Rethinking vibration when braking
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Originally Posted By: mechanicx
Sounds like you're within specs, and good work. Hopefully now, your brakes will never develop pulsation and last until the pads have worn out. Then it'll be worth the extra steps. Keep us posted.
It has been a year. Today I installed a shim to correct for 0.006". The 0.003" one I initially installed just barely was getting me within specs and I have been hearing the passenger rotor making a noise when cold. It sounded like before I installed the shims when it was hitting a high spot each rotation at slow speeds. I recently installed new struts so maybe that had some impact on the noise? With the new shim it indexed at a little over 0.001. Brakes went a year/about 20,000 miles and worked good overall. Pads still have a lot of life left. I cleaned and lubed the guide and lock pins and cleaned and adjusted my rear brakes. I will test them out when I take my stepfather out to eat tomorrow. I want to wish everyone a Happy Fathers Day. I could not have done this without your help!
Sounds like you're within specs, and good work. Hopefully now, your brakes will never develop pulsation and last until the pads have worn out. Then it'll be worth the extra steps. Keep us posted.
It has been a year. Today I installed a shim to correct for 0.006". The 0.003" one I initially installed just barely was getting me within specs and I have been hearing the passenger rotor making a noise when cold. It sounded like before I installed the shims when it was hitting a high spot each rotation at slow speeds. I recently installed new struts so maybe that had some impact on the noise? With the new shim it indexed at a little over 0.001. Brakes went a year/about 20,000 miles and worked good overall. Pads still have a lot of life left. I cleaned and lubed the guide and lock pins and cleaned and adjusted my rear brakes. I will test them out when I take my stepfather out to eat tomorrow. I want to wish everyone a Happy Fathers Day. I could not have done this without your help!
Make sure the hub is free of rust where the rotor rides (grind down to clean metal). Also make sure there is no rust on backside of rotor where it rides on the hub. This should correct your runout. It is EXTREMELY rare to use shims to correct rotor runout.
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Originally Posted By: mattd
Make sure the hub is free of rust where the rotor rides (grind down to clean metal). Also make sure there is no rust on backside of rotor where it rides on the hub. This should correct your runout. It is EXTREMELY rare to use shims to correct rotor runout.
^^^
This.
Before buying anything or putting a dial indicator on, clean all contact points of dirt/rust/corrosion between the wheel/rotor and rotor/hub. That's most likely the cause of your problem.
Wire brush, wipe off with WD40, schmear a little anti-seize, replace, and you're good to go.
Make sure the hub is free of rust where the rotor rides (grind down to clean metal). Also make sure there is no rust on backside of rotor where it rides on the hub. This should correct your runout. It is EXTREMELY rare to use shims to correct rotor runout.
^^^
This.
Before buying anything or putting a dial indicator on, clean all contact points of dirt/rust/corrosion between the wheel/rotor and rotor/hub. That's most likely the cause of your problem.
Wire brush, wipe off with WD40, schmear a little anti-seize, replace, and you're good to go.
Scott_Tucker and Rocko1 hit the nail on the head.
Rotor runout is a distant 3rd as far as causes of brake pulsation. Pad deposition and mismachined/non parallel rotor faces are 90+% of the problem.
You can turn rotors on the hub and have perfect .000 runout, and have one hard stop/pad bake session and have pedal pulsation all over again with a perfectly in spec rotor.
Likewise you can have a rotor horrendously out of spec as far as runout is concerned (due to a newb idiot banging on your brake lathe arbor)and have no ill effects at all, except for some abnormal wear on any surface the pad bears against on the spindle.
Measure runout first, if it anywhere near spec, deglaze the rotor with a roloc disk and you likely will fix the problem. Don't get obsessed with runout as being the root cause of the problem.
Rotor runout is a distant 3rd as far as causes of brake pulsation. Pad deposition and mismachined/non parallel rotor faces are 90+% of the problem.
You can turn rotors on the hub and have perfect .000 runout, and have one hard stop/pad bake session and have pedal pulsation all over again with a perfectly in spec rotor.
Likewise you can have a rotor horrendously out of spec as far as runout is concerned (due to a newb idiot banging on your brake lathe arbor)and have no ill effects at all, except for some abnormal wear on any surface the pad bears against on the spindle.
