Rebuilding K75/K100 Front Brake Calipers

[frankenduck]

Here's link I stumbled across that somebody might find useful:

Rebuilding the K75 front calipers


And here's what I was really looking for - the part  number for caliper rebuild kits: 34112310493

That kit works for front and rear calipers on 2V bikes and rear calipers on 4V bikes.

[dfx]

I've just received 2 of these kits and I'm a bit confused. In each kit there are the two bolts that hold the two caliper halves together, two dust covers and two seals for the cylinders (seen here http://www.realoem.com/bmw/en/showparts?id=0504-EUR---K589-BMW-K%20100%20RT%2084%20(0504,0505,0514)&diagId=34_0618). There are also two small o-rings which can't be seen on the parts diagram. I thought there would only be the one which is for the hole where the brake fluid passes from one caliper half to the other. Is the other one a spare or is it used somewhere?
Also, I read the article on rebuilding, but how do you blow out the cylinder when the air just comes out the other holes in the caliper? I'm considering refitting the caliper with the old o-ring in order to use the brake lever to pump the cylinders out.

Any help would be appreciated, thanks!

[Scott_]

When I did mine, I didn't split them.
I used air to push out the pistons, one at a time. Then I cleaned out the one half of the caliper as best as I could with brake cleaner, put in the new piston seals and new pistons on the one side.
Repeat the process for the other side.

I have heard/read of people having leaks at the split joint after splitting the calipers, equally I have read of others not having any problems at all, but I figure that if it isn't leaking as it is, why disturb it and take that chance. YMMV

[Elipten]

I agree.  Unless it is leaking where it splits, do not separate.  I have not  heard of too many home mechanics splitting the caliper and getting it back together with no issues


Sent from my iPhone using Tapatalk

[dfx]

I'm only doing mine because one caliper was leaking! I found the bolts loose. But what about those o-rings? Why 2 of them?

[Scott_]

Possibly the kit repairs more than one style caliper, one that does use the o-rings? Or uses both of them.
I can't say for certain.

[Dennis de Vries]

I've split, cleaned and rebuilt them more then once. No leaks yet, and it makes it so much easier to work on them...

Verstuurd vanaf mijn SM-G920F met Tapatalk

[dfx]

Job done.

If I ever have to do that again I must remember :

• If no compressed aire is available to blow out the cylinders, take the pads out and pump the brake until the cylinder comes out a fair way[ without letting it pop out. When the caliper is on the bench the cylinder can easily be levered out with a flat screwdriver on either side/li]
  
  • Don't bother unscrewing the rigid brake pipe at the caliper; unscrew it at the junction with the rubber hose, then take the bleed nipple and use this to block the rubber hose while the calipers are off the bike
  
  As for the extra o-ring I think I found out what is was for : I clumsily tipped the box of seals over, and I was left with one o-ring.

[bilohak]

What should I expect to pay for a rear caliper k75s rebuild kit? and what's best source? in U.S.

[johnny]

greetings bilohak...

whats the part number...

say what... you didnt look it up...

ok... here is how...

if you want to know what parts fits your moto...

1st... getts the last 7 digits of your vin and put in here to see what your moto really is...

2nd... then pick your moto here...

3rd... after you figger out the exact part number put it in here to see what all motos it fits...

4th... then put your questions in here and  search it...

5th... make your post... include the part numbers you looked up... include screen prints to demonstrate you doing the minimum...

when you do the minimum your post will stand on its merits... if you choose to not do the minimum... mystic red will have your post locked and pinned up on the wall of shame... and you will  be sanctioned for a time... plenty enough time to figger out how to getts part numbers and screen shots in your next post...


j o

[motodude]

From memory, the two O-rings go between the caliper halves. Where the bolts go through.

Tom

[lilau3]

1 o-ring for front caliper. 2 o-rings for rear caliper.

The Brembo rebuild kit I got only had one of the small o-rings so I ended up having to buy more; this is the size:
O-Ring Brown FPM 75 Duro BS610 - 0.266 X 0.070"
Cross Section: 1.78mm
Inside Diameter: 6.75mm
Outside Diameter: 10.31mm

I haven't found an official figure for torquing the caliper halves together so I went with 50Nm, slowly building up to that on each side to hopefully prevent any warping.

I kept everything immaculately clean so fingers crossed no leaks.

The bike is a 1988 LT with ABS and both front and rear brake pads were the same size. I believe after mid-1998 the front brakepads are slightly larger.

This info may be useful to someone.