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Old 06-22-2010, 11:01 AM   #16
C Squared
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Quote:
Originally Posted by BMWzenrider
Ok, the single-disk R100R came with the 13mm master.
The DUAL-disk R100R came with the 15mm master that you are looking for.

Now for the bad news...
That is a handlebar unit that is unique to that model bike.
It ONLY came on the R100R/Mystic models...
There does not appear to be any other compatible master cylinder in that size.

I would check with the usual suspects at the various BMW boneyards to see if they have what you are looking for.

Otherwise, the part is listed for $286.58 on the MAX BMW online parts fiche.


HTH
Yea, I just can't see $250+ for a MC

I am looking into a rebuild kit and then see if I can have my 13mm machined out to 15mm. And maybe sleeved?

32712314027 HANDLE UNIT, RIGHT - D=15MM $286.58
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Old 06-22-2010, 11:02 AM   #17
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Quote:
Originally Posted by Beemerboff
So, to get back to the origonal question , if you are aiming for a m/c ratio in the upper 30s and have have a single 38 mm twin piston caliper , a 9 mm m/c is the way to go, or the the nearest you are going too get to it, whichj is the 11 mm Guzzi item.
Yes, if you look at the chart of ratios that I posted, the best you would do with a single 38mm Brembo style caliper would be a lever ratio of 23.87 with a Guzzi 11mm m/c.

I would guess that it would feel pretty stiff...

Better to look around for someone who has a cast-off 48mm caliper from a GS who upgraded to a 4-6 piston caliper... IMHO...
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Old 06-22-2010, 12:45 PM   #18
AntonLargiader
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Quote:
Originally Posted by C Squared
Yea, I just can't see $250+ for a MC

I am looking into a rebuild kit and then see if I can have my 13mm machined out to 15mm. And maybe sleeved?
If you're looking on the used market, possibly you could use an Oilhead control housing. These are 20mm, but (and I think this is where dissimilar lever ratios step in) they are used on the exact same calipers where the R100R uses a 15mm MC. So if you're looking for the same effect as the 15mm R100R MC, you should find it in the 20mm R1100/K1100 MC. You can probably change out the clutch side and have matching 1100-style housings.

Hmm, I actually have all this stuff lying around. Maybe I'll update my K75 with it.
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Old 06-22-2010, 06:40 PM   #19
AntonLargiader
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Karl,

I only found an old K lever and an R1100 lever. OK, also an F650 lever but I can't make sense of it without the other parts. Measured to the center of the fingers:

R1100 lever: 130/18mm or 7.2 leverage
K75 lever: 85/18mm, or 4.7 leverage

That's a huge difference. It confirms my suspicion that the highly revered ratio tables are garbage without figuring in ALL of the information. We have people thinking a 10% difference in the piston ratio is meaningful and the lever can vary by 50%. Go figure.
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Old 06-22-2010, 08:06 PM   #20
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A quick check on current superbikes in a showroom is informative, all the brake levers have a long soft, spongy pull, and are adjustable so that it can be minimised.

Lever advantage looks to be at least 7 to 1 and probably 10 to 1 on most.

My local brake guy does rebores / resleeves on just about anything you can name, using a proprietry multi head machine so it shouldnt be that hard to find someone stateside who has the same set up
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