Measure runout first, if it anywhere near spec, deglaze the rotor with a roloc disk and you likely will fix the problem. Don't get obsessed with runout as being the root cause of the problem.
Originally Posted By: MONKEYMAN
Originally Posted By: mechanicx
Sounds like you're within specs, and good work. Hopefully now, your brakes will never develop pulsation and last until the pads have worn out. Then it'll be worth the extra steps. Keep us posted.
It has been a year. Today I installed a shim to correct for 0.006". The 0.003" one I initially installed just barely was getting me within specs and I have been hearing the passenger rotor making a noise when cold. It sounded like before I installed the shims when it was hitting a high spot each rotation at slow speeds. I recently installed new struts so maybe that had some impact on the noise? With the new shim it indexed at a little over 0.001. Brakes went a year/about 20,000 miles and worked good overall. Pads still have a lot of life left. I cleaned and lubed the guide and lock pins and cleaned and adjusted my rear brakes. I will test them out when I take my stepfather out to eat tomorrow. I want to wish everyone a Happy Fathers Day. I could not have done this without your help!
I still believe run out is the main cause of pulsation, or more precisely causes rotor thickness variation that causes pulsation. Pulsation caused by pad deposits induced thickness variation is not real for the most part IMO. Unless your rotors have corroded and the pads have cooked the lining off how could rotor deposits persist on a rotor that does not have run out? they wouldn't, They'd be ground flat during off brake driving and on braking.
When I get run out under .002, I never seem to run into pulsation rearing its head. This assume decent quality pads and rotors which you should always be using. If run out is above .002 or specs pulsation is almost certain to show up no matter what you do. Like clockwork due to run out induced thicknes variation.
Definitely clean the rotor and hub mounting interface. Clean the rotor mounting surface before having them machined.
If run out is above .003 with a machined or new rotor, the hub has way too much run out and really should be replaced instead of using a correction plate.
I'm a little confused if you have pulsation or run out problem again, or just brake noise. Brake noise and pulsation can be separate issues with separate causes.
*Important* when you shimmed the rotor again, did you machine or replace the rotor first and measure run out? Any rotor that's been ran with excessive run out, should be turned or replaced to correct thickness variation first. If the excess run out is corrected the rotor might eventually wear in even but you don't want to count on it.
Originally Posted By: mechanicx
Sounds like you're within specs, and good work. Hopefully now, your brakes will never develop pulsation and last until the pads have worn out. Then it'll be worth the extra steps. Keep us posted.
It has been a year. Today I installed a shim to correct for 0.006". The 0.003" one I initially installed just barely was getting me within specs and I have been hearing the passenger rotor making a noise when cold. It sounded like before I installed the shims when it was hitting a high spot each rotation at slow speeds. I recently installed new struts so maybe that had some impact on the noise? With the new shim it indexed at a little over 0.001. Brakes went a year/about 20,000 miles and worked good overall. Pads still have a lot of life left. I cleaned and lubed the guide and lock pins and cleaned and adjusted my rear brakes. I will test them out when I take my stepfather out to eat tomorrow. I want to wish everyone a Happy Fathers Day. I could not have done this without your help!
I still believe run out is the main cause of pulsation, or more precisely causes rotor thickness variation that causes pulsation. Pulsation caused by pad deposits induced thickness variation is not real for the most part IMO. Unless your rotors have corroded and the pads have cooked the lining off how could rotor deposits persist on a rotor that does not have run out? they wouldn't, They'd be ground flat during off brake driving and on braking.
When I get run out under .002, I never seem to run into pulsation rearing its head. This assume decent quality pads and rotors which you should always be using. If run out is above .002 or specs pulsation is almost certain to show up no matter what you do. Like clockwork due to run out induced thicknes variation.
Definitely clean the rotor and hub mounting interface. Clean the rotor mounting surface before having them machined.
If run out is above .003 with a machined or new rotor, the hub has way too much run out and really should be replaced instead of using a correction plate.
I'm a little confused if you have pulsation or run out problem again, or just brake noise. Brake noise and pulsation can be separate issues with separate causes.
*Important* when you shimmed the rotor again, did you machine or replace the rotor first and measure run out? Any rotor that's been ran with excessive run out, should be turned or replaced to correct thickness variation first. If the excess run out is corrected the rotor might eventually wear in even but you don't want to count on it.
