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Rebuilding F4i Calipers - advise?

Old 08-13-2010, 12:23 PM
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Rebuilding F4i Calipers - advise?

I picked up a complete front brake setup from an F4i yesterday for $100, not sure if I got a good deal or not, seems like that's about what they go for on ebay. Looks like the bike they came off was sitting outside it's entire life, all the hardware is rusty, and the calipers themselves are pretty dirty...

I want to clean them up before I install them, and depending how they clean up maybe i'll repaint them. I'm thinking about ordering all new hardware (4 torx/2 Hex bolts each) from Ronayers.com or similar.

I've never rebuilt calipers before, so I wanted to see if anyone here has some tips or advice before I tear everything apart. Should I replace all the piston seals when I take it apart? I haven't decided if it's a good idea or not to split the calipers apart to clean/paint. Whats the best way to get the old paint off? sand/media blasting a bad idea?

any recommendations would be greatly appreciated.
Thanks
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Old 08-13-2010, 12:31 PM
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If you take it apart replace all seals.. Have a VERY clean, dust, dirt, lint free area. Have lots of clean brake fluid on hand.. Use it as a cleaning agent... everything gets coated well with clean fresh brake fluid before assembly.. Worry about cleaning the excess brake fluid off AFTER the calipers are together.

Yes those are pretty beat.. even the black paint is faded.

Your price is, well a bit high..
for $100 I would have wanted a clean set. But that’s past so no worries.. Just go from here.
IF you find the pistons damaged when you get um apart.. I’d rethink building this set. As it’s going to take some work and $$ to make those nice and useable again.



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Old 08-13-2010, 12:32 PM
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Just priced out some parts...

4 - 8x40 Torx
4 - 8x35 Torx
4 - Pin Hangers (Hex)
4 - Piston Seal set #1
4 - Piston Seal set #2
2 - Spring Pad

Comes to $120 on Ronayers. Any other parts i would need? Maybe there is are brake pad kits that come with the pin hangers and spring pad?
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Old 08-13-2010, 06:33 PM
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You may be able to get away with using the original seals. I prefer to replace, but if cost is an issue, you can soak them in water and simple green - do not soak in kerosene or other solvents - kerosene will swell the rubber. You can then soak them in DOT-4, then wipe them off.

There is a way to get the pistons out, but I have had a few shots so maybe later. Use duplicolor caliper paint - nice stuff.

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Old 08-13-2010, 06:51 PM
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Originally Posted by residentg View Post
You may be able to get away with using the original seals. I prefer to replace, but if cost is an issue, you can soak them in water and simple green - do not soak in kerosene or other solvents - kerosene will swell the rubber. You can then soak them in DOT-4, then wipe them off.
With all due respect, don't even think about it. The cost of new piston seals is nothing compared with your life, or crash damage to your bike.

Since they were stored still hooked up to the master, the caliper internals may be quite clean...depending on whether the previous owner kept clean fluid in it. But the seals should be replaced regardless.
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Old 08-13-2010, 08:09 PM
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To get the pistons out , remove all lines , wrap a wrench in a paper towel . Put this in center of caliper and spray compressed air into the orifice your line was attached to . The wrench will provide a stopping point for the pistons . Then you can remove pistons by hand . Replace all seals and crush washers to avoid future leaks and perhaps a accident .
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Old 08-13-2010, 08:31 PM
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Originally Posted by motormouth View Post
To get the pistons out , remove all lines , wrap a wrench in a paper towel . Put this in center of caliper and spray compressed air into the orifice your line was attached to . The wrench will provide a stopping point for the pistons . Then you can remove pistons by hand . Replace all seals and crush washers to avoid future leaks and perhaps a accident .
This is the way I do it. Clean everything very well and i also use this when reassembling calipers. It works much better than brake fluid for me.

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Old 08-14-2010, 05:16 AM
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Originally Posted by VTRsurfer View Post
With all due respect, don't even think about it. The cost of new piston seals is nothing compared with your life, or crash damage to your bike.

Since they were stored still hooked up to the master, the caliper internals may be quite clean...depending on whether the previous owner kept clean fluid in it. But the seals should be replaced regardless.
I agree, ands stated that I prefer to replace, I eren replace the mounting bolts, however, not everyone has the cash. The good news about leaking seals is that they let you know by dripping on the floor.

The alternative is not to rebuild the calipers and have gummed up pistons grinding away at the seals.
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Old 08-14-2010, 06:32 AM
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Originally Posted by 8541Hawk View Post
This is the way I do it. Clean everything very well and i also use this when reassembling calipers. It works much better than brake fluid for me.

Attachment 9898
Good stuff .. I've used it, but it's hard to find on the shelf,, and I never seem to remember to order it in time for use (note to self,, get on line an order a bottle NOW) So brake fluid it most days.. works well enough....use cheap stuff, DOT 3, it's just going in the drain bucket anyway. ,, Fill lines and bleed with the same from a new bottle, then flush one last time with your fav fluid (EBC 5.1 is mine)
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Old 08-14-2010, 11:50 AM
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So is sand-blasting a bad idea?
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Old 08-14-2010, 12:07 PM
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Originally Posted by heng47 View Post
So is sand-blasting a bad idea?
Well you need to make sure that you don't get anywhere near the piston bores and also you would need to do a very thorough cleaning to make sure you removed all the media from the blasting.

So yes you can do it but you need to be very careful. A good wire brush usually does a fine job on the outer surfaces.

Now cleaning the pistons and the internal parts of the caliper is a whole different story.
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Old 08-14-2010, 12:34 PM
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And make sure you cover the sealing surfaces and openings for the brake lines, where the crush washers seat. Also, don't split the calipers unless you have new o-rings for the crossover. If the bores need cleaning up, use crocus cloth with a sideways motion around the bore, not up and down. Then clean well with brake fluid.
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