Best way to correct rotor runout
#1
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Best way to correct rotor runout
I am just fininshing my complete brake job. I have purchased new slotted rotors from VBP. My problem is runout; I believe the rotors are good and that it is my hubs that are out. My hub runout is .004 and .008 (fronts) which translates to .006-.016 on the rotors respectively. Reading through the archives there are a couple of ways to correct this.
1. Turn the rotor/hub assembly
2. Turn the hub only
3. Shim the rotor
4. Purchase new hubs
I think the best solution is #1, as I believe most hubs will be out due to the way the general designed them (they turned the rotor/hub as a unit). Shimming doesn't seem very secure to me. BTW, I have cleaned and deburred all parts.
Please give me your thoughts and experiances.
1. Turn the rotor/hub assembly
2. Turn the hub only
3. Shim the rotor
4. Purchase new hubs
I think the best solution is #1, as I believe most hubs will be out due to the way the general designed them (they turned the rotor/hub as a unit). Shimming doesn't seem very secure to me. BTW, I have cleaned and deburred all parts.
Please give me your thoughts and experiances.
#2
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Re: Best way to correct rotor runout (70vert)
What's the total runout on your front assemblies w/the rotors on? You can always take a grinder and grind down your high spots. You should at least do that over the rivit holes. You should have .005 or under when the rotor is on. Did you try moving the rotor to different postions to see if where you came out the lowest for your run out? Don't shim it. It's only a temp fix.
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Re: Best way to correct rotor runout (Van Steel)
Why is shimming only a temp fix? The shims don't go anywhere. For .016 runout I would make sure if was really .016 runout then chuck the rotor in my lathe and with a dial indicator make it run out .016 then lightly face the mounting surface. Did this to one rotor that had .012 runout.
For small runout say .006-8 I would shim. Turning the hub and rotor as a unit is a pain and who can do it right?
Also wheel bearing setup is very critical.
For small runout say .006-8 I would shim. Turning the hub and rotor as a unit is a pain and who can do it right?
Also wheel bearing setup is very critical.
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Re: Best way to correct rotor runout (Van Steel)
The hubs are now very clean. I did grind the "lips" around the holes were the rivits where. Total runout (on the assembly) is .006 on the right and .016 on the left.
I did try all 5 rotor to hub positions with all combinations or rotor and hub, i.e. the right hub/right rotor, left hub/right rotor, left hub/left rotor, and right hub/left rotor. I got nearly the same runnout in all configurations; that is why I believe all runout is in the hubs not the rotor.
BTW, that was sooo much fun.
I did try all 5 rotor to hub positions with all combinations or rotor and hub, i.e. the right hub/right rotor, left hub/right rotor, left hub/left rotor, and right hub/left rotor. I got nearly the same runnout in all configurations; that is why I believe all runout is in the hubs not the rotor.
BTW, that was sooo much fun.
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Re: Best way to correct rotor runout (norvalwilhelm)
[QUOTE]Why is shimming only a temp fix? The shims don't go anywhere. /QUOTE]
I'm wondering the same thing, I shimmed my rears nearly three years ago, I checked them last summer and they were still right where I left them and the run-out had not changed.
I'm wondering the same thing, I shimmed my rears nearly three years ago, I checked them last summer and they were still right where I left them and the run-out had not changed.
#6
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Re: Best way to correct rotor runout (Smokehouse69)
Way too much runout. If you working on the fronts be sure about anything in between the rotor and hub. I like to use a file so that I don't take off more then I want. I also use a 2" die grinder with scotchbrite pads to celan up without grinding off. For shims I use ss shim stock with a punch kit to get clean holes. Then I use a hammer to press,not hammer, them flat. The last new front rotor I bought(made in the USA, BTW) had .009" runout. I was able to shim it down to .0025-.003" If you have a good, experienced brake shop around they can set up the fronts on your hubs and "KISS" cut them to true them up. Be aware that yo only have .035" between new and disgard thickness so that's why I prefer to shim if I can. I haven't had a shim failure yet.
Rear rotors are different snice you can't get the spindles out very easily. I have turned rotors and spindles in a lathe to true them. They were bolted or riveted together first and turned as a unit. This requires a lot of work that the average guy or garage is not going to do. I have shimmed rear rotors both new and used to get down as close as .0005" TRO. It take time,tools,and understanding buy you can do it. ask more questions and give it a shot.
Gary
Rear rotors are different snice you can't get the spindles out very easily. I have turned rotors and spindles in a lathe to true them. They were bolted or riveted together first and turned as a unit. This requires a lot of work that the average guy or garage is not going to do. I have shimmed rear rotors both new and used to get down as close as .0005" TRO. It take time,tools,and understanding buy you can do it. ask more questions and give it a shot.
Gary
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Re: Best way to correct rotor runout (gtr1999)
Another thought, if I turn the hub/rotor assembly to get the rotor true, won't my wheel have runout due to not turning the rotor/wheel mating surface? I think I should have the hub only turned.
The thing I don't like about shims is they significantly reduce the wheel/rotor purchase area.
The thing I don't like about shims is they significantly reduce the wheel/rotor purchase area.
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Re: Best way to correct rotor runout (70vert)
The thing I don't like about shims is they significantly reduce the wheel/rotor purchase area
I had a rear runout of about .006. I used 2 .002 stainless shims, one on each of 2 studs and got rid of the runout. Do you really think that a .002 shim is going to affect the metal to metal contact of the rotor, retain heat or put excess pressure on the studs?
A small shim on the stud affects the outer edge of the rotor more then the thickness of the shim. I agree .016 is getting excess but a .010 shim would bring that into line. Personally I would chuck the rotor, indicate it on a lathe and with a plastic hammer cause a .016 runnout then true the mounting surface. No shims and the rotor would run true. I have small drilled dimples in a wheel stud, the rotor and the rim , paint the dimples red and everytime the wheel is reassembled I line up the dots.
Things go back true.
I had a rear runout of about .006. I used 2 .002 stainless shims, one on each of 2 studs and got rid of the runout. Do you really think that a .002 shim is going to affect the metal to metal contact of the rotor, retain heat or put excess pressure on the studs?
A small shim on the stud affects the outer edge of the rotor more then the thickness of the shim. I agree .016 is getting excess but a .010 shim would bring that into line. Personally I would chuck the rotor, indicate it on a lathe and with a plastic hammer cause a .016 runnout then true the mounting surface. No shims and the rotor would run true. I have small drilled dimples in a wheel stud, the rotor and the rim , paint the dimples red and everytime the wheel is reassembled I line up the dots.
Things go back true.
#9
Re: Best way to correct rotor runout (norvalwilhelm)
GM recomends shimming the rotors with full contact shims to correct runout.
The rotor should first be turned to correct excessive thickness variation if needed.
They advise to no use more than one shim between rotor and hub!
The rotor should first be turned to correct excessive thickness variation if needed.
They advise to no use more than one shim between rotor and hub!
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Re: Best way to correct rotor runout (70vert)
3. Shim the rotor
Then use arbor shims over the lugs to get it within .005 circular runout near the rotor edge.
Why machine a perfectly good rotor? Mass is good in terms of braking performance.
I have even better results when re-shimming after the rotor is slightly broken-in (<.002).
#11
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Re: Best way to correct rotor runout (norvalwilhelm)
I know you all going to laugh, but I shimmed one of my rear rotors with...get this....aluminum foil off the kitchen roll.....think I wound up with 3 layers on one stud....and the adjacent studs had 1-2 layers just for grins....
hey, it works.... :D
hey, it works.... :D