Rambetter

Trek T2000 with 2 caliper brakes and mounts for a rear disc:



I wanted to get thoughts as to putting on a rear disc to be used as a drag brake. The distance between the mounting holes is 51 mm.

Some thoughts regarding this:

- In my case I'd need an Arai-to-disc adapter (https://www.endless-sphere.com/forums...y_history=true) that screws on to the left side of the hub and "creates" the 6 holes needed to mount a disc.

- Would be inclined to use a bar end shifter on friction mode. Any other thoughts on this? The bike is a full-blown racing bike with 31.8 mm drop bars and "wing" tops.

- Cables and cable housing: The housing used should presumably be 5 mm brake housing (the spiral kind), and not derailleur housing that has strands going lengthwise. However, if using a shift mechanism to actuate the drag brake, the cable that fits the shift mechanism would probably need to have a derailleur cable end. Therefore the cable would be thinner, and perhaps not suitable to be used for braking purposes, let alone being too thin to be ideal for the larger inner diameter brake housing.

Bezalel

You're not using this brake for stopping so just use shifter cables and housing.

TandemGeek

Disc brakes don't have the heat capacity to work well as drag brakes; if you really need a drag brake get a drum. The disc will quickly overheat and fade with prolonged use and be worthless.

If you just want to have a an auxiliary brake as a "belt & suspenders" just in case you find yourself over-using your rim brakes, then a disc isn't a bad choice as a back-up to get you stopped so that your rim brakes will have a chance to cool-off.

Rambetter

Yes, it's more the second point. The backup.
Besides I have an Arai in my closet that came off my other tandem. It's just too big and clunky to look cool on my racing tandem. :-)

twocicle

seems you are overcomplicating things.

have you tried running just a disc on the rear? typically that is quite adequate for a non-loaded tandem.

veggie

I don't know how I'd feel with an essentially threaded on disc rotor. Seems like eith enough braking it could unscrew itself

Chris_W

Some engineer has thought this through for you, and the threading is in the correct direction so that it will tighten as you brake rather than loosen. Plus, there is a grub screw that holds it in position. The only problem we've had with ours is getting the thread-on disc adapter off - the best method I found was to clamp the adapter in a large vise (it has two flat sides) and put all your weight into turning the wheel (don't forget to loosen the grub screw first).

Rambetter

Wow good point. I was thinking a strap wrench might do the trick but if you're putting yours in a vise and turning the wheel with all your might, the strap wrench might not work after all.

So my latest idea is to use a bar-end brake lever to actuate the disc in the rear. I honestly want to keep both calipers front and rear for the normal braking.

Here is the idea: https://www.cyclingnews.com/features/...-part-9/164632

Chris_W

Or you could use a CX / bar-top / interruptor lever for the extra brake (these are normally setup to operate the same brake as the main levers, but they can be setup with a completely separate cable).

Rambetter

I think I would kind of prefer having the extra lever (if there is one) near the drop, for descents. The bar end mounting hole would be ideal because then it wouldn't infringe on my drop (making it shorter if clamped around the bar).

JanMM

Works for us.

Carbonfiberboy 

You might want to have a look at this recent thread, which contains a lot of good information and opinion:
https://www.bikeforums.net/showthread...mano-Ice-Rotor
note:
https://www.bikeforums.net/showthread...1#post15986117

Rambetter

Regarding the Shimano Ice Rotor threads: I read the recent Spyre thread almost in its entirety. I came to the conclusion that I would rather not try the Ice rotor.
It seems (based on a lot of opinions from other people and their experiences) that a Hope 2 piece rotor would be the thing to have.

Regarding having just the disc and no caliper: yes, this might be for the future. I'm so new to disc brakes that I want to "ease in" to knowing how to use them and maintain them properly. Then we'll see. At some point I may remove the rear caliper and re-route the brifter to the rear disc.

By the way I have ordered the Spyre non-carbon model that comes with 160mm disc. We'll see when it gets here.

Monoborracho

When we had our Seven built we spec'd it with cantilevers and a rear drum for several reasons, similar in nearly all respects to the Blayleys.

