Need Rotor Runout Help
11-29-2020, 10:38 PM
#1
Racer
Thread Starter
Need Rotor Runout Help
I just changed the front rotors on my 72. In checking the runout, I come up with 34 thousandths on the drivers side and 5 thousandths on the passenger side. Even after clocking the drivers rotor 180 degress, it still comes up about the same. Can I turn the rotor to correct this much runout or do I need to try and exchange for a replacement rotor. If it can correct by having it turned, should I also turn the passenger side?
11-29-2020, 10:39 PM
#2
Racer
Thread Starter
I just changed the front rotors on my 72. In checking the runout, I come up with 34 thousandths on the drivers side and 5 thousandths on the passenger side. Even after clocking the drivers rotor 180 degress, it still comes up about the same. Can I turn the rotor to correct this much runout or do I need to try and exchange for a replacement rotor. If it can correct by having it turned, should I also turn the passenger side?
11-29-2020, 11:00 PM
#3
Team Owner
The amount of runout was the same....was the 'direction' (+/-) of the runout the same? Flipping the rotor around 180* and keeping the indicator at the same location might find the same amount of runout, but in reverse. Check it again and note the direction of the indicator swing.
11-29-2020, 11:12 PM
#4
Racer
Thread Starter
The amount of runout was the same....was the 'direction' (+/-) of the runout the same? Flipping the rotor around 180* and keeping the indicator at the same location might find the same amount of runout, but in reverse. Check it again and note the direction of the indicator swing.
11-30-2020, 01:27 AM
#5
Burning Brakes
First and foremost let’s check somethings.
1. Do we have lug nuts or nuts at least on two of the studs? Some folks swear you have to have 5 on torqued to spec but it shouldn’t really matter in this case because your way out.
2. The quality control of anything for these cars is pretty suspect anymore. Are you sure the rotor is fully seating on the hub?
3. Is the hub rust free around the hub and wheel studs? A rust build up on the hub (or rotor) can cause rust jacking and throw everything off. Gotta have it clean.
4. Are you perhaps seeing wheel bearing endplay as well? .001-.005” is normal endplay on the wheel bearing. Make sure you aren’t changing your measurements by accident by pushing or pulling the hub in/out while checking. Check your endplay, maybe that’s where your seeing all this runout.
Recheck yourself and make notes/magic marker markings to determine where the high spots are and if it’s in the rotor or in the hub if you truly have that much runout. If everything is right and it does have runout and it follows the rotor as you index it then you know it’s the rotor. If it follows the hub position then you know that too.
As for the rotor with .005 I’d index it a couple of times and see if you can cancel it out. If you’ve done that a .003 shim kit should get you straightened out.
1. Do we have lug nuts or nuts at least on two of the studs? Some folks swear you have to have 5 on torqued to spec but it shouldn’t really matter in this case because your way out.
2. The quality control of anything for these cars is pretty suspect anymore. Are you sure the rotor is fully seating on the hub?
3. Is the hub rust free around the hub and wheel studs? A rust build up on the hub (or rotor) can cause rust jacking and throw everything off. Gotta have it clean.
4. Are you perhaps seeing wheel bearing endplay as well? .001-.005” is normal endplay on the wheel bearing. Make sure you aren’t changing your measurements by accident by pushing or pulling the hub in/out while checking. Check your endplay, maybe that’s where your seeing all this runout.
Recheck yourself and make notes/magic marker markings to determine where the high spots are and if it’s in the rotor or in the hub if you truly have that much runout. If everything is right and it does have runout and it follows the rotor as you index it then you know it’s the rotor. If it follows the hub position then you know that too.
As for the rotor with .005 I’d index it a couple of times and see if you can cancel it out. If you’ve done that a .003 shim kit should get you straightened out.
Last edited by kossuth; 11-30-2020 at 01:28 AM.
The following 2 users liked this post by kossuth:
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11-30-2020, 02:58 AM
#6
Racer
Thread Starter
First and foremost let’s check somethings.
1. Do we have lug nuts or nuts at least on two of the studs? Some folks swear you have to have 5 on torqued to spec but it shouldn’t really matter in this case because your way out.
2. The quality control of anything for these cars is pretty suspect anymore. Are you sure the rotor is fully seating on the hub?
