Rear-brake rubbing and moving

Gunjira

Maximum Pace
Oct 2, 2009
1,003
176
83
Tokyo
#1
I hope I can get closure on this issue, which I never resolved since I got this bike, complete with an Ultegra brake-set.

The problem is that the rear-brake will always somehow move around, so I end up with a shoe rubbing on the rim. The rim itself is perfectly true.

I have tried:
-centering the brakes perfectly and tightening them with force many times.
-replacing the toothed washer between brake and bridge.
-locking everything down with loctite centered perfectly.

Still to no avail. Usually it takes less than 20km before one side starts rubbing again. So I have to open the brakes almost all the way again. Riding this way is especially annoying riding downhill in the drops, because the rear brakes will not grip before pulling them almost all the way.
 

FarEast

Maximum Pace
May 25, 2009
5,528
538
193
Yokohama
#2
ok, yes the Ultegra washer is crap and is really just a spacer. I would suggest going to one of the larger bike stores that stocks little things like Y's in Shinjuku or Yokohama and picking up 2 DuraAce washers that have teeth or a DIY store may also sell them but you want to make sure they have been treated not to rust.

If this doesn't resolve the issue it could be that the bolt that locks the brake in is the wrong length.

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These come in numerous lengths and if you have one that is too long all you will do is tighten it against the thread and it will never tighten to 100% capacity.

let me know how you get on.
 

GSAstuto

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Oct 11, 2009
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tokyo
www.roadfixie.com
#3
BTW - Y's in Shinjuku (downstairs) was kind enough to give me a couple different brake bolt nuts so I could get the right one exactly for my frame. So, for sure I know they have a good stock of these in their mechanic's box.
 

Gunjira

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Oct 2, 2009
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83
Tokyo
#4
Thanks for the tips!

I pretty much ruled out the bolt, since it doesn't penetrate past the bridge.
Upon seriously researching this and looking around, it turned out, that the washer I was using didn't engage properly on the brake side. Since the bike is second-hand, it might have been from a different brake OR maybe during use it filed away the brake side bolt.

Anyways, I got a DuraAce washer at Y's custom with the same inner hole diameter, but smaller total. This way it engages with the flat surface of the brake bolt > problem solved.

Along with the new Dixna J-Fit (recommend!) handlebars, this takes biking to a new comfort level for me. Must ride now!
 

FarEast

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May 25, 2009
5,528
538
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Yokohama
#5
Glad the washer sorted it all out..... actually it sounds like the bolt is the issue if it doesn't penertrate the frames as on all my bike the bolt rests on a flange inside the rear stay or front fork.
 

Gunjira

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Oct 2, 2009
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83
Tokyo
#6
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A picture is telling more than thousand words.
What you see in the middle is the part that caused my problem. It is the last solid part of the brake body before the bridge. With the washer I had previously the teeth on that side did not engage with the outer side of said part. The new Dura washer has a smaller diameter, so I'm fine:happy:

Didn't even realize there were different size washers. But hey, Campa delta brakes used a special hex key for adjustments:rolleyes:
 

Gunjira

Maximum Pace
Oct 2, 2009
1,003
176
83
Tokyo
#7
Sorry to bump this up, turns out I actually bend the rear when sprinting out of the saddle. With the break shoes set for tight clearance, the rim touch on one side and move the brake while slowing me down in the process as well. Just had it happen to me at Tokyo Enduro.
Will open the brakes up until I can afford a new, stronger wheel.

In retrospect that must have been how I ruined my wheel on the first ever TCC ride I partook at the beginning of the year.
 

FarEast

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May 25, 2009
5,528
538
193
Yokohama
#8
Gunjira, sounds like the wheel needs a service. A lot of factory built wheels require the spoke tension upped after about 1,000km. If you are doing hill repeats or can put out over 1000w this can be a lot sooner.

I have my wheels serviced abut every 4 to 6 months to have them re-tensioned, especailly my super light wheels.
 

andywood

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Apr 8, 2008
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Niigata
#9
What wheels are you using?

You should check that your rim is running true by spinning it with your brakes almost closed. You can make minor adjustments to the spoke tensions to get it right.

If the problem is only with hard efforts, there are two things you can do to keep the wheel "true". I have tried this for my training wheels:

1. Bind the spokes together at the point where they cross.

2. Get really hard rims.

I used to do the former on my training wheels (Mavic Open Pro). The only problem is there is a lot of stress on the rims and cracks will appear eventually. For me after about 20,000 km.

Now I'm trying the 2nd option with Swiss DT rims. The rims are really tough. I broke a spoke last week and the rim stayed almost true. I expect to have more spokes breaking through the season but hope to have less stress applied to the rim.

Hope this helps.

Andy

www.jyonnobitime.com/time
 
Jan 14, 2007
2,514
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Noda
japanichiban.com
#10
Does your thigh bump into the cable? Mine used to when doing sprints and sometimes knock it so hard the pads would rub.

One way to check would be...does the pad rub on the cable side only?

One solution is to shorten the cable as much as possible so it doesn't curve up to your thighs...
 

Phil

Maximum Pace
#11
Don't know if this would help at all and apologies if already known, but a lot of folk set their dual pivots brakes up with tighter-than-necessary clearances (I know I used to). Park Tools recommends 3-4 mm on either side, which gives your wheel a little more leeway to flex and gives your fingers better purchase to operate the brakes. As long as you don't bottom out the lever on the bar you don't lose any stopping power.
 

Gunjira

Maximum Pace
Oct 2, 2009
1,003
176
83
Tokyo
#12
Thanks Phil, your advice mirrors my findings.
Without being able to get a higher quality replacement wheel or lacing the spokes together, I just have to find the sweet-spot with a couple of mm distance.

I don't like it too loose, because it feels like less control when braking in the drops. On downhill your hands cramp earlier when you have to put tension on the levers just to feather the brakes.

When I tried to salvage my prior more mediocre rear wheel after exactly the same thing happened, I turned them in to Ys road Ueno because I had broken two spokes on a little hill in Kanda. They replaced the spokes, trued the wheel and set the brake-shoes to just 1mm clearance. Maybe they were proud of their handiwork with trueing, but basically this has led me down the wrong path. From now on I'll live loose.