Those Penskes made me soil my office chair.

 

Erik's setup

 

I apologize if my question slightly off-topic, but with the suspension setting are you typically running a square setup with the wheels?

Do you have any insights about what the wheels should be based on the suspension setting? Or does it really matter - meaning regardless of the setup you can run whatever wheels you want.

 

Check out Howard Colemans thread. It's pretty awesome for different suspension setups.

 

Yeah I have studied his thread repeatedly. My friends and I have even utilized his suspension settings for setting up our cars on track. However I was interested in understanding how the wheel size can either improve or degrade the setup. I understand Howard's setup is staggard. But then I have read of a few others who run a square setup with 9" wheels all around. I guess in the end it doesn't really matter. I was just curious to know if there was an optimal wheel setting based on Howard Coleman's or anyone else's suspension setting.

 

the short answer is yes. the long answer is that usually the suspension is setup around the tires. the suspension is basically reacting to the grip that the tires make.

so just generally building a race car you build it around the tire. if you want a for instance, we usually run Nasa's PT/TT with a 225/45/15 R6, and after 2 seasons on the Hoosiers we're pretty well dialed (and 5 seasons before that on other tires).

we had the opportunity to run USTCC before the WTCC race, so we did. the spec tire for that is a nittos in 225/??/17 235/45/17 and 245/50/17. we picked the 235, as its just about the same OD as the 225 and its wider. the 245 is almost an inch bigger in OD, so for an NA honda, that duck didn't hunt.

testing reveals that the car sucked on the nittos. we tried a bunch of stuff and ended up with a different alignment, different spring rates (slightly), different shock settings, and a different sway bar setting.

so your tire choice has a HUGE impact on the suspension setup in a race car. Howards setup is nice however, because its not 100% race car, and doesn't require such a specific suspension setup.

 

Hi guys.
When measuring the ride hieght of the car. We're exactly are you guys measuring from?? Ground to lip of guard??
Thanks guys

 

Don't know about others, but from the bottom of the rim to the guard to get it ballpark - lots of bouncing of the suspension, then onto the scales.

A quick spin of the wheels referencing a fixed point while on a hoist might tell if you've got lots of radial runout from flintstone wheels too, which can drive you nuts....and very common!

 

Bringing this back.


Updating my FD SSM build this winter. My Penskes are one and a half season old if anyone is looking to upgrade to a proven national podium finishing SSM coilover setup. They are on the forums here or pm me of you're interested.

I've ordered completely new Penskes going for more aggressive rebound valving and from the Clovis upper mount to the tripoint upper pillowballs (buys me an extra 1/2in of shock travel).

Spring rates last 2 seasons were 1100lbs x 4. Dialing that back next season two 1000 f 850 r.

Also switching to Moonface roll center adjusting front LCA. I use LCA offset pillowball bushings from SuperNow to get camber in the 3.4/3.3 area.

Planing to lower my ride heights next season to around 5.5in to the frame rail. Currently at 6-6.25in.

Was running 315/30/18 Hoosier A6s in 18x11 at all four corners. Now I'm going to rear flares with rear 18x12 Rotas 25mm offset 335/30/18.

 

The biggest improvements to the performance have come recently from the 315 wide front tire fitment.

Also forgot to mention, the full solid pillowball bushings in the rear helped tighten up the rear and keep the oversteer in check.

 

Wheel size and offset?

 

I bet your set up would be better with 295/30/18's all around on the 11" wheels.

That width is what the time attack guys all run on 11" wheels. the reason it is faster is because there is no time delay or lag in steering input when the tires are under tension stretched, it also has more tire on the ground since the shape of the tire isn't a muffin top.

It's also the reason that almost all race cars also stretch their tires.

 

Toe! Toe! Toe!

Someone mentioned it way up high in this thread, and it got dropped.

For every track we went to, camber and toe made the biggest differences in giving the driver confidence.

Big fast track like Daytona, Watkins Glen, we ran minimal toe (.5 m&m out in the front, .5-.7mm in at the rear).

Tighter tracks we might up the rear toe another .25mm in.

Toe in or no toe in the front is ok for a street car as it makes for a "safety push" which most people eliminate with over springing the car and running no toe in the rear. This makes the car hard to catch mid-corner when you go to throttle especially after a hard trail brake maneuver.

Give this a shot- we used it on RX8's as well as FD's. Works great on road courses, but for autox might be a bit tame.

Set front as low as you care to, with out getting near bump stops. Set the rear about .5" higher, measuring of jack points in pinch seam.

2.1-2.3 neg camber front
2.3-2.6 neg camber rear

Max out the caster as much as your arms will let you for more wheel feel.

.5mm toe out front
.75mm toe in rear

Both bars set in mid position or maybe just a bit less front bar.

This is a good spot for most road course, just to start. The confidence level will dictate adjustments from there. With 10 drivers in completely identical cars, you would not believe how much different we had to set them up to account for experience and bad habits.

We ran compression pretty low on whatever shock we were required to use, but pretty high (ESP in the rear) on rebound. This let the car take a set on corner entry and hold it. Low rebound on stiff springs makes any car pogo just about apex, making it hard to go back to full throttle. You end up carrying maintenance throttle when a lighter sprung car is already hammer down.

If you have shocks that have remote nitrogen canisters, you can alway back off a good bit on spring pressure and fine tune it with a bit extra can pressure. We ran the motons and JRZ shocks as much as 50 psi higher to make the car hold a set better in mid corner using the lighter spring.

When you corner weight the car, don't just full the seat with weight. Place some in the floor board ( like 25-30lbs) and if you run a cool suit, full it with water. You would be surprised on the FD how this little bit makes a difference. It has barely more track and wheel base than a Miata, so little stuff counts.

On tire size, be careful. Sometime there can be too wide. When you scale up the contact patch, you are spreading out the weight. Porsche cup cars run a relatively narrow 275 up front. Too much wider, and the 325 rears would push right past them, no matter how much steering input you give.

Call your tire rep and ask him what tire temps you should see.
Hoosier used to want about a 35-40 degree spread, where as Michelin would hand us a base sheet for most tracks and tell us to be in the realm in order to not have the tire burst! ( ESP Daytona where we had to run no more that 1.8 neg camber on the right rear or else!)

 

Sorry- forgot to point out that those toe settings were at each corner. Some drivers would actually run a lot less at the fast tracks if they were good. Others had bought cars outside the talent range, and we would run these numbers up to keep them pouted in the right direction. Made the car numb, but kept them out of the topiaries at Barber