Sentosa

Do you have lock nuts on each wheel. Sometimes they weigh more than the actual nuts. This happened on my BMW several years ago and removing the lock nuts fixed the wheel balance problem.

C300Kid

Update..

So I put this issue aside for a bit because I've been too busy to worry about it. Tonight I pulled the receipt out from Tire Place #2..the one that was supposed to have done a road force balance on a Hunter GSP9700 machine. The receipt lists "spin balance" as the work that was done, and they charged me only $40. Should I assume that they did not do a road force balance considering the low price I was charged? I'd also assume they'd list "road force balance" rather than "spin balance" on the receipt, but I could be wrong.

Anyway, I'm gonna take it back and see what they say. If they didn't do the road force balancing I'm gonna ask them to do it and only charge me whatever it cost over and above the $40 they charged me already, since I specifically asked for it from the beginning. I'm thinking it was somehow lost in translation however.

C300Kid

I don't think I have locking lug nuts but I'm not sure.

C300Kid

Nah, it occurs randomly. It seems to be more related to road surface rather than speed.

JimPap

Just thinking outside the box, if it seems more related to road surface than speed, is it the exposed aggregate type of road surface where its more likely to show up? If not, what kind?

Are you hearing any noise from the front end that might be a front wheel bearing? Any changes in brakes? Checked shocks/springs/engine mounts.

Glyn M Ruck

Absolutely - rotate the bad tyre on the rim - reinflate & balance. Where is the valve balance dot on that tyre compared with the others? If this does not work toss the tyre.

Finish balance the wheels on the car. Most aftermarket wheels have a 66.6mm bore. This can cause trouble. Also remember you have increased the scrub radius on the front of that car which will amplify these problems.

C300Kid

There is no bad tire though, The only reason I thought so was because one wheel had 14 weights on it. I looked again and they're only 1/4 ounce per weight so 14 weights is only 3.5 ounces. That's pretty normal.

C300Kid

Thinking about it more..im not sure it has to do with the kind of road im on. I mean, i'll be driving 75mph with cruise control on and it'll be silky smooth then randomly start vibrating..no change in road, no change in speed, no change in anything.

Sometimes it'll vibrate for 35 seconds and get smooth again, other times it'll vibrate the remainder of my trip.

I'm not hearing any noises but I also haven't had any of the above checked. I just assumed since it started the day I got new wheels/tires it has to be that.

I mean, I guess it's possible im just feeling amplified road feel as a result of my new tires being high performance..I can't imagine it's normal for the steering wheel to shimmy though like it does. I still think it's a balance problem.

Glyn M Ruck

People can only respond to what you tell them. You might even have a minor (at present) delamination taking place on one tyre.

You need to go through this methodically. I would start with front wheels off on a balancer & check for horizontal & radial runout on the tyres AND rims & work from there.

Try putting your 17" wheels back on the front & make sure the problem goes away. I'm pretty sure it will but check. One thing ticked off the list.

JimPap

What a mystery.

You wouldn't have one of those code checker to see if its something with the engine?

C300Kid

The problem is my old wheels don't have tires on them now bc they had to be dismounted to remove the tpms..so I'd have to have to pay another $100 to have them remounted and rebalanced to find out something I'm already 90% sure of.

I think my best bet is to bring it back to tire shop 2 and have them do a road force balance. If this doesn't solve it..bring it to my MB dealer and let them figure it out.

Glyn M Ruck

Fine - let them check the balance but check run out of rim & tyre at the same time. This has to be a starting point.

Benz is likely to tell you to return the car to standard.

Glyn M Ruck

An OBDII/CAN scanner is of no use for this.

JimPap

Unless its the engine that's shaking causing the same sensation.

I'm definately not an expert in this area but it seems to me that if he held the car at 75mph via cruse control and it would on its own start shaking, then maybe its not the tires at all. Therefore, the code checker.

C300Kid

Hmm..I never even considered this. What's funny is the car used to start really rough. Like..when Id start it, it'd sound and feel like a tractor motor for a couple seconds..then smooth out. I seems to have stopped doing this, but oddly the rough starts stopped around the same time the vibrations started.

Also, thinking back..when I got the wheels balanced at the second shop, the car drove flawlessly for almost a week..then the vibrations started.

Maybe it IS engine related and it's just a fluke that it happened when I got new wheels.

There's so many things this could be..

C300Kid

Then again..I only really notice the steering wheel shaking..if it were the engine I'd think it'd be the car.

Glyn M Ruck

The engine can't cause steering wheel shake.

C300Kid

That's what I figured. Thanks for all the info btw..I really appreciate it.

Doanster

Even though the spare is not the same rolling diameter as your 18" setup, swapping it in should allow you to at least narrow it down to the specific wheel/tire combo that's causing your vibration. My bet has always been on a bent/non-true wheel...

ps You've checked all the bolts to make sure they're torqued down, right?

C300Kid

They can't determine if there's a bent wheel with the road force test?

Doanster

They should be able to, but what if it's not grossly bent? Wheels that are not bent, but rather non-true can still be balanced via stick on weights, but if you hit that certain frequency, you'll get vibrations.
The spare tire (or borrow someone else's MB wheel/tire) is a sure way to narrow down which corner is causing you your problems. The rest is just leaving you with more questions and possible culprits. Start with a baseline and check things off one by one. Your dealer isn't going to give you the time of day unless you're going to pay for every second of labor they spend trying to diagnose the problem. First thing they'll say is: "You're running an aftermarket wheel, one that we didn't install."

C300Kid

good to know..thanks for the info everyone. honestly i have no idea how to change the wheels out with the spare but i'll see if one of my friends can help.

Glyn M Ruck

Once the wheel is on a Roadforce balancer - all you have to do is spin it slowly by hand with a reference point to check for wheel and tyre run out both laterally and radially if it's not obvious to the eye. If you want to get sophisticated about it you can use a dial gauge.

While rotating slowly first check against the side of the rim at the tyre bead if the rim deflects from side to side (bent) or up & down (out of round) Then do the same thing with the sidewall of the tyre - does it deflect from side to side & finally the tread - does it deflect up & down while rotating which means it's out of round & needs to be ground round or replaced.

This is really very simple - In racing I've done it 1000s of times.

Checking for delamination in the tyre is a little more difficult. You need to look for a bump in the sidewall or tread where air has entered between the construction layers of the tyre.

Good luck

JimPap

Thought I'd read up on the Roadforce balancer.

Anyone else interested, go here http://www.gsp9700.com/pub/features/how.cfm

Glyn M Ruck

Roadforce balancing is excellent but it can't do what a finish balance with the wheels mounted can.