Yesterday I started pulling all the parts from my old bike to put on to my new frame. While doing this I decided to give my brakes a good cleaning. I notice that the piston on my front caliper seemed to be extended all the way out. When I tried to back out the adjustment knob it would go a few turns then stop like it suppose to. Yet the piston was still almost fully extended?
So today I started messing with it again. I would try turning the knob again to the point where the torque arm started moving. I gave it a little more force and then it gave way and start to turn again. I did this a few more times and now I am to the point where the piston is close to being flush with the caliper body.
Now before I attempt to take it apart does anyone know what could be the cause of the knob jamming up like this?
Its a very simple system, the adjuster pushes and pulls on the piston. If you have run these for awhile they could have some lubrication issues.
Now i would remove the pads, you a very light oil with one of the fine tips that gets into cracks and crevesises. You just a bit and lube the sides of the piston. Hold the brake so the adjustor knob is pointed down, and then work the adjuster a bit to distribute the oil over the piston. Once it runs smooth, then use several rags and really remove excess oil. You could use some alchol on a rag for your final cleanup to make sure you get as much surpluss oil as you can.
Very light on the oil, very very light.
Now if i am wrong, (and lord knows i may well be way off base here) wiser minds then mine will come by and correct me the error of my ways. LOL LOL
BB7 Service Manual: http://cdn.sram.com/sites/default/files/techdocs/service_manual_bb7__bb5.pdf
Old BB7 Service Manual: http://cdn.sram.com/sites/default/files/techdocs/Avid%20BB7%20Overhaul%20Guide.pdf
Don't know about the new BB7's but with the old BB7's when you turn the outer pad adjuster and move the pressure foot (what the pad is seated against and what you call a piston) inwards and then turn the outer pad adjuster the opposite way to move pressure foot outwards it won't move by itself, the pressure foot needs to be pushed into position by the pad pushing against the rotor when the torque arm is engaged or by pushing it with the flat edge of a screwdriver.
I didnt run them that long but I did ride with them across a section of a river several times last year :-). Either way there was some small debris under the piston/ pressure foot (force of habbit to call it a piston lol). I wasn't able to remove the entire assembly since there is a lock ring tool needed to do so. since cleaning what I was able too and messing with it is seems to have gotten some what better. I do have a new issue now lol. I took the piston out and well now I can't seem to get it back in lol. I don't k ow how clear this image is but the pressure ring is extending past the grove where it fits into. So my few attempts to push it back in have failed and I ended up with a bit of a rough edge under the groove now.
From the Old BB7 Service Manual.
A bit of grease on the spring clip that's on the pressure foot and around the hole in the drive cam might make it a bit easier to join the two pieces together.
The most common problem that doesn’t require disassembly:
A common BBDB/BB7 call we get is about a caliper with the outboard pressure foot dislodged. If the outboard adjustment knob is turned too far clockwise without the rotor in the caliper (wheel off or caliper removed), the outboard pressure foot can be pushed out of the drive cam and float free in the caliper body. The brake is not broken and it doesn’t need to be disassembled to replace the pressure foot.
To replace the pressure foot, turn the outboard adjuster knob counter clockwise until it stops. If the knob doesn’t stop, then the footscrew (you can see the end of the footscrew in the center of the knob) has become disengaged from the knob, and possibly from the threads inside the drive cam. In this case, remove the knob, then use some small needlenosed pliers or a Schrader-valve tool to turn the foot screw all the way back out until it stops. Once this is accomplished the pressure foot can be replaced. Relocate the pressure foot into the bore, then give it a firm push in the center. It will “click” back into place.
If you removed the outer knob, replace it, and you’re done!
The splined lockring tool is called a MDT-1 tool, part No.11.5365.102.900
If you want one you should be able to find one on ebay.
Does the type of grease matter? Right now all I have is automotive grease. And the spring clip is it suppose to be that big?
Thanks for the part number I will be grabbing one off of ebay.
I didn't read thru this thread but after a quick glance I'd say take a look at these vids on you tube... from the looks you have the newer model BB7...
New (2007 and up) Avid BB7 cleaning PART 1 - YouTube
part 2 (you tube didn't allow over 5 min vids at the time)
Part 2 BB7 (newer) improve perform - YouTube
but to make sure...
whichBB7.mov - YouTube
and if they are the older body caliper...
New (2007 and up) Avid BB7 cleaning PART 1 - YouTube
Last edited by thomllama; 01-16-2013 at 04:16 PM.
From the old manual
I have no idea on how your grease would compare with the grease listed above.
Use a grease with a minimum temperature rating of 400 degrees Farenheit such as Tri-Flow High Performance Synthetic Grease with Teflon or Pro-Gold EPX Cycle Grease.
The spring clip does look to be spread open a fair bit but if it's no larger then what it was when you removed the pressure foot, you should be able to push the pressure foot back into the drive cam.