George3

Last season my car was running great, but I wanted to do some improvements. So, I've done some mods to my GT3 over the winter:

New Toyo RA1's
New CCW Wheels
Track Alignment (-2.6 F / -2.2 R)
Corner Balancing

I've done two track events this spring since the mods were done and the car feels great on turn-ins . . . BUT . . . I feel a slight side-to-side shimmy on the high speed straights that it didn't have before.

It's not giving me that warm and fuzzy feeling at 150 mph.

What could be causing that?

.

doc2s

what's the toe set at?

mooty

1. you sure the tires didn't rotate on rim to get out of balance?
2. how much tread you got on the toyo's? some reported instability with new tread depth until worn.

George3

3-track days on the NEW RA1's, and these were not shaved from the start. So I started with full tread depth. Tread block issue?

Toe from my print-out:
FL 0.00* FR -0.02*
RL 0.16* RR 0.15*

mooty

probably not tread block issue then, if you got 3 track days already.

toe doesn't look bad. i am toe out and no shimmy.

George3

No, I meant tread block issue . . . as in, there is still a lot of tread on the tires and the tread blocks are still large and possibly flexing (?) .

.

str8ner

George,

It is likely from your tires. I felt the same thing with the r888 full tread. Not a good feeling under braking at 150. This should go away as the tires wear down. To confirm this try a MPSC or a Hoosier and you will not have any of this. I will try to have my next set of R888 shaved to 3/32.

Stephan

George3

Stephan-
I just ordered a set of R888, 255/35 F and 315/30 R.
Did you have any rubbing issues in the front with this size?
I'm having a little rubbing in the front right with my 245's now.

rmag

I've been running f R888, 255/35 F and 315/30 R on CCW C14's (same as Stephan), and neither of us have had any rubbing issues with them.

George3

My rubbing is on full turn lock on the right wheel only. This is with the 245's on CCW C10's. No issues while driving at speed, because I don't turn the wheel to the full lock position.

Maybe I need a 2mm spacer.

.

rmag

Ah, just saw your alignment settings. Stephan and I are both running basically 1.9-2.0 F, 2.0 R camber. That extra .6 you got is probably the difference

340Elise

I think that your 245 front tire with the 40 aspect ratio is the culprit for both of your issues. I read on here not to long ago that the 40 front and 35 rear aspect ratios will give you the correct outer diameter as stock, but at very high speeds the car is not nearly as stable with these higher sidewalls.

As for your rubbing, my guess is that it will go away when you switch to the 255 35R 18 tire. And as stated above, it could take care of your high speed wobble.

But always make sure that your wheels are road force balanced before you explore other options.

mooty

i know what you mean.
but after 3 days of track, you should have worn the tread blocks enough so they wont squirm or cause instability.

mooty

no.
i run 245/40 and 305/35 RA1 on RS.
it doesn't wobble and there is ZERO rubbing. (except full lock)
you dont need front spacers, other than u turns, you wont be at full lock

mooty

i am not sure that's it either.
i run a lot more camber than he does.

most likely it's the tires. wear the tread a bit more see if that helps (assuming it is balanced correctly)