[Slurry]

I am once again having to perform maintenance on my brakes due to noise/rubbing/poor performance (yea disc brakes are so awesome). While i was futilely trying to straiten my rotor with cresent wrench, i noticed that my brake pads weren't parallel to my rotor, and it seemed that every time i pulled the brake lever, the pads would be off to different degrees of severity. The pads seemed to form more of a 'v' profile instead of two flush surfaces - my ascii diagram: This \ || / instead of this | || |. I took the pads out and tried to spread the flimsy little spring, but it didn't change much when i reinstalled the brakes.

What can i do to fix this?

 

[cobba]

The \ || / look is most likely from the way the spring holds the pads in place.
Do your pads & disc look like |||| or like \||/ when you squeeze the brake lever?

Have a look at the manual and see if your setting up your brakes properly: http://www.sram.com/_media/techdocs/2006_BB5and7_English.pdf

 

[Bikinfoolferlife]

Kinda sounding like you're a train wreck when trying to adjust your brakes, not good. Calm down, it's all logical and has a solution. Futiley wielding a crescent wrench on your rotors doesn't sound too good, may as well put it down and stop harming the rotors if you're not truing them (or explain what it is about truing that's eluding you). Be more concerned with the pads having alignment with the disc in the other direction (i.e. when looking down at the rotor, the pads should be an equal distance from the rotor at each end of the pad). Maybe a reinstall or at least a review of the instructions would be a good idea. Who installed your brakes?

 

[Slurry]

If i squeeze the lever all the way down, the pads sit flush, its just that they are misaligned when they retract, and are often off enough that they will contact the rotor (granted the rotor is currently warped a bit). As far as truing the rotors, i can definitely isolate the bad spots, but i cant ever bend them the right amount with the crescent wrench (its either too much, not enough, or it ends up bending another spot too). Im more worried about the pads right now.

 

[KevinB]

If i squeeze the lever all the way down, the pads sit flush, its just that they are misaligned when they retract, and are often off enough that they will contact the rotor (granted the rotor is currently warped a bit).

It sounds like you may have a weak or broken spring. I had a broken spring in a brand new pair of BB7 calipers one time. Replacement pads come with the springs. Don't know where or if you get the springs by themselves.

As far as truing the rotors, i can definitely isolate the bad spots, but i cant ever bend them the right amount with the crescent wrench (its either too much, not enough, or it ends up bending another spot too).

The trick is to make very slight corrections to the rotor and check your work after each adjustment. You should definitely try to avoid overshooting when making these adjustments.

 

[KevinB]

Don't know where or if you get the springs by themselves.

Found 'em:

http://aebike.com/page.cfm?PageID=30&action=details&sku=BR6948
-and-
http://www.harborcountrybike.com/ProductDetails.asp?ProductCode=BKPD8008&click=2

 

[Bikinfoolferlife]

If i squeeze the lever all the way down, the pads sit flush, its just that they are misaligned when they retract, and are often off enough that they will contact the rotor (granted the rotor is currently warped a bit). As far as truing the rotors, i can definitely isolate the bad spots, but i cant ever bend them the right amount with the crescent wrench (its either too much, not enough, or it ends up bending another spot too). Im more worried about the pads right now.

About that retract thing, only one retracts, the other is stationary. Meant to point that out earlier. Sounds like you just need to be a little more patient with the high spots, be sure to track that high spot as it comes from between the pads and out where you can work on it, too.

 

[Slurry]

Yea i guess i just get frustrated with them. I will be working at a shop soon so i might take the opportunity to get some of those nice morning star wrenches and the truing gauge (Drumsticks and ROC tec). I guess i should also take the time to ask if anyone here has any experience with those - the both seem like they would help a great deal and are made well, but I can say for sure without having tried them.

 

[fixbikeguy]

No offense, but I hope you're not going to be the mechanic at the shop you'll soon be working at. Maybe read up more on how to do repairs before attempting them or get some help from a mechanically inclined friend.

 

[Slurry]

I have never worked with disc brakes before getting mine a month ago, so I don't appreciate having my total mechanical skill based off of not knowing if my disc brake pad return spring is worn out.

Truing rotors with a crescent wrench would be kinda like building a wheel without a tensiometer, at least for me.

 

[dtmartin46]

I have a similar issue with a BB7 front brake... Your 'ASCII' diagram is exactly what mine looks like.

