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Mucky rotors?

Old 03-07-2016, 11:18 PM
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Mucky rotors?

So tonight I swapped front wheel on my bike. I keep a set of spare wheels with tires ready to go in case I have a bad flat, a dead tire or bad bearings.

Done this a zillion times but the result was weird.

Before I put the wheel on I cleaned the rotors with simple green. I didn't rinse them just wiped them dry.

When I went for a test ride, the brake lever pulsed badly. I know the rotors are strait since I just rode the bike a few minutes earlier (I swapped the rotors onto the new wheel.)

When I came back I sprayed the rotors with brakecleaner which improved the feeling but not totally.

I suspect contaminated rotors and then pads too. (they are 2 days old but were fully bedded in.)

Anyone have this happen? I have done this a zillion times and never had this happen. I wondered about if I swapped sides on the rotors but was very careful to not do that.
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Old 03-08-2016, 02:30 AM
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Get the bobbins that hold the rotor to the mounting plate spinning. I just put a bolt through with a nut and spin it with the drill.
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Old 03-08-2016, 06:52 AM
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My guess is you have dirt that is sitting between the wheel and the disc. When you swapped rotors, miniscule particles of dirt layed either on the disc, or the wheel itself, which now sits between the two of them. The discs fail to sit perfectly on the wheel, and as the wheel spins, it wobbles, causing the pulse in your lever.

If I were you I'd start there, and remove and clean the surface areas again with B & P cleaner to be sure there is no dirt left in between the discs, and wheel.

Last edited by Jack Flash; 03-08-2016 at 07:14 AM.
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Old 03-08-2016, 07:07 AM
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Ah, yes, thanks flash and spokes, you guys are both right.

This was a really quick fix just before I needed to get cross town late at night so it didn't get my attention.

I agree with both of those assessments and will implement them asap. Always good to have another brain involved.

Flash I just painted the spare wheel last season before storage so that would do it too, tape gunk or something.

Last edited by smokinjoe73; 03-08-2016 at 07:32 AM.
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Old 03-09-2016, 07:17 PM
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OK so flash you were right on. I disassembled everything and the wheels had crud where the rotors mate to it. I got the rim on ebay last fall and painted it but never cleaned that spot.

Thanks.
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Old 03-09-2016, 07:41 PM
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Did you take any pictures Joe? It would be interesting to see how little crud causes such a big problem.
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Old 03-09-2016, 09:47 PM
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No, I was in a mad hurry to remove the front wheel, the rotors, then clean it with a scotch brite wheel, a wire wheel, and a scraper then get it back on and go to work.

It was not much gunk at all, just some caked on crud bits and maybe some masking tape chips from when I painted the wheels.

I know better but all my spare wheels are usually pristine.

I haven't had this issue since my van wheels had a slight high speed wobble. I tried expensive high speed balancing but no help. Then a mechanic friend told me to scour the hubs and wheels where they met. Just a little rust on the hubs but cleaning it made the van butter smooth at 80mph. (!)

The effect on the vtr brake lever was alarming. Huge movement of the brake lever pulsing.

Now its back to perfect. Again, I knew better but had a brain fart. Needed some other mechanical minds to put other eyes on it so to speak.
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Old 03-10-2016, 10:42 AM
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Originally Posted by smokinjoe73 View Post
OK so flash you were right on. I disassembled everything and the wheels had crud where the rotors mate to it. I got the rim on ebay last fall and painted it but never cleaned that spot.

Thanks.
What's important is it's fixed...at very low cost.
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Old 03-10-2016, 10:51 AM
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Originally Posted by VTR1000F View Post
Did you take any pictures Joe? It would be interesting to see how little crud causes such a big problem.
It really doesn't take much. Look at the diameter of the disc. Half a millimeter at the center becomes three-four at the other end of the disc.
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