU GT3U T3 T4 STL Race 1 | STL | 10 | Scion FRS | 6/11 | 1:27.827 | 1:27.638Amy Mills | +0.189s (0.22%) | 120.12/11 | 121.8Roldan de Guzman | -1.8 mph (-1.5%) |
| Oregon 2025 | Grp 5 STU GT3U T3 T4 STL Qual 1 | STL | 10 | Scion FRS | 10/10 | 1:30.398 | 1:27.639Jon Davies | +2.759s (3.15%) | 116.010/10 | 119.2Roldan de Guzman | -3.2 mph (-2.7%) |
| Oregon Region Hoosier SCCA Super Tour @ Portland International Raceway | Grp 4 STL.STU,T2,T3,T4 Race 2 | T4 | 10 | Scion FRS | 2/10 | 1:29.992 | 1:29.463Marc Cefalo | +0.529s (0.59%) | 114.03/10 | 118.3Dereck Ambrose | -4.3 mph (-3.6%) |
| Oregon Region Hoosier SCCA Super Tour @ Portland International Raceway | Grp 4 STL.STU,T2,T3,T4 Qual 2 | T4 | 10 | Scion FRS | 3/9 | 1:29.479 | 1:28.890Rick Delamare | +0.589s (0.66%) | 112.95/9 | 119.0Dereck Ambrose | -6.1 mph (-5.1%) |
| Oregon Region Hoosier SCCA Super Tour @ Portland International Raceway | Grp 4 STL.STU,T2,T3,T4 Race 1 | T4 | 10 | Scion FRS | 3/8 | 1:29.729 | 1:28.513Marc Cefalo | +1.216s (1.37%) | |||
| Oregon Region Hoosier SCCA Super Tour @ Portland International Raceway | Grp 4 STL.STU,T2,T3,T4 Qual 1 | T4 | 10 | Scion FRS | 9/8 | 1:27.626Marc Cefalo | |||||
| Oregon Region Hoosier SCCA Super Tour @ Portland International Raceway | Grp 6 EP,FP,HP,GTL,B-Spec,T4 Qual 2 | T4 | 10 | Scion FRS | 3/5 | 1:29.772 | 1:29.020Roldan de Guzman | +0.752s (0.84%) | |||
| Oregon Region Hoosier SCCA Super Tour @ Portland International Raceway | Grp 6 EP,FP,HP,GTL,B-Spec,T4 Race 1 | T4 | 10 | Scion FRS | 3/6 | 1:30.897 | 1:29.814Roldan de Guzman | +1.083s (1.21%) | |||
| Oregon Region Hoosier SCCA Super Tour @ Portland International Raceway | Grp 6 EP,FP,HP,GTL,B-Spec,T4 Qual 1 | T4 | 10 | Scion FRS | 6/6 | 1:30.440 | 1:29.020Roldan de Guzman | +1.420s (1.60%) | |||
| Hoosier SCCA Super Tour (Oregon Region) | Grp 2 STL,STU,T2,T3,T4 Race 2 | T4 | 10 | Scion FRS | 2/4 | 1:31.745 | 1:29.883Derrick Ambrose | +1.862s (2.07%) | 113.94/4 | 117.5Derrick Ambrose | -3.6 mph (-3.1%) |
| Hoosier SCCA Super Tour (Oregon Region) | Grp 2 STL,STU,T2,T3,T4 Qual 2 | T4 | 10 | Scion FRS | 2/2 | 1:34.053 | 1:33.662Roldan de Guzman | +0.391s (0.42%) | 111.72/2 | 112.0Roldan de Guzman | -0.3 mph (-0.3%) |
| Hoosier SCCA Super Tour (Oregon Region) | Grp 2 STL,STU,T2,T3,T4 Race 1 | T4 | 10 | Scion FRS | 4/4 | 1:32.162 | 1:30.591Derrick Ambrose | +1.571s (1.73%) | 112.83/4 | 116.8Dave Mead | -4.0 mph (-3.4%) |
| Hoosier SCCA Super Tour (Oregon Region) | Grp 2 STL,STU,T2,T3,T4 Qual 1 | T4 | 10 | Scion FRS | 3/3 | 1:33.965 | 1:31.364Derrick Ambrose | +2.601s (2.85%) | 110.53/3 | 116.6Derrick Ambrose | -6.1 mph (-5.3%) |
Indianapolis Motor Speedway (2.59 mi)
| Event | Session | Class | # | Car | Pos | Best lap | Class best | To class best | Trap | Class trap | To class trap |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Runoffs 2021 | T4 Race | T4 | 10 | Scion FR-S | 4/46 | 1:57.342 | 1:55.929John Heinricy | +1.413s (1.22%) | 121.027/46 | 127.3Alexander Schefer | -6.3 mph (-4.9%) |
| Runoffs 2021 | T4 Qual 3 | T4 | 10 | Scion FR-S | 17/45 | 1:56.964 | 1:54.397Stephen Blethen | +2.567s (2.24%) | 122.027/45 | 127.0Raymond Blethen | -5.0 mph (-3.9%) |
| Runoffs 2021 | T4 Qual 2 | T4 | 10 | Scion FR-S | 12/44 | 1:56.719 | 1:55.292Michael Borden | +1.427s (1.24%) | 123.810/44 | 126.2Richard Dickey | -2.4 mph (-1.9%) |
