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Old 06-02-2012, 01:17 PM   #1
GodOmelet OP
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Bluhduh Weak Braking on a 77 R100 /7

Hi Everybody,

I'm somewhat aware that the above title may be redundant... I've been reviving/restoring this bike since February, and at long last have gotten her out on the road. My last airhead was an 87 R80 with dual disk brakes up front, so I guess that's my benchmark for stopping power, at least for airheads.... I remember my girlfriend bumping helmets with me despite my efforts to make the stops gentle when she was riding pillion. While I don't want to recreate that situation (though having a new gf/passenger wouldn't be bad thing), I wouldn't even put someone on the back of this one with this insipid braking.

It's been 6 years since I've been on a big bike, so it could just be me at this point. Nevertheless, I am not sure that the single disk is enough to save just me in an emergency situation, let alone a pillion. Even with both front and rear brakes applied, the resulting stopping distance feels more like a truck than a motorcycle. The pads are in good shape thickness-wise front and back, if unevenly worn (one is much thicker than the other on the front). I bled and adjusted the system, and it has a stainless line to the front caliper. Could it be that I need to rebuild/replace the master cylinder and/or caliper to get more grab? I just don't know what these brakes should be capable of. (By the way I only weigh 170 now, as opposed to 200 when I had the R80)

Is there an economical or aftermarket method to arrive at bike with robust stopping power? Short of exchanging the entire front end, is there a way to add a caliper on the other side, or a bigger caliper on the existing disk? I see that my wheel can accomodate a disk on the other side, but it seems that the only way to make that happen is to get a front end from a later model year. I apologize if this has already been covered elsewhere. Thanks. Mark

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Old 06-02-2012, 01:30 PM   #2
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Well, a lot of people mention that these front brakes are a suggestion at best. I would have agreed until I rebuilt the caliper and MC. It certainly is not a modern disk brake now, but even two up I am comfortable/confident.
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Old 06-02-2012, 01:41 PM   #3
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Eh? Everything is relative

When I bought my 89 gs with single rotor everyone told me the front brake sucked!!!

But I almost locked the front brake first couple rides thought it was way to much. Compared to my 1974 r75/6. The gs brake are great!!




Now I have developed a feel for the gs brakes and my r75/6 brakes are good for that historic bike even with a sidecar.
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Old 06-02-2012, 01:42 PM   #4
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back in 77 ... disc brakes were just getting started. leverage ratio used by BMW were generally too low. in other words bore diameter of brake master cylinder were too large in relationship to caliper bore.

brake leverage ratio were about 16:1 vs modern bikes are 28:1 or higher. less fluid is moved, but at lower finger pressures. brake calipers requires very little movement to operate, so higher leverage ratios could be used.

modern improvement includes, larger brake rotor diameter, dual brake rotors and multiple brake pistons, etc. for airheads going to a 320mm brake rotor is a popular mod.

but first you need to make sure your stock brakes is the best it can be ...

replace your pads, measure disc thickness, make sure your brake hoses are not collapsed and caliper pistons are not semi-frozen. note 30+ year old pads can look good, but are way too hard.

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Old 06-02-2012, 02:20 PM   #5
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It is the infamous single ATE brake system. Later Airheads had Brembos. To use the Brembos you will have to change the entire front end. And some don't like the handling of the more modern front. This can also be an expensive way to go.

It's popular to make the single ATE into a dual ATE. That will require several parts and a change of some parts you now have. There's a lot of mixing and matching the parts. Stock dual set ups have 40 mm calipers and 17 mm Master Cylinders. Your single has a 38 mm caliper and 13 or 14 mm MC. These #s can be juggled to increase effectiveness but that's not really the problem to this conversion. An extra rotor, new calipers, maybe another MC and another brake hose all adds up but the part that cost the big bucks is a right side fork leg that takes the ATE caliper. They are currently going for $250 or more on Ebay, when they show up. The whole dual set up will bring more. If you are in England these parts can be had cheaper there. The market for used dual ATEs is a lot less volatile in other parts of the world.

