Mountain Biking - My Avid BB7 discs are rubbing against the pads

Guys,

The subject line speaks for itself. I got the 160mm discs from Pricepoint and installed them both and both discs rub against the pads. Is that normal? Both discs rub against the pads at certain point. What can I do to 'true' the rotors?

Thanks,

Ricardo

Guys,

The subject line speaks for itself. I got the 160mm discs from Pricepoint and installed them both and both discs rub against the pads. Is that normal? Both discs rub against the pads at certain point. What can I do to 'true' the rotors?

Thanks,

Ricardo

As Hank has so wonderfully put it a few times:

http://www.ted-kyte.com/3D/Pictures/Crescent%20Wrench.jpg

Well your rotors are brand spanking new so are you sure they are bent?

Try playing around with the red wheel adjuster what-nots on the sides of the calliper.:D

. . . both discs rub against the pads.Actually, it's the other way around. The pads are rubbing against the discs. Your brakes came with a good set of instructions. Follow them. Make sure your caliper placement is set up (shimmed) exactly like the instructions say; THEN adjust your inner and outer pads.

You also need to make sure that you have the rotor mounts torqued to the same spec. If one is quite a bit different the rotor will flex. Assuming the rotor isn't warped, you should be able to get them trued up and get your calipers set so that nothing is rubbing.

You must follow the BB7 installation instructions very carefully. Most times when I've read someone having problems immediately after installation, it is usually due to how it was installed. I know because I had the same problem. I scanned through the instructions and missed a crucial step. Once I followed the instructions properly it was like butter.

Edit: Typos and poor grammar.

If you have older brake lines they might need replaced. When replacing both my front and rear brakes they didn't have the smooth pull to them like the POS stockers did. After installing fresh cables the difference was awesome... Just an FYI

Well guys,
thanks for the recommendations. I've installed the brakes TWICE per the instructions. Step by step all the way yet they are rubbing. The torque thing might be the cause. I dont have a proper Torx wrench with the gadget to measure the proper torque. Where can I find one?

Thanks,

Ricardo

Does the rotor contact the slot in the caliper body at any point in its rotation (pads backed off all the way)? If so, you don't have your 2/3 - 1/3 gap set right yet:

http://www.sram.com/_media/techdocs/2006_BB5and7_English.pdf - Page 7

Sometimes you still need to shim between the disc tabs and the adapter slightly because there is not eough side-to-side adjustment to locate the caliper properly.

http://www.parktool.com/images/products/productimages/spr_DT-2_200598_61713.jpg (http://www.parktool.com/images/products/productimages/spr_DT-2_200598_61713.jpg)

Aye, its not as stylish as an adjustable wrench, but gets the job done.

Ricardo your missing something here man. I can't figure out how a brand new set of calipers and rotors are having problems. Can you take some pics???

I just installed a rear bb7 on my bike last night with no problems at all. Swapped over my cassette to my new wheelset also...:D

Well guys,
thanks for the recommendations. I've installed the brakes TWICE per the instructions. Step by step all the way yet they are rubbing. The torque thing might be the cause. I dont have a proper Torx wrench with the gadget to measure the proper torque. Where can I find one?

Thanks,

Ricardo
this is likely NOT the problem.

It is possible that the rotor is bent. Spin the wheel and look at it and you should be able to tell. A little bit of motion is okay, maybe a millimeter or so, but more than that could be a problem. When you say they are rubbing, does that mean you have backed the pads out all the way and they are STILL rubbing? or are you trying to keep the pads too close to the rotors? All of this should be pretty obvious. Not to be a jerk or anything, but if you can't figure this one out then you might reconsider working on your own bike.

It is possible that the rotor is bent. Spin the wheel and look at it and you should be able to tell. A little bit of motion is okay, maybe a millimeter or so, but more than that could be a problem. When you say they are rubbing, does that mean you have backed the pads out all the way and they are STILL rubbing? or are you trying to keep the pads too close to the rotors? All of this should be pretty obvious. Not to be a jerk or anything, but if you can't figure this one out then you might reconsider working on your own bike.

