Been working on this problem. Got my one side to .002 runout but the other side is .007 in all positions
I checked all the hubs and they are within .0005 total runout
The bolt area of the rotor is the same .0005 runout when mounted to the hub
I bought a new rotor from Autozone to try to get the car back on the road. That was worse than the one I had. .010 runout on the rotor and .007 runout on the bolt area. This has been returned
I brought the original rotor back to the place that cut it and they were working to get it within spec
I question the shim idea because if you shim between the rotor and hub doesn't that make the wheel mounting not proper? Will this not cause vibration also? or will the tire take this up?
Rotor runout
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Q45tech
- Moderator
- Posts: 14296
- Joined: Tue Apr 30, 2002 3:19 am
- Car: 1990 Q45 342,400 miles 22 years ownership with original engine
1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl
Measure the inside of wheels [even brand new] they are no where near flat parallel..........you are making the outside of the rotor hat flat with a shim...........assuming the rotor truing lathe is set correctly the edge of the rotor is also flat [after truing.
It almost never is the rotor it is the hub that is bent [rusty warped] and a 0.0005" hub gets amplified by the distance the [hub diameter vs rotor diameter].
The wheel runout lateral specs are 10 times the hub...0.005" and 2.5 times the rotor max 0.002".
Watch out and measure bearing and kingpin runout as this laterial run out can let the tire qiver in and out as it rotates causing a 55-70 mph vibration.
All these runouts plus tire wheel balance problem make for a complex series of vibrations which come and go in frequency and amplitude ever 1 mph difference and with acceleration, decel and cruise.........15 -20 different vibrations plus these change with inflation pressure as the tires warm up.
It almost never is the rotor it is the hub that is bent [rusty warped] and a 0.0005" hub gets amplified by the distance the [hub diameter vs rotor diameter].
The wheel runout lateral specs are 10 times the hub...0.005" and 2.5 times the rotor max 0.002".
Watch out and measure bearing and kingpin runout as this laterial run out can let the tire qiver in and out as it rotates causing a 55-70 mph vibration.
All these runouts plus tire wheel balance problem make for a complex series of vibrations which come and go in frequency and amplitude ever 1 mph difference and with acceleration, decel and cruise.........15 -20 different vibrations plus these change with inflation pressure as the tires warm up.
Got my recut rotor back and just trying one position I got it to .0015 runout
The only reason I questioned the shims was it seemd that my runout was from some debris on the lathe causing the hub to not be concentric to the braking surface.
I did read in a few places that the shims that gm uses are not to be reused. This does not make sense as stainless steel does not creep and as long as the rotor is cut the same and measured when reinstalled. Just seemed weird.
I guess it comes down to what you said. Hub runout will cause problems that are exagerated by rotor and rim and wheel. I still think that .0005 run out on a hub is excelent on a 10 year old car (or even a new one). Machining cast iron is terrible at best because it is so abrasive and wears cutters as you go.
Based upon my experience with aftermarket rotors, rotor hat .006 runout and braking surface .010 runout. It is well worth the money for the factory units.
Also find a good shop to have the rotors cut and let them know you will be checking runout. Only one store in town by me who even cuts rotors but the guy made right and recut for me
Thanks Q45tech for the session. I am really enjoying learning more about cars in this manor. MAybe this strng can help someone else out.
The only reason I questioned the shims was it seemd that my runout was from some debris on the lathe causing the hub to not be concentric to the braking surface.
I did read in a few places that the shims that gm uses are not to be reused. This does not make sense as stainless steel does not creep and as long as the rotor is cut the same and measured when reinstalled. Just seemed weird.
I guess it comes down to what you said. Hub runout will cause problems that are exagerated by rotor and rim and wheel. I still think that .0005 run out on a hub is excelent on a 10 year old car (or even a new one). Machining cast iron is terrible at best because it is so abrasive and wears cutters as you go.
Based upon my experience with aftermarket rotors, rotor hat .006 runout and braking surface .010 runout. It is well worth the money for the factory units.
Also find a good shop to have the rotors cut and let them know you will be checking runout. Only one store in town by me who even cuts rotors but the guy made right and recut for me
Thanks Q45tech for the session. I am really enjoying learning more about cars in this manor. MAybe this strng can help someone else out.
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Q45tech
- Moderator
- Posts: 14296
- Joined: Tue Apr 30, 2002 3:19 am
- Car: 1990 Q45 342,400 miles 22 years ownership with original engine
1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl
Old dirty lathes, warped retaining assembly, failure to use new bits, sloppy machining, [people who work for " just brakeo" are of low technican competance and training why else would they work for so little money] are all indicators of cost cutting competition.
When I do mine I spend 15 minutes cleaning T3 machine and changing bits, sanding surfaces, checking things!
If I did your rotors like I do mine I would want $45 dollars each if you handed them to me already cleaned and sanded in side as it would take me over 30 minutes to do each one imagine what you get for $10!!!!!!!!!!!!!!!!!!!!!.
Not to say a $9/hr trainee can't do almost as well IF he applies himself but what incentive is there for him to do so?He will be beat if he takes more than 10 minutes. After all the average customer doesn't have a clue.
I have some doubts about not reusing the shims [they sell shims afterall] but you must remeasure to make sure.
I seems that the right front always is worse as the right front tension rod and upper link, tire and wheel see the most stress from the rougher road edge vs center of lane.
People just do not know how much better [lower vibration] the Q feels without the warped rotor hitting the brake pad at every revolution......if it matches the tire or is 72, 144, 216, etc degrees out of phase........very complex vibration equation.
Trick on the front is to lift the car and spin the tire listening for the "shih,shih" sound of the pad hitting the warped rotor every revolution.
When I do mine I spend 15 minutes cleaning T3 machine and changing bits, sanding surfaces, checking things!
If I did your rotors like I do mine I would want $45 dollars each if you handed them to me already cleaned and sanded in side as it would take me over 30 minutes to do each one imagine what you get for $10!!!!!!!!!!!!!!!!!!!!!.
Not to say a $9/hr trainee can't do almost as well IF he applies himself but what incentive is there for him to do so?He will be beat if he takes more than 10 minutes. After all the average customer doesn't have a clue.
I have some doubts about not reusing the shims [they sell shims afterall] but you must remeasure to make sure.
I seems that the right front always is worse as the right front tension rod and upper link, tire and wheel see the most stress from the rougher road edge vs center of lane.
People just do not know how much better [lower vibration] the Q feels without the warped rotor hitting the brake pad at every revolution......if it matches the tire or is 72, 144, 216, etc degrees out of phase........very complex vibration equation.
Trick on the front is to lift the car and spin the tire listening for the "shih,shih" sound of the pad hitting the warped rotor every revolution.