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Old 10-02-2010, 07:38 AM   #16
x3300
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Quote:
Originally Posted by fishkens
I mean, do the pistons really care if the guys on the one side of the are a little bit deeper in their bores and the fellows on the other side are a little bit prouder in their bores?
Just for anyone interested, pressure in hydraulic systems was explaned by Bernoulli:
Bernoulli's principle
Relationship of Force Pressure and head
-x3300
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Old 10-02-2010, 07:46 AM   #17
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Made the mod to my K75. Used the same master cylinder. Shimmed down the caliper and enjoy much better braking power. The key is the mounting points; they are similar, I think 65mm eye to eye if I recall correctly.

Can post pics if anyone is keen.

Quote:
Originally Posted by Christos 1983
i am an owner of a bmw r100gs p-d.i have change the standard calliper with a 4-piston nissin from gsxr 750,i have put metal brake lines and a brake disk from cbr 900.now i have stronger brake but i have more 'travel 'in the brake lever...i want to change the master cylinder to reduce the 'travel' and make the brake feeling more instant.From what bike can i put?the master cylinder from a 1100-1150 is suitable?
thanx guys!

sorry about my english but i am from greece and i have not practised them for a long time....
Christos, I think you are better off playing with spacers, springs and oil than changing a master cylinder. Nothing wrong with your English! :)

Cheers

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Old 10-02-2010, 08:19 AM   #18
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bikecat i have read threads you have started and i have seen that you are an owner of a r100gs '88.
i have made the following modifications:
1.front usd wp forks from ktm lc4,top yoke from suzuki rm 125/250,lower yoke from ktm lc4 too.ihave made spacers to fit gsxr's caliper.I have left the standard bmw wheel rim and axle.
2.rear shock ohlins
3.renthal fat-bar
With the ohlins and the usd wp i have enormous better handling.But the brake feeling is something i want to upgrade.

i am concerning about my english because i live in Greece and first time i write at a universal forum.

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Old 10-02-2010, 08:33 AM   #19
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You guys got me thinking, for some reason my front wheel is dished to the right side 5 mm. I was thinking, I could install the Brembo caliper and change the wheel spacers. This would center my wheel and the caliper would bolt right up, right?
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Old 10-02-2010, 10:15 AM   #20
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Quote:
Originally Posted by x3300
Just for anyone interested, pressure in hydraulic systems was explaned by Bernoulli:
Bernoulli's principle
Relationship of Force Pressure and head

-x3300
Thanks for the links.

So, centering the caliper perfectly over the disc is not needed to equalize pressure but, depending on the depth of the cylinders and other clearances of the caliper relative to the disc, spokes, etc., it may be needed to allow new pads to be fitted or to keep the disc, spokes, etc. from rubbing on the caliper.

That's what I was thinking but I was interested to hear if that thinking was correct.
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Old 10-02-2010, 10:34 AM   #21
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Christos - there are other master cylinders available for the G/S, 12-13-14-15 mm bore but they don't have the bonjo fitting like the R100GS, a straight thread in fitting like what's found on the G/S.

Plus using a G/S type MC you'll need to change the brake lever mount.
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Old 10-02-2010, 10:51 AM   #22
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Quote:
Originally Posted by One Less Harley
...Plus using a G/S type MC you'll need to change the brake lever mount.
The GS used the G/S-style master cylinder through 1990. After that, AFAIK, you can only get them in 13mm and 15mm for the K-style controls.

Are you sure the MC is threaded differently for the banjo bolt vs. the straight-in hose? I've never run into that as a problem. Then again, I rarely work on G/Ses and I can't recall ever reinstalling one of those ancient straight-in hoses on a new MC.
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Old 10-02-2010, 10:54 AM   #23
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there are other master cylinders available for the G/S, 12-13-14-15 mm
you mean magura master cylinder from other bmw bikes..master cylinder 15mm had bmw r80 g/s 81-88 and paralever 88-90.i have a gs pd '91.I don't know if is suitable m/c from 1100/1150 models

