Jump to content
HybridZ

Shimmy, not wheel balance.


Recommended Posts

I put the Sportmax wheels on my car with new BFG Comp T/A KD tires on it over a year ago. They were mounted and balanced by a local shop I trust. They were silky smooth for about 10K miles. Little by little I began to get a bit of steering wheel shake on the highway. I rotated the tires front to back this Winter but I still have the shakes up front. It now starts very lightly at about 40mph and increases in frequency and intensity as speed climbs. Around highway curves with medium and high G loads, the vibration pretty much goes away and comes back on the straights.

 

I just brought the car to the same guy that mounted them and he said they were still all balanced. He only added a tiny bit of weight to one of the rear wheels which made no difference to me. He also inspected the tires and wheels for bubbles or visible runout but didn't notice any.

 

My brake rotors are new and dead straight. I have a whole thread about making them perfect with a dial indicator.

 

My only ideas are to add some negative toe up front. I run 0 toe right now. I also want to run a dial indicator on all of the rims for runout.

 

I am also going to check wheel bearing play and for any play in the front end.

 

Any other ideas?

Link to comment
Share on other sites

The inner tie rods are actually spring loaded. I took mine apart a couple of years ago because there was some play in one of them. I can't remember exactly how I did it, but I increased the preload inside the inner joint a little. You may be right that it's time to replace them. I will check them tonight.

Link to comment
Share on other sites

I hope so. He did a great balance job when he mounted the tires. I will check to make sure. He does use a pretty sophisticated looking balance machine. FWIW.

The best machines still have the button that changes them to a static balance. People like static balance for looks, and you'd be surprised how many tire shop guys don't know the difference.

Link to comment
Share on other sites

I specifically told him that I want stick-on weights anywhere they need to be, inside or on the outside of the rim. Besides, there are already weights stuck on the outside from when he mounted the tires. You never know though...it was St. Pat's day.

Link to comment
Share on other sites

Has the car sat any lenght of time to flat spot the tires??? Did the tire machine have a ROAD FORCE feature?? It's a drum that contacts the thread and rotates. It measures sidewall stifness,tire and or wheel runout etc......I've seen brand new tires with high road force that you could never get the shimmy out. index_gsp9700_1.jpg

Link to comment
Share on other sites

Nope I don't think his machine is that high tech. The car sat on jackstands all winter this time and the tires were new last Spring. They might need a good heat cycle in them but I think they are pretty round.

 

I jacked up the front tonight and felt a hair of play in the front wheel bearings, so I added some more preload to them. Then I added about 1/16" of toe in. I also brought the air pressure from 28 to 34psi. When I took it back out for a drive, there was no vibration at 40. At 60, I could barely feel it and at 80 it was better than it was at 60 before. I think it's partially due to slightly off tires, and it was being amplified by the loose front bearings. It's not completely gone but it's better.

 

Maybe I need to drive it some more to get the tires softened up and then allow them to cool while driving. Otherwise, I'll try to find somewhere that has the fancy balancer like the one above.

Link to comment
Share on other sites

Nope I don't think his machine is that high tech. The car sat on jackstands all winter this time and the tires were new last Spring. They might need a good heat cycle in them but I think they are pretty round.

 

I jacked up the front tonight and felt a hair of play in the front wheel bearings, so I added some more preload to them. Then I added about 1/16" of toe in. I also brought the air pressure from 28 to 34psi. When I took it back out for a drive, there was no vibration at 40. At 60, I could barely feel it and at 80 it was better than it was at 60 before. I think it's partially due to slightly off tires, and it was being amplified by the loose front bearings. It's not completely gone but it's better.

 

Maybe I need to drive it some more to get the tires softened up and then allow them to cool while driving. Otherwise, I'll try to find somewhere that has the fancy balancer like the one above.

First check the tires on the vehicle for runout. Out of round tires will yield what you are encountering. Then follow the advise on Road Force and Dynamic Balancing and do it in the order spelled out here. Zero toe-in should make no difference unless there are really loose steering components.

Link to comment
Share on other sites

Hey Dave,

Since we're fellow alumni........We have 2 of those new fangled machines at work. I don't mind helping you out. Wheels off the car. (New stricter rules at work) We could do 2 a day if you can't transport 4 at once. I'm in Mahwah,.you're in suffern....Tommy

Link to comment
Share on other sites

Yeah same High School and same College just about 9 years apart! Let me put the car on jackstands next week and I'll set up a date with you and the tire machines. I can carry all four in my WRX or the minivan. Thanks.

 

I like to run zero toe. It gives a really nice turn-in without too much tramming on the uneven roads. Toe-in is stable but turns-in slower.

Link to comment
Share on other sites

I have a shimmy from a bent inner tie rod...its pretty bad though. Anyway I just ordered a set from rock auto.... 9.99 each. Hope they are the right ones!

Let us know if they are the correct parts!!!!

 

FYI,..Bent steering/suspension components do not normaly cause a vibration/shimmy.

Link to comment
Share on other sites

I would check the outer race on the outer front wheel bearings. I had one go bad, slop and it caused me to have a shimmy starting at 35 mph. The z dealer many years ago missed it and replaced the whole strut and that did not work. I finally found it by accident when checking the bearings.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...