Do your front wheels shake?

[motion]

I've tried everything to get mine to stop. Every time I replace tires, I take it to a place that does the on-car balance. It usually takes a couple of times to get it half way right. Even then, it still shakes at various speeds and times. In the 40,000 miles I've put on the car, I've never had it be perfect.

What are your experiences with this? And, how important is it to have the valve stem mounted at the red stud position? (I'm going to give that a try this weekend).

[rickeolis]

It could really only be a couple things, other than loose parts on the car: Wheel balance or alignment.

[Jdub]

Do you clean your wheels thoroughly before mounting the new tires? there might be some crud on the inside rim keeping you from getting a nice balance. You might also consider having the wheels themselves checked for out of round and balance.

John

[pbs911]

Are you using spacers? Are they hub eccentric? Try taking the spacers off and drving, if you can.

[motion]

Wheels are spotless. No spacers. The balance guy balances them perfectly according to the machine. Then they shake while driving. What would alignment have to do with it?

[boyo]

Do you have the balancing done early in the morning?

Soft compound tires?

It may sound weird, but on my Boxster I'd always get front wheel shake in the AM, but not after it had warmed up. I guess from sitting overnight with the weight on one spot, as soon as they warmed up it was a smooth ride. Just a slight deformation in the tire due to the cold.

Problem was lessened by a switch from Pirellis to Yokos.

-Boyo

[Don Plumley]

Yeah - mine does this as well, most noticeable over 70mph. Just a little shake in the wheel. But it did not always - I'm guessing it has something to do with alignment as I was monkeying around with the ride height adjustment bolts - so I am assuming that a corner balance and alignment is necessary...

Don

[robtoyz]

Check your rims, could be out of round or put other rims, if the wheel shake dissappear you found the problem.

[rickeolis]

If the 2 front (back too) tires don't run perfectly parallel to each other, they will tend to hop around at higher speeds. \ / as opposed to | |

[stormcrow]

Could be your steering rack may be loose. Had a TR-7 with rack and pinion steering and problem was worn bushings.

Steve

[Superman]

True, the steering mechanism (tie rods, steering rack) must be tight, otherwise the wheels can wobble. Also, if a wheel is bent then balancing will not eliminate the shaking.

I personally don't think the folks that operate those balancing machines know what they're doing, by and large. Yes, they can follow the instructions in the book that came with the machine, but the old grey-haired guys with a floor jack and a pair of pliers can balance wheels better than the young guys with the fancy computerized machines.

[turbo dave]

I had a worn steering shaft bearing and original front bushings & tie rods (on a '73), just replaced them with polyurethane front bushings, new steering shaft bushing, and turbo tie rods. The vibration used to be mild on normal driving, terrible under hard braking. Front end vibration gone! Not to mention much tighter handling & turn in. Very happy with the mods, and I haven't even done a new alignment & corner balance yet!

[LeeH]

Hunter, the company that seem to have a hold on balancing equipment, makes a machine that gives each tire a "road test" by applying a rolling sensor to the tire while it's on the machine.

You can locate one of these from Hunter's web site.

Click on "wheel balancers" on the left hand column.

[Eric Coffey]

Motion-

I think you are on the right track about the valve stem/red stud thing. You want to make sure the valve stems are aligned with the red-dot studs. After doing my brakes a while back, I noticed the same (slight vibration) symptoms on the first outing. It turned out I put one of the front wheels on with the valve stem opposite the red stud. After putting the wheel back to it's correct alignment, the problem went away. If that doesn't do it, then there are plenty of things to check:

front alignment (camber/caster/toe).
shocks.
steering rack.
hubs (warping from over-tightening wheels).
tie rods.
ball joints.
suspension bushings.
out-of-round wheels.
etc., etc., etc...

[T Bird]

Motion
I was recently advised by a reputable mechanic that tire balancing machines generally have an adjustable tolerance. In other words, the shop doing the balance can set the machine so that it shows that a tire is balanced even if it really isn't perfectly balanced. The theory here is that for 99% of the universe of tires, a tire balanced to within, for example, 1/2 ounce, is "good enough." In your case, what's good enough for a soccer mom in a Dodge Caravan may not be good enough for you.

You may want to ask the shop to set their balancing machine up so that there is no tolerance. This way, you get a perfectly balanced tire. If they are unwilling to do it because it will take more time to get the tire balanced, go somewhere else.

[Nickshu]

Find a shop with the Hunter GSP 9700 Vibration Control System.

Hunter's website has a thing where you can type in your zip and it will tell you where one is near you. www.hunter.com

As LeeH said above, this is a super-cool setup that allows the wheel to be balanced while simulating road force against the tire. They remove the tire, balance the rim itself and then reinstall the tire "indexed" (tires are marked by the mfgr with heavy and light sides) to the rim's balance and then balance the whole thing together with the simulated road force.

Worked for me on a non-porsche that I had the same problem---I chased a vibration for a year until the Hunter balance cured it. $25 a wheel, but it worked. Sounds like you've ruled out other issues....wheel bearings, brakes, alignment (unlikely), etc?

Nick.

I know this will sound stupid, but check if your tires are round. My brand new SP9000 weren't at the front and had to be shaved. That and balancing the wheels on the car solved my shaking problems.

I still have problems with flat spots in the morning when the car has been standing overnight. Goes away after 10-15 minuttes of driving.

[motion]

OK, I just put the 7" and 9" Cup 2 Mille Miglias from my project car on. Took care of the shake! So the problem is evidently out of round wheel(s). This makes sense, since it has been a constant problem, through various alignments and tire replacements.

Just as a note, the PZeros on the new wheels feel *dramatically* different than the Dunlop 8000s on the Fuchs. They are much harder and transfer more road feel to the steering wheel. Much harder to turn the wheel as well. The switch to 17" wheels definitely affected my acceleration as well. I've driven for about 10 miles and already had a front fender rub on the tire. The fenders looked like they had been previously bent and cut for the Fuchs 7s and 8s, but I'll have to go in and roll a little more. Should only need a 1/4" or so.

[dhaines]

I still would not rule out that the tires are not round. They can be in balance but still be out of round. My friend with at 944 just went through this. Take them to a "good" tire shop and have them checked out. Tire or rim a good shop should catch it....

[JMPRO]

I would have the wheels and tires balanced on the car and indexed with a mark to the hub and roter. That is the only way i could find balancing bliss w/ my car. Like you all was fine untill i fiddeled w/ the ride higth and created an alignment problem then the shaking started again. Now its new tires, alignment and on the car balancing again.
I just saw a new product called " Equal" thats supposed to end you balancing problems forever. It is a granular substance that is put inside the tire and seeks out the imbalance and deposits itself at the right place to correct it.I have nothing to do w/this product and don't know how it works but its an interesting idea.
Jerry, no pimping going on here........