i have thought to put master cylinder from japan sbk(i wonder if anyone did this so i will have a ready and trusty modification) ...i will have problem with the right standard hand guard because is screwing on the fluid reservoir..but i will change it with Acerbis.
please help,modifications in 2-valve bmw are not famous in Greece..
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Old 10-02-2010, 11:29 AM   #24
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Quote:
Originally Posted by Toyanvil
You guys got me thinking, for some reason my front wheel is dished to the right side 5 mm. I was thinking, I could install the Brembo caliper and change the wheel spacers. This would center my wheel and the caliper would bolt right up, right?
Would that change the tracking, i have never checked my tracking on the GS, does a GS front an rear wheel line up in a straight line like most bikes?

Edit. the motor also sits closer to that side, i would guess the Final drive is also set off to the right, mmm questions for the guru's.
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Old 10-02-2010, 01:49 PM   #25
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Quote:
Originally Posted by Christos 1983
...i have a gs pd '91.
You don't have any bolt-up options. You already have the 13mm which is the smallest. If you want smaller, you could have your existing MC sleeved down and use a 12mm piston because I think the it is the same basic configuration as the 13mm one you have.
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Old 10-02-2010, 04:26 PM   #26
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"Are you sure the MC is threaded differently for the banjo bolt vs. the straight-in hose? I've never run into that as a problem. Then again, I rarely work on G/Ses and I can't recall ever reinstalling one of those ancient straight-in hoses on a new MC."


The banjo bolts at the bottom, but I believe the thread is that same.

Aton, you should have those fork caps soon, if not already,Thanks
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Old 10-02-2010, 04:38 PM   #27
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Quote:
Originally Posted by One Less Harley
The banjo bolts at the bottom, but I believe the thread is that same.
Anyone have a picture of that? It's on the bottom for the K controls, but I've never seen the type we're talking about with anything but a side fitting.

My '88 had a straight-in hose and now it has an aftermarket one with a banjo bolt. Same MC.
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Old 10-02-2010, 05:30 PM   #28
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Quote:
Originally Posted by Christos 1983
now i have stronger brake but i have more 'travel 'in the brake lever...i want to change the master cylinder to reduce the 'travel' and make the brake feeling more instant.
Quote:
Originally Posted by AntonLargiader
You don't have any bolt-up options. You already have the 13mm which is the smallest. If you want smaller, you could have your existing MC sleeved down and use a 12mm piston because I think the it is the same basic configuration as the 13mm one you have.

something to think about ...
It would appear that he is having the same experience that I had when I changed from dual twin pots ( Brembo ) to four pots ( Brembo ) and kept the original master ~ too much lever travel .Went from a thirteen to a twenty ,problem solved .The master needs to shift more fluid for the travel to retain the same 'feel' = bigger master .



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Old 10-02-2010, 05:40 PM   #29
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Quote:
Originally Posted by FR700
something to think about ...
It would appear that he is having the same experience that I had when I changed from dual twin pots ( Brembo ) to four pots ( Brembo ) and kept the original master ~ too much lever travel .Went from a thirteen to a twenty ,problem solved .The master needs to shift more fluid for the travel to retain the same 'feel' = bigger master .
.
A 20mm master cylinder? Where does that MC/caliper combination fall on the chart below? Just curous because 20mm sounds big.

Or maybe I misunderstood your post.

http://www.vintagebrake.com/mastercylinder.htm
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Old 10-02-2010, 05:51 PM   #30
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Quote:
Originally Posted by fishkens
A 20mm master cylinder? Where does that MC/caliper combination fall on the chart below? Just curous because 20mm sounds big.

Or maybe I misunderstood your post.

http://www.vintagebrake.com/mastercylinder.htm

I ride a K100 .The twenty came from a K1100 .I used the forks ,front wheel and brakes from an 1100 but didn't have a servicable front master .Brakes were nice ,but the lever comes back nearly to the bars .Swapped masters for a K1100 and all is good ... except that now my 'flip-a-lever' cruise control will not work .

Was just reading the thread regarding front floating rotors ... a K100 rotor ( four bolt ) has the same bolt spacing and back spacing as an R80/100 G/S .Direct swap/interchange



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