The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: Blackjack on December 29, 2010, 05:42:18 PM
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Anyone know what it is?
This is pure laziness, cause I could pull it apart an measure it, I know.
But, if you already know....
Also, I've not ridden the bike, I'd like a bit of feed back on just how "wooden" and 1970's the (ATE) brakes feel.
I'm slightly tempted to use a set of Kawasaki ZX *** R discs (assorted diameters, 5 stud fixing) and some disc adapters (R65's having ridiculously deep bells) along with some decent modern 4 pots and associated m/cylinder.
But nowhere near as tempted by the idea as I am intimidated by the cost....
Dual disc by the way.
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There should be a two digit number cast on the bottom side of the master cylinder, if you have a dual disc, it's most likely a 15 mm master cylinder .
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But beware - a dealer installed the wrong replacement master cylinder on my 1981 dual disk bike. That one should be 16mm. One silly millimeter longer, but it makes a huge difference in how the lever works.
And yes, the ATE brakes are very wooden. They work ok, but when you reach the braking point, the lever doesn't move any more, even though added pressure does increase the braking force. So, there's no real feedback.
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I have both the Brembo and ATE left side caliper, they look the same mechanically and dimensionally, is one better than the other?
The 16mm Master cylinder is the rectangular one right?
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The 16mm Master cylinder is the rectangular one right?
16mm is for a twin disc set up. With a single disc I imagine it would be truly awful.
Single disc should be 13mm 78 - 80 and 12mm 81 - on
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For dual disk, it's 16mm from 78-81, 15mm 82-on. Same years for ATE vs. Brembo. But the master cylinder is round 78-80 and rectangular 81-on. So, 81 is a weird year, with the bigger bore, the rectangular MC and the ATE brakes.
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Thanks chaps, that's what I needed to know.
I'm on the hunt for something a little cleaner looking for the cafe racer.
I was thinking that a 14mm was worth a try, based on previous experience, so I googled 14mm master cylinder, just in case I can't find one in the workshop.
Turns out that there's quite a few threads on Advrider about fitting smaller m/cylinders to BMWs.
Here's one of them, if you're interested,
http://www.advrider.com/forums/showthread.php?t=403427
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That's a good thread from advrider. I think I would also consider 14mm on a twin disc set up but not smaller
We also had a discussion here on master cylinder sizes recently and there is some info that might help with your decision.
http://www.bmwr65.org/cgi-bin/yabb2/YaBB.pl?num=1290616014/3#3
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14mm would seem to answer the case.
But if I should happen to find a 13mm, then I might chuck it on and see what it's like.
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The ADVRider thread was probably me asking much the same questions over there.
My 1984 single disk has a 12mm master cylinder. I believe the factory master cylinder for a twin disk setup, eg: R65LS is 15mm, but apparently other sizes in 1mm increments exist too.
A smaller master cylinder diameter will give you better leverage; eg: less force but more lever travel for the same braking outcome.
Obviously you do not want to run out of lever travel!
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I prefer the 13mm with the dual discs. And the ATE calipers work very well when everything is set up properly - fresh fluid and decent pads. And make sure the pistons aren't corroded or pitted.
Don't let anyone tell you the ATE brakes don't work well! They do! I used to think the single disc ATE systems were horrible until I rode one that was set up properly.
By the way, the Master Cylinder size is cast into the bottom (underside) of the outlet near where the brake line attaches.
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Hey, My R65 does have the 16mm reservoir yet it only has a single disk.
:D
What do you mean by awful? reduction of braking power?
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Hey, My R65 does have the 16mm reservoir yet it only has a single disk.
What do you mean by awful? reduction of braking power?
Julio it's all about the ratio of master cylinder area to caliper piston area which amplifies the force you apply at the lever.
The difference in area between a 12mm and 16mm master cylinder is huge the 16mm being almost double. Therefore with a 16mm master cylinder on a single disc set up you have much less amplification and you are going to have to pull literally twice as hard on the lever to get decent braking. The lever is also going to be really solid and devoid of feel.
I think you need to change to a 12mm.
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Or get a second brake disc .
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Julio,
That sounds like you're saying you have the rectangular reservoir?
I don't know, but I'd imagine that BMW made single disc versions with the rectangular reservoir, but they would have had a 13mm cylinder bore.
Not trying to be pendantic, just that if you're messing with brakes it's best to be crystal clear about what's being said...
On a different note, while personal preference comes in to it, riding ability probably dictates how useful it all is. Watch the back wheel..
http://www.break.com/index/biker-falls-over-highway-mountain-railing-1973929
Scared of the front one you think???? :o
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All I know is that with a 15mm bore on my dual disk setup, the brake lever went to about a 1/2" off the handlebar before there was any brake action. They worked fine otherwise, but I couldn't do two-finger braking, as I do on my other hydraulic brake bikes.
When I bought and installed the correct 16mm MC, the braking point was well off the bar, just like on my other bikes.
And while the ATE brakes do stop the bike in a reasonable manner, they just don't have the feedback qualities of the later Brembos. At least, IMHO.
