Running tires backwards
 

The front wheels were run reversed for at least 200 miles. When I noticed, I switched them. Now there is a definite shimmy in the steering. I took the wheels to a shop and had them balanced and the shimmy is still there...

Ideas?

What kind of tires? Why were they on backwards in the first place?

I didn't notice when I picked up the car. They are Perelli HP's. H rated. They look like some sort of semi-performance touring tire. They are directional.

I wouldn't trust them. Could be the belts seperating & coming apart.

Particularly some of the news that is out recently. I was watching national news this week and a guy in an old sports car flipped his car when his tires separated - bad news. Old tire just disintegrated. I would ask the manufacturer?

Been my experience that running unidirectional tires in the wrong direction esseitially ruins them rather quickly. Think in terms of taking a rope and rather than stretching it, you try to compress it - the fibers separate.

Same type of thing happens to the belts in the tires. Their designed to be stressed and run in one direction only. Once they get stressed in the wrong dirction their essentially ticking time bombs.

You've got 200 miles on them, but there's no way of telling how long they were driven before you got the car (???), I'd lose them ASAP.

pschrup's right. They're headed for failure. IMHO, when you replace them, ask the folks doing the work to take a chunk out of the side of them or render them unusable in some other fashion. I've heard of cases where these can fall into the hands of less than reputable folks then they get resold to some poor unsuspecting driver.

I agree the belt may be coming apart inside the tyre. Steve

I read a news release about 10 years ago from Goodyear stating that the problem of tread separation due to reverse rotation was completely solved. No longer were they recommending you keep them turning the same way. In fact they went as far as to suggest you start rotating them diagonally like was done with bias ply tires.
Of course you shouldn't run directional tires backwards due to the function of the tread pattern. But it wouldn't worry me one bit if my tires were run backwards for any amount of distance.

dvkk...It wouldnt worry you if you remounted and balanced and they had a shimmy after running them in reverse? What is your opinion on why the tires now have a shimmy?
Matthew

In this case I would be keeping a watchful eye on them. I can't explain why the car now has a shimmy, and it may be that tire replacement will cure it.

I remember overhearing a guy at an autocross event talking about purposly running his tires backwards. I checked his car and his directional tires were indeed all reversed. Don't know why he did this.

If the tire's old and has issues, replace it for that reason. But there is absolutely NOTHING damaging from running modern directional tires in either direction. Not sure I'd do it in a rainstorm, but that's another issue. Track guys do it all the time to equalize wear. I've done it with street tires after a track day to get rid of some of the built up rubber.

Anyone who says it can damage your tread or cause tread separation on an otherwise healthy modern tire, please provide evidence...

RallyJon,

HOW LONG have you driven the unidirectional tyres in the wrong direction? 200 miles? 500 miles? Non-stop? or is it more like 50?

I'm not suggesting that a few miles on an occasional basis will damage them, however we're talking at least 200 miles - likely many more. Your starting an apples to oranges comparison here...

I'm searching, I'll find you your evidence. In the meantime, all I can give you is my personal experience with an identical situation some 6 years ago on with a set of Dunlops on my GTO. Same situation, I bought the car, PO put the tires on 3000 miles prior, shimmied and shaked like a fly girl. Balanced, rotated, (completely mind you...) replaced suspension, even had the damn tires dismounted to look inside thinking there was something foreign (like water...) inside. It was then that we discovered that were mounted backwards. Bear in mind that these were NEW tires - PO gave me the paperwork, so last thing on the mind for failure. Got on the phone with the mfg, talked to a couple SAE friends of mine, and a college roomate engineering in product development for Goodyear, consensus was to replace the tires they were cooked from running backwards. Not one of them disagreed.

Can I PROVE that this was the problem? After spending the lucre on everything else suspension-wise, I wasn't about to send them off to a lab to have them cut up and analyzed, so no, I can't. Old tires - problem, New tires - no problem. Seems pretty clear cut to me.

I stand by my original response.

That's it then . . .I don't want to take any chances on reverse rotations. . . I'm having my reverse gear taken out.:rolleyes:

I completely agree with RallyJon. Consider the forces on a performance tire; braking, accelerating, cornnering, centrifical forces at 140mph . . .if a tire is going to hold up to those forces, tooling around with them on backwards is nothing.

fwiw, my old dunlops would induce a shimy on cold mornings, after the car sat for a while. (flat spots) They would go away when warmed up.

:D :D :D

You have one of those? I thought that's what a clutch was for... ;)

From Goodyear's web site:

My directional tires were mounted incorrectly and are rotating in the wrong direction. What should I do?


Tires with a "directional" tread design are intended to roll and perform in a given direction. The sidewall will have arrows indicating the rolling direction fo the tire. If installed in the wrong direction the tire will not perform its intended function. However, no damage or premature wear to the tire will result. The tire should be dismounted and remounted to roll in the proper direction.

Well ... radial tires can develop a tread "squirm", regardless of how or why it happened. It's pretty easy to see, find a clear area to drive the car (parking lot or such) have someone drive the car slowly toward and away from you, kneel down and watch the face of each tire, you can actually see the tread "squirm" on a "bad" tire as the tire rolls, if that's the problem. Back in the old days (when radials were a new thing) that's how I (we) diagnosed this problem, however, I haven't seen it for quite sometime (at least 20 years) given the newer, better, materials and manufacturing techniques.

Jerry M
'78 SC

I've been running race tires backwards for years. As a matter of fact, I always run on race tires backwards. Why? I'm too cheap to buy new track tires, so I get take-offs and have them mounted backwards to get more life out of them. Except for the old BFG R-1's, they were special.

Rob
1980sc

Installed my tires wrong
Felt a shimmy at high speeds
Balance did not fix

So you're saying running the tires backwards actually *adds* tread back to the tire? Cool!

I work in tire manufacturing. Most tires are produced with two belts, one on top of the other. Both belts will have and angle of about 25 degrees. The belt cords run in different directions so they cross each other. The rotatation of the tire will not affect the belt package.

High performance tires also have an overlay of nylon spiraled around the tire to keep the tire from "growing" at high speed. Ever seen a top fuel car tire grow as it accelerates? That is bad in a production car.

The tread pattern is what dictates the direction of the tire.

Wear could be affected. Wet weather traction will be worse if run backwards.

Other than that no harm.

As far as the shimmy. Since the tire is a directional tire the wear might be different than normal due to the directional tread pattern.

It could be a million things. Wheels, lug nuts too tight causing a wrap to the wheel, or even suspension problems.

Hope this helps