Round brake replacement

[JJH]

I have a 79 with the round brake reservoir.  It is leaking from a crack.  This is a NLA part (the system).  What options do I have for replacing this with the newer rectangle  reservoir system.  It is set up with a single front brake.

Thanks,  John in MO

[Matt Chapter]

I don't know if the newer square style is a bolt on replacement, but I do know you'll want the same diameter master cylinder to maintain similar brake feel.  Perhaps looking at the parts fiche for the different models would illuminate more.

My other piece of advice is to buy a new part as opposed to scrimping and rebuilding a used part.  In this case, I've found that used cylinders with high usage just don't rebuild as well as a new one.

[wilcom]

It is set up with a single front brake.

If your going to buy a new MC it might be a good time to convert to dual disc...... the MC change is one of the major expenses doing the upgrade. Some stay with the smaller MC and dual disc's, still something to think about.

[Tony Smith]

I have a 79 with the round brake reservoir.  It is leaking from a crack.  This is a NLA part (the system).  What options do I have for replacing this with the newer rectangle  reservoir system. 

John, firstly you might check Motobins as they still had stock of the round M/C the last time I was looking for one (a while ago). Personally I wouldn't buy one because you cannot buy new reservoirs for them anymore - in another forum someone claimed you can still buy the reservoir direct from Brembo (which would make sense) but he went silent when I and quite a few others requested details. I emailed Brembo but did not get a response.

So, your option is to install the later "square" M/C.

The good news is that it will bolt right in.

The bad news is that there may be some "yebbutts" in the process.

I've done some mixing and matching with R65 M/C and I've found that:

The levers do not sometimes interchange, so if you buy a new M/C buy the brake lever for it as well.

The brake light switch (if you model uses a handlebar switch) may not fit the new M/C, and the switch you buy that does fit may not "interact" with the lever correctly - in my case the core of a Bic biro was used to extend the operating bit of the switch so that it did turn my brake light on and off rather than simply remaining on all the time. Of course if you have a model that has a hydraulically operated switch, then you do not have this problem.

[JJH]

Thank you for your replies.  Tony, the "yeah but" comments are especially helpful.  Looking at all the round to square parts, it can start to become slippery slope.  Can you change the brake handle alone or do you need the bracket?  If you need the bracket then you are changing the cam.  The 79 cam is for a dual throttle, the 81 is for a single, and down the rabbit hole you go.

[amyrick65]

Hi JJH. I´m having the same issue right now. What did you end up doing? Did you have to change the brake lever too?

[Justin B.]

Since you have a "First Generation" R65 you shouldn't have brake light switch issues as it's a pressure switch teed off a brake line. 

When you take off your throttle assembly don't loose the little "perch wedge" as they have been NLA since right after the invention of dirt.  I wish I had a picture but IIRC it's a little piece of metal, triangular in cross section, about a half inch lone and maybe 1/8" thick?  I really can't remember but without these sometimes the controls don't stay as secure to the bar as is wanted.

[Barry]

While you'll want the master cylinder sizes something like the same size don't worry about them being exactly the same because they never were.  For example on a single disc the 78-80 models with a round reservoir had a 13 mm and then 81 -on  models with a square reservoir had a 12 mm which is actually an improvement.  If you are replacing a single disc master cylinder you really don't want a 13mm as it was a poor choice of size by BMW.