|   Screwed up my Avid pistons - now what? | bthart
Mar 22, 2003 4:10 PM | | Howdy. So I had a little spare time while cleaning up my bike, and I decided to try popping out the pistons on my Avid mechanical discs to clean them. Inboard one came out nice enough, just screwed the red knob clockwise till it popped out. Couldn't get the piston out of the slot, but I greased the threads anyway and screwed it back in.
Then I screwed the outboard piston out, and instantly realized that it was gonna be a pain to put back in. I decided to try pressing it back in place with the inboard piston screwed most of the way out and a spacer between the pistons. It didn't work, and then when I went to screw the inboard piston back in, it wouldn't go. Looking at the threads on the piston, sure enough, I broke them. I must have had very little thread engaged when I tried to force the other piston in.
So... now what? I thought about opening the brake up, pulling the piston out, putting it through a die to clean up the threads, and trying to get it back in. I'm assuming the piston is aluminum (or something softer than the piston housing, anyway) and that I haven't ruined the threads on the brake body. Any thoughts on the decreased strength of the threads holding the piston in place?
And how do I open the brake up (If I should at all)? It looks like it takes some sort of wierd torx screw with a high spot in the center?
And last of all, how the heck to I press the outboard piston back into its home?
Thanks for listening to my rambling, and for any suggestions.
Brian |
| I'll bet you wanna know right now | Sparty
Mar 22, 2003 5:07 PM | | If it were me, I would. But I would resist my impatience and instead wait until Monday to call Avid. They may be able to help you right over the phone or direct you to a shop with the proper caliper disassembly tools. In any case, they could verify what the right thing to do is.
Sorry I can't help you personally.
Maybe somebody who has dismantled a caliper &/or repaired piston threads will come along here, but actual experience goes a lot farther than speculation in situations like this. Personally, I'd wait to act 'til I'd heard the voice of experience.
Good luck.
--Sparty |
| re: Screwed up my Avid pistons - now what? | Trailripper
Mar 23, 2003 7:15 AM | | About the Torx screw with the high spot at the center, it's called "Resistorx", you can get a screw driver like this in any hardware store, I've a set of those from Facom.
Can't help you on the rest, but I guess you probably have to send it for your LBS or an Avid agent, so you can send two ways fully disassembled or half disassembled, and maybe if you open it up you can put it together later.
That's just my opinion, don't hold me responsible if you open it and get it worst. |
| Those torx bolts should <b>never</b> be removed! | shiggy©®
Mar 23, 2003 10:43 AM | | They reinforce the caliper body. Removing them does nothing to disassemble the brake.
I believe Avid has a special tool to do the job. Heff has the instructions somewhere. |
| Heff - do you have the instructions? | bthart
Mar 23, 2003 5:16 PM | | |
| re: Screwed up my Avid pistons - now what? | Theoted14
Mar 30, 2003 11:53 PM | | GOOD NEWS Brian, I did the same thing to my brakes a couple of days ago. Like you I popped out the outer piston heard the snap and knew something was different with that one. I tried for two hours to get it back in, got pissed off and walked away before I did something I would regret. The next day I tried again and succeeded. Here you go
Don't try and open the housing because it ONE PIECE and you'll just break it (the bolts you see are just there to reinforce the forging).
You'll need a small screwdriver and a micro screwdriver.
Hold the brake housing with the opening facing you and the outer side (where the piston is going to fit)on the bottom. If you'll notice the hole has a big champher to help guide the small "C" clip in the hole when compressed.
line up the piston with the hole and apply just enough pressure to THE BACK OF THE PISTON to make it slide in the hole when you compress the clip. By pressing the back of the piston it tilts bakcwards
giving you a larger opening in the front to work from. Now that you can see the clip,rotate the small clip around the shaft so that the opening is on one side while applying pressure downward with the larger screwdriver press the clip from the front ( the back of the clip is already in the hole)with the micro screwdriver.
When the clip is compressed enough the piston will slide back into the hole from the downward pressure of the larger screwdriver. After I did this the first time I took it apart again and lubed everything up with some dry lube teflon spray. It was a piece of cake once I knew how to do it.
If you have any questions just email me
Have a great day
Ted |
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