Steering wheel shudder
03-14-2008, 03:07 AM
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Steering wheel shudder
When the car is first driven after cooling down I get a strong steering wheel shudder when applying the brakes at freeway speeds. The shudder disappears when speed drops under 50 and is not as pronounced after repeated braking or on longer trips. Since this only happens when braking I assume that it'* a front brake problem. I flushed the system last year after changing front rotors and pads. The car does not pull to one side when this happens. Struts and tie rod ends were also changed last year.
Thoughts?
Thoughts?
03-14-2008, 09:43 AM
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Re: Steering wheel shudder
Originally Posted by sp4149
When the car is first driven after cooling down I get a strong steering wheel shudder when applying the brakes at freeway speeds. The shudder disappears when speed drops under 50 and is not as pronounced after repeated braking or on longer trips. Since this only happens when braking I assume that it'* a front brake problem. I flushed the system last year after changing front rotors and pads. The car does not pull to one side when this happens. Struts and tie rod ends were also changed last year.
Thoughts?
Thoughts?
If this was occurring before and after new rotors were installed, then it could be a worn ball joint or drive axle, but this is less likely than excessive rotor runout.
03-14-2008, 10:41 AM
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Re: Steering wheel shudder
Sounds like warped rotors. Was it doing this immediately after the rotors were replaced last year, or has it come on gradually? Uneven tightening of lug nuts can cause warpage.
If this was occurring before and after new rotors were installed, then it could be a worn ball joint or drive axle, but this is less likely than excessive rotor runout.
Could it also be a caliper problem? I flushed the lines at 160K, the fluid was dark brown. With all that gunk in the brake fluid, could I have a sticky piston in one caliper?
On my old 1986 6000STE, I replaced the front calipers at around 170K which is where the Bonnie is now at. With the power bleeder, it is pretty easy to flush and bleed the system.
03-14-2008, 12:09 PM
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You can measure if the rotors are warped (or have it measured) by fixing a dial indicator against the rotor and watching the deflection of the needle as you spin the rotor. Steering wheel shaking is usually caused by a wheel out of balance, but is not often present only upon braking as you describe. Wheel balance and tire problems could be tested by swapping the wheels front to back to see if there is any difference. I would not think it likely that such violent shaking would be caused by sticking caliper pistons or pads. It may be worthwhile to have your ball joints checked, also check to make sure the bolts that hold the calipers to the knuckle are tight, and check for play in the hub (wheel) bearings.
Also, did you have outer and inner tie rods replaced or just the outers? You may also want to check to see if the bolts that hold the steering rack to the subframe are tight. I have not heard of it, but I suppose it may be possible for a steering rack to wear in such a way as to cause the problem. If that were the case, though, you should have noticeable play in the steering wheel before the wheels actually begin to move one way or the other.
Also, did you have outer and inner tie rods replaced or just the outers? You may also want to check to see if the bolts that hold the steering rack to the subframe are tight. I have not heard of it, but I suppose it may be possible for a steering rack to wear in such a way as to cause the problem. If that were the case, though, you should have noticeable play in the steering wheel before the wheels actually begin to move one way or the other.
03-16-2008, 11:31 PM
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Originally Posted by bill buttermore
You can measure if the rotors are warped (or have it measured) by fixing a dial indicator against the rotor and watching the deflection of the needle as you spin the rotor. Steering wheel shaking is usually caused by a wheel out of balance, but is not often present only upon braking as you describe. Wheel balance and tire problems could be tested by swapping the wheels front to back to see if there is any difference. I would not think it likely that such violent shaking would be caused by sticking caliper pistons or pads.
After looking at another post I also pulled the rear drums, a lot of dust inside, I snugged up the adjustment wheel on the rear brakes quite a bit on both sides. After cleaning everything looked normal, no broken parts. The other posts indicated that rear brakes out of adjustment can contribute to the feeling of warped rotors by amiking the front brakes work harder.
