Contour Enthusiasts Group Archives Forums Modifications Suspension Side-to-side oscillations

My '98 SVT has 100,000 miles, just put new Fuzion ZRi's on replacing badly worn Yoko ES100's. I'm noticing that the car (especially rear end) slowly shakes side-to-side when hitting minor road imperfections, bumps. Car doesn't bounce up and down. Allignment was set to spec at same time. Mechanic friend suggested rear struts. Anybody have a similar problem? I replaced all original (cracked) springs with factory replacements in the last 14 months/20,000 miles. Struts seemed fine then. The old Yokos would tramline a bit, but I thought just because they were worn. I've thought it could be the Fuzions having softer sidewalls, or tread compound/design. I increased tire pressure and the problem diminished but still is bad. Any help would be great.

Thanks,

Brad

Same problem...I just live with it.

That sounds like a tire problem. Either they are not properly balanced or they have an internal problem. This is uncommon for a Bridgestone (Fuzion is part of the Bridgestone family). You probably have a tire with a belt that didn't get properly placed during build. Get back to the tire shop!

Two of you with the same problem. This is starting to not look so good for Fuzion. I hope they get it worked out before I need a set of tires. The place I bought my Daytons from has replaced the Daytons with Fuzions. Until now, they sounded like a good tire.

I was conerned about tires too but... I think if the balance was off they would vibrate - they don't at all. As far as slipped belt - how to tell. I mail ordered from Tire Rack and had a tech at Porsche Audi dealer install after hours. Anything's possible. Anybody else have an issue like this? If so what kind of tires. Anybody fix problem with new suspension components or new tires?

Thanks,

Brad

There are several aspects to tire balance. The two main ones are radial imbalance and lateral imbalance. Radial imbalance gives you the shakes. Lateral imbalance gives you the side to side shimmy. You are more likely to have a lateral imbalance if you have wheels that won't properly center on the sheel and/or balancer. You are also likely to have lateral imbalance if you try to balance on a single plane with stick on weights. It is best for balance to use weights on the inside AND on the outside. A belt that is out of position can also give you a problem with lateral balance.

I would say to have a good hard look at the balance before doing anything else.

If you have your stock rims and tires put them on and see if anything changes.

These are stock rims w/ new tires. I've also got some snows on 15" rims that'll go on soon. They feel very different anyway so that may not help. Never thought about 2 axis of balance. Would the lateral balance set up a high speed situation like other imbalance? My situation does 2 things: Darty steering, seems to follow road imerfections and bumps and imperfections set a slow side-to-side "wobble" in rear. This wobble is much slower than any tire vibration I've felt. Maybe once per 1-2 sec. instead of a few times per second for tire vibes. Sort of like worn out shocks moving up and down over a bump - except this is side to side.

Thanks,

Brad

That sounds like lateral imballance, or perhaps loose lug nuts.

Radial imbalance shows up at roughly 55 to 60 MPH. Lateral imbalance shows up at a much lower speed.

Most vibrations show up at a specific rpm (for that component, not necessarily engine speed), and it returns on multiples of that speed.

Lateral imbalance usually shows up about 25 to 30 MPH and repeats at double the speed.

Steering can be edgy with lateral imbalance because the sideways shake nibbles at the steering.

The tire itself is "too" soft. The tire sits up on the tread blocks but when lateral force is first applied the tread blocks give side to side.

This is very common on all season or cheaply made performance tires.

The only way to help alleviate some of this problem is to increase the air pressure.
Any type of moderate performance or above series tire will require significantly more air pressure then the "standard norm" or "OEM recommendations" The 28-32 psi range (i.e. OEM) should be relegated to Le Sofa cruisers that always feel squishy and floaty.


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Of course that takes "as a given" the tires have been properly balanced and the suspension has been checked.