Alignment problems? Check your tire circumference

Hopefully this of help to anyone with strange tracking problems.

I had my car aligned months ago and after that it drove perfectly straight. I rotated the tires and suddenly the car tracks to the left pretty hard. I took the tires off and measured the circumference using a tape measure around the center of the tread, and found:

LEFT RIGHT
88.63 88.00
88.25 88.25

So the left front is significantly longer than the right front. I'm going to play with pressures and see if I can even it out.

Are these the same size/brand tire?

My recommendation to anyone buying a new tire is to buy TWO new tires and put them on the front. Make the worst of what's left the spare. Having two identical tires in front eliminates the usual suspects.

If you moved the tire from side to side, that could be your issue. Not all, but a good percentage of radials will pull if moved from side to side in the front. If you swap them on the rims, while keeping the direction of rotation the same, that usually cures the issue.

A half inch in curcumference should not make a noticable difference in the "pull" of a front end, but that much on a posi will make it work a lot.

If you have an open rear, I would put the odd tires on the rear.

Rotating the tires is supposed to geve more even tire wear, but on today's tires, if you inflate them properly, you can get equal tire wear all around. I have never purposely rotated tires because of wear patterns. The only reason I have rotated tires is when I had front end issues, and they were worn on the inside or outside. Then the fronts went on the back on the same side.

From the measurements you stated, your car should pull right if anything. You may also have a broken belt in one of the "now" front tires. You would not notice it on the rear, but it will make the car pull on a front wheel. The larger diameter of the left tire may be an indicator of a broken belt as well.

I didn't know that they were still recommending that you don't swap sides with radials.
They still take some kind of a 'set', eh?

Sometimes, and you can never tell until you put them on the car. The statement goes: put them on and see what happpens. It is not a recomendation but a common practice. The one tire that is much larger in curcumfrence would tend to make me look at that tire carefully. It is "odd", and that is the side it is pulling toward.

Well, different diameter tires (or one tire low on air, for that matter) changes the scrub radius of the side it's on. That would cause a pull.

For the record, all the tires are the same brand, and I believe they were purchased and mounted at roughly the same time. I tried lowering the tall one to 32psi and raising the short one to 40psi and that helped, but the pull was still there. I will try swapping the fronts side to side and see what happens.

Also, I don't have a steering damper on the front right now. The car was pretty flighty at 70+mph... but then, Pennsylvania roads suck too. I likely have something loose in the front suspension, as I could occasionally feel a tapping through the steering wheel.

The tapping may be a broken belt in the tire.

Sometimes tires get a separation, and it will tap where the bubble is. check for a unusually worn spot at some point on one of the tires. It may be as small as a 3-4 inch area.

The lack of a steering damper may not be a bad thing, especially when you have wierd tire issues.

sherlock9c1 wrote:

... The car was pretty flighty at 70+mph...

Maybe you don't have enough 'toe-in'. It's easy to check.
I've noticed in the past when I didn't have enough (or any) toe-in. The thing felt 'flighty', same as you.

Could be not enough toe. Last summer I aligned the car myself with toe plates and it drove fine but I was suspicious I had put too much toe in, so I had the car aligned. The shop told me I had way too much toe but forgot to print out a before sheet so I don't have that data. It never felt flighty after I did it but it feels flighty now.

The other curious thing is that when I back up and turn the wheels all the way to one side, the front tires squeal now. Almost like one wheel is dragging. It never did it this loudly after I aligned it. So I'm wondering if the zero toe is affecting that too.