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pulsing front brakes?

Old 10-08-15, 10:05 AM
  #1  
gt3racerich
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pulsing front brakes?

Hello all.
I just started riding again after a long while. I am pretty good at maintenance and the bike is working great. After a few rides I cleaned up my Zipp 404's that are around 14 years old.
After putting them on the bike i am getting a very pronounced pulsing in just the front brake. The wheels are in great shape, they are true, and never did this before. The only thing I did was wash the bike and the wheels. When I put my other wheels back on I do not have the problem. There are black marks from the brakes on the wheels but no more so then other wheels. When I run my fingers around the rims they are completely smooth.
Any thoughts on what might cause this would be greatly appreciated.
Thanks in advance, Rich
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Old 10-08-15, 10:15 AM
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corrado33
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Hit the wheels with some rubbing alcohol and LIGHTLY touch with a scotch bright pad.

The black marks from the pads changes the friction coefficient and makes the brakes pulse. My guess is that the black mark is hiding an "unsmooth" spot.

If that's not the case, make sure the brakes are toed in correctly.
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Old 10-08-15, 10:16 AM
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Secret Squirrel
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Are these wheels the 404-Alloy composite clinchers with the aluminum braking surface?
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Old 10-08-15, 10:20 AM
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gt3racerich
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corrado33, Thanks, I will try that.
Secret Squirrel, Yes, aluminum braking surface.
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Old 10-08-15, 10:26 AM
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Works for me:

SandFlex Flexible Abrasive Block, Fine Grit, 3" x 2" x 3/4" followed by Alcohol wipe on braking surface. Abrasive block keeps rim surface flat. Use coarse file to knock "shine" off brake pads.

SandFlex Flexible Abrasive Blocks - Rockler Woodworking Tools
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Old 10-08-15, 10:36 AM
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start by replacing the brake pads..

FWIW , I fitted very abrasive pads* and did a few steepish down hill rainy stops , and wore thru a Mavic Hard anodized Brake track ,

to the base aluminum, Then replaced the pads with a more rim friendly compound .. Kool Stop .. the braking has been fine ever since.




* In my specific case it was Magura's rim brakes .. They have Kool Stop Molding their pads , then shipped them to Germany ,

now KS has the complete product.. as does the MFG..

I assume you have a road brake.. there are rather abrasive pad inserts made.. to do similar..

Last edited by fietsbob; 10-08-15 at 10:48 AM.
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Old 10-08-15, 10:50 AM
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I would start with cleaning the rims like mentioned above and maybe a light sanding on your brake pads. It is less likely but an extremely worn out rim can cause pulsing if the brake track has worn so thin it is causing the rim to bulge in spots. That would also mean your rim is beyond the point where you should have replaced it. Usually with lighter weight rims, after you have worn .5mm or so off the brake track they are due for replacement. You would also notice the brake track feels very concave.
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Old 10-08-15, 11:47 AM
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Thanks for all the quick replies.
Chris, I never really used those wheels that much so I don't think they are worn.
I just tried rubbing alcohol and scotch bright. It is better but there is still some pulsing. The pads work well with the other wheels but I will try that next.
One other question specific to those wheels if I may.
I am having a very hard time mounting tires to these wheels. As careful as I am I just damaged a new tube. It almost seems like I am on the verge of ripping the tire, that is how hard it is to mount them. The tires are Vittoria Tecno pro, if that makes a difference. I have never had a problem mounting other tires and wheels.
Any tips or info would be greatly appreciated.
Thanks again, Rich
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Old 10-08-15, 02:42 PM
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Originally Posted by gt3racerich View Post
Thanks for all the quick replies.
Chris, I never really used those wheels that much so I don't think they are worn.
I just tried rubbing alcohol and scotch bright. It is better but there is still some pulsing. The pads work well with the other wheels but I will try that next.
One other question specific to those wheels if I may.
I am having a very hard time mounting tires to these wheels. As careful as I am I just damaged a new tube. It almost seems like I am on the verge of ripping the tire, that is how hard it is to mount them. The tires are Vittoria Tecno pro, if that makes a difference. I have never had a problem mounting other tires and wheels.
Any tips or info would be greatly appreciated.
Thanks again, Rich

It does indeed make a difference for the tires. Your specific tires have a kevlar bead which is VERY tough. It makes the tires very hard to mount. There are lots of videos on how to mount those types of tires more easily on youtube.

This one shows a MTN tire but the procedure is the same regardless.
https://www.youtube.com/watch?v=zkIr...annel=MadeGood
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Old 10-08-15, 04:24 PM
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Originally Posted by corrado33 View Post
It does indeed make a difference for the tires. Your specific tires have a kevlar bead which is VERY tough. It makes the tires very hard to mount.
You may be able to ease your mounting difficulties if you replace the commonly-used Velox cloth rim tape with a thinner type such as Continental Easy Tape or a couple of layers of filament-reinforced packing tape. The thinner, slicker tape will allow you to more easily slip the bead to the center of the rim and create slack to get the rest of the bead over the rim.

If you resort to using a tire bead jack you will need to have it with you when you ride, or risk getting stuck with an un-mountable tire if you should get a flat.
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Old 10-09-15, 07:00 AM
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gt3racerich
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So the problem is caused more by the tires then the wheels. That is good to know.
I understand about getting the bead to the center of the rim, I do have the thicker rim tape as I was concerned about getting flats caused by the wheels. For whatever reason I do get more flats when riding these wheels and tires.
I just looked at the bead jack and ordered one. I only ride these wheels when my wife is available to pick me up. I could never fix a flat with this wheel/tire combo on the side of the road anyway so at least it will help me at home.
Thanks again to all that replied, I have learned a lot.
Rich
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Old 10-14-15, 08:20 AM
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dsbrantjr, thanks for the bead jack info.
I just used it and mounted the tire without any issues.
Rich
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