3. Is the hub rust free around the hub and wheel studs? A rust build up on the hub (or rotor) can cause rust jacking and throw everything off. Gotta have it clean.
4. Are you perhaps seeing wheel bearing endplay as well? .001-.005” is normal endplay on the wheel bearing. Make sure you aren’t changing your measurements by accident by pushing or pulling the hub in/out while checking. Check your endplay, maybe that’s where your seeing all this runout.
Recheck yourself and make notes/magic marker markings to determine where the high spots are and if it’s in the rotor or in the hub if you truly have that much runout. If everything is right and it does have runout and it follows the rotor as you index it then you know it’s the rotor. If it follows the hub position then you know that too.
As for the rotor with .005 I’d index it a couple of times and see if you can cancel it out. If you’ve done that a .003 shim kit should get you straightened out.
1. Do we have lug nuts or nuts at least on two of the studs? Some folks swear you have to have 5 on torqued to spec but it shouldn’t really matter in this case because your way out.
2. The quality control of anything for these cars is pretty suspect anymore. Are you sure the rotor is fully seating on the hub?
3. Is the hub rust free around the hub and wheel studs? A rust build up on the hub (or rotor) can cause rust jacking and throw everything off. Gotta have it clean.
4. Are you perhaps seeing wheel bearing endplay as well? .001-.005” is normal endplay on the wheel bearing. Make sure you aren’t changing your measurements by accident by pushing or pulling the hub in/out while checking. Check your endplay, maybe that’s where your seeing all this runout.
Recheck yourself and make notes/magic marker markings to determine where the high spots are and if it’s in the rotor or in the hub if you truly have that much runout. If everything is right and it does have runout and it follows the rotor as you index it then you know it’s the rotor. If it follows the hub position then you know that too.
As for the rotor with .005 I’d index it a couple of times and see if you can cancel it out. If you’ve done that a .003 shim kit should get you straightened out.
11-30-2020, 03:51 PM
#7
Team Owner
If you can minimize the .005" runout on the 'good' rotor by re-positioning it, then do so. A .005" runout reading is really very acceptable.
12-01-2020, 01:45 AM
#8
Old Fart Pilot
Not to hijack this thread, but how exactly is runout measured?
Is runout the total "play" between the highest spot on the rotor to the lowest spot or is half that value (i.e. from a mid-point on the rotor + value to high point or - value to low point)?
For example, my new TA's from VanSteel had the rotors preinstalled & aligned but my measurements showed a difference of .0035" between the absolute high spot to the absolute low spot on the rotors. Is that OK?
Additionally, now that I think of it, that was measured with the rotors in a horizontal position. Should I recheck it with them in a vertical position like they'd be when mounted on the car?
NEVERMIND - Gary R graciously answered my questions via an e-mail concerning my steering box rebuild he's going to do. He confirmed that runout is the total difference from high spot to low and while he measures in the vertical position, it can also be done horizontally. I thought that was the case, but just wanted to be sure. I'm learning soooo much!
Thanks,
paul
Is runout the total "play" between the highest spot on the rotor to the lowest spot or is half that value (i.e. from a mid-point on the rotor + value to high point or - value to low point)?
For example, my new TA's from VanSteel had the rotors preinstalled & aligned but my measurements showed a difference of .0035" between the absolute high spot to the absolute low spot on the rotors. Is that OK?
Additionally, now that I think of it, that was measured with the rotors in a horizontal position. Should I recheck it with them in a vertical position like they'd be when mounted on the car?
NEVERMIND - Gary R graciously answered my questions via an e-mail concerning my steering box rebuild he's going to do. He confirmed that runout is the total difference from high spot to low and while he measures in the vertical position, it can also be done horizontally. I thought that was the case, but just wanted to be sure. I'm learning soooo much!
Thanks,
paul
Last edited by nwav8tor; 12-01-2020 at 01:24 PM.
12-04-2020, 06:58 AM
#9
If you have switched your rotor 180 deg and the runout is the same then i suggest your rotor is good.
Your runout is probably from the hub.
Remove the rotor and check your wheel bearing is good and adjusted correctly first, then check the hub for runout.
regards
Norman
Your runout is probably from the hub.
Remove the rotor and check your wheel bearing is good and adjusted correctly first, then check the hub for runout.
regards
Norman
Last edited by Nosheruk; 12-04-2020 at 06:59 AM. Reason: spelling