850G Brake Pistons Front and Rear Identical?

[Guest]

I'm getting ready to rebuild the rear brake calipers on an '82 GS 850G. This is probably an old question, but my guess is, rear calipers have the same pistons as the front. The seals for both front and back calipers are the same, part # 69107-05CF0, so the diameter must be the same. So dimensionally (is that a word?), the only thing that can be different is the height of the "can".

I've never had the rear caliper apart before, so pardon my ignorance - on this bike, is the rear piston (actually there are two, it's a double squeeze caliper) identical to the front piston? If they're the same, that would be cheaper for me, because I have some spare front caliper pistons.

[BassCliff]

Hi,

When checking the parts fiches, the part numbers are different. I don't think they're the same. The rears look deeper than the fronts.


Thank you for your indulgence,

BassCliff

[salty_monk]

I doubt it. That doesn't mean they wouldn't work but you'd have to check it carefully. Probably the same bore if the seal is the same which is half the battle.

You'd have to be sure that they go in far enough for when running new pads & that they can't jam or fall out when the pads get low (remember rotor tolerance too they will come out further to a rotor on minimum T tolerance than on a new thick one)... other than that it's not rocket science.

Dan

[Dogma]

The pistons may be the same diameter, but they are definitely different lengths.

[psyguy]

as dogma says.

i have done the brakes recently and the front pistons wont fit at the back.

and vice versa? maybe

[DPage]

OK, I'll buy the whole rear piston set, which is two pistons, internal seals and cover boots. You can't buy the pistons without buying the other stuff. For the record, the complete set part # is 69100-34851 (replaces 69100-34810). I'm starting to get extra seals and boots for both front and rear, which maybe isn't a bad thing . . . Let's hope my old rear pistons are re-usable

[twr1776]

While you are ordering the small rubber washer/seal between the caliper halves is not a bad thing to get since you will have the calipers split anyway

[DPage]

Good point - they call it a seal in the parts fiche, #69107-34200, about $6. I'll get that too.