Weak R65 front brake?

[Allred]

I am looking at an '83 model R65 with 54,000 miles.  Possible purchase.  Pretty good condition with only a couple of minor issues, except, the single disc front brake is VERY weak!  I am used to airhead brakes, having ridden a number of them over the years, most recently an '83 R100RT, which I would characterize as a two or three finger, moderate pressure brake for short stopping distance.  

This particular R65 however, requires my whole hand, as hard as I can grip, and then yields only moderate slowing.  In an emergency I don't think this bike can stop quickly at all.  It has new pads, and the rotor is not grooved.  I can see no contamination on either.  What could be wrong?  I cannot believe BMW would have sold a bike with such poor stopping ability.  Something must be wrong, but I can't spot it.  I've searched the archives, but found no reference to weak brakes, so maybe it is not an endemic problem?

This is a deal breaker, unless there is something that can be done for better brake performance, I'll have to pass on this deal I believe.

Feed back will be appreciated!

Thanks,

Allred
R65 wanna be

[MrRiden]

Pads and rotors good leaves only the Master cylinder, hoses and caliper. Does it still sport the hoses that were put on it at the factory? Color of fluid in the master? I'm voting on a badly corroded caliper piston. Parts are readily available and a properly maintained single disc does have very good to excellent stopping power. The bike you are lookin' at has some deferred maintance I'd say!
rich

[montmil]

Could be it might benefit from fresh fluid and purging air out of the brake line. It's easy to do and it takes just a few minutes.

Monte

[airhead]

+1 with Rich on a corroded/seized caliper piston, not too rare on bikes that age especially if regular brake maintenance isn't carried out. Can be reasonably easy to fix, right along to new caliper needed. You won't know till it's in pieces.
Look hard at the disc pad/rotor relationship when getting someone to pull the lever. If it seems to push from one side only, that's your man.


Bill........................;-)  

[not-so-fast-ed]

I vote with both..   Flush the system with new fluid while bleeding any air out.   If it still seems marginal,  pull the caliper, disassemble (compressed air and a vise, were helpful in blowing out the pistons and working on the caliper on my "Mono"), and go with new pistons, seals and hose.   Don't forget to grease the pistons with the special grease that is included with the kit (just plain brake fluid wasn't enough to get the job done on mine).  

Be sure to clean (sand & degrease) the pads a bit if they're glazed at all before they go back in.

Can't address the master cylinder issue,  If it doesn't leak, and pumps fresh fluid OK,  I wouldn't think it's a problem.

There's probably someone here that has a similar year model and has more experience on your type system.  Mine is Brembo, but you may have the ATE unit.  The Brembo kit I used had everything including new bolts.

Give us some idea of where you are and what sort of asking price the owner is trying to get.  Repairs can be reasonable if you can do it for the cost of parts.

Good luck,
Ed

[Rob Valdez 79 R65]

There is no reason the brake system can't be restored to full power in just a couple of afternoons (with parts on hand).

The brake system on my '79 only differs slightly from the one you are looking at.  I rebuilt mine a couple of years ago.
I did not have the issues you are seeing, but then, I am the original owner, and I renewed the brake fluid every few years (not good, do it every year!).

Here are a few photos of the work I did:


Click on the picture for more

Parts are available.  The caliper pistons are only available from Motobins in England, but since it is only a single caliper system, you have already saved 50%!

I think, on any new-to-you bike of this vintage, the brake system should be rebuilt upon receipt; unless there is documentation proving it has been done recently.

Your brakes are your life...

[nhmaf]

I think that a whole new M/C will cost in the neighborhood of $140, if you have to resort to replacing it after flushing
and replacing fluid.  If it has the original (cracking?) rubber brake hoses, they do cause significant power loss with age.

[mikethebike]

It's usually a corroded piston issue in the caliper.  I've done a few caliper/piston rebuilds on various bikes and the difference is amazing.  Repair kits are usually fairly cheap.  The most difficult part is usually releasing the piston but if you have some movement, you're already half way there.  Sometimes you can just push the piston out by removing the caliper but leaving the fluid lines attached, then remove the pads and carefully squeeze the lever until the piston moves right out. Prepare for fluid loss so keep away from disc and pads. (A plastic bucket is useful)
Mike

[Ed Miller]

It's usually a corroded piston issue in the caliper.  I've done a few caliper/piston rebuilds on various bikes and the difference is amazing.  Repair kits are usually fairly cheap.  The most difficult part is usually releasing the piston but if you have some movement, you're already half way there.  Sometimes you can just push the piston out by removing the caliper but leaving the fluid lines attached, then remove the pads and carefully squeeze the lever until the piston moves right out. Prepare for fluid loss so keep away from disc and pads. (A plastic bucket is useful)
Mike

What he said.  And eye protection, oh my....  

[DgM]

Brembo calipers can be rehabilitated to good as new by Goldline in Seattle, WA.  Straight shooters, excellent work, pleasure to do business with, very familiar with Brembo products - same basic brakes as six piston automotive calipers, just fewer parts.  
http://www.goldlinebrakes.com/

[Allred]

 

The problem was found, and solved!  Prior owner or maintenance provider had installed a new master cylinder, but unfortunately, the wrong one!  A single disc R65 calls for a 12 mm master cylinder piston, the one installed was to large, a 15 mm.  Expensive, but effective, a new proper sized MC piston was installed, in a sense providing more "leverage" than the larger one (physics of hydraulics can be tricky) and now there is adequate brake power, plus a much better "feel" to the system.

So...lesson learned:  Just because new parts were installed, doesn't necessarily mean they were the correct ones!   I've found several other minor maintenance glitches on this bike, none real serious, and am slowly setting them right.

Thanks to all who commented.

Allred

[not-so-fast-ed]

Way to go, Allred.  Good job!
Nice feeling when the brakes work as advertised...    

[Rob Valdez 79 R65]

That is great, Allred.  Thanks for the feedback, very important.


So apparently you could not resist buying the bike!  

[Allred]

That is great, Allred.  Thanks for the feedback, very important.


So apparently you could not resist buying the bike!  

No, couldn't resist, and now after addressing some of the issues with the bike, I couldn't be happier!  I have owned several BMW's recently, and hordes of other bikes over the past 40+ years.  I still own two larger BMW's, but find myself riding the R65 almost exclusively now, for around town, to & from work, and short day trips.  It is slightly smaller, lighter weight, and very comfortable to me.  Makes my R100RT feel clumsy, and my R1150RT feel top heavy and overweight!

I'll keep working on a few remaining issues, front fork springs seem to be awfully stiff, and look like aftermarket, so that's next, right after overhauling both carbs to produce a stable idle, and perhaps improve mileage a tad.

Photo soon as I can resize it to fit on forum.    Thanks to all for the encouragement!  

[drewboid]

Congrats on buying a great bike. Save that 15mm master cylinder - it is useful if you decide to go to dual front disks. I did on my fiance's bike and it made a world of difference in stopping ability.
I like her R65 - really a lot more fun in the turns than my R1100R or even the R75/6.