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Julio,
That sounds like you're saying you have the rectangular reservoir?
I don't know, but I'd imagine that BMW made single disc versions with the rectangular reservoir, but they would have had a 13mm cylinder bore.
The single disk version of the master cylinder with the rectangular reservoir as fitted to 1981 through 1984 R65s is 12mm.
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All I know is that with a 15mm bore on my dual disk setup, the brake lever went to about a 1/2" off the handlebar before there was any brake action. They worked fine otherwise, but I couldn't do two-finger braking, as I do on my other hydraulic brake bikes.
When I bought and installed the correct 16mm MC, the braking point was well off the bar, just like on my other bikes.
And while the ATE brakes do stop the bike in a reasonable manner, they just don't have the feedback qualities of the later Brembos. At least, IMHO.
This sounds like your rubber brake hoses have got old and soft and are expanding under pressure, using up some of your lever travel. Going to a larger master cylinder allows you to move more fluid but at a lower pressure, compensating for the expansion of the soft hoses but reducing the braking force at the calipers for a given lever force.
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All I know is that with a 15mm bore on my dual disk setup, the brake lever went to about a 1/2" off the handlebar before there was any brake action. They worked fine otherwise, but I couldn't do two-finger braking, as I do on my other hydraulic brake bikes.
When I bought and installed the correct 16mm MC, the braking point was well off the bar, just like on my other bikes.
And while the ATE brakes do stop the bike in a reasonable manner, they just don't have the feedback qualities of the later Brembos. At least, IMHO.
This sounds like your rubber brake hoses have got old and soft and are expanding under pressure, using up some of your lever travel. Going to a larger master cylinder allows you to move more fluid but at a lower pressure, compensating for the expansion of the soft hoses but reducing the braking force at the calipers for a given lever force.
Nope. PO put stainless braided lines on it. And with the correct 16mm MC on the bike, the brake lever works correctly.
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Darryl,
I replaced my original 16mm master cylinder with a 15mm master cylinder on my 81 R65. I have the dual ATE discs up front and replaced the original brake lines with stainless through Ted Porter's Beemershop recommendation and supply. I researched this the best I could and am more than happy with the resulting function of my front brakes. The larger master cylinder gives a bit more of a wooden feeling at the lever but still has good adequate feel and feedback (modulation). With adequate bleeding the lever travel is 1/2 throw to the handlebar. I feel like I could stand the bike up on it's front wheel if I had that kind of skill. I'm attaching the link to Mike Morse' brake ratio chart for you to view. Take a look - it's very helpful and will give you a good direction of different combinations.
http://www.vintagebrake.com/mastercylinder.htm
-Mike V.
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Well, I don't know what to say about it that I haven't already said.
With the 15mm MC, even with a careful brake flush, the brake lever comes back so far to the bar that it would trap my two fingers on the bar before ANY braking would occur. The braking action was otherwise acceptable. As the MC has no adjustment for the lever position makes this unacceptable to me.
OTOH, when the correct, original 16mm MC is mounted, the lever moves back a bit and then the braking action begins, and again, the action seems acceptable.
I can't really tell the difference in how much "feel" there is; both MCs seem to be somewhat wooden relative to what I am used to on more modern bikes (R1100RS, R1200ST). The braking delivered by either MC is much closer to what I am used to getting from my R90S's dual ATE (single piston) brakes (which also have braided steel lines).
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My '81 R65 came from the factory with the 15 mm master cylinder, I'm the original owner, and the only person that has worked on the bike since I took delivery of it 30 years ago .
I have about .5 inch (12mm) lever travel with 1.5 inches (37mm) clearance between the lever and hand grip with the brake fully applied .
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To clarify my post and support Bob's mention, my 81 R65 came with a standard OEM 15mm master cylinder. I replaced the destroyed original 15mm (bore pitting) with the larger 16mm master cylinder. This has worked well for me. Couldn't ask for better brakes on my R65.
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mine is a square reservoir 13 mm and its a single disc 1980
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With the 15mm MC, even with a careful brake flush, the brake lever comes back so far to the bar that it would trap my two fingers on the bar before ANY braking would occur.The braking action was otherwise acceptable.As the MC has no adjustment for the lever position makes this unacceptable to me.
Darryl,
I struggled with the lever position (compressed) on my rebuild also. I felt as though it was too close to the bar. I continued to bleed the system so many times I probably went through a full liter of brake fluid. I found the more I bled the system the more lever I obtained. Each time I saw microscopic bubbles surfacing in the reservoir. I continued the bleeding process for probably two days since i was unsure all the air was removed from the system since I completely rebuilt both the calipers, new lines and new MC. I tapped on the components, turned the bars fully to the left, bungied the lever and let sit. Repeated the bleeding over and over. I ended up with sufficient lever travel not pinching my fingers during hard braking. My lever travel pretty much equals Bob's posted values.
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The picture is from realoem.com, note item #2, from 09/80 to 09/81.
I first bled the brakes myself, but then a good friend, who is a former chief mechanic at a BMW dealership, visited me and he bled the unit as well. I seem to recall using a zip-tie to hold the lever under pressure. Anyway, the lever position never moved forward.
