weird tramlining issue after rear tire replacement

[KevinC]

Background: '05 ZHP coupe, 77k miles, full suspension refresh at 53k including shocks FCABs, RTABs, in perfect alignment.

So.. after about 22k on my PSS's, my rear tires were shot. Very disappointing as the car is just my DD and driven like an old lady for the most part. Fronts still have a ton of tread. I saw no reason to spend for PSS's again when Conti DW's are well-rated and cheaper, and given the car's mission, should be more than adequate. So I replaced the rears a few weeks ago with DW's. Still have the PSS's up front, for now.

So immediately after the new tires, the car is squirrelly as hell, tramlining badly, especially on sweepers on the freeway, where it feels like I'm steering a boat. It's as if all steering precision is gone. In a straight line, it's mostly fine. Doesn't pull at all. Generally feels like driving on grooved pavement, or on shitty run-flats, or on an icy surface.

Thought maybe the issue was new tires being greasy, give 'em a few hundred miles. Nope, no change. So I'm baffled. I broke down and ordered a pair of DW's for the front the other day, they'll be in this week. But I'm skeptical that that's the issue - the fronts still have a lot of tread, and it doesn't seem that this should be happening just because the tires aren't identical.

Anyone have any theories? I want my old car back!

[Dave1027]

I had the same exact problem when I put Conti DWs on my rear wheels. Exactly. If the search function worked better on this forum you could find my post where I posted verbatum.

At first I thought the Contis were garbage but now I'm loving them and did install two more of them on the front last november. I'm going to tell you how I solved it and many won't like what I have to say. I had to go to a non-standard alignment. I running the rears with much less camber. I have them at -0.7° and the toe at 0.1°. As a matter of fact, I'm running those same specs on all four wheels. Feels great very precise. Handles and rides nicely. I also will likely be getting more miles out of these tires.

[Johnmadd]

Ineresting, I also have this exact issue after 2 new rear dws'.

[KevinC]

Weird! Dave, did you replace the fronts before your new alignment setup.. and if so, did it cure (or at least help) the problem? Or did you align it at the same time the fronts were replaced?

I'll have the fronts on by Tuesday or Wednesday of this week and will report back. I don't really want to mess with the factory alignment specs, but if this doesn't solve the problem, I'll have to figure it out somehow. I want my old car back!

[Dave1027]

Weird! Dave, did you replace the fronts before your new alignment setup.. and if so, did it cure (or at least help) the problem? Or did you align it at the same time the fronts were replaced?

Actually, I did the alignment first before getting the fronts. If the alignment did not fix it then I would not have bought the Contis for the fronts. After I fixed the weird feel on the rear end with the alignment I was happy with the contis and decided to go ahead with two more in front to replace my half worn Bridgestones that were making a lot of noise. After I did that, to my amazement the steering became more stable. I was not expecting that. Basically these Conti DW's are sweet as long as you don't camber them too much. That was my conclusion.

[KevinC]

Update: my front tires came in today. I now have DW's all around. Drove home and.. yep, that did the trick - I got my old car back. No more squirreliness, no more feeling like I'm driving on an NHL rink, no more feeling like I'm pointing a boat around the big freeway sweeper I drive daily. In fact.. I REALLY like the changes these tires have brought. They are clearly lighter than the PSS's, I can totally feel a difference in unsprung weight in the way the car steers, handles, and handles a lousy road surface. I'd guess at least 2 pounds at each corner. Anybody know where I could find the weights of each tire? And, the sidewalls are a little softer than the PSS's - turn-in is not quite as crisp, but the car rides more smoothly overall. I think these are a perfect match to the ZHP, for anyone not needing 10/10th's performance of the PSS. I'll continue to run them on my Z4MC, but I'm more than happy with the DW's for my ZHP.

Edit: found tire weights really easily. Fronts: 20.3 vs 22.8, 2.5 lbs lighter.. rears: 22.2 vs 22.2 - identical, which is interesting given the big gap with the front size (these are stock sizes btw). The fronts totally confirm what I'm feeling.