chaadster

This past Monday I made the 500+ round trip to Chicago (7hrs door-to-door-to-door; not bad, eh?) and noticed I was getting a bit of general vibration at speeds beyond 80mph, more or less consistently.

Last night, Bigmac was telling me how happy he was with his Road Force balance and new alignment job, about how they smoothed things right out and reduced front end hunting.

I'd had the Road Force thing done Spring '07, but figured that I might as well have it rebalanced.

Well, I just got home from a few miles of runnin' at triple digit speeds (on my friendly, neighborhood private road course, of course!), and can report that the Road Force balancing did the job for me, too.

I guess that while I can understand how roads--especially crappy MI ones-- can bang wheels outta true, I'm a bit surprised to be noticing the difference so quickly and clearly.

So...how often do you balance check your wheels?

hacker-pschorr

There was a discussion about this in the racing forum a few months ago. I know we are not talking about the track, but they only balance the wheel, without the tire installed.

Tim Murphy did a test on his car, under hard take-off's he was rotating the tire about 90 degrees on the wheel.

To answer your question: I balance my wheels / tires whenever I put new ones on.

ErnestSw

AHAH!! It never occurred to me that the tires would rotate on the wheels, but it makes sense when you consider the forces.

chaadster

Hmmm...yeah, that's interesting Hacker. I never considered that the tire would slip on the wheel either. Do you think that's a phenomenon limited to cars with the power of a Murph Supershark, or do you think most NA 928s have the power to do that?

perrys4

Wouldn't the simple wear of the tire cause the need for rebalancing every so often? Mine did the same thing on my trip to the SD GTG. Over 80 I was getting vibration. I attributed some of it to my worn motor mounts but I think a rebalance would help.

IcemanG17

With my stock 16" wheels-tires I noticed vibrations at certain speeds....once I put the new 18" CIII's on that were road force balanced....its smooth as glass

bd0nalds0n

I would think a bad alignment would exacerbate things, esp. if you've got a toe problem causing inner wear--you'd expect the tire to come out of balance pretty quick.

Not many people seem to do it any more, for cosmetic reasons I guess, but a tire balanced on two planes (with weights put at the correct places on the inner and outer part of the wheel) will exhibit less hop and wobble, whereas you might not get the same level of precision with just one weight placed on the inner part of the rim.

I pretty much only have them balanced with a new tire, but Discount Tire will rebalance them for free as part of their mount/lifetime balance price.

bigmac

Interesting the fronts on my car were on Andrew's car and I am sure he had them road force balanced but they were 2 & 4 pounds out at my rebalance.
On my Audi with 17" PZ Neros dynamically balanced by a good local shop, one way 40 pounds off at dynamic balance. Mac

bigmac

Interesting the fronts on my car were on Andrew's car and I am sure he had them road force balanced but they were 2 & 4 pounds out at my rebalance.
On my Audi with 17" PZ Neros dynamically balanced by a good local shop, one was 40 pounds off at dynamic balance. Mac

dr bob

Brian--

You can work with your tire installer to get the right settings into the balancing machine for weights inside of the spokes, while maintaining the benefits of dynamic balancing over static.

---

The WSM has a whole section on balancing that's a pretty interesting read. I stumbled on it (again) while researching some alignment and front suspension stuff. In that section, they talk about using the correct "tire paste" when mounting, and recommend that there be no hard driving for the first few hundred miles. I'll speculate that it's to allow the paste to cure and help hold the tire correctly on the wheel. Tire shops seem more inclined to use a rubber lubricant to assist mounting. Except on race tires, I've never seen "tire paste" used.

They also discuss the issue of the tire moving on the rim. More than a small amount, IIRC on the order of 3/8" or so, deserves an bead break and remount in the correct orientation. For those launching hard and spinning the tire in the rim by 90 degrees, you may want to buy a tire machine to use after each g-tech test run.


When doing a luxury-car balancing job, the first step is a wheel balance with no tire mounted. Find the heavy spot and mark it on the weel.. Take the opportunity to verify runout at the same time, and toss the rims that are out of spec. Then the tire goes on, and an initial reading is taken to discover the heavy point on the tire. Rotate the tire on the rim to have the two heavy points opposite each other. Only then do you start to add balancing weight to correct the net imbalance.

In the wayback days, final balancing could be done on the car to offset imbalance in rotors. I suspect that the Porsche factory did that on the cars before they left for the dealers; This drove the need to put an indexing mark on one stud to make sure that the factory balance was maintained following service by a dealer. That mark means nothing of course if the tire/wheel assembly is not balanced on the car, but it does give us something to discuss and beat up.

The WSM further details that the hub needs to be at a specific clock poistion when the wheel is hung on it, again to help maintain some consistency when chasing vibration issues. Does it make a difference for us mere mortals? I hope not, cuz I have been less than diligent about rotor position with the red stud up when I pop the wheels on and off. From now on though...

AO

That usually only happens on freshly mounted tires. That's why you shouldn't do burnouts on them until the bead has had a chance to "set."

justin

V2Rocket

That's also why many race cars have screwed-on tires