There is another way to get a right side fork leg. I give you a link to a conversation we had not long ago about this solution;

http://advrider.com/forums/showthread.php?t=738951

So that covers the newer brakes swap, the addition of another caliper, both of these are expensive, maybe. What can be done for a reasonable couple hundred dollars? A handlebar mounted MC is the easiest sometimes. Eliminates the cable going under the tank and another size can be used. This is a good solution.

Even if it is a steel brake line now it might be old.

New pads can be a help.

After market semi floating rotors are not cheap but they are a big improvement.

And rebuilding the stuff you currently have might help.

Good Luck with it. If I wanted to improve a system with out the second caliper I'd try all that other stuff.
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Old 06-02-2012, 02:26 PM   #6
Boon Booni
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My R90/6 has been upgraded to dual ATE calipers with Galfer floating rotors and stainless steel lines. I still have the under tank master, though it is new and designed for dual calipers.

It's still a poor system. It's the one thing that I really hate about my airhead.

IMHO, If you want good brakes, you've got the wrong bike.

That said, dual ATE is a big improvement over single ATE.
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Old 06-02-2012, 02:52 PM   #7
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I run dual ATE's on my race bike...they pull up from 180+kmph just fine and I hardly even bother with the rear brake.
Mine has the DIY second leg with the welded tang as mentioned in the linked thread.
The whole set up consists of:
Brembo 13mm master cylinder on bars
stainless lines
under tank junction box
40mm calipers
cast iron discs.
I think it just has standard pads from Motobins.
Set up the swing pivot is easy.

I have dual Brembos on my 70's Italian bike and they are ok...but I would not describe them as " night and day" better....
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Old 06-02-2012, 02:54 PM   #8
Boon Booni
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Quote:
Originally Posted by Voltaire View Post
Brembo 13mm master cylinder on bars
This.
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Old 06-02-2012, 04:59 PM   #9
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11 to 13mm master and ferodo platinum pads!!!
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Old 06-02-2012, 05:24 PM   #10
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note... adding a second caliper and/or changing to a multi piston caliper and/or smaller brake master cylinder all will increase your leverage ratio. which reduces ft lb energy needed to pull in your brake lever.

my dead stock 74 R90S with 13mm ATE BMC and dual ATE calipers stops from high speeds quite nicely.

BMC rebuild, new hydraulic lines and new pads did wonders... lever requires a strong grip to pull it down. but it does the job.
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Old 06-02-2012, 06:25 PM   #11
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Thanks!

Wow, this is a lot of great stuff! Boon Booni has offered to let me see his dual ATE setup, so I can decide whether that would be a good route.

I like the idea of fresh pads and a MC/caliper rebuild. Stands to reason that a bike that's been sitting for a decade, albeit in a garage would have some need of intensive brake therapy.

Thanks Charlie for the link to your thread also. Great info to work with!

Whatever I end up doing I'll post pics to show how it goes.

I'm just glad to be riding, even if it is at a slightly increased chance of catastrophe.... I already found some cool old roads down by the river on the Wrong Side of the Tracks.... Kinda reminds me of some Stephen King book I read.

Mark
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Old 06-02-2012, 08:07 PM   #12
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Short of getting a later model front end? Getting a later model front end is the shortest way to the best fix. Brembo's are night and day better when you are comparing brakes and not bikes. Like I have said before, if you don't think so you are not getting into those Brembo's near as hard as you could be.

