Re: 2. Bremsscheibe

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Abgeschickt von Bernd Bauer am 24 Juli, 2002 um 12:05:49

Antwort auf: 2. Bremsscheibe von Johannes am 24 Juli, 2002 um 00:17:21:

Hi Johannes,

: Meine Frage: Gibt es Modelle, deren linker Bremssattel, spiegelverkehrt zum rechten Bremssattel einer R100GS ist?


: Hat jemand schon Erfahrung mit einer zweiten Bremsscheibe?

Ja hier. Ich habe im Moment bloss keine Zeit, aber ich habe vor kurzem was dazu auf der airlist gepostet. Ist leider auf englisch, aber vielleicht hilft es Dir schon mal weiter:

> - How did you mount the caliper to your right fork leg
> to add the second disc? Is this a custom job or is
> there a BMW part out there that I simply need to order
> >from Moto-bins?

Well it is not an OR but an AND ;-)
This means that it is a custom job, but there is a BMW part that
you simply have to order at Motobins.
The whole trick is to get a right fork leg and modify it so that
it will fit on the left side.
I don't know if it is possible at Motobins, but at German
used parts dealers you can order a used right fork leg and they
will do the customising for you.
But we are not talking about rocket sience here, so that a
local shop should be able to do this job for you.
All that has to be done is to enlarge the axle bore, remove the
reflectors on both sides and you have to grind off 1-2mm at the
fixing points for the caliper ( otherwise the left caliper would touch the spokes).
Then a nice paint job and you are finished.

For a used right fork leg I had to pay 120$ and another 100$ for the customizing
and the paint job.
I could have saved 50$ if I would have done the paint job myself, but I wanted
a professional look for the German TUeV.
I told them that I used R100R parts for the modification, so that they accepted
it and put their stamp in the bikes documents ;-)

Then you will need a left caliper, the BMW part number for this one is 34 11 1 454 185
D=48. Until '88 it was used on the R65, R65RT, R80 and R80RT ( all with single disc ).

My brother installed the dual disc kit on his R80 exRT so that I got my left caliper for free.
Sometimes it is good to have a brother ;-)

If you install a second big caliper then I recommend that you also use a bigger master cylinder.
I first tried the stock 13mm MC, but with this one you have a very big brake lever travel.
Of course you now have a 'one finger brake', but I never liked the big lever travel furthermore
I never had an exact pressure point.

I have two friends who made the same brake mods and both of them had the same problems
with the small MC. So I don't think that it was caused by trapped air. ( I have bleeded the system
very religiousy in order to get rid of the probs )

As a consequence I have switched to the 15mm MC of the R100R. This one is much better.
Now I have an exact and steady pressure point ( with the smaller MC it was moving ) and I can still
stopp the bike with two fingers.

This MC doesn't fit on the pre 91 GS models, because of the differnt switches.
But I know that there is a 14mm and a 15mm MC available for the pre 91 models.
( Just can't remember the details right now )
Or you use two D=38mm calipers then you can keep the original 13mm MC.

My keyboard is almost melting, but we are close to the finish line :-)

What still is missing are the brake lines and discs.
For the pre 91 GS with the non floating disk you just have to get a second one
of the same kind. Those are used on a lot of airheads so that they are pretty easy to get.

But the floating discs for the later GS are do differ between left and right, so that one
should try to get a left disc from the R100R.
It is possible to use two right floating discs, but it looks strange because of the way
the holes are oriented in the discs.

As for the brake line, you can install a second one or you can connect the calipers
with one of the BMW brake pipes. The pipe is cheaper, but with a second line
it is easier to bleed the brake system and it should perform slightly better (?).

I installed the pipe, because the longer hollow screw that would be needed for the second brake
line would scratch the tank of my PD.
But this only refers to the post 91 R100GSPD, on the other models this problem doesn't

It is some work to do this mod, but IMO the result is worth the effort.
And if you use used parts then it isn't too expensive.
BTW Fallert, Wuedo and Lottmann offer dual disc kits for the GS,
but they ask 1200-1400$ for it!!!

Gruesse aus Koblenz
Bernd Bauer
89-93 R100GS/PD ( on the road again )


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