The spring for my pad assembly is new, thats the first thing I changed out, but it's still wonky. I believe your issue might be inside the brake. When I disassemble mine, and take the pad assembly completely out, one of the drums is wobbly as hell. (The one that moves in and out when you pull on the brake) You may want to remove your pad assembly and tap the drums around a little with a little screwdriver. Hope this makes sense?

My brake still works, so i've just said 'meh, flock it' so far it's ok, just a little rubbing.

 

[Slurry]

Yea, i did some more tinkering today. It seems most of the actual rubbing came from the rotor hitting part of the spring clip that was bent out in the far back of the caliper. I had to take the wheel out and bend the spring clip with a screwdriver while the pads were still installed, holding the rear of the spring clip with some pliers. I also noticed a lot of grime in the 'piston' (drum?), and that it had a significant amount of play in it like you said. I managed to clean it out as best i could without dissembling the caliper entirely, though its still has a bit of play in it.

Maybe this is just considered acceptable by manufacturers or happens with use.

 

[dtmartin46]

'piston' (drum?)

Yeh, thats what i meant. My parts vocabulary sucks.

I personally think the 'play' on the piston means the brake is on it's way to being buggered... I compared it to my rear BB7, which doesn't have any play in the piston.

 

[Bikinfoolferlife]

Yea i guess i just get frustrated with them. I will be working at a shop soon so i might take the opportunity to get some of those nice morning star wrenches and the truing gauge (Drumsticks and ROC tec). I guess i should also take the time to ask if anyone here has any experience with those - the both seem like they would help a great deal and are made well, but I can say for sure without having tried them.

I have the R2.O.C.tec tool set, good stuff, but still use an adjustable crescent for truing my rotors. It's not the tool that makes the difference, it's how you use it...and fwiw rarely whip out the R2.O.C.tec set except when I'm on the road, then it's my truing stand for wheels (and maybe a rotor, but usually just do that by eye).

You and dtmartin might want to download the service manual for your brakes and do an overhaul. http://sram.com/_media/pdf/avid/dealers/TM_MY09_E.pdf

 

[fixbikeguy]

I have never worked with disc brakes before getting mine a month ago, so I don't appreciate having my total mechanical skill based off of not knowing if my disc brake pad return spring is worn out.

Truing rotors with a crescent wrench would be kinda like building a wheel without a tensiometer, at least for me.

Problem solving is a big part of being a bike mechanic. Sometimes you just need to figure it out. Sorry, but that's just the way it is.

 

[Slurry]

Problem solving is a big part of being a bike mechanic. Sometimes you just need to figure it out. Sorry, but that's just the way it is.

Uh, I was trying to problem solve. That's what this whole thread is about. As far as 'just needing to figure it out', that's what asking others for advice is for, which is what I'm doing. You act like I read a simple bike repair manual, didn't see a solution to my problem, and then just decided that there was no way to fix it.

Why are you going out of your way to patronize me?

 

[fixbikeguy]

Uh, I was trying to problem solve. That's what this whole thread is about. As far as 'just needing to figure it out', that's what asking others for advice is for, which is what I'm doing. You act like I read a simple bike repair manual, didn't see a solution to my problem, and then just decided that there was no way to fix it.

Why are you going out of your way to patronize me?

Sorry, I work with a guy who can never figure things out for himself. He gets the advice and solution from me and claims it as his own and it chokes me. He gives up and can't problem solve at all so he gets all the answers from everyone else.
Again Sorry...had a bad day.

 

[osmarandsara]

Yeah, even with a brand new spring, your brakes will never retract evenly and will always look like this \ | | / because the H-clip spreader only applies force on one end of the break-pads......

But don't worry about it, you brakes will work fine because the caliper piston applies force to the center of the brake pad giving you even wear on the rotor......

The H-clip is actually not even necessary for your brake to operate.....its there so that its makes it easier to remove and install your wheels by preventing the rotor from catching on the pads......

 

[Bikinfoolferlife]

Uh, I was trying to problem solve. That's what this whole thread is about. As far as 'just needing to figure it out', that's what asking others for advice is for, which is what I'm doing. You act like I read a simple bike repair manual, didn't see a solution to my problem, and then just decided that there was no way to fix it.

Why are you going out of your way to patronize me?

With all due respect, you do seem to be somewhat oblivious to the basic workings of the brake...your very title of the thread shows you don't understand them.