| Runoffs 2021 | T4 Qual 1 | T4 | 10 | Scion FR-S | 13/44 | 1:57.602 | 1:55.780Michael Borden | +1.822s (1.57%) | 119.332/43 | 125.6Derrick Ambrose | -6.4 mph (-5.1%) |
| Runoffs 2021 | Grp 3 Run 3 B-Spec,FP,GTL,HP,STL,T4 Sun | T4 | 10 | Scion FR-S | 4/13 | 1:58.821 | 1:57.203Thomas Fowler | +1.618s (1.38%) | 123.54/13 | 124.8Alexander Schefer | -1.3 mph (-1.0%) |
| Runoffs 2021 | Grp 3 Run 2 B-Spec,FP,GTL,HP,STL,T4 Sun | T4 | 10 | Scion FR-S | 6/12 | 2:00.085 | 1:58.305Rick Delamare | +1.780s (1.50%) | 120.76/12 | 125.4Alexander Schefer | -4.6 mph (-3.7%) |
| Runoffs 2021 | Grp 3 Run 1 B-Spec,FP,GTL,HP,STL,T4 | T4 | 10 | Scion FR-S | 2/11 | 1:59.763 | 1:58.694Rick Delamare | +1.069s (0.90%) | 121.56/11 | 124.3Alexander Schefer | -2.8 mph (-2.3%) |
Portland International Raceway
| Event | Session | Class | # | Car | Pos | Best lap | Class best | To class best | Trap | Class trap | To class trap |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Oregon Region Hoosier SCCA Super Tour @ Portland International Raceway | Grp 6 EP,FP,HP,GTL,B-Spec,T4 Race 2 | T4 | 10 | Scion FRS | 4 |
Road America (4.05 mi)
| Event | Session | Class | # | Car | Pos | Best lap | Class best | To class best | Trap | Class trap | To class trap |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Runoffs 2020 | T4 Race | T4 | 10 | Scion FR-S | 8/19 | 2:41.019 | 2:37.881Chi Ho | +3.138s (1.99%) | 124.19/19 | 128.6Chi Ho | -4.5 mph (-3.5%) |
| Runoffs 2020 | T3,T4 Qual 3 | T4 | 10 | Scion FR-S | 10/19 | 2:42.085 | 2:37.403John Heinricy | +4.682s (2.97%) | 124.67/19 | 130.2Chi Ho | -5.6 mph (-4.3%) |
| Runoffs 2020 | T3,T4 Qual 2 | T4 | 10 | Scion FR-S | 10/18 | 2:44.421 | 2:37.617John Heinricy | +6.804s (4.32%) | 120.414/18 | 128.4Chi Ho | -7.9 mph (-6.2%) |
| Runoffs 2020 | T4 Qual 1 | T4 | 10 | Scion FR-S | 13/17 | 2:46.503 | 2:39.113John Heinricy | +7.390s (4.64%) | 120.113/17 | 127.4Richard Dickey | -7.3 mph (-5.7%) |
Unknown track (4.05 mi)
| Event | Session | Class | # | Car | Pos | Best lap | Class best | To class best | Trap | Class trap | To class trap |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Runoffs 2020 | Grp 7 Run 3 T2,T3,T4 | T4 | 10 | Scion FR-S | 7/10 | 2:46.829 | 2:39.090Chi Ho | +7.739s (4.86%) | 122.65/10 | 123.9Brent Simonson | -1.3 mph (-1.0%) |
| Runoffs 2020 | Grp 7 Run 2 T2,T3,T4 | T4 | 10 | Scion FR-S | 7/9 | 2:50.774 | 2:39.275Nick Leverone | +11.499s (7.22%) | 122.27/9 | 126.0Roldan de Guzman | -3.8 mph (-3.0%) |
| Runoffs 2020 | Grp 7 Run 1 T2,T3,T4 | T4 | 10 | Scion FR-S | 8/10 | 2:53.677 | 2:39.877Nick Leverone | +13.800s (8.63%) | 123.34/10 | 127.0Nick Leverone | -3.6 mph (-2.9%) |
Letters to Fastrack
T2/T3/T4 Rules Clarification for Mazda RX8 Spec Line
#34395 from Colin Koehler · Rule change · TB 23-08 (2023-08 Fastrack)
In T3 Spec Lines, Mazda RX-8 Base/R3/Sport/ GT (04-12), change notes as follows:
"Use of 2009 R3 transmission is permitted with alternate gear ratios as listed. R3 transmission must be paired with the listedalternate final drive. Front sway bar permitted 32mm MAX rear sway bar 19 MAX, Front springs max 750, 500 rear. Cold air
intake permitted. Header permitted. Aftermarket flywheel and single disc clutch permitted with no weight penalty."