Handle bar mounted MC and steel braided lines are barely a fix. It really takes two of those calipers to make much of a brake. I have never seen steel braided lines get old. I am sure it has happened somewhere? Floating rotors in themselves do not improve braking. They reduce the chance of the rotor warping for radial expansion. Our rotors rarely warp. Pulsing rotors are usually caused by a thin spot in the rotor, not a warped rotor. I don't think our bikes need them. They do provide yet another wear item in the system. The buttons wear out regularly. The rotors get loose and make noise, etc.. You are not going to get them to work as good as the brakes on your '87 no matter what you do. Even if you could, the flimsier forks are not going to let you use them without flexing the forks more than the later beefier setup, locking the suspension up, and having to get back out of them for chatter. I wonder who it is that says the earlier forks work better? Anyway, good luck!

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Old 06-02-2012, 09:59 PM   #13
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Quote:
Originally Posted by supershaft View Post
Short of getting a later model front end? Getting a later model front end is the shortest way to the best fix. Brembo's are night and day better when you are comparing brakes and not bikes. Like I have said before, if you don't think so you are not getting into those Brembo's near as hard as you could be.

Handle bar mounted MC and steel braided lines are barely a fix. It really takes two of those calipers to make much of a brake. I have never seen steel braided lines get old. I am sure it has happened somewhere? Floating rotors in themselves do not improve braking. They reduce the chance of the rotor warping for radial expansion. Our rotors rarely warp. Pulsing rotors are usually caused by a thin spot in the rotor, not a warped rotor. I don't think our bikes need them. They do provide yet another wear item in the system. The buttons wear out regularly. The rotors get loose and make noise, etc.. You are not going to get them to work as good as the brakes on your '87 no matter what you do. Even if you could, the flimsier forks are not going to let you use them without flexing the forks more than the later beefier setup, locking up the suspension up and having to get back out of them for chatter. I wonder who it is that says the earlier forks work better? Anyway, good luck!
If getting a later model front end (say, off an 87 R80? ) is the way to go, and has other benefits besides better braking like you say, I'll definitely keep an eye out for one. What range of years are compatible with the /7? Would a new front end still benefit from a billet style triple clamp I've seen so many folks with? I'm definitely wanting to get some more stiffness in this bike. It does feel flexy/mushy. Thanks.
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Old 06-02-2012, 10:07 PM   #14
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Quote:
Originally Posted by GodOmelet View Post
If getting a later model front end (say, off an 87 R80? ) is the way to go, and has other benefits besides better braking like you say, I'll definitely keep an eye out for one. What range of years are compatible with the /7? Would a new front end still benefit from a billet style triple clamp I've seen so many folks with? I'm definitely wanting to get some more stiffness in this bike. It does feel flexy/mushy. Thanks.
I think 81 to 84 forks are the best solution for your bike. A good alloy top tree will make it better. I don't think spoke wheels will clear the calipers. I would run some Lester mags tubeless. Personally I would just start with a Monolever but that's just me. For starters I prefer 18" front wheels, beefier forks, beefier axles, and better wheel bearings. Plus Mono's have beefier Brembo calipers than the twin shocks have. They look the same but they are not the same! They flex less.

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Old 06-02-2012, 10:23 PM   #15
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ATE brakes can be made to work farily well, but for what it is worth to change to dual ATEs with a handlebar m/c and new stainless lines, well, you could find a complete donor front end from an 81-84 period R100 with dual Brembos. You may pay a little bit more, but then you will have the beefier forks that can handle the stopping power much better, with less flex.

A lot of the problems that a lot of people complain about with the brakes on Airheads can be fixed by doing a complete overhaul or replacement to Brembos. This is even a good time to consider a Brembo rear brake. People are always pulling them off and converting to drums because they are not willing to set them up properly. You can usually pick them up for very reasonable prices.

I have heard from lots of people that complain about the Brembo rear brake being near to useless. Problem is that they just don't have a clue how to set them up properly. Install a stainless line and reverse bleed. I have corrected 100s of peoples opinions about the rear disk by just doing a good reverse bleed, All of a sudden they have a solid working rear brake that can lock up the rear wheel if not careful. You have to re-learn how to use it and most people just can't believe the difference.

But, all that being said. You will never match the modern brakes on the newer bikes.
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