Steering wheel shaking >60mph after new wheels

[romster]

Hello all,

I have just gotten some modifications done to my 1985 carrera. I've had 16in Maxilite fuchs installed all around, 7j front and 8j rear. The fronts are on SportContacts 205/55 and the rears are on 225/50 Exaltos. Previously, I was running 6j fronts and 8j rears from factory, same tyre dimensions but all SportContacts (during the swap one rear SportContact tyre was accidently slashed, hence the new Exaltos)

Now, at highway speeds, the steering wheel starts shaking somewhat violently from left to right, about 1inch left to right at a frequency of twice per second, at the position of my hands. It gets more intense the faster the speed (50-70mph).

I'm getting it back to the shop tomorrow, but would be curious if anyone has any pointers or things to look at. I was thinking it needs realignment, but after searching a bit I hear it shouldn't really be necessary. I'm assuming the balancing was done well. Tyre pressures were rather high at first, but after lowering them to factory spec I saw no change. I would not suspect bearings or suspension to be the culprit, that would be very coincidental.

[ChrisHamilton]

Wheel balance. Someone either didn't do a good job, didn't know how to do it, or forgot to balance a wheel. I would go to a different place than where you took it to have your wheels changed.

[romster]

Originally Posted by ChrisHamilton

Wheel balance. Someone either didn't do a good job, didn't know how to do it, or forgot to balance a wheel. I would go to a different place than where you took it to have your wheels changed.

Thanks. On a level of 1 to 10, how certain would you be? Car itself doesn't feel shaky, it's just the wheel. If we can't find anything tomorrow and you're very certain, then I'll get it done tomorrow right after I leave the shop.

[Jonny042]

Wheel balance.

You wouldn't think it would be complicated, but it seems to be a challenge.

A good tip is to mark with sharpie the location of whatever wheel weights they stick on, and make sure the wheels are clean enough such that they will stick, and stay stuck.

It really sucks when you pick up a fresh set of wheels and tires from the tire shop, throw them in the back of the truck, and find a loose wheel weight in the bed when you get home.

[bkreigsr]

I think your answer is in your first paragraph.

Porsche recommends that all four tires match - not in size, but the manufacturer and tire model.

Tire construction varies greatly among manufacturers.
Your harmonic imbalance could be the result of this.

And, yes, a dynamic balance seems in order.

[phelix]

New wheels can look clean but still have wax or other coatings on them; if someone just slaps weights on without cleaning the mounting surface with a good solvent they can quickly fall off. I had exactly this happen a few weeks ago.

Also worth checking the clearance between the wheels and the calipers - some are very tight and the caliper can sort of scrape the weights off.

[Discseven]

I've run different brand tires front and rear. Never an issue. Will credit that to the person aligning and then balancing the wheels. Some shops know how to do this with precision----others don't. When steering parts are in good form and this work is done correctly, there should be zero vibration of the s-wheel. You might want to post asking for recommendations for a qualified balance & alignment shop in your area. I've heard worn ball joints can cause steering vibrations but don't know this first hand. Wheels should be checked for being perfectly round. Knew a fellow with a 356 who got new wheels and no one could set the car up so it wouldn't vibrate. Eventually someone who knew their chit found the problem. 2 of the 4 NEW wheels were out of round.
.

[romster]

Originally Posted by bkreigsr

I think your answer is in your first paragraph.

Porsche recommends that all four tires match - not in size, but the manufacturer and tire model.

Tire construction varies greatly among manufacturers.
Your harmonic imbalance could be the result of this.

And, yes, a dynamic balance seems in order.

To clarify, all 4 wheels were replaced. I got new 8j's on the rear to replace the factory 8j's.

[romster]

Originally Posted by phelix

New wheels can look clean but still have wax or other coatings on them; if someone just slaps weights on without cleaning the mounting surface with a good solvent they can quickly fall off. I had exactly this happen a few weeks ago.

Also worth checking the clearance between the wheels and the calipers - some are very tight and the caliper can sort of scrape the weights off.

Thanks. They were all painted (full black including rim, front and back) and coated before balancing, so this could be the case, will look tomorrow.

[GH85Carrera]

Wheel balance.

Find a place that does "road force" balance, and a guy that is not a beginner. My 911 had a shake until I found a road force balance.

[shoooo32]

Just for grins, double check for bearing play by pull/pushing on the top of the tire. I thought I threw a weight once and it turned out to be excessive play in the bearing. 10 minutes (in the valet spot at a fancy hotel in Denver!) I had it adjusted and the vibration disappeared.

[phelix]

IMHO just start with simple rebalancing. Odds are high a weight has come off.

[2.7RS]

Put old wheels drive 60 mph and report back.

[romster]

Update. No signs of weights having flown of, no play in wheel mounts or bearings either. Could be tyres were balanced wrongly, will check tomorrow and re balance if needed. Strange stuff.

Any pointers as to what it could be if balance and alignment all checks out?

[phelix]

If you hear hoofbeats don't start looking for zebras.

[jpnovak]

Check wheel bearing play.

What kind of struts do you have? Common for Bilstein to have wear in the internal strut guide bushings. This causes play between the strut housing and damper. Can be hard to determine for someone not looking. it can also show up after a service where the front suspension is in full droop and then recompressed.

[romster]

I'm seeing now that the new 7js up front have a different offset than the stock 6s that were on there previously, 23.3 vs the original 36. Could this be a reason for it? I mentioned realignment should not be necessary, but going from 16x6 with 36 to 16x7 with 23.3... thoughts?

Originally Posted by jpnovak

Check wheel bearing play.

What kind of struts do you have? Common for Bilstein to have wear in the internal strut guide bushings. This causes play between the strut housing and damper. Can be hard to determine for someone not looking. it can also show up after a service where the front suspension is in full droop and then recompressed.

The previous owner put in new Boges (170 147) in 2009. Good call on the suspension. I'll keep it in mind as a potential issue. Would there be easy symptoms that are observable in the garage (and not at 60mph on the highway)?

[romster]

Second update. Wheels rebalanced, pretty much gone at 50, but anywhere above 60, though it's less, is still not at all correct. Hope to bring it in for a realignment tomorrow or Friday to see if that'll fix it. Still heavily leaning towards it being the new wheels, but perhaps it's a blind spot and I'm wasting all of this effort while it's just a (highly) coincidental steering column or suspension thing. At least that's something they will all be able to check.

[phelix]

Are you using the factory alloy wheel nuts?

Are you able to try the old wheels to see if the issue is caused by the new wheels?

[manbridge 74]

We road force balance every wheel. That said, I have seen excessive run-out in even new wheels. Do fronts spin evenly while looking at the wheel rim edge?

Might PM used Fixer here. He is a distributor for these in USA.