Slight shimmy under braking at 60 mph
12-24-2002, 11:52 AM
#1
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Join Date: Nov 2002
Location: Oregon
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Slight shimmy under braking at 60 mph
Recently noticed a slight instability (steering wheel shakes a little) when moderately braking from around 50-60 mph.
No shimmy when braking really hard or braking at slower speeds.
The pads themselves look OK... front rotors are grooved (but they have been grooved since day one).
Any suggestions please?
No shimmy when braking really hard or braking at slower speeds.
The pads themselves look OK... front rotors are grooved (but they have been grooved since day one).
Any suggestions please?
12-26-2002, 12:02 AM
#2
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Location: Reno, NV
Posts: 18,369
Car Info: 1993/2000/2001 GF4 mostly red
Re: Slight shimmy under braking at 60 mph
Originally posted by Ichiro
Recently noticed a slight instability (steering wheel shakes a little) when moderately braking from around 50-60 mph.
No shimmy when braking really hard or braking at slower speeds.
The pads themselves look OK... front rotors are grooved (but they have been grooved since day one).
Any suggestions please?
Recently noticed a slight instability (steering wheel shakes a little) when moderately braking from around 50-60 mph.
No shimmy when braking really hard or braking at slower speeds.
The pads themselves look OK... front rotors are grooved (but they have been grooved since day one).
Any suggestions please?
12-26-2002, 03:37 PM
#3
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Join Date: Nov 2002
Location: Oregon
Posts: 52
Thanks!
I probably should get the tires balanced regardless, but if it were an unbalanced tire wouldn't I also notice it during acceleration or cruising on the highway (which I don't) ?
I have aftermarket 17" wheels which came mounted with tires and no weights at all (vendor claimed the tire were perfectly balanced without any extra weights).
I probably should get the tires balanced regardless, but if it were an unbalanced tire wouldn't I also notice it during acceleration or cruising on the highway (which I don't) ?
I have aftermarket 17" wheels which came mounted with tires and no weights at all (vendor claimed the tire were perfectly balanced without any extra weights).
12-26-2002, 06:29 PM
#4
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Car Info: 1993/2000/2001 GF4 mostly red
You'd only notice it during certain speed ranges, regardless of whether it was acceleration or braking. And what company sold you the wheels? I can go along with one wheel not needing weights, but no way in hell they got all 4 right the first time.
12-27-2002, 03:58 AM
#5
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you got screwed
first of all were did you buy the rims and second of all from experience if you feel that shaking that bad at different speeds its either the rim is out of round your tire is seperating or you have a broken belt in the tire. if they can do all four without adding weight he must be gahndi cause its like 1 out of like 20 that you can do it take it to a different tire store for instance i work at dicount tire and i would have them inspect your wheels we do it for free and have it balanced and rotated that is going to cost you around 25.00 and with that inspection roto balance they will tell you if your wheel is messed up or if your tire is seperated.
oh i was just thinkn to make sure you have the rite bolt pattern and offset cause that could do it too.
p.s if you go to the nearest balancing place ask them to 3 spin your wheels with tape weights. and make sure they start from scratch meaning take off the old ones first. any more problems with it let me know
oh i was just thinkn to make sure you have the rite bolt pattern and offset cause that could do it too.
p.s if you go to the nearest balancing place ask them to 3 spin your wheels with tape weights. and make sure they start from scratch meaning take off the old ones first. any more problems with it let me know
12-27-2002, 10:49 AM
#7
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Have you done any hard braking recently? Track day? Auto-X? Emergency stop? LA freeway chase?
Have you recently installed new brake pads?
This can be many things, including a slight DTV (disk thickness variation) problem. Which can be pad material bonded to the rotor or uneven wear of the rotor itself. The shimmy would come from a change is brake torque as the pad goes over the low spots. It's very minor since heavy braking (high pressure on the pads) is enough stop the judder.
To solve this problem is easy, have the rotors "lightly turned"
This all assumes it is the brakes and not the tires, suspension bushing, shocks or steering rack/links.
My Technical Website on Brake Systems
Have you recently installed new brake pads?
This can be many things, including a slight DTV (disk thickness variation) problem. Which can be pad material bonded to the rotor or uneven wear of the rotor itself. The shimmy would come from a change is brake torque as the pad goes over the low spots. It's very minor since heavy braking (high pressure on the pads) is enough stop the judder.
To solve this problem is easy, have the rotors "lightly turned"
This all assumes it is the brakes and not the tires, suspension bushing, shocks or steering rack/links.
My Technical Website on Brake Systems
Last edited by romanom; 12-27-2002 at 12:53 PM.
12-27-2002, 10:58 AM
#8
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Location: Oregon
Posts: 52
I got the wheels/tires from Evolution in Wisconsin about 10K miles ago ... tire pressure & treadwear are OK. I'm going to get them re-balanced today.
So it's really unlikely all 4 were self-balanced?
Do tires need re-balancing as they wear down anyway?
Romanom (I remember you from the old i-club as the brake expert):
No hard braking or even a car chase recently ...
Can I get the rotors turned at any decent shop or does it require special equipment / skill?
So it's really unlikely all 4 were self-balanced?
Do tires need re-balancing as they wear down anyway?
Romanom (I remember you from the old i-club as the brake expert):
No hard braking or even a car chase recently ...
Can I get the rotors turned at any decent shop or does it require special equipment / skill?
12-27-2002, 11:13 AM
#9
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Originally posted by Ichiro
No hard braking or even a car chase recently ...
Can I get the rotors turned at any decent shop or does it require special equipment / skill?
No hard braking or even a car chase recently ...
Can I get the rotors turned at any decent shop or does it require special equipment / skill?
The rotors should be turned while still mounted on the car. This does require special equipment, but the actual turning process is very easy. Just ask if they turn brake rotors on the car or not. Most of the auto repair chains do turn the rotors on the car and any professional shop will also do it this way.
However, if you have access to a micormeter you can check the thickness variatio of the rotors yourself. Just measure the thickness at various points on the rotor.
yeah the old board has a few to many jack-asses on it for my taste. And believe it or not it was at a BMW event some one told me about this I-club.
My Technical Website on Brake Systems
Last edited by romanom; 12-27-2002 at 12:53 PM.
01-10-2003, 01:13 AM
#10
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Originally posted by romanom
However, if you have access to a micormeter you can check the thickness variatio of the rotors yourself. Just measure the thickness at various points on the rotor.
yeah the old board has a few to many jack-asses on it for my taste. And believe it or not it was at a BMW event some one told me about this I-club.
However, if you have access to a micormeter you can check the thickness variatio of the rotors yourself. Just measure the thickness at various points on the rotor.
yeah the old board has a few to many jack-asses on it for my taste. And believe it or not it was at a BMW event some one told me about this I-club.
I noticed a bit of thermal judder apearing back in cars lately from residual stress in rotors that causes temporary distortion at certain temperatures. This has been occuring in the 90 to 100 kmh ( 55 to 60 mph) speed range.
We're working on a new disc for Audi for this same reason.
Or wheel bearings!
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