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Discussion Starter #1
I've got a really bad vibration from 50 MPH +. It gets a little better under braking, but not much better.

Please read what I've done.

1.) Wheels and tires are fine. They were checked twice.

2.) Rotors have been changed out. With new bearings.

3.) Stainless steel caliper sleeves didn't help. (thanks Wayne and Richard for the idea)

4.) Flaming river rack with bump steer kit.

5.) No rag joint.

6.) New ball joints top and bottom.

7.) New tie rod ends.

any ideas????
 

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FFCobra Fanatic
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381 Posts
I never had a vibration from the wheel bearings but do know that if they are making noise the noise will go away under braking. So maybe you have a wheel bearing vibration and that's why it gets better under braking? Just a thought.

Chad
 

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you checked the wheel balance? thats usually the problem. also check to see if the weighs have fallen off (although mine have before with little effect)

be sure to mark the wheel and tire after the mounting and balance. if they havent dried completely after the mount, they can rotate on the rim under braking (or accel).

-james
 

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Premium Member
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I too had a vibration above 50...

It took 4 trips to the tire shop for them to get the balance right.

Mike
 

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FFCobra Fanatic
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I have a shake at around 60, on mine. Have balanced the wheels a couple of times and it is still there.....

I suspect that my spinners on my wheels may have something to do with it.

Do you have the Halibrand type wheels?
Try driving it without the spinners on the front wheels & see if your shake goes away.
 

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Senior Charter Member
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226 Posts
Me too! I've had a front end shimmy also. I've had the front end aligned, wheels balanced twice. Never seems to improve. Very smooth up to about 50 or 55, but above that it's pretty anoying. Seems like it may be more common then any of us thought.

[ July 06, 2002, 05:12 PM: Message edited by: Barry N ]
 

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MotorCity Madman
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72 Posts
As odd as it sounds, I had this issue on my daily driver. After 2 balances and 1 alignment I still had speed shakes between 45 and 60. The rims where balanced on the outside before and I hate that.
I had them balance with the stick on weights in the inside of the rim both times and still the shake was there. On a suggestion from a co-worker I had them rebalance with the weights on the outside. No more shake. I can't imagine why it makes a difference, I have other cars that the rims are balanced on the inside. Why it made a difference in this case I don't know. Go Figure.

[ July 06, 2002, 06:32 PM: Message edited by: Carbon ]
 

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Discussion Starter #10
Hum, seems like a common problem. Could it be the lower control arm bushings? I have new a-arms, but I hear that Ford had a problem on some Mustangs.
 

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MotorCity Madman
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72 Posts
What kind of tire wear do you have? are the inside blocks wearing high/low? Speed shakes are a result of something out of balance. bad tire, rim, bearings loose, or balance. It seems you have eliminated a few of these already.
Did this just start? If so it may be tire related.
What parts of the equation were changed prior to this starting? A trip to the track perhaps?
I don't think control arms bushings would cause such a repeatable (only at 50mph) shake condition.

BTW, the site looks great. keep up the good work..
 

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FFCobra Craftsman
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1,067 Posts
Bill,
If you can, put a different pair of wheels/tires on the front, even if you have to barrow a pair from a buddy. If the problem is gone you know it's your wheels/tires. Every now and then you'll get a tire that just isn't round. No amount of balancing will solve the problem.

Greg
 

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i checked my wheels and tires for radial and lateral runout... but it turned out to be my tires.

-james
 

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Glad you got it fixed. Just wanted to add that water in the tire can cause it too.

Sean
 

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IF YOU are using the rubber bushings in the front rack.. did you put the pipe spacer inside the rubber bushing...if you are using the aluminum offset bushing this can't be the problem...
 

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There are 2 settings on most tire shop balance machines:
1. Static- This balances the up and down force of the tire and one weight is used (inside or outside or stick on in center) This is the setting most shops would use to balance if you do not want weights on the outside.

2. Dynamic or normal (default on most machines) This is both the up and down force (radial) and side to side force (dynamic) This is balanced by weights on the outside and inside offsetting the radial and dynamic unbalance of the tire/wheel combo. This is the best type of balance short of balancing on the car. You can do this without putting weights on the outside, but will require some trial and error and effort by the technician. Put stick on weights inside the wheel as far to the outside as you can get for the outside weight. This will be slightly more weight than the readout shows because the position is inside and at a smaller diameter than the machine expects. After the outside reading is zeroed, put weight on the inside as normal to zero the balance there. I spent many years doing this, so I know it works with wheels with a deep inside like the Mustang and Cobra wheels.

Find a good tire shop and make friends there.

Of course no amount of balancing will cure a vibration from an out of round tire.

Good luck.
 

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Discussion Starter #17
Thanks everyone. I'll keep trying. I have tried another set of wheels. I have Cobra-R's with Kuhmos and it still does it. This is nothing new, it's always been here. All new parts! Aluminum bushing in the steering rack.
 

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I had the same problem with 2 sets of wheels and tires, which made me think it was something else for a long time. It turned out that the front wheels were out of balance on one set and the back wheels were out of balance on the other set, but the wobble felt the same.
 

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FFCobra Craftsman
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1,333 Posts
Bill -

I had a similar problem like this on my BMW 540 with 18" wheels and aftermarket suspension and brakes. Did all the things you have; turns out my wheels were very slightly out of round. I needed to get the tires shaved every 4-5K miles.

I had them checked for lateral runout, but that was OK. Turns out the bolt centers were very slightly off. After slight shaving, everything would be OK for 2-3K miles then it came back. Three tire shops never found it, a race shop I work with finally checked and figured it out. The error is less than 0.1" but multiplies with tire wear.

The wheels are in a box in my sideyard now!

Worth looking into.
 

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Same problem here. I've found the Radial T/A's to have a bunch of runout. So much that you can plainly see it with the naked eye if you jack the car up and spin the tire.
 
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