Disc runout
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Joined: May 2021
Posts: 65
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From: Jacksonville, FL
Thanks for coming back to the discussion GTR. I thought hand grinding was probably a bad idea but I am glad to have that twice confirmed. I read through your article a few times when you sent the link. Extremely helpful!
I will check and grind the holes. These Power stop rotors seem very well made and the fit is very snug. Then I will shim my way out of this hole. 🤞
I will follow up on the results if I don't have hide from the divorce lawyers. I kid!
I will check and grind the holes. These Power stop rotors seem very well made and the fit is very snug. Then I will shim my way out of this hole. 🤞
I will follow up on the results if I don't have hide from the divorce lawyers. I kid!
Safety Car
Joined: Jul 2005
Posts: 3,691
Likes: 833
From: WI
One last thought on the rotors. The original C3 rotors I've seen were square-cut inside. The inside corner of the rotor was square. However, I have seen some new, replacement C3 rotors which are slightly radius-cut on the inside edge (the outer area where the hub face goes).
The issue can be: the hub face may be too wide and the rotors with the radius cut won't fit 'flat' onto the hub face (due to the radius).
I know this is hard to explain ...(and probably harder to follow), but check the inside edge off your new rotors and see if the are square edged inside or slightly rounded on the inside corner. It might be you need to bevel the outer edge of your hub face. I suspect this has made a lot of C3 owners scratch their heads when they went to put on rotors. It would be impossible to get them to sit 'true' if they didn't completely sit on the hub face.
BTW, it's not the spindle that's off on C3s. It's the hub that weren't always machined 100%. This has been an issue going back to 1965.
The issue can be: the hub face may be too wide and the rotors with the radius cut won't fit 'flat' onto the hub face (due to the radius).
I know this is hard to explain ...(and probably harder to follow), but check the inside edge off your new rotors and see if the are square edged inside or slightly rounded on the inside corner. It might be you need to bevel the outer edge of your hub face. I suspect this has made a lot of C3 owners scratch their heads when they went to put on rotors. It would be impossible to get them to sit 'true' if they didn't completely sit on the hub face.
BTW, it's not the spindle that's off on C3s. It's the hub that weren't always machined 100%. This has been an issue going back to 1965.
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Joined: May 2021
Posts: 65
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From: Jacksonville, FL
Holy cow! Really not my first choice of words. I know exactly what you are describing! That is amazing!I will check that in the morning before work. Was a little suspicious of how snug the new rotors fit around the outer part of the hub but shrugged it off as just a really tight fit. I will be looking at both of these areas much more closely. And it is good to know that it is the hubs that are the offenders and not the spindles. It will keep my mind from wandering there. I over think things. Which I can testify is not a measure of intelligence. Thanks!
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Joined: May 2021
Posts: 65
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From: Jacksonville, FL
Thanks GTR, Ground the outer edge of the hub, hat holes and wire wheeled the ID of the hat. Put the rotor back 180⁰ from 0. Maybe improved the runout by .001. The ID seems very snug but not uneven. Will do more diagnosing when my back recovers in a few minutes. Feeling like it is a rotor runout issue but I want to be sure.
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Joined: May 2021
Posts: 65
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From: Jacksonville, FL
Thanks Mark! I saw the attachment. Did some grinding and cleaning this morning and the hub looks much better. The hub has a beveled outer edge. I am going to pull the hub ( again) in the morning to confirm what looks to be about a 1/4 inch gap, maybe a little less between the OD of the hub and the inner hat.
To address the ID fit, I put some grease on the back of the hat and tightened the rotor to the hub. Then I removed the rotor. The grease looked evenly distributed on both surfaces and all the way around. If you're not fully unconscious yet I will continue.
For now I don't think there is a fitment problem. Rechecked the runout with rotor on at the 0⁰ mark and at 180⁰ mark from 0⁰. The 0⁰ point and .015⁰ point remain the same in relation to the marked points on the hub. I even checked the hub for runout. I don't remember the exact measurements but the low and high spots were at the markings on the hub.
If any of this winded dialogue needs clarifying please let me know. My interpretation, tests and results are all subject to my own worst enemy.
To address the ID fit, I put some grease on the back of the hat and tightened the rotor to the hub. Then I removed the rotor. The grease looked evenly distributed on both surfaces and all the way around. If you're not fully unconscious yet I will continue.
For now I don't think there is a fitment problem. Rechecked the runout with rotor on at the 0⁰ mark and at 180⁰ mark from 0⁰. The 0⁰ point and .015⁰ point remain the same in relation to the marked points on the hub. I even checked the hub for runout. I don't remember the exact measurements but the low and high spots were at the markings on the hub.
If any of this winded dialogue needs clarifying please let me know. My interpretation, tests and results are all subject to my own worst enemy.
