Good post, Mark. I am a big fan of my Avid disc brakes on my Trek 8000. I was "forced" to make the switch from Avid rim brakes due to rim wear through problems of riding in mud, grit and wet conditions year round on the trails here in Austria. I guess once you have a rim explode the fear never quite leaves you that it could happen again. (Nor does the ringing in the ear ever seem to subside...) So I switched to the Avid disc brakes and am sold on these brakes. They have hydraulics coming out this summer as well. I use the middle sized rotors 185mm and imagine that the large rotors of 203mm would be the proper application for a tandem off road. I've been riding for a year in the Alps on the Avids and have never had overheating problems or been at a loss for stopping power using these brakes.
Anyway, back to this 1999 Cannondale MT800 that I have purchased.
http://www.cannondale.com/bikes/99/model-95MT8.html
It has the Shimano tandem specific hubs. The rear hub (Shimano FH-HF07) has the threads for the drum brake. And the frame has rear disc brake mounts as well as the drum brake mount with a 145mm rear drop out spacing. I have to assume that Cannondale has this bike set up properly to accept the drum brake with the way it came in terms of spacing. However, although it sure looks to me that this Shimano FH-HF07 tandem rear hub could be a 135mm hub that is simply on a 145mm axle with spacers, the Shimano parts table lists that hub as only coming in 140/145/160mm. But I simply cannot tell as I have never looked at tandem hubs before and perhaps having 20 or 21mm of spacers between the hub and the dropout on the non drive side is normal. Does anyone know anything about this particular Shimano tandem hub (in terms of spacing) and what the normal amount of spacers on the non drive side is in mm? As I mentioned, according to the Shimano parts list, this tandem hub comes in 140/145/160mm. It comes from the 19998/99 Shimano parts group:
http://www.bikepro.com/products/shim...b98_table.html
http://www.fa-technik.adfc.de/Herste...o/Gruppen.html
There is a 6 hole disc brake rotor adapter part available ($25) that threads on to the drum brake threads on the hub which allows you to use a disc brake on drum brake threaded hubs. If the spacing all checks out, perhaps this is an option. I would simply need the part and I could try my rear Avid from my Trek on the bike to see if the spacing all works out. If not, I'm only out $25.
If that doesn't work, then it looks like I either go with the drum brake and keep the Avid Single Digit 5's that came on the bike - or I invest in a new wheelset with tandem specific disc brake hubs (145mm in the rear). The latter would of course be about $1000 investment, but the bike would then be properly set up for both road and off road descents.
BB