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Old 06-26-2014, 03:48 PM   #1
victorlaszlo OP
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R80/7 1978 - How to improve brakes?

I just got my second /7, an R80 is now joining my R100RS 1983 in the garage.

The bike is lovely and runs super sweet but the brakes really aren't good.

It has double front disks, the old style grey BMW variety, and rear drum.

I bled the brakes and it made no difference. Left it to the local BMW specialist who had a look at it, improved them slightly and declared "Thats as good as they are ever going to get.". And the setup with remote master cylinder under the tank is spongy to say the least.

Rear brake close to non-existent compared to the R100 and to my 1967 Vespa...

Now, I'd love to ride it actively through the rush hour traffic to work but am currently almost afraid of doing so due to the lack of brake action.

So, what can I do? I suppose going full hydraulic with a handlebar master cylinder should improve brake action somewhat, but I fear the callipers aren't good enough.

Do any other callipers fit to the forks on the -78 /7 with spoked wheels?

And what can be done with the rear brake? Will changing brake shoes do any difference or is it a dead race?

Thankful for any advice - cheers V
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Old 06-26-2014, 04:10 PM   #2
yankeeone
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I have the same model bike, and just rebuilt the master and the caliper. I had to replace the brake light switch,and that started the whole thing. Master rebuild kit and new switch installed, still not great. I had to undo the master clamp and raise the rear of the master, tap it with a screwdriver while I forced brake fluid up the system from the caliper with a syringe. This got all the air out of the line and master. Before I did this the lever would almost hit the grip, now it only goes about 3/4 of an inch at the tip of the lever. Stops pretty good for a single disk.
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Old 06-26-2014, 04:11 PM   #3
victorlaszlo OP
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Did you rebuild it because it was leaking..?


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Old 06-26-2014, 04:26 PM   #4
yankeeone
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Once I got in there for the switch, I found it was time- much gunk and corrosion, also the return hole was partly clogged so the brake was not releasing properly. Surprisingly it was not leaking.The bike had sat for twenty five years before I picked it up so I new I was going to get into it.
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Old 06-26-2014, 04:32 PM   #5
victorlaszlo OP
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Will try this but is raising the master really necessary? Any issues forcing up the fluid or as simple as disconnecting the hose from the calliper...?


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Old 06-26-2014, 04:39 PM   #6
yankeeone
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When you look at the master, you will see the hi spot is at the switch end, forward on the bike, so when you raise the master this helps the air out. look around the net there are descriptions of bleeding back. you just use the bleeder and a syringe with a tube on the end to push the fluid up. let the air raise into the syringe before you push it thru.
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Old 06-26-2014, 05:06 PM   #7
victorlaszlo OP
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But when I was bleeding it I remember that the inlet was at the bottom of the reservoir, cantered. It does sit slightly sloping with the high end forward but as the inlet is below the hugest point is raising really necessary?

And of so, how much? Just to level or more?

Thanks for the advise - V


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Old 06-26-2014, 05:33 PM   #8
yankeeone
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Right, but the fluid travels up through the reservoir and allows the possibility of air trapped up by the switch. on my bike the brake line comes in the side of the master.I picked the master just past level and tapped it with a screwdriver handle.
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Old 06-26-2014, 06:35 PM   #9
beemerphile
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A 13mm handlebar mounted master cylinder and stainless hoses made a great difference in my 1976 R75/6. It has dual ATE's from a 77 RS that as I remember are 40mm pucks instead of 38mm. Maybe most of them are 40mm, I don't know, but the M/C makes a difference. The 13mm is not as firm feeling as the larger ones, but it gives better leverage and when properly bled, I have never had the lever get too close to the grip. As usual with ATE's getting the eccentrics set right is important as are good HH pads and clean rotors - properly bedded in.
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Old 06-27-2014, 01:01 AM   #10
chasbmw
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Quote:
Originally Posted by beemerphile View Post
A 13mm handlebar mounted master cylinder and stainless hoses made a great difference in my 1976 R75/6. It has dual ATE's from a 77 RS that as I remember are 40mm pucks instead of 38mm. Maybe most of them are 40mm, I don't know, but the M/C makes a difference. The 13mm is not as firm feeling as the larger ones, but it gives better leverage and when properly bled, I have never had the lever get too close to the grip. As usual with ATE's getting the eccentrics set right is important as are good HH pads and clean rotors - properly bedded in.
This is the way to go, when adjusted properly the brakes will be almost as good as Brembos. You can get a 13mm handlebar MC with twin throttle cables, the controls will switch right over. It's the change in size of the MC that makes this work. The original design was far too conservative.

You can order a new MC from Motobins, or if you are lucky Motorworks might have a second hand one in stock. Remember specify 13mm, twin pull throttles
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Old 06-27-2014, 01:35 AM   #11
victorlaszlo OP
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Sounds great! These are te callipers I have:



And this is the bike:



Are these the bigger or smaller callipers?

Bests Victor


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Old 06-27-2014, 02:15 AM   #12
chasbmw
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Almost certainly 40mm callipers, the 38s were only fitted until end 75 model year and are I think only in black.
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Old 06-27-2014, 03:13 PM   #13
Stan_R80/7
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Quote:
Originally Posted by victorlaszlo View Post
Sounds great! These are te callipers I have:



Snip!
The '40' shown in this photo on the caliper denotes the piston diameter in mm.
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Old 06-27-2014, 05:59 PM   #14
Nailhead
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I've been going through essentially the same headaches with my RS: my Honda MiniTrail had MUCH better brrakes. They're simply terrifying, and I mean the fronts-- the rear seems to work alright. Hell, it has to.

This is what I've learned so far:

The pad/caliper alignment to the rotor is CRITICAL, for two reasons: 1. The pad has to utilize the entire surface of the rotor to be effective, obviously. 2. If the caliper is allowed to remain out of alignment long-term, it will wear the caliper to compensate (This I've deduced from a cocked wear pattern in one of my front calipers. See my "Found...Lousy Brakes" thread for pix.) and result in a caliper that will not hold adjustment, no matter how many red lines you draw on your rotor. It is intensely frustrating, and looks goofy.

The "Sharpie-on-Rotor" method of adjustment MAY not be the most effective. I haven't tried this method yet (the reason for the uncertainty), but it just makes so much sense: pump the front brake until it's as firm as it can be & secure the lever to the bar with a velcro strap, bungee, etc. Rotate the eccentric back & forth until it feels centered. Reinstall the cap & you're done. This method courtesy Ken in Oklahoma on Boxerworks, apologies for any inconsistencies.
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Old 06-27-2014, 08:08 PM   #15
Rob Farmer
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The state of the discs is really important with ate calipers. Then tend to wear the disc on the inside close to the hub because it's the first point of contact with the pads. If the discs worn there you'll never get them set properly and they will always feel spongy. The difference in feel and operation when new discs and pads are fitted is amazing. I'm not saying you should go straight out and fit new parts but it's worth checking that the back of the disc is flat.

This is the handlebar conversion on my old 78 RS. If you buy the master cylinder you'll need the splitter unit to replace the under tank master cylinder


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