03-17-2008, 03:36 AM
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Found the following by Googling "allowable rotor runout" at this URL:
http://www.aa1car.com/library/procut02.htm
Some excerpts:
Sorry I did not include proper method for pre-loading rotor before measuring runout, but it looks like your 0.035" measurement puts your rotors out of spec. Either turn them or replace them, taking care to clean the hub/rotor mating surface and to carefully torque the clean, dry lug nuts. If you still have a shaking wheel when braking, look to other causes.
http://www.aa1car.com/library/procut02.htm
Some excerpts:
Originally Posted by Russ Dobson
GENERAL MOTORS PRESENTATION
Russ Dobson - GM Service Operations, Warren Tech Center
BRAKE PULSATION & RUNOUT PROBLEMS
Brake pulsation is a high warranty issue for GM.
NOTE Very important to clean any rust/dirt/corrosion from hub anytime rotor is removed from hub. Cleaning is critical!
Must measure assembled lateral runout to see if correction is needed. Must be less than .002 in. If more than .002 runout, may not create a brake pulsation right away but it will appear within few thousand miles.
If a customer has a brake pulsation, you know you have variation so rotors will have to be resurfaced or replaced. GM says measuring rotor thickness variation is very hard to do accurately in the shop, so why waste time trying to measure it? GM spec for maximum allowable thickness variation in rotors is 0.025 mm (0.001 in.).
In the real world, the only things you can measure accurately are rotor thickness and flatness. You can't measure rotor thickness with a high degree of accuracy unless you measure about every couple inches all the way around the rotor. If the rotor pulsates, it has thickness variation and is bad.
To measure lateral runout, mount rotor on hub, install special conical washers (J45101-100) on lugs, then install and torque lug nuts to specs. This simulates wheel load on the rotor. Then you can accurately measure runout. Maximum runout will vary according to the vehicle, but on Chevy Malibu should only be 0.04 mm (0.0015 in.) max.
Major cause of rotor runout is rust & corrosion between hub and rotor, and improper lug nut torque loading. That'* why it is so important to inspect and clean mounting area between hub and rotor.
Lug nut torque is very important. GM guy says leaving only a single lug nut loose or undertorqued may create as much as .003 in. of lateral runout in the rotor!
GM says it is not necessary to resurface rotors every time pads are replaced. Do not reface new rotors. Latest GM warranty bulletin says .002 in. is maximum lateral runout for rotors.
Never use grease or lubricant on lugs, nuts or between mounting surfaces. Dry and clean only.
For 2003 model year, GM has changed to a new wheel design with a "flat" hub surface that mounts flush against the rotor and hub. Most GM OEM wheels have a slightly conical mounting surface that helps clamp the rotor against the hub (spring back effect) -- but on the Malibu this increases rotor distortion due to design of rotors and hub. By changing to a flat wheel, rotor distortion is reduced -- but it also requires very accurate torquing of lug nuts.
Technicians must use a torque wrench or torx sticks.
Russ Dobson - GM Service Operations, Warren Tech Center
BRAKE PULSATION & RUNOUT PROBLEMS
Brake pulsation is a high warranty issue for GM.
NOTE Very important to clean any rust/dirt/corrosion from hub anytime rotor is removed from hub. Cleaning is critical!
Must measure assembled lateral runout to see if correction is needed. Must be less than .002 in. If more than .002 runout, may not create a brake pulsation right away but it will appear within few thousand miles.
If a customer has a brake pulsation, you know you have variation so rotors will have to be resurfaced or replaced. GM says measuring rotor thickness variation is very hard to do accurately in the shop, so why waste time trying to measure it? GM spec for maximum allowable thickness variation in rotors is 0.025 mm (0.001 in.).
In the real world, the only things you can measure accurately are rotor thickness and flatness. You can't measure rotor thickness with a high degree of accuracy unless you measure about every couple inches all the way around the rotor. If the rotor pulsates, it has thickness variation and is bad.
To measure lateral runout, mount rotor on hub, install special conical washers (J45101-100) on lugs, then install and torque lug nuts to specs. This simulates wheel load on the rotor. Then you can accurately measure runout. Maximum runout will vary according to the vehicle, but on Chevy Malibu should only be 0.04 mm (0.0015 in.) max.