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Originally Posted By: MONKEYMAN
It has been a year. Today I installed a shim to correct for 0.006". The 0.003" one I initially installed just barely was getting me within specs and I have been hearing the passenger rotor making a noise when cold.
See, now, that's not the way to do it. You don't use the rotor for a year and then apply a shim to correct runout. Shims can only work when the two surfaces of the disc lie on or very near planes that are parallel.
Measure runout and apply shim only with freshly machined (new are freshly machined) rotors unless you are ready to dump some time into it.
If you've run the rotors with excessive runout and aren't turning them you need to first measure thickness variations and verify that they're under spec. Then you need to measure runout on both surfaces of the disc and apply the shim such that runout on both surfaces will be less than 2/3 of spec. This may or may not be possible.
It has been a year. Today I installed a shim to correct for 0.006". The 0.003" one I initially installed just barely was getting me within specs and I have been hearing the passenger rotor making a noise when cold.
See, now, that's not the way to do it. You don't use the rotor for a year and then apply a shim to correct runout. Shims can only work when the two surfaces of the disc lie on or very near planes that are parallel.
Measure runout and apply shim only with freshly machined (new are freshly machined) rotors unless you are ready to dump some time into it.
If you've run the rotors with excessive runout and aren't turning them you need to first measure thickness variations and verify that they're under spec. Then you need to measure runout on both surfaces of the disc and apply the shim such that runout on both surfaces will be less than 2/3 of spec. This may or may not be possible.
I cleaned rust as good as I could. Noise is gone. Brakes have never worked better. Replacing hub is expensive, that is why I went this route. If you should replace a hub with over 0.003 runnout then why do they make a shim to fix it? I guess my ignorance is working out for now. Looks like my pads have another 30,000 miles remaining if my driving routine remains the same. I appreciate the comments. It could be cleaning and adjusting rear shoes I installed 40k is making my braking seem so much better? This is a learning process. If I have problems I will let you know. I was thinking I will make working on my brakes my annual Father's Day project. Hope you all had a good one!
Originally Posted By: yonyon
Originally Posted By: MONKEYMAN
It has been a year. Today I installed a shim to correct for 0.006". The 0.003" one I initially installed just barely was getting me within specs and I have been hearing the passenger rotor making a noise when cold.
See, now, that's not the way to do it. You don't use the rotor for a year and then apply a shim to correct runout. Shims can only work when the two surfaces of the disc lie on or very near planes that are parallel.
Measure runout and apply shim only with freshly machined (new are freshly machined) rotors unless you are ready to dump some time into it.
If you've run the rotors with excessive runout and aren't turning them you need to first measure thickness variations and verify that they're under spec. Then you need to measure runout on both surfaces of the disc and apply the shim such that runout on both surfaces will be less than 2/3 of spec. This may or may not be possible.
+1. I forgot to add at the end that it's about impossible to accurately measure rotor run out with dial indicator unless the rotor is machined smooth or new.
Although, I believe if you start with a new rotor or properly machined and cleaned mounting surfaces rotor, it's usually safe to assume thickness variation is within spec, and if installed rotor run out measured with a dial indicator just on the outside surface of the rotor is within spec, then it is in spec on both sides.
Originally Posted By: MONKEYMAN
It has been a year. Today I installed a shim to correct for 0.006". The 0.003" one I initially installed just barely was getting me within specs and I have been hearing the passenger rotor making a noise when cold.
See, now, that's not the way to do it. You don't use the rotor for a year and then apply a shim to correct runout. Shims can only work when the two surfaces of the disc lie on or very near planes that are parallel.
Measure runout and apply shim only with freshly machined (new are freshly machined) rotors unless you are ready to dump some time into it.
If you've run the rotors with excessive runout and aren't turning them you need to first measure thickness variations and verify that they're under spec. Then you need to measure runout on both surfaces of the disc and apply the shim such that runout on both surfaces will be less than 2/3 of spec. This may or may not be possible.
+1. I forgot to add at the end that it's about impossible to accurately measure rotor run out with dial indicator unless the rotor is machined smooth or new.
Although, I believe if you start with a new rotor or properly machined and cleaned mounting surfaces rotor, it's usually safe to assume thickness variation is within spec, and if installed rotor run out measured with a dial indicator just on the outside surface of the rotor is within spec, then it is in spec on both sides.
