New rear tires, loose steering, tire squirm
 

I just replaced my rear tires on my 16' sport with the new Firestone Indy 500 tires (which are actually re-branded bridgestone re-003). I didn't change sizes they're 275/35R19. The old rear tires were pretty worn out and didn't have much tread left, but the fronts still have tons of tread and look almost new, so I figured I'd just replace the rear tires only. Well now I'm experiencing loose steering/wandering, especially at highway speeds, and it just gets worse and worse the faster I go. I checked all the lug nuts and they're on tight, so that's not it.

The only two things I can think of is that maybe the car was lifted wrong? I bought the tires from tirerack and had walmart install them, and they used a scissor lift, which it looked fine on the lift, but idk. The other thing I found with some research is called "tire squirm" and people says it's just a new tire thing and they need to be broken in by driving them a few hundred miles.

Maybe you guys know something I don't. I'd like to hear some possible solutions. I just want to get back to enjoying my Z :driving: Thanks

Assuming that you've got the same kind of tiers front and rear, it's most likely because they're new. New tires are slippery sometimes until you scrub off the mold release. If it's still that bad after 150-200 miles, get your alignment checked.

I'm still running the factory bridgstone potenza's up front since I didn't think that running a different tread pattern for front and rear would make a difference since people mix the two all time like when they use drag tires in the back and stocks up front.

I'm still driving the car and I'm definitely going to try your suggestion to see how they feel after a couple hundred miles.
Thanks

You're not running just a different tread pattern but a different carcass, sidewall, jointless belt, compound, etc. The factory Potenzas have some serious components; 2 ply rayon carcass, aramid(kevlar)-nylon hyrbrid JLB and 140 treadwear compound.

That's true, I haven't considered that. The firestones were about half the price of the potenza's and since I like to have fun in my Z I decided to go with the lesser priced tires because I know they'll only last me about a year. But could the construction difference be the cause of the front end drifting around?

Having two different tire compounds front and rear can cause funky handling. Wait a few hundred miles. If it doesn't get better, have the alignment checked. If it's in spec, then get a new pair of the same tires for the other end of the car.

This phenomenon has been discussed many times before on here. If you did a search you'd find out that when you mix noticeably different tread pattern and compound tires front and rear the handling of the car can turn to sh!t.

I checked the search before posting. I didn't see anything that related to me. I'll give it a few hundred miles and see if goes away, and if not I'll have to get some of those same firestones for the front and see if it helps. Also might consider an alignment check before replacing them though. Those miles should go by pretty quick given the amount of driving I do. Thanks guys

It can definitely alter the steering of the vehicle for partially the same reason sidewall height affects steering. Greater bulk deformation of the tire can cause a lag between steering input and output. Below the limits of traction, tire construction can have more to do with how the car feels than tread compound or pattern.

Also, check your tire pressures on all 4 corners.

She was about 34psi cold all the way around, that's what walmart set it at. I used to run about 36psi cold and it had very even tread wear. Ran it like that for 26k miles.

I'm gonna give it a couple hundred miles and stop back in to post the results.

Also just found this on another forum (bimmerfest)
(You should make sure that the rear tire sidewalls are at least as stiff as the front sidewalls.
Otherwise, the car will have terrible steering response and may cause wandering issues on the highway...)

OP, after all the outstanding posts on the superlatives of various Michelin, Bridgestone and Continental tires, you went and purchased Firestone tires. Not judging you at all (*disclaimer as too many people are ultra sensitive) just wondering why?

Are you confusing me with someone else? This is my first and only thread/post pertaining to tires.

To answer your question on why I went with the firestones. It was price, good reviews both on tirerack and youtube, and I figured I'd try them out.

No, I am not confusing you with anyone. Nor was I even suggesting that you wrote anything about tires. I am referring to the other members post's pertaining to their experience with tires other than the oem Bridgestones. Did you read any of those reviews? Just wondering what prompted you to purchase Firestone tires?
That's it, that's all. Thanks.

It's cool. I did read the reviews on many other brands before going with the firestones. The firestones were $169 per tire and had tons of good reviews and from what I found through some research they seem to be identical to the bridgestone re-003's which also have great reviews. They seemed worth trying out, but I have to say I'm now wondering if I made a mistake by buying them.