Major cause of rotor runout is rust & corrosion between hub and rotor, and improper lug nut torque loading. That'* why it is so important to inspect and clean mounting area between hub and rotor.
Lug nut torque is very important. GM guy says leaving only a single lug nut loose or undertorqued may create as much as .003 in. of lateral runout in the rotor!
GM says it is not necessary to resurface rotors every time pads are replaced. Do not reface new rotors. Latest GM warranty bulletin says .002 in. is maximum lateral runout for rotors.
Never use grease or lubricant on lugs, nuts or between mounting surfaces. Dry and clean only.
For 2003 model year, GM has changed to a new wheel design with a "flat" hub surface that mounts flush against the rotor and hub. Most GM OEM wheels have a slightly conical mounting surface that helps clamp the rotor against the hub (spring back effect) -- but on the Malibu this increases rotor distortion due to design of rotors and hub. By changing to a flat wheel, rotor distortion is reduced -- but it also requires very accurate torquing of lug nuts.
Technicians must use a torque wrench or torx sticks.
03-17-2008, 08:19 AM
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Turning them will only buy you time at this point. Your rear brakes were the final straw.
If you don't want this to happen again:
1. Use non-generic quality rotors.
2. Keep the rear brakes maintained.
3. Clean off the back of the wheel and the hub face, as well as wire brush the threads of the lug studs.
4. Apply a drop or two of oil to each lug stud before putting lugnuts on to insure proper torque.
5. Stage-torque. 75ft/lbs in a criss-cross pattern, then 100ft/lbs in the same pattern.
Trust me. I've fought warped rotors more than most.
If you don't want this to happen again:
1. Use non-generic quality rotors.
2. Keep the rear brakes maintained.
3. Clean off the back of the wheel and the hub face, as well as wire brush the threads of the lug studs.
4. Apply a drop or two of oil to each lug stud before putting lugnuts on to insure proper torque.
5. Stage-torque. 75ft/lbs in a criss-cross pattern, then 100ft/lbs in the same pattern.
Trust me. I've fought warped rotors more than most.
03-17-2008, 11:06 AM
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Originally Posted by willwren
Turning them will only buy you time at this point. Your rear brakes were the final straw.
If you don't want this to happen again:
1. Use non-generic quality rotors.
2. Keep the rear brakes maintained.
3. Clean off the back of the wheel and the hub face, as well as wire brush the threads of the lug studs.
4. Apply a drop or two of oil to each lug stud before putting lugnuts on to insure proper torque.
5. Stage-torque. 75ft/lbs in a criss-cross pattern, then 100ft/lbs in the same pattern.
Trust me. I've fought warped rotors more than most.
If you don't want this to happen again:
1. Use non-generic quality rotors.
2. Keep the rear brakes maintained.
3. Clean off the back of the wheel and the hub face, as well as wire brush the threads of the lug studs.
4. Apply a drop or two of oil to each lug stud before putting lugnuts on to insure proper torque.
5. Stage-torque. 75ft/lbs in a criss-cross pattern, then 100ft/lbs in the same pattern.
Trust me. I've fought warped rotors more than most.
Since we're due for new tires, that probably means retorqueing the wheels after installation since I've never seen a tire shop stage torque with such precision, especially on an older car.
03-19-2008, 08:15 PM
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What are the recommendations for new front rotors, pads, and possibly calipers? The last rotors I got at Napa and Kragen didn't last as long as I would have expected, before warping. I still am bothered by the strong steering wheel shudder when braking from 70 to 50mph. The shudder virtually disappears when braking at speeds below 50mph.
03-19-2008, 10:24 PM
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I had the same issue/symptoms exactly. I just finished putting on the premium line of Monroe'* rotors ($37.10CAD each). No shudder at high speed braking now.
Not a lot of kilometres on them as of yet so will see how well they do over the long haul. Wish I had spent more time cleaning where they sat on the hub after reading these posts though.
Not a lot of kilometres on them as of yet so will see how well they do over the long haul. Wish I had spent more time cleaning where they sat on the hub after reading these posts though.
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