Originally Posted By: MONKEYMAN
I cleaned rust as good as I could. Noise is gone. Brakes have never worked better. Replacing hub is expensive, that is why I went this route. If you should replace a hub with over 0.003 runnout then why do they make a shim to fix it? I guess my ignorance is working out for now. Looks like my pads have another 30,000 miles remaining if my driving routine remains the same. I appreciate the comments. It could be cleaning and adjusting rear shoes I installed 40k is making my braking seem so much better? This is a learning process. If I have problems I will let you know. I was thinking I will make working on my brakes my annual Father's Day project. Hope you all had a good one!
You can use a .006 shim if you do not want to replace the hub. Sorry I meant to say if over .006 correction is needed replace the hub. I'm just worried that your brake noise wasn't really caused by a rotor run out issue. And if you used the .006 shim without measuring actual installed rotor runout (on a rotor that had a smooth measurable surface), that you may have overcorrected and have excess run out now. Brakes will work good for now but could pulsate a few thousand miles down the road.
Since you don't have pulsation now with reusing the rotor, I have to assume there was not an excessive run out problem before. The .006 shim without measuring run out may cause a problem rather than an improvement down the line. Does that make sense?
But who knows maybe the .006 shim actually lowered your rotor run out. Maybe you were borderline at .002 run out with the previous .003 correction and now you're at .001 with the .006 correction (assuming the .006 plate's high mark and the rotor was installed in the same and proper location of course).
I cleaned rust as good as I could. Noise is gone. Brakes have never worked better. Replacing hub is expensive, that is why I went this route. If you should replace a hub with over 0.003 runnout then why do they make a shim to fix it? I guess my ignorance is working out for now. Looks like my pads have another 30,000 miles remaining if my driving routine remains the same. I appreciate the comments. It could be cleaning and adjusting rear shoes I installed 40k is making my braking seem so much better? This is a learning process. If I have problems I will let you know. I was thinking I will make working on my brakes my annual Father's Day project. Hope you all had a good one!
You can use a .006 shim if you do not want to replace the hub. Sorry I meant to say if over .006 correction is needed replace the hub. I'm just worried that your brake noise wasn't really caused by a rotor run out issue. And if you used the .006 shim without measuring actual installed rotor runout (on a rotor that had a smooth measurable surface), that you may have overcorrected and have excess run out now. Brakes will work good for now but could pulsate a few thousand miles down the road.
Since you don't have pulsation now with reusing the rotor, I have to assume there was not an excessive run out problem before. The .006 shim without measuring run out may cause a problem rather than an improvement down the line. Does that make sense?
But who knows maybe the .006 shim actually lowered your rotor run out. Maybe you were borderline at .002 run out with the previous .003 correction and now you're at .001 with the .006 correction (assuming the .006 plate's high mark and the rotor was installed in the same and proper location of course).
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Basically the high spot of rotor was the same. The notch on the new shim ended up in about the same spot. There was very little rust so I am thinking my readings were accurate. The problem with learning as I go is knowledge comes after it is needed. This is a learning experience. It do not think I over corrected since the last shim put me right on border of the normal specification. This shim put it right were I thought it would based on the video linked in this thread.
Originally Posted By: mechanicx
But the excessive run out is what leads to thickness variation or lack of parallelism. The excessive rotor run out wears the rotors unevenly after a few thousand miles leading to thickness variation which causes pulsation.
I was scratching my head on this, until I did a further search. From Raybestos:
Quote:
What are the effects of excessive lateral rotor run-out? With
excessive run-out, the rotor wobbles as it turns (Fig.1). Uneven rotor wear occurs with the brakes not applied causing rotor thickness variation.
Search raybestos BPI 03-02 to find info.
But when the brakes are applied with excessive lateral run-out, the edges of the pads would still contact and wear a disc properly ... alas, it's the rubbing on the disc when brakes aren't engaged.
But the excessive run out is what leads to thickness variation or lack of parallelism. The excessive rotor run out wears the rotors unevenly after a few thousand miles leading to thickness variation which causes pulsation.
I was scratching my head on this, until I did a further search. From Raybestos:
Quote:
What are the effects of excessive lateral rotor run-out? With
excessive run-out, the rotor wobbles as it turns (Fig.1). Uneven rotor wear occurs with the brakes not applied causing rotor thickness variation.
Search raybestos BPI 03-02 to find info.
