Ride height

[Exhlr8n]

Anyone running the taller Michelins (30/65/18) and 31/71/18 or Pirellis slicks on their Comp Coupe?

Curious about your chassis height front and back. The Factory Comp Coupe book I have has the recommended heights in it. I'm probably going to start with that.

But would appreciate any suggestions from those with the taller tires.

Thanks,

Tom

[SilverACR]

i Don’t have taller tires, but can’t see you needing to change height because of taller tires. The height and rake is part of the cars aero and suspension, so I would think frame to ground would need to stay by the book. Obviously you can’t rub tires, so that could change your height if that’s your concern.

[Exhlr8n]

The last true wheel to wheel race that the car was in was Pittsburgh. I just found out that they set the rear fairly high because Pittsburgh is very bumpy and the taller rears were rubbing a little. I have done a few track days (Hpde) with the car and the current set up has been causing some excess oversteer, especially during hard braking and acceleration out of a turn after a rise in elevation. I haven't experienced any understeer, so that's good.

Heading to Laguna Seca on May 27th.

Plan A: Is to set both heights to book values as a starting point. If I start to get any understeer, I'll raise the rear a little at a time till I get it more neutral. At least this is my plan for now.

Plan B: Any input from others that may run a similar set up would be greatly appreciated.

[str5010]

Side note: Pittsburgh has been resurfaced and is no longer bumpy! Haha

I don't have useful VCC setup data for you unfortunately, but in trying various tire heights on my ACR I'm still adjusting accordingly to maintain the original ride height and rake when measured from chassis to ground. This impacts aero performance.

[Exhlr8n]

We had "7" VCC @ Willow Springs back in March. Most run the R7's. I noticed how much lower their cars were than mine. I think I'll get a handle on it soon.

[str5010]

They certainly could have found that a lower ride height than that which is prescribed in the original manual worked better for them based after any number of changes from the original configuration right?

[steve911]

Yes you will have raise the car a bit. hose tires are almost an inch taller. There are several of us in the Chicago club that are running those tires. The suggested ride height for the rear will allow some rubbing. We went up 3/8 of an inch and it help a lot.

The other thing to consider now is that rear fender liners for the Gen 3-4 are a thing of the past. You don't want to wear them out...

[Exhlr8n]

For Laguna, I lowered the rear on the Comp Coupe about 1/2". It now sits @ 4.75" from frame (Still an inch over book " 3.875" with the Hoosiers) Didn't notice any rubbing of the rear Michelins. And raised the front 1/4" to 3 5/8" (Book calls for 3 3/8"). So ended up with about 7/8" rake (Book calls for 1/2"). Car handled much, much better, no oversteer and only a touch of understeer, lowered the front 1/8" and it settled down nicely. Overall, happy with the changes. Next outing I will lower the front back to its original starting point of 3 3/8" and lower the rear another 1/8"-1/4" as long as there isn't any rubbing.

[GTS Dean]

I assume you guys adjusting your wing angle of attack after changing the chassis rake? If not, you're changing 2 variables at once.

[Exhlr8n]

Yes, I did take some rear wing out also! I put it in a more neutral (Mid) position. Prior to the above adjustments I kept adding more and more wing downforce in an attempt to reduce the oversteer, but it didn't help enough. For me, the change in rake and wing set up is a big improvement over the previous set up. Hopefully minor tweeks here and there are all I need going forward.

Thanks..!

[Arizona Vipers]

Yes, I did take some rear wing out also! I put it in a more neutral (Mid) position. Prior to the above adjustments I kept adding more and more wing downforce in an attempt to reduce the oversteer, but it didn't help enough. For me, the change in rake and wing set up is a big improvement over the previous set up. Hopefully minor tweeks here and there are all I need going forward.

Thanks..!

With the michelin's tire pressure IMO is more important than even rake/frame height etc. Did you take pressures hot right off the track? What were they?

[Exhlr8n]

Yes AZ, pressure checks before each session and immediately after. Most of my track days with this set up have been colder days, 50-75 degrees F.

Starting Cold @ 22-26 psi, hot 29-32 psi. Very greasy for the 1st 1-2 laps. Do you have other suggestions for Psi?

I can say the rake change made a huge difference the last outing @ Laguna Seca.

Might be looking for some replacements Tires, especially the Fronts..!

[Arizona Vipers]

Yes AZ, pressure checks before each session and immediately after. Most of my track days with this set up have been colder days, 50-75 degrees F.

Starting Cold @ 22-26 psi, hot 29-32 psi. Very greasy for the 1st 1-2 laps. Do you have other suggestions for Psi?

I can say the rake change made a huge difference the last outing @ Laguna Seca.

Might be looking for some replacements Tires, especially the Fronts..!

29-32 hot is good, but did you take those pressures right off a hot lap, no cool down lap? Because that's 4-5 psi right there. If you aren't taking them right in the hot pits, even with no cool down lap I'd add 3psi to whatever you're showing.
And yep the Michelin's take forever to warm up, Not sure if you saw my tire warmer set up at Willow Springs or not. I might have a brand new set of fronts S9L's for you. They are on national backorder right now, I paid $650 each for them to use at Viper Rendezvous but ended up not going.

[FrankBarba]

Arizona....Contact Rich Marzel i'm sure that he can help you out with the info your looking for...

[Arizona Vipers]

Arizona....Contact Rich Marzel i'm sure that he can help you out with the info your looking for...

He doesn't run the Michelin's, he tried but with the McCann racing bodywork on his Comp Coupe they didn't fit in the rear. I actually bought his test-fit of Michelin's from him when he learned they didn't fit. His car is so badass.....

[Exhlr8n]

Those Psi are usually after a cool down lap. I will modify as you suggested! (Great info, thanks)

Yah I saw those tire warmers..! Let me see if I can squeeze those fronts in the budget.

I do not have any track days scheduled till Oct 5th+6th @ Willow Springs with Scott's group from West Coast. Too damn hot out there for me (Even with the Cool Suit)

Having fun at Laguna.

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[GTS Dean]

Those Psi are usually after a cool down lap. I will modify as you suggested! (Great info, thanks)

You really should have a buddy in the pits to record tire PSI and temps when you come right off the track from a good string of fast laps. Then go back out and make your cool-down lap. You should be recording your baseline pressures @ temp, then ambient air and track temps at hot check. Do your aero and alignment setups at hot inflation pressures. Temps/pressures after cool-down are useless, period.