Utility Cycling - Switching to disc brakes?

My frame and fork have the correct mounting surfaces for disc brakes but my hubs are an older Shimano design. Is there any way I can avoid buying new wheels if I decide to switch to disc brakes (I'm still not convinced I need to do this, just thinking about it). If I could only afford to switch one, which one would be the wisest, front or rear?

Anyone have disc plus rims brakes, maybe using the rim brakes to slow the bike downhill?

BTW, the bike is a tandem, meant to post this in the tandem forum. Regardless, you guys know alot about big heavy bikes. Go disc or stick with center pulls?

Disc, being much more powerful and efficient, it should be installed on the front wheel. Personally, I know of no adapter that can be applied to a wheel so a disc can be mounted, but then, I've never looked for one.

is this a road tandem?

if so you'd also need to ensure that you order a "road caliper" for the disc brake.

i.e. Avid BB7 "road"
http://www.universalcycles.com/shopping/product_details.php?id=19182&category=19

meaning that the leverage in the caliper matches the pull ratio in a road lever.

that is: MTB and Road levers have different pull ratios. due to obvious different types of brakes.

FRONT or REAR?
well... most of your effective braking force comes from the front.
i've seen plenty of tandems using a rear disc brake as a "drag brake"

there is more to the equation than what's been revealed so far.

more info is really needed.

road tandem or MTB
groupo?
wheelset
etc...

and possibly what kind of riding the tandem is subjected to.

personally, I use a Big Dummy and its loaded quite a bit, i use a 203mm front rotor with heavy duty "metalic" pads. like EBC Gold using Avid BB5's

i prefer Avid Mechanical disc brakes, they are easy to set up, and easy to work on... if you ever need to work on them.

peace...d

It's a road tandem with 26 inch wheels. Big Bummy front fork.

http://home.swbell.net/hebert11/iphone_5-22-09_007.jpg

Pic is worth a thoussand words.

thats a really nice tandem
it looks like it has a campy groupo

by the looks of the set up
the riders are not that tall

what I'd do, is simply ride it until the front wheel wears out
then i'd start thinking of a disc brake.

unless of course you simply want a disc brake
it would be easy
just use an Avid Mechanical "road" caliper.
you'll need a front wheel with a hub that accepts a disc brake rotor.

if you have a wheel built up
you can choose a rim that has a flat braking surface to accept those canti brakes
in that, its simply that much more versatility
if you're going to get another wheel, why limit yourself?
unless of course, you simply don't like the look.

here's a front wheel
http://www.universalcycles.com/shopping/product_details.php?id=28547&category=3662
it's a 26" mtb wheel, with a hub for disc brake rotor
the rim is almost like the wtb DH rim.
http://www.wtb.com/products/wheels/rims/dhfr/speeddiscxl/
the other thing you could consider is the lacing pattern.
rather than the 32h that is stated on the webpage, you could go for 36h, 4 cross.

it would be pretty darn strong!

and use
a brake like this:
http://www.universalcycles.com/shopping/product_details.php?id=19182&category=19

there are a bunch of different sized rotors
140mm
160mm
there used to be 165mm
185mm
and
203mm

and different brake pad compounds

if you dealing with a bunch of weight, and extended braking
i'd choose 203's with metalic pads
that is what I use on my Dummy

smaller rotors have less leverage, which requires more force at the pad to get the same amount of braking power.

so if you use a 140mm rotor, and organic pads
compared to
203mm rotors and metalic pads

the smaller rotor is going to eat up those organic pads much quicker
but the pad "feels nicer" thru the lever.
albeit, its a very subtle difference

changing rotor size(s) is easy
all you need are the appropriate disc brake caliper adaptors, per size
http://www.universalcycles.com/shopping/product_details.php?id=178&category=20

a 185mm rotor would be a happy middle ground.
185 is heck-a-strong
and there is a chance that you could actually use a 160 instead

if you live in the flats... 160 would probably be enough.
and you could get away with simply using the stock pads that come with the "road caliper"

Thanks for all of the info.

I went with an Avid BB7 160 rear. I'll probably convert the front later in the year. Found a used Phil tandem disc capable rear hub on Ebay. Got a good deal on the hub and it was laced to a 26 inch rim that matches my current rims.
Thanks again.

I went with an Avid BB7 160 rear. I'll probably convert the front later in the year. Found a used Phil tandem disc capable rear hub on Ebay. Got a good deal on the hub and it was laced to a 26 inch rim that matches my current rims.
Thanks again.

make sure the disc brake caliper is a road version, to match the brake levers.

Yes the model I ordered was the road model. Thanks.

Changed my mind and went with the 203 rotor.