2 to 4 piston caliper conversion

[Milo_357]

Has anyone installed a 4 piston caliper on the front end of their bike?

I have seen the picture of a R80RS on Snowbum's site of one that was converted from a 2 piston to 4 piston Brembo.  I have an '82 R65.  The caliper I have is off a '99 K1200.

I know the main difference between the 4 piston caliper and the 2 piston is that the older 2 piston has a brake pipe from the caliper to the brake hose, and the 4 piston has a circular brake hose ending that a banjo bolt goes through into the caliper.  Was the caliper used in the R80RS conversion an older caliper that still used the brake hose?  If need be I can easily replace the brake line, unless the caliper I have can be modified to take a brake hose.

Secondly, do anyone know how much needs to be milled off the brackets to make the caliper fit correctly?

Thank gang,

Dell

[Bob_Roller]

You're pretty much in uncharted territory there !!!!

[tvrla]

Are the mounting holes the same distance center to center?

There are so many slight variations between calipers and their mountings that it's impossible to tell without careful measurements. For instance, our calipers sit in front of the mount and thread into the fork. Newer calipers sit 'behind' the mount and the bolt threads into the caliper.

I'm afraid that's the first difficulty you'll encounter.

Then there's the mounting hole distance, the off-set, and the angle matching the disc ensuring full pad contact.

I hadn't heard of the R80 being easily adaptable to the four piston calipers, but do know about he R100GS. As far as I know, even though our Brembo calipers look like all the others, they have a unique mounting which prevents any direct cross-over adaptations from other beemers.

[Julio A.]

The mounting bolts have the same distance.

If you were to tap out the threads on the caliper, it would bolt right up.

If you would connect the caliper the same way as you would the 2pot caliper, the slot in the caliper would be directly be blocked by the fork.

If you use spacers and bolt it the other way around so that the caliper would align with the disk rotor, the thicker 4pot caliper body would be in the way of the front wheel.

The only logical solution is to shave a good 20mm(approx) from the caliper body, something i don't have the resource to do.

I heard that the wire spoked wheels are a tad bit thinner
(Is this true? ), making the mod more feasible.

The Brake lines are no big deal. I am using banjo bolts on my oem caliper and master cylinder right now. They don't seem to mind.

I'm using the caliper from a wrecked R100 Mystic BTW. Which I confirmed remained the same caliper used in the R1100's.

[wilcom]

Dell

Did you get your stock brakes working? The last  I remember you just got your 16mm MC installed but didn't add the second rotor so you still had NO brakes even though you no longer have a leaking MC.

Once you get the stock double disc system working correctly you will be much less interested in 4 pot conversions.

Let us know what's going on with the stock system

[Milo_357]

Dell

Did you get your stock brakes working? The last  I remember you just got your 16mm MC installed but didn't add the second rotor so you still had NO brakes even though you no longer have a leaking MC.

Once you get the stock double disc system working correctly you will be much less interested in 4 pot conversions.

Let us know what's going on with the stock system

I ended up not going with the dual front brake due to the fact I did not have the proper front wheel.  Now Julio seems to be implying I may be SOL without a wire spoke front wheel, and I have a snowflake.  This is because the caliper and wheel would strike each other if I spaced the caliper out to fit the disk, correct Julio?

Is this true even WITH the deeper dish R65 carrier?  I'm guessing so...

*sigh*  

Oh well.  I think I am going to have a bunch of brake stuff for sale in the near future as I go back to the straight single front brake.

Thanks for the help gang,

Dell

[wilcom]

Dell...............

I have a 1979 with dual disc. I converted it years ago. I bought a caliper and disc off an 81 R65 and bought a 15 mm master cylinder from BMW, screwed it together WITHOUT A HITCH, BOLT ON AND GO!!!

Yes, I have a snowflake front wheel.  

Take some pictures of your set up, forks, caliper and rotor with part numbers and lets figure this out, you've been without brakes too long. I'll pull mine apart and check part numbers and let's see where the difference lies.

