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Old 04-21-07, 07:39 PM   #1
TCR
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Avid BB7 Mechanical Disk Brake Questions...

New to MTB'ing so I know nothing when it comes to these things.

It looks like the rotor is slightly warped on the front. Even when I turn the red knobs on each side all the way out the rotor still rubs in one spot and there's a visible wave in it. However, it doesn't appear to be that bad. Currently the rotor is up against the one side - not centered - and I don't know how to fix this. So...

1) How do rotors get warped in the first place? Can they be fixed? Do I need to buy the exact Avid rotor is there others that will work just as good?

2) How do I adjust the centering of the rotor? Is it with the #1 and #2 bolts? That looks like a torx bolt but it has a dot in the middle. What tool works on that?

3) What is the tiny #4 hex bolt for?

Sheesh, I thought working on my roadie was confusing.



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Old 04-21-07, 08:26 PM   #2
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You can probably gently bend it back using an adjustable wrench.
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Old 04-21-07, 08:39 PM   #3
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Read this:

http://www.sram.com/_media/techdocs/...03-install.pdf

It's for the earlier bbdb (you can search for the BB7, but the BB7 manual is multilingual and harder to follow, IMO)

Basically, you need to fix the out of true rotor (bend back or replace)
Then replace pads if needed (if your pads are not worn evenly, you will probably want to replace them) and follow the caliper truing intructions.

Caliper truing is done by loosening bolt 5 and 6 and using the red dials to clamp the pads onto the rotor. Then you tighted up 5 and 6 (there's a lot of float in their bolt holes) and back off the red dials until the rubbing goes away.
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Old 04-21-07, 09:02 PM   #4
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Thanks phantoj! Didn't realize there was lateral play if bolts 5 and 6 were loosened.
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Old 04-21-07, 09:58 PM   #5
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Yep... push up on "3," and loosen 5 and 6. Then tighten them again. Also make sure the wheel is in the dropouts correctly.
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Old 04-21-07, 10:10 PM   #6
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For best alignment you are supposed to first loosen #5 and #6, then grip the brake levers as much as you can and tighten #5 and #6 while still gripping the levers. This obviously assume the rotors are straight. If a rotor has a bend try straightening it as suggested above or probably better replace it.
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Old 04-21-07, 10:22 PM   #7
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Quote:
Originally Posted by gpelpel
For best alignment you are supposed to first loosen #5 and #6, then grip the brake levers as much as you can and tighten #5 and #6 while still gripping the levers. This obviously assume the rotors are straight. If a rotor has a bend try straightening it as suggested above or probably better replace it.
if you do that on a BB7, you'll end up with the rotor pressed against one of the pads. that method works pretty well for hydraulic brakes most of the time however, the easiest way for me to do it is to just do it by eyeballing it. put the inboard pad closer to the rotor than the outboard pad and you'll be golden. once you get the hang of it, it's very easy to get the pads parallel to the rotor.

as for bolts #1, and #2, don't touch them, they are tamper-proofed for a reason.

the cheater way to align the caliper to the rotor on the BB7 is to just use the two red dials and move the pads to where you want them in relation to the rotor.
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Old 04-21-07, 10:23 PM   #8
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Quote:
Originally Posted by gpelpel
If a rotor has a bend try straightening it as suggested above or probably better replace it.
Should I replace it with an Avid rotor or are others just as good? For example, will this work:

http://cgi.ebay.com/Disc-Brake-Rotor...QQcmdZViewItem
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Old 04-22-07, 07:03 AM   #9
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Quote:
Originally Posted by smittyben
any rotor of the right size will work, i have like 5 extra rotors that will all work, most of them are hayes

that rotor is 180mm check if its the right size
Cool, guess I'll try straightening it and start looking for a new rotor 6-bolt, 185mm rotor.
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Old 04-22-07, 09:27 PM   #10
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Quote:
Originally Posted by smittyben
did you check what your other ones where
It's an Avid 185mm. I assume this Avid G2 Clean Sweep Disc Brake Rotor, 185mm, will work? It has a slightly different look (design) but I guess it will work fine, right?

http://cgi.ebay.com/Avid-G2-Clean-Sw...QQcmdZViewItem
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Old 04-22-07, 09:29 PM   #11
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My method for this brake is a slight change from others. If you've not gotten your brakes to where you want them you might give this a shot.

1) First thing set the spring tension that you feel is nice. You do this by loosening bolt #3 (or the cable anchor bolt) and lifting the arm that bolt #3 is attatched to till you feel that the initial spring pull is comfortable. The tension you feel in that arm will be roughly equivalent to the tension you feel when you pull on your brake lever.

2) Loosen bolts #5 and #6 so there is play in the whole brake caliper.

3) Using the pad-adjustment dials (those big red ones that I think you labled #4) you want to tighten BOTH pads in evenly onto the rotor until there is no play in the caliper and the wheel doesn't move much when you spin it.

As far as I'm concerned, at this point that caliper is centered relative to the Rotor. As long as your rotor is true you should be able to Tighten down on bolts #5 and #6 and then back out the two brake pads. What you're going for is pulling on your brake lever and getting a solid hit on the brakes when the brake lever is parallel to your handlebars. Not mushyness mind you but you grab the brake when that wheel is spinning and it stops the wheel dead without the feeling that you have to squeeze the brake lever harder to get more braking power.

Have fun!
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Old 04-22-07, 10:08 PM   #12
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Quote:
Originally Posted by TCR
Should I replace it with an Avid rotor or are others just as good? For example, will this work:

http://cgi.ebay.com/Disc-Brake-Rotor...QQcmdZViewItem
Personally, I'd not use a generic rotor. By using Avid parts, if you have a problem you at least know it's not due to part incompatiblity or subpar quality. But I'm really a disc brake newbie.

Don't forget to check to see if your current rotor is fastened tightly to the hub! That should be Step #1.
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Old 10-15-07, 06:48 AM   #13
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you say it looks warped,just buy a new rotor there cheap.
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Old 10-15-07, 07:54 AM   #14
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you say it looks warped,just buy a new rotor there cheap.
They're not terribly cheap. If it's fine otherwise, at least trying to bend it back into true should be attempted. It's steel, after all.
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