In T4 Spec Lines, Mazda RX-8 Base/R3/Sport/ GT (04-12), change notes as follows:
"Mazdaspeed radiator #0000-01-8501 allowed. Use of 2009 R3 transmission is permitted with alternate gear ratios as listed. R3transmission must be paired with the listed alternate final drive. Mazdaspeed coil spring kit #QSEA-34-01Z allowed. 60mm flat
plate restrictor required. OE Rear spoiler allowed #F151-V4-920F. OE front air dam allowed #F151-V4-900f-BB. Springs Allowed:
Show 2 more lines
(F) Mazda Motorsports- 0000- 04-9700-08 or Eibach- 0800.250.0700 (R) Mazda Motorsports- 0000-04-9400-07 or Eibach
0700.250.0400, and helper 0000-04-9926 allowed. Alternate sway bars allowed max 32mm (f) 19mm (r)."
T4 BOP for 2013-2016 FRS BRZ
#31691 from Colin Koehler · Not recommended · Minutes (2022-01 Fastrack)
Thank you for your letter. The performance adjustments published are the result of thoughtful consideration, data collection,
and analysis from all of the touring races throughout the 2021 season. Decisions are not based solely on a single event but all
touring races throughout every region. No BOP decision is made quickly or without careful consideration. We ask that you bring
out your cars and race. Without data on the adjusted cars further corrections can't be made. Please participate. The more data
we get, the better our corrections will be. Wider wheels would save on tire wear, but it would increase the speed of the car,
throwing off the well established BOP.
T4 T4 Rules Change Proposal
#31690 from Colin Koehler · Not recommended · Minutes (2022-01 Fastrack)
Thank you for your letter. Camber- The current BOP is very close. This change will throw that off. Some cars can achieve camber
and others are very limited. 3.5 degrees is attainable by most cars under the current bushing and top hat rules.
Adjustable shocks- It is true that some people will arrive at the track with 3 sets of non-adjustable shocks and they'll choose the
best option. If single adjustable shocks were allowed, you'd move the problem upward. The same guy would arrive with 3
options with different rebound valving. The TAC feels that single adjustable shocks wouldn't help.
Oil pans- Recent changes were made to allow alternate oil pans, or modifications.
T4 BOP request for the 13-16 FRS/BRZ
#31689 from Colin Koehler · Not recommended · Minutes (2022-01 Fastrack)
Thank you for your letter. The performance adjustments published are the result of thoughtful consideration, data collection,
and analysis from all of the touring races throughout the 2021 season. Decisions are not based solely on a single event but all
touring races throughout every region. No BOP decision is made quickly or without careful consideration. We ask that you bring
out your cars and race. Without data on the adjusted cars further corrections can't be made. Please participate. The more data
we get, the better our corrections will be. Wider wheels would save on tire wear, but it would increase the speed of the car,
throwing off the well established BOP.
T4 Support Dec Prelim Fastrack BOP
#31688 from Colin Koehler · No action required · Minutes (2022-01 Fastrack)
Thank you for your letter and support.
T2/T3/T4 Feedback to May Fastrack item: 29428 (T2-T4 Swaybars) Opposes
#30668 from Colin Koehler · Taken care of · Minutes (2022-02 Fastrack)
Thank you for your letter. Please see letter #29428 in current Fastrack.
T4 Discontinued P/N on Spec Line for T4 FRS/BRZ/86
#30208 from Colin Koehler · No action required · Minutes (2021-04 Fastrack)
Thank you for your letter. The availability issue is improved. Recent part number corrections have been made
T4 Request FRS/BRZ Tire section width reconsideration to 235
#28612 from Colin Koehler · Not recommended · Minutes (2020-10 Fastrack)
Thank you for your letter. The data available on the FRS-BRZ shows that it is competitive as classed.