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-   -   Airhead Rear Disc brakes (http://www.advrider.com/forums/showthread.php?t=675393)

davemon 04-06-2011 10:19 AM

Airhead Rear Disc brakes
 
I realize the brakes on the airhead leave a lot to be desired but anyone figured out how to make the rear disc on a 77 R100S work? Caliper change?
Master cylinder change? Mine won't lock the rear wheel if I stood on it with both feet. Not really willing to go to drum but looking for a fix.

Hawk Medicine 04-06-2011 12:47 PM

77 R100S with a rear disc?

The "S" bikes were manufactured with drum rear brakes.

wirewrkr 04-06-2011 02:01 PM

Quote:

Originally Posted by mymindsok (Post 15603175)
77 R100S with a rear disc?

The "S" bikes were manufactured with drum rear brakes.

Until 78.

supershaft 04-06-2011 08:53 PM

It is a REAL job to get all the air out of that system. I suspect that is your problem. That and/or a shot rubber line.

bmweuro 04-06-2011 08:57 PM

It could have been made from 9/77-12/77. The only way to get the rear disc to work is a smaller bore master cylinder like a 12mm. Modify the mounting to use an earlier K100 with ABS, R1100 or R1150 rear brake master cylinder.

Reryder 04-06-2011 09:05 PM

New brake hose is a must on these old Airheads. The originals have all swelled up and choked the hole down the centre by now.

And that rear brake is a bitch to bleed for some reason. Taking caliper off and hanging it so rubber hose is vertical helps, as does a vacuum bleeder.

Can't remember exactly but I think there were two sizes of master cyl bore, the later ones being smaller and more effective. You can get the old ones sleeved to fit the later piston/seal.

supershaft 04-06-2011 09:47 PM

Good advise you guys! Yea, the master cylinder bore is too big on those but still . . . the smaller MC's don't work well with junk lines full of air either! I really was going to say something about that but I though about first things first. :norton

fishkens 04-06-2011 09:53 PM

I never liked the rear disc on my 78. Seemed like way too much crap not doing 1/2 what the drum could do. Plus it made getting the wheel off more difficult.

But it sure looked good. :lol3

Melrone 04-07-2011 09:17 AM

Had the same priblem with my 81 RT a few years back.I ended up replacing the master cylinder,new steel line,and a steel braided line to replace the rubber line.I then added a little wxtra line off the fluid resivoir so I could rise up above the master cylinder and then pumped the hell out of the pedal till I had a real brake..It was apain in the asss but it worked.Your right it does look good:deal

Caddy82rats 04-07-2011 02:03 PM

what have worked on my RS :
I put old break pads, a crew driver between break pads.
I pupm on break pedal
Twist the larg flat screw driver, brake fluid and air goes back in brake fluid tank.
I do again and again that

davemon 04-08-2011 03:22 PM

The bike is a 78 from the engine number
I have replaced the rubber hose with a top grade one from a place in Ohio. New pads and bled the hell out of the system. Roughed up the rotors a bit with some emory cloth and cleaned out the cooling holes. So it looks like a rebuild of the master cylinder and getting the rotor turned

Hawk Medicine 04-08-2011 09:49 PM

Quote:

Originally Posted by davemon (Post 15621468)
The bike is a 78 from the engine number
I have replaced the rubber hose with a top grade one from a place in Ohio. New pads and bled the hell out of the system. Roughed up the rotors a bit with some emory cloth and cleaned out the cooling holes. So it looks like a rebuild of the master cylinder and getting the rotor turned

Whats wrong with your rotor?

boxerboy81 04-09-2011 12:08 AM

Two mates of mine replaced their rear steel brake line and rubber hose with a custom one long stainless steel brake hose.

Both are very happy with the solution. This comment was as significant for the rear brake as it was for the front.


Quote:

I finally got around to having a good ride on the RS today after fitting the new braided brake lines front & rear...Should of done it years ago as it made a world of difference, just amazing really ........ http://boxerworks.com/forum2/images/.../icon_razz.gif

davemon 04-10-2011 06:59 AM

The hose I put on was from Spiegler and the rotors are running straight but pretty polished.

bmweuro 04-10-2011 12:41 PM

You can waste as much time and money and thought on this as you want. Unless you go to a smaller bore master cylinder nothing will really change. These things were crap when they were new.


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