tire deformation question.
 

So I test-fitted a set of 04 STI rims (17x7.5 +53) that I have some rubber (old re01-r 235/40) mounted on that needs to be finished off on track/autox.
It fits but I can barely squeeze my fingertips between sidewall and the spring seat (see pic).
My question is - by how much the tire could deflect up top while cornering?

http://i.imgur.com/RSXXX.jpg

Not that much. You're good.

pics?

Yeah, I hope it isn't that much in this light car, with sidewalls being fairly stiff as well. In a few of my first slow subies, that I autocrossed on AS crap-tires, there was quite a bit of deflection.

Just wondering if there's a ballpark 'safe' distance to the suspension pieces for decent street tires.

If you're asking for pics of 04 bbs on the car - I just tested one ;)
I'm still unsure of a jacking point for the whole front of the car...

I'm not sure about a ballpark. But when you're cornering hard, the worst deformation is on the outside tire. On that tire, the contact patch is being pushed in towards the car which means the top of the tire will want to push out away from the car, so clearance will increase. The inside tire is the opposite but doesn't have anywhere near as much load on it.

One at a time. One at a time.

I never thought about it properly, but my gut feeling tells me otherwise. I'd expect the whole thread to shift inward in this case. I might be wrong though.
UPD: sample video
I'm not that dedicated.

http://youtu.be/EsjJz6zb8g8

On yokohama ad08
Rear tires

:needpics:

Interesting, though I'd like to get better views of the top of the tire. I've seen suspension clearance that small or less without issue. I was always of the impression that the outer tire carcass acted like a gyro and deformed to the opposite direction at the top, but it might just be resetting to center.

I think the tire in the second vid is a Bridgestone Potenza RE11.

My mistake it is re11

FINALLY someone took a pic...thank you thank you thank you ... now I can calculate my own stuff....I have the same tire/size 235/40/17 on factory option BBS wheels which are 17x7...sooo I should be good..:) I had been asking for that view of the strut/tire for a while now..Appreciate that...now as long as the Stocker BRZ Wheels clear Subaru 4 pots..I will be good :D

Bill

Just to put your mind at ease, that's a bias ply tire. Radials have much stiffer sidewalls and don't see nearly as much lateral deformation at the top of the tire. Here's a more relevant video, a radial passenger car tire being massively abused at Calspan.

Warning: turn down your speakers.

[ame="http://www.youtube.com/watch?v=nmo_dkNZIHM"]Tire Force Test - YouTube[/ame]

^Thanks for the earful, lol.
So, in general, how much would you suggest as a 'safe' clearance? I knew a few guys at autox who seemed to be okay if a credit card can be placed between the tire and the strut. In their worst case, however, the tire would be rubbing the paint off the strut body, not trying to get itself ripped by the edge of the spring seat.

Hey, I did warn you. ;)

I'd feel comfortable with 3/8" personally. Less than that and I'd put some masking tape on the spring seat, do some aggressive driving then check for signs of rubbing.

Thanks. That's a number I ran into more than a few times when I tried searching a bunch of different forums; although it seemed to come more often from people driving on R-comp tires.

I would like to request someone have a accurate measurement for the clearance we are talking about here (stock tire/wheels) so we have a "control" to work from for those of use that don't have their cars yet.

re: tire stress video

it's amazing what our tires can do, absolutely amazing

Personally I think that is two close for street use. Autocross is a controlled environment.

Back in my tire days. A Dunlop tire at Daytona would grown 70mm at 190mph. Now tire pressure also will effect the sidewall as well. Each tire has a designed sidewall spring rate. So each tire is going to be different. I think with coilovers you will have extra room. But I would run a 5mm spacer.

Cornering loads could very well come into contact. As with other parts flexing in the suspension. The a arms mounts will move around a bit. The rubber bushings are going to have some play. Look at the cheap front a arm mount. Tell me that thing is not going to move under a good cornering load.

I think the STi BBS wheels are going to look nice. And might even drive up the price again on those wheels. But until someone comes out with control arm bushings, coilovers , I'd run 5mm spacers to be safe.

Oh and if your camber bolts slip. That will get nasty!

That is a pretty nifty trick :D