the blur

My truck developed a shimmy in the steering wheel at 40 mph. very pronounced. Found a 1" drywall screw in the front tire. nothing big, just a standard drywall screw. went to tire shop, patched tire from inside, and I watched him balance it perfectly. This shop does all my race tire work, and I know all the guys, and they know how to repair tires. It was patched from the inside with a patch/plug that pulls through. I would go 100mph on this patch no problem.

drive truck home, same shimmy at 40 mph !!
went back to tire shop, rebalance all 4 tires, all balance perfect. 0/0 on re-check.
still have same shimmy at 40mph, and this is after I watch them balance all 4 tires perfectly. so now I have 4 balanced tires with a nasty shimmy.

So I decide to rotate repaired tire to the rear, SHIMMY GONE !!
So the cause of the shimmy was the tire with the drywall screw that got repaired properly.

so my guess is the 1" dry wall screw cut a steel belt inside the tire. (even though it balanced ok)
and it caused a shimmy. is this possible?
what else could have happened ?????
I'm still running the tire, but it is on the rear, where I can't feel it.
This is my 1500 series tow vehicle with goodyear oem "P" tires.

I just can't believe that a small puncture destorys the intergrity of a tire. any other ideas ??

C6400hp

The shops balancer has not been calibrated recently.

bobmoore2

It is possible the screw was in the tire long before the shimmy started happening. You could have hit something that bent the wheel or weakened a part of the tire, and when you looked at the tire you noticed a screw that had been there for some time before. In other words, the screw in the tire was not the root cause of the shimmy.

It sounds like you are experiencing what is called a "radial force variation". Basically that means that as your tire and wheel rotate through one circumference, the force applied to the pavement varies significantly enough that it is easily felt through the steering wheel. The tire & wheel are moving slightly up & down or side-to-side as it rotates.

Your tire & wheel could be in perfect balance, and still be out of round. Or the rim of the wheel could be bent slightly to the side in one place. Ask the shop to do a runout check on the wheel.

Or it could even be perfectly balanced and perfectly round, but have a spot in the circumference of the tire that is significantly harder or softer. As the tire rolls around, that one spot pushes against the pavement more or less than the rest, which makes the wheel move up and down slightly. To diagnose this problem the tire shop needs to use a machine that presses a big roller against the tire while it spins the tire. Not many tire shops have this machine.

Bob

varkwso

Go to a tire place that still shaves mounted (not new tires). My guess is a tire is slightly out of round. Really noticeable on truck tires and Corvettes at 140 mph.

We only have one place locally that will shave tires on the car. They helped me out with my Suburban with brand new Goodyears and several I have flatspotted at the track on my Vettes or Porsche.

Cobra4B

Find a shop w/ a road force balancer (fancy roller thing).

UstaB-GS549

Jack wheel off ground. Put a fixed object next to tire (toolbox or hold a pencil if you have a steady hand). Spin tire by hand and watch for run-out. If it is the tire, you should be able to see either side to side runout or O.D. run-out.

You can check the rim the same way. The damage should be obvious if anything significant is there.

davidfarmer

did the tire run low for very long? I've had tires get carcass damage that vas virtually invisible due to running severely underinflated.

the blur

the tire was never ran under 25psi. and even so, not for very long at all. GMC specs 30psi. So I don't think that is it.

I went as far as flipping the tire inside out on the same rim, and the shimmy is still there. So something failed that is causing an imbalance.

The solution is the tire is on the rear, and the truck rides fine.

I don't know enough about tire construction, but I wonder if there are laminated layers, or steel belts that make up the tire, and could they be so easily damaged?

But I can't just imagine a little screw can cause so much damage.

gonzalezfj

Ask any girl... she'll tell you.

Frank Gonzalez

Westwopper

Run a strip of duct tape around the tire... get a dial indicator and stand from harbor frieght... $22. Check run out... Should be less than .060 on a commercial truck... I assume less than that will work on your 1/2 Ton as well. Was the hole bigger than 1/4 inch? If the tire had a nail in it for a long time, it is possible that the 25 psi that you ran it at and the screw moving around cause some separation in that area. The only way to be completely sure about that is to double check the repair or send the tire to your local retread shop and have them run it through Sherography.

C6400hp

Have a different shop rebalance the wheel.

petefias

You identified the source of the shimmy. Now, do something about it: buy a new tire.

Kinkajou

Even if the wheel is perfectly balanced you can have a problem when the tire and wheel rotates loaded because the cords in the tire can separate a little while rotating giving just a little bit of inestability to the wheel / tire.

TedDBere

FRANK!!!