separating calipers bad?

[Session101]

So i recently did a front brake job on the bmw (ATE caliper). used EBC organic pads. so what i did was:

1) take plastic piece off
2) remove pins and spring piece
3) pulled pads, had to use a screwdriver and kind of pull them out a mm on each side at a time

finally the pads are out and the new ones to go in, problem the new pads don't fit. well i decide to open up the bleeder valve and try to push the pistons out so the pads would fit, i was planning on bleeding the whole system anyways to get some new fluid. still wasn't working the pistons were still too far out and hard to push back.. I decided to separate the caliper in order to gain more room (n00b idea) anyways it worked and i got the pads back in and put it all back together and bled the front brake till the line was clear. took the bike up and down the street and the brakes are WEAK, I couldn't stop this thing on a dollar bill..

i was suggested to keep bleeding the lines and do it about 3 more reservoirs worth.

did i just screw up the front brake by separating the calipers? i didn't think about the fluid that was going from one side to the other when i separated them, but the wheel spins just as free as it did before

[Barry]

did i just screw up the front brake by separating the calipers?  

I've done it with no problems and I don't see how it could affect brake efficiency as long as the two halves are firmly bolted back together, the internal passage is clear and there are no leaks. Out of interest what torque did you use on the clamping bolts because I recall not being able to find an recommended value.

When the system has been completely emptied I find it much easier to get a firm lever by refilling bottom up through the bleed nipple using a large syringe.  Even then tying the brake lever back over night always seems to improve things.

[Bob_Roller]

It just sounds like air in the system .

Sometimes the manual method of bleeding the brakes, pulling the lever and opening the bleeder screw won't get all of the air out .

I use a vacuum pump bleeder, you can get one at Harbor Freight for around $20 .

 If you use the vacuum method, put a few wraps of teflon tape on just the thread area of the bleeder screw, if you don't, you'll continue to get air bubbles, you'll be drawing air in around the bleeder screw threads and it looks like you still have air in the system .
 
While you're at it, there is a small hole next to the intake hole inside the master cylinder, make sure it's not clogged .

The next time you need to push brake pistons back in, use a wood wedge and tap it in between the pistons, to force them back in .

[Session101]

did i just screw up the front brake by separating the calipers?  

I've done it with no problems and I don't see how it could affect brake efficiency as long as the two halves are firmly bolted back together, the internal passage is clear and there are no leaks. Out of interest what torque did you use on the clamping bolts because I recall not being able to find an recommended value.

When the system has been completely emptied I find it much easier to get a firm lever by refilling bottom up through the bleed nipple using a large syringe.  Even then tying the brake lever back over night always seems to improve things.

i didn't do the reverse method, i don't think i have the air-tight supplies to do that,

checking my manual: http://i.imgur.com/pGAcJLK.jpg

i think its the lower ones, i didn't measure mine, just did them a little more than finger tight

[Session101]

i will take a look, thanks bob

[flybot]

If the calipers are not leaking there should be no harm by having separated them. I think the new pads just need a little bedding in. Put some miles on them with some agressive stops. If the brake lever feels mushy, then you need more bleeding to get some air out.

[Barry]

i think its the lower ones, i didn't measure mine, just did them a little more than finger tight  

Finding the caliper mounting bolt torque settings is not a problem. Its the bolts that clamp the caliper halves together that I couldn't find torque values for. In the end I made an educated guess of 15lbft  based on the thread size and materials involved.

See this earlier thread. http://www.bmwr65.org/cgi-bin/yabb2/YaBB.pl?num=1270141341/0#0

Thinking about it again, I didn't have a copy of the genuine BMW workshop manual at the time and I do now.  Don't know if it has a  torque value but if it does I'll post it when I get home from work.

[Rob Valdez 79 R65]

When you reassembled the caliper, did you make sure the small o-ring was in place?



This very important part is not available from BMW or any other supplier (in onesies) that we know of.

On of our members (Mike V) bought a bag of 100, and makes them available to forum members.  You should check with Mike if you need a new one.

When I rebuilt my brakes in 2006 this option was not available and I reused the old o-ring and everything was fine.

My brake rebuild pictures: http://www.pbase.com/tomfarr/r65_brakes

[Mike V]

I just sent some out this morning to Dave R.  I'm running short - only about 4 or 6 left.  Contact me with your mailing address soon by PM if you need a couple.

-Mike V.

[Session101]

i didn't check the o-ring as i only loosened the bolts to separate the calipers enough to slide the brake pads in, then just tightened the  bolts evenly to the rotor.

would you say that if there is no leaks, and no leaks when the brakes are being bled. that the connection would be secure (as far as the o-ring?) because it has to travel from one side of the caliper to the other?

[Mike V]

i didn't check the o-ring as i only loosened the bolts to separate the calipers enough to slide the brake pads in, then just tightened the  bolts evenly to the rotor.

would you say that if there is no leaks, and no leaks when the brakes are being bled. that the connection would be secure (as far as the o-ring?) because it has to travel from one side of the caliper to the other?

Session,

Tough call.  There's been plenty of posts here of re-using the o-rings with no problems. For me, it was essential since my 81 R65's brake system was a pretty sad case after sitting unprotected for many years and frozen solid brake system. I would think if the o-ring was in a solid state and still had some amount of production beyond the caliper half with the o-ring seat it would be ok.  If you have the system in place and assembled with no leaks I would guess you will be fine.  Keep an eye on it and look for weeping with miles.  If you notice some leaking, let me know and I'll get some o-rings to you.

-Mike V.

[georgesgiralt]

Hello !
IMHO, as you have a concern, I would buy a repair kit and do a full refurb, replacing the O-ring as you are offered a couple.
This way you'll be perfectly confident on the effectiveness of the callipers.
To bleed the brakes, it is easier to pull the liquid from the calliper using a depression system than to push it from the master cylinder.
Another way which is also efficient is to fill the system from the lower part using a syringe until the master cylinder bowl is at the correct level.

[Barry]

I checked the BMW workshop manual and there was no mention of torque values for the M8 bolts that clamp the caliper halves together. No surprise then that it's missing from all the other manuals like Haynes etc.

The condition of the O ring is important but to be honest I'd be more concerned about the tightness of the clamping bolts as "a little more than finger tight" if that's what you really meant sounds like it might not be enough. On the other hand you don't want to strip the threads so an accurate toque wrench is essential.  For the figure all I can say is 15ftlbs worked for me. Personally I wasn't prepared to risk anything higher.

In another thread Bob mentioned a max. hydraulic pressure of 200 PSI which taking the piston area into account results in approx. 630 lbs pushing the caliper halves apart.

It's possible to attempt a calculation of how much clamping force is applied by by a particular torque value although it's far from an accurate thing to do in practice. For an M8 bolt at 15ftlbs the clamping force is in the order of 1 ton for each bolt which would seem to be enough.

[bruce_launceston]

Interesting, I have just had a look at one of the genuine Brembo rebuild kit that I have and the kits do include the small 'o' ring and they have 2 M10 bolts that are for reassembling the caliper halves.

Despite this the comprehensive instructions that come with the kit show the pistons and seals being removed without splitting the caliper halves and therefore there are no torgue values given for reassembly.

They do give torque values for tightening the caliper back to the fork leg.

[Red_Hen]

Motobins UK sells a Brembo kit that includes the O rings

http://www.motobins.co.uk/bmw-parts.php?model=R%20Series%202%20valve%20Twin