I just bought two rear tires for my car. The rears were burnt to a crisp and they were making the car shudder. I wasn't in the best financial standing and had to put up with it for 4 months and daily drove the car at speeds that were just under the 'shaky zone' (80-85). I finally got new rubber slapped on the rear and the ride is nice and smooth now even at speeds of 80 to 90mph. (I live in Florida, these are common commuting speeds believe it or not!)

The only problem is sometimes I feel like the car is floating, drifting, and flexing. For example, if I'm at 65 or 70 and I turn the wheel for an evasive lane change, it feels like the entire body is flexing like a sponge. I can't remember if it was like this before with the old rears simply because I wasn't driving aggressively with bald tires.

Steering response is slow at best. I can actually wiggle the steering wheel left and right about an inch and a half before it actually turns. Is this normal? I'd like it to be a little sharper and more precise.

I went with non runflats for the rear and I like the ride so far and will be getting a matching set up front--but for now I have the runflats on the front. So two different types of tires and two different brands.

• Should I get an alignment now or when I finally have the front tires on?
• Do you think that the shuddering threw the alignment out of whack?
• Is the flexing caused by non runflats or the fact that I have two different sets of tires?
• Maybe it's because the new tires haven't 'broken in' yet?

I was thinking of getting an alignment package from Pepboys. I can get some sort of unlimited alignments for a year for like 60 or 70 bucks. I was thinking of going that route and getting an alignment immediately, then again once I get the fronts on. I also wanted to try the difference between zo6 alginments and standard C5 to see if that would make a difference.

I have future plans on getting the bumpsteer, suspension, and swaybar mods but not until first or second quarter of 09.

Side note: I watched the dealership mount, balance, and install the rear tires.

 

Ttt

 

I'm dealing with the same issue right now. My rear first generation Michelin Pilot Sport A/S ZPs wore out before the fronts which are still fairly good. I replaced just the rear's with the new A/S Plus ZPs. The first few times on the highway I thought something was seriously wrong and it felt marginally out of control especially wiggling the wheel at high speed. Felt like the whole car was swaying back and forth.

It's because the fronts are trammeling the highway and are worn out in comparison to the rear which are brand new with lots of grip.

The more I drive it the more defined it feels. You can actually feel the front tires track the road surface on their own and it takes a lot more work to keep it steered.

Mine was perfect before hand with just 30K miles, but until I get those fronts replaced it's screwy right now.

I should just get them ordered and installed and quite squeezing the quarters.


Oh, central FL here. So yeah I know what you mean, except they are using cameras more and more now to control speed on some sections of I-4.

 

Interesting, i just put the same tires on my car last night and drove it to work and back today....same thing! I replaced all four tires though, but it feels downright spooky on the highway. Its been 21k miles since my last allignment so maybe im just due. Going to have that done friday. Kind of weird though, even if i needed an alignment in my old worn tires (Kumho runflats) they seemed to handle better than these new ones. Or maybe im just not used to them yet...

 

What tires did you install?

 

I had my alignment done not too long ago, right after I got it lowered. Also got my new wheels and tires put on a few days ago and everything seems fine. My guess, is that your car was already due for one, and the new tires just exaggerated that effect.

-Alex

 

an alignment is most likely in order

 

Michelin Pilot Sport AS Plus ZP

im guessing i was just due an alignment and didnt realize it since i dont drive the car much.

 

Well I'll know for certain myself when I get the front one's replaced. Yeah same tire.

 

Your running apples & oranges on that car. Get a match and do the 4-wheel at an alignment shop recommended by a vette club or survey here for a good shop that does nothing but alignments. Pep-Boys? I just don't know abt that. At your speeds of 90 I'd protect my wellbeing, esp in that part of the state.

 

I'm not sure I would just get an alignment as an experiment to see if it improves things. I'd look at the wear pattern, first. I'm going on 41,000 miles on my PS2's after my F1's only lasted 24,000 miles. But both of them wore perfectly even. The PS2's have worn the most evenly of any I've ever had on a car....so when I replace them, I am not sure I want them to futz with my alignment. It seems to be fine as evidenced by the ride and wear pattern.

 

How many miles do the tires have on them? I got new tires a couple of months ago and it took forever to break them in. I thought tire break in was supposed to be 500 miles. My BFGroodrich g-Force A/S took about 1,000 miles before they stopped feeling "slick" and actually started gripping like my old tires.

New tires are always going to be less responsive than worn tires, so there is nothing you can do about that until the tires break in. It's because they grip better. Although, running a higher tire pressure would increase responsiveness. Then again, some tires are just more responsive than others.

You also have a point about the "flexing". Your rear tires ride fine and your front are hard as a brick. That has to make for strange driving characteristics. You may want to mess with the tire pressure a little, that could help. Perhaps a little more pressure in the rears?

I would save up for two matching tires in the front and an alignment. That's the right way to do it.

 

Runflats have much stiffer sidewalls. I bet some of what you're feeling is the softer sidewall of the non-runflats. Also, new tires have much deeper tread depths than old worn out tires (thank you, Capt. Obvious!). Point being, you could be also feeling some tread squirm. Tread squirm is part of why racers will shave brand new tires down to a shallower depth. Tread wear occurs so slowly under normal conditions, that you never even notice the tires reacting faster, you just sort of adjust to them as they go. Now throw brand new tires on and it's a sudden, drastic change that's easy to notice. Especially if you get non-performance oriented all-season tires.

So, now you got softer sidewall, deep treaded tires in the rear (this adds up to a slower reacting tire) and stiff sidewalled, shallow tread tires in the front (this makes for a twitchier, faster reacting tire). Get a matching set of new tires on the front, sooner the better. I don't think it will solve what you're feeling though, i think it's just the new tires you're getting used to. Don't just pump more air into them.

However, it certainly won't hurt anything (but your wallet) to get the alignment checked. It's a good idea to that once in a while anyway.