Automotive Questions and Answers -

Auto Repair

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Questions and Answers

Bouncing Firebird

Q. My car: 1989 Pontiac Firebird Formula 5.7 liter fuel injected (TPI), 4 speed automatic, 87,000 miles, No ABS. Has P/S, A/C and cruise. WS6 suspension package, T-Tops, 245/50R16 tires all around.

What I've done so far:
When driving around town, if there is anything resembling a bump in the road, if feels like the front end of my car just goes all over the place. I know there will be pulling because of the wide tires, but this is just unnerving. It seems like it just suddenly jumps (not pulls) to the left or right. In traffic I'm afraid it could end up in the other lane. On the highway, I've never noticed a problem.

What I've done so far:
I've taken it to several shops, and they couldn't find anything wrong with the suspension. One shop, after seeing what I was talking about, took a while looking the car over, and said the idler arm might be worn enough to contribute to the problem. I had it replaced, and it corrected the problem for about a week. The wandering has since returned.

I've also had the shocks/struts replaced, the wheels aligned, and the bearings repacked. I'm confident that this is not because of the wide tires. I had an older Trans Am with 235s which never did this, and when the idler arm was first replaced on this car, it handled as I would have expected it to.

Thanks for your help, and time.
David

A. I think the problem could very well be with the tires. One thing few people realize is that the tires are an integral part of the suspension system. A tire of the proper size and inflation is also a spring, absorbing some of the bumps and harshness of the road.

Older cars were fairly tolerant of different tire sizes and would accept them without too many problems. But as time progressed and weight reduction became more important, tires became a critical part of the suspension system so any radical changes impacted the handling and performance of the car.

If you want to keep these tires, and I suspect you do after the dollar investment you made in them, I would recommend going to a speed shop and look at replacing the standard struts with Koni struts. Koni specializes in performance shocks and a good speed shop can match you up to a set that will compensate for the tires and get you the handling you need.