Our disc is controlled by a barcon on the left side of captains bars. It doesn't really work as a drag the same way the Arai did on our old tandem. A short pull will usually slow the tandem until it stops. If you wish to use it as a drag it will be more of a slow down-release-gather speed-slow down, etc. It simply will not work as a drag with a barcon on the hills we have been on. A cycle cross type lever might do the job because you could moderate the pressure. I might try that next time I wrap the bars.

Just my experience. We don't use it much and we are a 300+ team. The calipers do a great job for us with lots if room for big tires and fenders. But, it's there if we need.

Rambetter

Interesting. Thanks for sharing. So correct me if I'm wrong, it sounds like you have a left side drop bar end shifter acting as an actuator for a rear disc (not drum) brake.

I thought about left vs. right and decided that the right side seemed more natural for a rear auxiliary brake actuator because then I could use that in addition to modulating the front brake.

I have a pair of bar end TT brake levers on order and will only need 1 so if you wanna try it give me a holler.

I can imagine myself screaming down Mount Palomar with a hairpin coming up, and worried that the rims are overheating. I'd put my right hand on the bar end brake lever to slow down before the turn, then shift my hands near the brifters for the actual turn. If, as I'm slowing down [using the bar end lever], I realize that I need to stop very very quickly I could engage my left hand to actuate the front brake without letting go of the disc brake actuator.

Rambetter

BTW the auxiliary brake levers that I ordered are these: https://www.ebay.com/itm/Tektro-RX-5-...item43c280410e

I don't particularly care for the carbon (although if it breaks I still have both brifters); but I do like how the levers themselves are short and seem to have good clearance.

veggie

That's right, I totally forgot that drum brake threading is opposite. I remember trying to get a drum brake off a wheel, not fun.

zonatandem

We are happy with caliper brakes, front and rear.
Been doing that on tandems since 1975.
Our first tandem in '75 had an Atom drum brake. A real PIA!
Have ridden a tandem with discs front and rear and we thought it was a bit of overkill for us and more finicky than rim brakes to adjust.
Have ridden in 30+ states; in our younger days have done our share of hairy/long descents including Kitt Peak in AZ (7% and 11 miles long of twists) with good old Mafac cantis. Works for us.
However we all have a 'comfort zone' and seems like you've found yours.
Pedal on!
Rudy and Kay/zonatandem

Paul J

This weekend I looked through the tandem pictures on the R&E site and saw a few of the bikes set-up with bar-end and disc. I'm curious if any of those owners are on the forum and could share how they are using this set-up? SOme have the disc set-up on the stoker's bar, I think that is how Mel from Tandem's East has their bike set-up.

Team Fab

If you want to use a disk as a drag brake you could try the new carbon fibre disks. They should be able to take the heat. Has anyone on the forum tried them yet?

Bad1

The bike is a full-blown racing bike, wanting a drag brake?

akexpress 

I think Ritterview took one for the team on that experiment!!

Carbonello

I got my Arai drum brake shaved by Mel at Tandems East. I only install it when I might need it. Looks better.
ARAI DRUM
Shaved down
Send us your new
or old drum with exchange
Cost $40

swc7916

Our R+E Rohloff tandem is equipped with a disc drag brake. I rarely use it, mostly because I haven't found a good location for the control. We originally had it set up on the stoker's barend, but my stoker would always apply too much braking and cause us to slow down rather than just maintain speed. I had it moved to a downtube position (like the old downtube shifters) but there are other cables in the way and it is awkward to use. My next step is to replace the brake levers with a set of Campy ergo levers and use the right shifter to control the drag brake. (Another possibility is to just ditch the rear rim brake altogether and route the right lever directly to the disc.)

My observation is that the disc is very touchy as a drag brake. Drum brakes don't have enough power to stop the bike, but a disc does and they're harder to modulate with a shift lever.

Monoborracho

Correct. It is a BB7 setup with the caliper on the chainstay.

I actually would prefer the right side for the barcon also, but the LBS had it on the left, and I just left it that way. My old tandem drum brake was on the right. As stated, I'll probably either put it on a cross lever or perhaps move the barcon to the right side the next time I wrap the bar. Truthfully, it hasn't been a problem because you pull-slow down-release-speed up-pull-slow down. If you really had a panic stop it would be better on the right. But we toured two weeks in Ireland last summer as is.