I bought the 16mm MC from Motobins, and after installation, it set up immediately to the correct position.
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This is the first I've seen RealOEM, or the BMW parts catalog specify the 16 mm master cylinder for bikes manufactured from 09/80-09/81 .
This is a relatively recent change, in the last year or so .
They used to have both the 15 and 16 mm master cylinders listed in that picture .
If I ever have to replace the part I'll get the 16 mm .
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Just to add to the discussion... my 1981 came from the factory with 16mm rectangular master cylinder and dual ATE calipers. According to my serial number it was manufactured in 10/80. Braking feel is pretty much as Darryl describes it. I replaced the MC a couple of years ago and replaced the rubber lines with stainless but the 'feel' really didn't change dramatically. Adequate but not spectacular compared to modern systems. Back in 1981 they were the best brakes I had ever experienced on a motorcycle - much better than most other bikes of similar vintage.
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I'm wondering if my bike, being built at the model year change over , it was made 09/80, the ninth bike off of the production line (serial number 6385009) for the '81 model year for the North American market has anything to do with it .
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just a shade tree estimate tells me it would cost more to add a rotor than what I paid for the bike.
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I didn't get this bike new; in fact a friend is the original owner, and he gave me the bike a year ago. I don't know the complete history of it, but he told me that the MC had been replaced by his local dealer, quite a long time ago.
I noticed the brake lever situation right away, as we were pushing the bike to load it into my pickup. I asked Jim what was up with the brakes. He thought it was completely normal; certainly, that's the way he had been riding it for a long time. (The bike came to me with 169,000 miles on it!) He didn't think it was odd, even in comparison to his current bike, an F650 single.
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I think Julio A. made a posting a few months ago about a later K series four piston caliper that had the same bolt hole pitch as the R65 caliper .
That would be an interesting upgrade to say the least !!!!!!!!!!
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Those calipers fit right into the mounts on the R65's Forks but does not clear the rims if it is aligned with the disk. But when I made it fit and it cleared the wheels, there was no way to have the disk go into it.
Now I have a pair of four pot brembo calipers w/ brackets, an extra ATE and brembo left caliper(excluding the one currently installed on the R65), a spare right brembo caliper that only fits the R100, and a brand new spare disk that I recently found out came from a different and incompatible airhead.
I also have a ridiculous quantity of spare brembo pads but no ATE ones. So when I wear out my current ATE pads I will be replacing the whole caliper with my spare Brembo caliper. ;D
All of which is collecting dust on my cabinet....
They make a good display piece though.
Haha, there were a lot of attempts to convert the thing to a dual disk.
Everything failed miserably. :D
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OK, area of a circle is Pi R2, so for a 16mm master cylinder that 64Pi, ignore the Pi.
For a 15mm its 56.25Pi, again ignore the Pi.
64 divided by 56.25 gives you 1.1377777777.
So for a given amount of travel a 15mm piston displaces around 13.7777% less fluid than a 16mm one.
So unless there was something else amiss, the difference in travel would be a little under 14% greater, for the same pressure at the pads.
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You can modify the pads for the Brembo calipers to work on the ATE calipers, you just need to remove material from the steel back plate .
About 20 minutes work on each pad .
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I didn't get this bike new; in fact a friend is the original owner, and he gave me the bike a year ago. I don't know the complete history of it, but he told me that the MC had been replaced by his local dealer, quite a long time ago.
I noticed the brake lever situation right away, as we were pushing the bike to load it into my pickup. I asked Jim what was up with the brakes. He thought it was completely normal; certainly, that's the way he had been riding it for a long time. (The bike came to me with 169,000 miles on it!) He didn't think it was odd, even in comparison to his current bike, an F650 single.
Hi Darryl!
I'm the guy who stayed at your place when you were gone to the autumn beemer bash this last fall! I was going to stop again on my way back from Los Angeles but ran out of time. Hope to make it to your tech day this spring.
Anyway, just wanted you to know the hot ticket is a 14mm master for the dual discs. I've even heard the 13 works very well, but haven't tried it yet. If you're having problems with the 15mm coming most of the way back to the bar, there's something wrong. Since it's already got stainless lines, it's got to be something with the caliper or master.
You got me!
But I do know the 14 works very well for me and I'm really happy with the results on several of my beemers. My understanding is that from the mid seventies into the 80s, hydraulic brakes were still a new thing on BMWs and the engineers still hadn't gotten the ratios right. Going to the 14mm with the dual two-pot Brembos gives great feel and control and none of that wooden feeling.
Terry
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Back in the 70's, disc brakes were not only a recent thing, tyres were made out of far more "excitibg" rubber compounds, and more critically, every one was used to drum brakes along with the higher lever effort that comes with them.
The difference in swept volume between a 15mm and a 16mm means that the 15mm cylinder's lever will travel about 1.13777 times the distance of the 16mm one to displace the same amount of fluid. This of course assumes that the 16mm and 15mm cylinders have the same lever ratio.