But when the brakes are applied with excessive lateral run-out, the edges of the pads would still contact and wear a disc properly ... alas, it's the rubbing on the disc when brakes aren't engaged.
Yes not just big aftermarket brake manufacturers talk about run out being the prime cause of TV and pulsation, all the automakers do too.
It can be a hard concept to visualize at first, but run out is caused by the rotor not being perpendicular enough to the axle centerline of rotation. So the rotor slightly wobbles horizontally as it turns. At first the floating brake pads and caliper together follow the wobble because the rotor thickness is the same and you don't notice pulsation.
Over time during off braking, the pads wear the rotor thinner (it only takes like less than .001" or so) on one side of the rotor and also on the other side about 180 degrees apart. The pads have basically worn away the wobble which wasn't causing a noticeable problem anyway. But the rotors thickness now varies and the pads and caliper piston move in and out and you have brake pulsation.
It can be a hard concept to visualize at first, but run out is caused by the rotor not being perpendicular enough to the axle centerline of rotation. So the rotor slightly wobbles horizontally as it turns. At first the floating brake pads and caliper together follow the wobble because the rotor thickness is the same and you don't notice pulsation.
Over time during off braking, the pads wear the rotor thinner (it only takes like less than .001" or so) on one side of the rotor and also on the other side about 180 degrees apart. The pads have basically worn away the wobble which wasn't causing a noticeable problem anyway. But the rotors thickness now varies and the pads and caliper piston move in and out and you have brake pulsation.
Makes me feel sorry for those of you in the Rust Belt.
We simply do not experience this issue in Florida!
We simply do not experience this issue in Florida!
Originally Posted By: SteveSRT8
Makes me feel sorry for those of you in the Rust Belt.
We simply do not experience this issue in Florida!
It's not a rust belt issue ... I live in Vancouver BC and it's certainly a rain belt but little snow. And I have pulsation on my Volvo 740 as well as a 2004 Sienna.
Makes me feel sorry for those of you in the Rust Belt.
We simply do not experience this issue in Florida!
It's not a rust belt issue ... I live in Vancouver BC and it's certainly a rain belt but little snow. And I have pulsation on my Volvo 740 as well as a 2004 Sienna.
Originally Posted By: NJC
Originally Posted By: SteveSRT8
Makes me feel sorry for those of you in the Rust Belt.
We simply do not experience this issue in Florida!
It's not a rust belt issue ... I live in Vancouver BC and it's certainly a rain belt but little snow. And I have pulsation on my Volvo 740 as well as a 2004 Sienna.
I think it is mostly an excessive hub run out issue and to a smaller extent rotor run out added to it. But most rotors turned or new have low enough run out and low thickness variation. This why with some cars you can put any pad or rotor you want on and they never pulsate while others develop pulsation no matter what pads or rotors you use. It's the hub, stupid lol.
Originally Posted By: SteveSRT8
Makes me feel sorry for those of you in the Rust Belt.
We simply do not experience this issue in Florida!
It's not a rust belt issue ... I live in Vancouver BC and it's certainly a rain belt but little snow. And I have pulsation on my Volvo 740 as well as a 2004 Sienna.
I think it is mostly an excessive hub run out issue and to a smaller extent rotor run out added to it. But most rotors turned or new have low enough run out and low thickness variation. This why with some cars you can put any pad or rotor you want on and they never pulsate while others develop pulsation no matter what pads or rotors you use. It's the hub, stupid lol.
After 15,000 with the proper shim several things happened.
I did not have that high spot when driving slow first part of day.
Minimal pulsation with highway braking and no pulsation with in town driving. On highway it would smooth out the more I used the brakes.
Just rotated tires and adjusted back brakes. Front Raybestos pads are half way worn. On box first installed them 5/11.
To summarize:
Braking has never been smoother. It was worth installing the proper shim since my rotors and pads have a lot of life left. I could not have gotten this far without everyone’s guidance. Thanks again!
I did not have that high spot when driving slow first part of day.
Minimal pulsation with highway braking and no pulsation with in town driving. On highway it would smooth out the more I used the brakes.
Just rotated tires and adjusted back brakes. Front Raybestos pads are half way worn. On box first installed them 5/11.
To summarize:
Braking has never been smoother. It was worth installing the proper shim since my rotors and pads have a lot of life left. I could not have gotten this far without everyone’s guidance. Thanks again!
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