Well, if I back them all the way they dont rub at all but if I set them up per the instructions, they rub a little bit at certain point.

Ricardo

Does the rotor contact the slot in the caliper body at any point in its rotation (pads backed off all the way)? If so, you don't have your 2/3 - 1/3 gap set right yet:

http://www.sram.com/_media/techdocs/2006_BB5and7_English.pdf - Page 7

Sometimes you still need to shim between the disc tabs and the adapter slightly because there is not eough side-to-side adjustment to locate the caliper properly.

That is not the case, it rubs against the pads when they are set up according to the instructions.

Ricardo

Your rotors may be alittle out of true. The rotor from my 07 Juicy 7 was a little whacked out of the box.

You might have to get the mounting tabs on the frame faced. Maybe they are not quite parallel or have paint build up. See link for further explanation:

http://www.parktool.com/products/detail.asp?cat=14&item=DT%2D1

Actually, it's the other way around. The pads are rubbing against the discs. Your brakes came with a good set of instructions. Follow them. Make sure your caliper placement is set up (shimmed) exactly like the instructions say; THEN adjust your inner and outer pads.


Avid mounting system is "tri-align". You don't shim anything.


You might have to get the mounting tabs on the frame faced. Maybe they are not quite parallel or have paint build up. See link for further explanation:

Avid mounting system is "tri-align". You don't need to face the frame. (unless of course it's an extremely poorly made frame and way out of alignment)

Avid mounting system is "tri-align". You don't need to face the frame. (unless of course it's an extremely poorly made frame and way out of alignment)


Tri-align isn't going to help you if there is excessive paint build up. I think a couple millimeters would be enough to make the disc rub.

that bike looks like it's probably got clear coat over aluminum, no paint so that's not the problem.

I think we have user error.

I could see maybe the front having problems or just the rear because of something being bent but both front and back having problems. I don't think so.

I have BB5s and according to my LBS there is ALWAYS a little bit of brakle pad rub against the rotor and there's nothing you can do about it.

Especially since I like my pads as close as possible to the rotor, I have to put up with a small bit of rub. It is only on one spot while the wheel is spinning.

BB5s don't have the adjuster on both pads like the BB7s do. It's pretty fool proof to setting the BB7s up to not have rub unless there is a problem with the rotor or frame mounts.

BB5s don't have the adjuster on both pads like the BB7s do. It's pretty fool proof to setting the BB7s up to not have rub unless there is a problem with the rotor or frame mounts.


True. But just a question to help myself make sense of it:

The BB5s do have an inboard pad adjuster and the outboard pad is adjusted using the cable barrel adjuster. What would be the difference in using the barrel Vs. a seperate outboard pad adjustment like on the BB7? Wouldn't both move the pad in and out anyway?

True. But just a question to help myself make sense of it:

The BB5s do have an inboard pad adjuster and the outboard pad is adjusted using the cable barrel adjuster. What would be the difference in using the barrel Vs. a seperate outboard pad adjustment like on the BB7? Wouldn't both move the pad in and out anyway?


The cable barrel adjuster is not used to adjust the pads. It is only to take slack out of the cable. BB7s are just easier to adjust.

My rear brake makes a peculiar sound when I hold down the lever for a couple of seconds. It sounds like a wwII plane got shot down and makes that falling sound, if ya know what I mean. :/

My rear brake makes a peculiar sound when I hold down the lever for a couple of seconds. It sounds like a wwII plane got shot down and makes that falling sound, if ya know what I mean. :/BB7s? Yeah, I hear it too. It's the buzzzzz of the slots in the disc. Most unique.

No MX1's. I bet its something with the pads, but slots in the disc? I rarely use my front brake. Not sure why, I just like stopping with the rear:D

I rarely use my front brake. Not sure why, I just like stopping with the rear:D

You mean skidding with the rear...:beer:

The cable barrel adjuster is not used to adjust the pads. It is only to take slack out of the cable. BB7s are just easier to adjust.


I think that is just for the BB7 and not the BB5. For the BB5, you have to adjust the barrel in order to account for pad wear.

A portion of the BB5 manual is below: