I have 275 40 17s on the front 315 35 17's on rear on 10 inch rims. I find the car shoots from one side of the road to the other and gets caught in the grooves in the road. Is this because the front and rear tires are different sizes? Can I adjust the caster maybe to help with it? I have a stock car so I understand bump steer ackerman steering caster and camber so if anyone has already messed with this can you help me out.

 

Big Tires get caught in the Grooves in the road a lot. I have the tires in my sig all around and i catch all the grooves. Sometimes it pulls me really hard.

 

I'm no expert by any means but maybe your toe setting is off? Should be 0 or slightly in.
Also 275 is a narrow tire for a 10" wheel

 

That effect is called tramlining. It's pretty normal with wide tires. I'm still on 245s and mine pulls all over the place, but Alaska's roads suck. Very noticeable grooves worn into the pavement from the studded tires. Toe out could exaggerate the problem.

 

Thqanks guys I will check the alighnment on the car Maine roads are probably not quite as bad as Alaska but I bet there close LOL. I figured someone on here might have put 315's all the way around and I thought it might help the problem having the same siz at 4 corners but man those tires look good on the car and it hadles like a formula one racer.

 

Hello,

What's going on is that "tracking" (the way the rear tire follows the front) get's screwed up when you run 2 tire sizes. This'll happen anytime you have a wider tire in the back. With a wider tire (315's vs 275, 40mm dif) The back tires stick out further on both sides (prob. 20mm further inside, and 20mm further outside, dep. on wheel offset). So, since the back tires stick out further than the front, when you get in a rut in the road, the back tires will hit the sides of the rut before the front tires do (since they stick out further). When they hit, it'll push the rear of the car back to the opposite side as the side they hit on. -Thereby angling the front of the car INTO the side of the rut that you just bounced off of. It's basically a continuos cycle. -On good roads, you never notice the issue. -It's a PITA on some roads though! -The only solution is to run the same size tires all the way around (or not drive on crappy roads). I used to have 275/315's and got so tired of it on the roads I had to drive to work I eventually went back to 285's all around. -Now that I've moved and the roads aren't as bad, I'm thinking of going to 285/325 for the added traction.

BTW, yes there are some people here running 315's all around. -The won't have the issues with tracking, but will still have bigger issues with ruts than someone with say 245's or 275s, as they'll still be more likely to bump the sides of the ruts with the front tires.

Hope that helps some,
-Justin

 

It's more due to the wider tires than the fact that tire are different sizes. The corvette has different front/rear combos for tires and it's not a problem. Wider tires effect the tracking, as well as the tires themselves. Having a slight toe-in will help. Toe-out will make it worse, and make the car "darty"

Dan