Rear disk brake

[marcmax]

Ran across this in the classified on IBMWR.

http://marketplace.ibmwr.org/ads/view/id/193402

Anyone have any ideas if something like this could be done to an R65?

[marcmax]

Let me try again.

http://marketplace.ibmwr.org/ads/raps/page/2

[marcmax]

Maybe the third time will work. Rear disk brake conversion set from a 1982 R100RT for a dual shock airhead

http://www.flickr.com/photos/kstoo/5219827596/in/set-72157625576825960/

[Bob_Roller]

First, the R100 bikes had a 19 inch rear wheel .

Second, you need a swing arm with the mounting bracket for the caliper .

Third you need a master cylinder for the rear brake and a place to mount it .

[Rob Valdez 79 R65]

First, the R100 bikes had a 19 inch rear wheel .

Second, you need a swing arm with the mounting bracket for the caliper .

Third you need a master cylinder for the rear brake and a place to mount it .

Fourth, you will be disappointed.

I've never heard raves from rear-disk-brake equipped airhead owners.  It was a marketing ploy gone wrong.

[marcmax]

According to several web sources the 82 R100RT had an 2.75 x 18 snowflake rear wheel and a 19" snowflake front wheel.

http://www.bmbikes.co.uk/specpages/R100RT.htm

Real OEM fiche shows the R100RT as having an 18" rear and a 19" front wheel.

Also the caliper bracket is mounted with a bracket attached to the real axle and uses a drag link to the swing arm to provide the counter force to the brake torque. Mounting a master cylinder for a rear brake is not complicated. I have mounted a Japanese bike rear m/c on my K75s while I was waiting for a rebuild kit for the BMW m/c.

Even a marginal rear disk brake has to be better than a marginal drum brake. Don't you think?

[Justin B.]

The R100 bikes do have an 18" rear wheel, it is the front that is 19".  I have the rear disc on my '81 R100RT (converted to R100T) and although it brakes just fine - I have no problem locking up the rear wheel - I can't really see any reason why I would go to the trouble if it wasn't already there.  Apparently BMW realized the rear disc wasn't better (and probably cost more) so they switched back to drum after a couple of years.  AFAIK they only put the read disc on the RT and RS models.

[tvrla]

The S also had a rear disc. And the rear's on the post 1970 airheads have all been 18", including the G/S and GS.

I'm also in the camp of preferring the drum rear - for a lot of reasons. Like, no better braking, less weight (unsprung at that), ease of wheel removal, cost, and complexity.

But, should you decide to convert, it's pretty easy: source a rear wheel, disc parts, mc, weld a bracket to the Swing Arm to receive the torque arm, and mount the master cylinder. Not a big deal.

[Barry]

personall

Fourth, you will be disappointed.

I've never heard raves from rear-disk-brake equipped airhead owners.It was a marketing ploy gone wrong.

I agree they were fitted to many bikes for marketing reasons and because they were cheaper. Generally the caliper and master cylinder down in the road muck tends to add maintenance grief. I would go out of my way not to have one. The rear drum brake is trouble free, almost maintenance free and it works well enough for my needs. An overly powerful rear brake is potentially dangerous as a locked rear rapidly causes the rear end to come around and if you release the brake in those circumstances you will tend to have a high side. I've only ever locked up the rear once in the wet. I released the rear brake very gradually but the snatch as the rear straighten up still gave me a scare I never want to repeat.

Perhaps I'm biased. Rear disc brakes are even a pain on my old Merc 190e because a separate very small drum is fitted for the handbrake and as a result the handbrake is rubbish - crazy idea.

[tvrla]

On top of all that, the rear disc tends to wear quickly and score badly from the road grime splashed up on it.

I'm guessing the problems were ironed out with the oilheads, but the drums are the best course of action with our airheads.

Your Mercedes may have had a horrible parking brake, but my Volvos always worked well with the same sort of system - all wheel discs, plus drums at each rear. Maybe that's part of the reason they're such tanks!

[Julio A.]

There may be a good reason why BMW reverted back to the Drum Brakes during the last generation of Airheads.