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burnedthetoast
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224 Posts
Discussion Starter · #1 ·
I'm attempting to put a BB7 brake w/ 160mm roundagon rotor on my Monocog 29er, and am running into a problem (which I'm sure is MY problem and not the bike's). When I mount the brake, I can't seem to get the rotor to spin freely - it seems like the "tips" of the rotor are knocking against something slightly as it spins. The monocog has a sliding brake mount and a track end, so it seems there's a decent bit of play there, but I can't seem to figure out whether my wheel placement needs to change, or if I'm mounting the brake incorrectly, or what. Any suggestions?
 

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Derailleurless
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9,122 Posts
...or just a couple of M6 washers from your hardware store. Avids aren't that picky.

In fact, you can use the flat washers that come with the brake as spacers, and use the hardware store washers as washers under the bolt heads, since the provided washers are usually thinner than what you'll find at Ace or True Value.
 

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burnedthetoast
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224 Posts
Discussion Starter · #4 ·
Thanks guys - I actually went out just after I'd typed the question and checked it all out again - and it is the bolts that are too long. I'll get some washers and it should work out fine (Nate - I'll probably take your suggestion on using the included washers as spacers).

Sure would be convenient if they'd thrown a couple more washers in the brake package though... or maybe mentioned to check it in the installation instructions!
 

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I like turtles
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6,374 Posts
The small metal nurled (sp?) thread-on nuts from your presta valves will work perfectly - that is how I mounted my BB7s on my Monocog.
 

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burnedthetoast
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224 Posts
Discussion Starter · #6 ·
TiGeo said:
The small metal nurled (sp?) thread-on nuts from your presta valves will work perfectly - that is how I mounted my BB7s on my Monocog.
You, sir, are brilliant!
 

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burnedthetoast
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224 Posts
Discussion Starter · #7 ·
New question:

Got the mounting all figured out, but now I'm having issues with the rotor. Everything seems to be good until I tighten up the rear wheel QR - at which point the rotor snugs up against the brake mount/outside side of the brake. It seems like maybe the stays are flexing a bit? Anyone have any experience w/ this or any ideas?
 

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Retro Grouch
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2,091 Posts
burnedthetoast said:
New question:

Got the mounting all figured out, but now I'm having issues with the rotor. Everything seems to be good until I tighten up the rear wheel QR - at which point the rotor snugs up against the brake mount/outside side of the brake. It seems like maybe the stays are flexing a bit? Anyone have any experience w/ this or any ideas?
This may seem to obvious an answer, but you need to adjust the cliper with the QR tight. I have the same issue with the fork on my SASS.
 

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burnedthetoast
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224 Posts
Discussion Starter · #9 ·
aka brad said:
This may seem to obvious an answer, but you need to adjust the caliper with the QR tight. I have the same issue with the fork on my SASS.
I tried that - that was actually how I originally went to set up the brakes (makes sense, right?). I only discovered that it seemed better w/ the QR loose when I loosened it to check that the wheel was lined up correctly in the slots.
 

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Registered
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195 Posts
BB7 Brake help

Not sure if This will help, but first make sure you have the right adaptor. The front and rear are different. Avid adaptors have the disc size and an F or R on them. If you have 160mm discs it should say R 160.

If the adaptor is correct, you can shim the caliper inboard with washers between the IS mount and adaptor. I've used the small thin washers from the Avid hardware, and it worked well.

Also, in case you didn't adjust them properly, here's how to do it. With the wheel out, Bolt the adaptor to the frame. Have the brake cable disconnected, or very loose (no tension) disconnected is better. Leave the caliper bolts just loose enough that the caliper slides inboard/outboard. Back the pads out almost all the way. Mount and tighten the wheel. Using the inboard pad adjustment wheel, align the caliper so that there is less gap to the outside of the rotor, and more gap to the inside of the rotor. The ratio is 1/3rd to 2/3rd. Once that's done, use the outboard pad adjustment to firmly clamp the rotor between the pads. While doing this press down on the caliper to keep it from rising off the adaptor. When the rotor is clamped, tighten the caliper mount bolts 8-10nm then back the pads clear of the rotor so that it spins freely. Adjust the inboard pad until it begins to rub while the wheel is spinning, then back it out one notch. Do the same for the outboard pad. Reconnect and tension the cable.
 

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burnedthetoast
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224 Posts
Discussion Starter · #12 ·
I do have the right adaptor - R 160, and I did follow the procedure above (which mirrors the instructions that come with it).

I've got the problem pretty much fixed now, but there's VERY little clearance (about 0.5mm) between the rotor and the brake body, even when I've adjusted it so it's as far out as the caliper bolts will allow. It works for now, but because there's so little room it'll be a pain to readjust whenever I swap out cogs.
 
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