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The pistons on my Formula ORO K18s are sticking and need servicing, I've not tried doing this before myself. I've found some instructions on the web [url=
]"Service Instructions"[/url] which look reasonably straight forward.
The bits that concern me are the need for a compressed air line to push the pistons out and the references to a specific type of silicon grease.
Has anyone done this themselves? How did it go? any tips?
let me know how you get on as I've got to get a goodrich kit and build mine up, looking at the guide it doesn't seem too hard
I just used a track pump sealed with my thumb to blow the pistons out of my juicy 5's. Use the adaptor that's meant for blowing up lilo's, airbeds etc.
Watch the pistons though, they'll fly across the room.
As for the grease, I bought rubber seal grease off ebay for a fiver. Seems to have worked but not sure you need it.
Stu.
are you on about the pistons in the lever end or the caliper? if you mean lever end, and theyre plastic and not metal, you can send them to propel, who will replace them free of charge.
You can use any brand of Silicon Grease, I have done this job on at least 6 pairs of Formula brakes and all work fine since.
Cool, I meant the pistons at the caliper end. Sounds fairly straight forward then. Guess I'll just have to give it a go and see what happens.
Thanks.
Well, it sort of worked, bought a bleed kit, fluids and some new seals, took the caliper off, split the caliper in half and got one of the pistons out fairly easily. The trouble is the other one is stuck fast. It wasn't moving when the lever was pressed when the brake was in one piece and I can't shift it no matter how much I jump up and down on a track pump!
So now I'm stuck. Does anyone know how to get the piston out of the caliper half? If necessary I guess I'll need to sacrifice the piston 🙁
Does anyone know how to get the piston out of the caliper half?
Reassemble the caliper, push the other piston back in, run some fluid in, then zip tie the working piston right back into the pot, it needs to be very firmly seated.
Stick some safety specs/goggles on, crank as much pressure through the caliper as you can until the stuck piston pops. Might need a wiggle.
It would have been easier to pop it before you took the whole lot apart. Next time work the pistons back and forth by finger/lever to check they are both moving OK.
Aaaah, the magic zip tie. That was the piece of the jigsaw that I hadn't thought of. I tried holding the working piston in place whilst pressing the lever in an attempt to free the stuck piston before I split the caliper. But I couldn't get it to work and couldn't think of a good way to hold the working piston in place.
Oh well, another evening in the garage....
8)
It easy once you've made the leap. IIRC the Oros should be pretty easy to do, you could zip two side by side vertically through the lever, plenty of space.
This is what I used to do with my hopes. My Oros have been so reliable I've not had to touch them once.
Thanks. Will give it a go.
Update:
Well it wasn't quite that simple. I re-assembled and bled the brake then put two zip ties around the free piston, but they just stretched and the stuck piston didn't move. So I put the caliper in a vice, a spanner over the good piston then 4 ties to hold the spanner in place.... the 4 ties stretched and the spanner bent! So finally I managed to squeeze a vise grip in place to restrain the good piston. Success!!!
Everything is now cleaned up, greased and re-bled (avid bleed kit) and seems to be working fine. Didn't bother with new caliper seals as the old ones looked ok.
The rear brake next, hopefully that will be a bit easier.
Flippin 'eck! Glad you got it all working again ...