You have the 16 mm master cylinder on now and it isn't leaking so that should not be an issue.........POST SOME PICS AND PART NUMBERS

Joe

[tvrla]

There are two ways to go (well, three):

1. Snowflake, deep dish R65 rotors

2. LS wheel, shallow dish rotors

3. R65 wire wheel, deep dish R65 rotors

If I recall correctly, you're putting an LS wheel on your bike?

The calipers are all the same for 79-84 R65s, so if you've got two, then you're all set in that department. So you just need the correct discs to go with the wheel.

[Julio A.]

Dell


Once you get the stock double disc system working correctly you will be much less interested in 4 pot conversions.

I agree; I scrapped my own project when I rebuilt my calipers.
When in good condition the brakes should be adequate.
I find mine ok; even if I use a 16mm MC on a single caliper.

If you really want to use the 4pot calipers, you do not need a wire spoked wheel. Rather, you need to extensively modify the caliper body.

[Milo_357]

There are two ways to go (well, three):

1. Snowflake, deep dish R65 rotors

2. LS wheel, shallow dish rotors

3. R65 wire wheel, deep dish R65 rotors

If I recall correctly, you're putting an LS wheel on your bike?

The calipers are all the same for 79-84 R65s, so if you've got two, then you're all set in that department. So you just need the correct discs to go with the wheel.

I can't believe how stupid I have been... Of course another deep dish 65 carrier would mirror the other side.  Sometimes I really have to question how my brain works sometimes.  If there is early onset alzheimers, I definatly have it...

btw, I was not able to use my R65LS wheel.  It was not "true".

Thanks for the reminders and help.

Dell

[tvrla]

Aw, don't kick yourself all around the barn yard! You're making me feel bad.

There's nothing like mechanics to show up our mistakes - and there's no explaining it right. I think you've got to be pretty damn humble to be a great mechanic - or awfully perfect.

Glad you finally figured it out! BTW, I'd like to get your bent wheel from you.

[Semper Gumby]

Dell...............

I have a 1979 with dual disc. I converted it years ago. I bought a caliper and disc off an 81 R65 and bought a 15 mm master cylinder from BMW, screwed it together WITHOUT A HITCH, BOLT ON AND GO!!!

Yes, I have a snowflake front wheel.  

Take some pictures of your set up, forks, caliper and rotor with part numbers and lets figure this out, you've been without brakes too long. I'll pull mine apart and check part numbers and let's see where the difference lies.

You have the 16 mm master cylinder on now and it isn't leaking so that should not be an issue.........POST SOME PICS AND PART NUMBERS

Joe

Hey Wilcom.  I need a 15mm round reservoir mastercylinder for my dual disc R65.  The 16mm is too much.  What bike did that come off/do you have a part number???

Thanks in advance...   [smiley=bmw_smiley.gif]

(tweak tweak)

[Milo_357]

Hey Wilcom.  I need a 15mm round reservoir mastercylinder for my dual disc R65.  The 16mm is too much.  What bike did that come off/do you have a part number???

Thanks in advance...   [smiley=bmw_smiley.gif]

(tweak tweak)

Ugh, don't tell me that Semper... I have a 16 I am going to try and use.

WILCOM!  What length bolts did you use when you bolted on the extra disc??  Not the standard ones that were on the bike with the single disc, they are too short, aren't they?

I have the LONG 80mm(?) ones from the R65LS, but I don't think I want those extra mm sticking out from the wheel, do I?

btw, I don't remember doing this, but somewhere along the line I bought a R65 brake disc.  Found it just laying there in the shop.  Coulda knocked me over with a spoon.  Maybe it came with the parts bike stuff and I just didn't realize it because a lot of junk came in parts bike in boxes.

HA!  

Thanks!

Dell

[Bob_Roller]

You need the 100 mm length bolt for a twin disc set-up .

The standard single disc uses a 70 mm length bolt .

http://www.realoem.com/bmw/showparts.do?model=0365&mospid=51899&btnr=34_0600&hg=34&fg=11

[tvrla]

Bob - if the standard length is 70mm, then the 80 the parts fiche calls for should be correct. All that's needed is enough length to traverse the extra disc, which couldn't be more than 10mm.

I'll bet the 100mm is for the LS with the wider hub and dual discs.