Framebuilding question: Can I drill this bridge to accept road calipers?

[4Rings6Stars]

I posted this on the framebuilding section of bikeforums but I'm not sure how active that forum is and I know a lot of framebuilders hang around here so I thought it might get more action.

I recently picked up a tandem with Phil Wood disc brakes as the only braking system. I've read a bunch about them and posted a thread on C&V and I've learned it's not advised to use them as the only brake system (although on my short rides so far they have worked brilliantly). I've decided my best bet for now would be to see about adding modern dual pivot road calipers. The fork crown is already drilled and the rear bridge is the right distance from the rim (same as fork crown hole - 51mm) to use Tektro R737 / R539 or similar brakes.

Can this bridge be drilled and a brake installed, either nutted or recessed, or would I need to have it reinforced? Or removed and replaced with a proper brake bridge?

I'm hoping not to have to repaint... Other options are to have cantilever/v-brake mounts added or maybe even a modern disc tab added in the rear. I don't like cantilevers and I'm very fond of the BB7's on my Soma so if I can't make calipers work without major effort I would like to see about adding a modern disc to the rear. I'm hoping I can make the brake bridge work since budget on this is very small...

Also, I'm told it's standard 1979 Imron paint but can't seem to find information out there about matching it. Is my best option to go to a dupont paint dealer and have them photograph it and mix a blend to touch up as necessary? Would they be willing to do such a small quantity?

http://i733.photobucket.com/albums/ww335/telepciaka/Bill%20Boston%20Tandem/100_1584.jpg
http://i733.photobucket.com/albums/ww335/telepciaka/Bill%20Boston%20Tandem/100_1583.jpg
http://i733.photobucket.com/albums/ww335/telepciaka/Bill%20Boston%20Tandem/1BBB922C-4357-4585-A59C-DF38CF67EECF-848-000000D19FB10D0C.jpg

[Louis]

Knowing nothing else about the bike other than what is visible in the pics, I would say no. Especially on a tandem.

Edit: I am not a framebuilder.

[Peter P.]

You COULD drill it through and it would work. I've seen some older bikes with hollow, tubular brake bridges running caliper brakes.

There are a couple problems, though.

You would have to find the concave spacers used, usually found on cheaper calipers, to cradle the tubular bridge.

The mounting bolt of the caliper you use would have to be for a NUTTED mount vs. an allen key mount. The larger diameter of the allen key mount would require too large of a hole through the bridge.

Lastly, you would have to remove that fender mount bolt and see how far into the bridge the threads extend. The brazed in threaded insert may extend too far into the diameter of the bridge to make drilling through it easy, if possible at all.

I have heard of clamp on cantilever bosses. They might be an option.

[Louis]

I recently picked up a tandem with Phil Wood disc brakes as the only braking system. I've read a bunch about them and posted a thread on C&V and I've learned it's not advised to use them as the only brake system

This is interesting. I thought that Phil only made top-shelf stuff. What are the issues with those?

[4Rings6Stars]

You COULD drill it through and it would work. I've seen some older bikes with hollow, tubular brake bridges running caliper brakes.

There are a couple problems, though.

You would have to find the concave spacers used, usually found on cheaper calipers, to cradle the tubular bridge.

The mounting bolt of the caliper you use would have to be for a NUTTED mount vs. an allen key mount. The larger diameter of the allen key mount would require too large of a hole through the bridge.

Lastly, you would have to remove that fender mount bolt and see how far into the bridge the threads extend. The brazed in threaded insert may extend too far into the diameter of the bridge to make drilling through it easy, if possible at all.

I have heard of clamp on cantilever bosses. They might be an option.

Thanks for the comments.

I have lots of spare nutted brake parts and Tektro has some long reach dual pivot available in nutted. I'm thinking that is what I will do if the consensus is the "tubular" brake bridge will be able to support the brake.

I've not heard of clamp on cantilever mounts, that kind of scares me but perhaps it's safer than using this brake bridge!

[David Kirk]

I wouldn't do it. The bridge material is thin and it could deform when you tighten the brake bolt down.

You could drill it and make a spacer for it so that you can tighten the brake down and not crush the bridge - a bit tricky but could be done I think.

dave

[4Rings6Stars]

This is interesting. I thought that Phil only made top-shelf stuff. What are the issues with those?

They were made only for a couple years and were supposedly pulled from the shelf because the braking surface was made from an asbestos material and was prone to fail without warning (shatter or crumble or something). The model I have (I'm told by the original owner) were a later iteration that weren't prone to this failure but I haven't been able to confirm that.

Also, I don't believe replacement parts are available. Check out the album I linked above for pictures of them, they are very cool and overengineered.

[4Rings6Stars]

I wouldn't do it. The bridge material is thin and it could deform when you tighten the brake bolt down.

You could drill it and make a spacer for it so that you can tighten the brake down and not crush the bridge - a bit tricky but could be done I think.

dave

Any suggestions for what a broke kid in Boston should do to get a reliable rear brake on this thing?

[Louis]

I would also be concerned about the bridge-seat stay joint, which may not have been sized to take braking loads. (Unless they used the same bridge on frames that used caliper brakes.)

[Louis]

How about just a front caliper as back-up? If it's back-up, then maybe that's enough.

What % of braking is provided by the front? A whole bunch on a single. Less so on a tandem. (I would think)

[4Rings6Stars]

How about just a front caliper as back-up? If it's back-up, then maybe that's enough.

What % of braking is provided by the front? A whole bunch on a single. Less so on a tandem. (I would think)

I'm new to the tandem world, but I understand optimal braking on a tandem involves use of both front and rear because the rear wheel won't lose traction / lift off the ground as it would on a single when a heavy brake load is applied to the front wheel.

I've thought of just using a front caliper as well. I might end up doing that for now at least.

Thanks again for all of the thoughtful comments, I really appreciate it.

[jr59]

I would not like my chances drilling that bridge.

I would think about having either a disc tab, or a new brake bridge put on.
I know you said it was a budget type job, but my, and my partners safety would out weigh any budget on this!

[4Rings6Stars]

I would not like my chances drilling that bridge.

I would think about having either a disc tab, or a new brake bridge put on.
I know you said it was a budget type job, but my, and my partners safety would out weigh any budget on this!

Exactly. That's why I'm asking around here and elsewhere (also emailed Bill Boston himself) to make sure it's done right even if it's done for short money.

Also, the original owner balked at me when I said I was going to have to upgrade the brakes. He put over 30K miles on it and said the Phil brakes worked better than any cantilever or drum brakes he had on other tandems. I think for now I will add a dual pivot to the front and see about having a modern disc added to the rear in the future.

[jr59]

Exactly. That's why I'm asking around here and elsewhere (also emailed Bill Boston himself) to make sure it's done right even if it's done for short money.

Also, the original owner balked at me when I said I was going to have to upgrade the brakes. He put over 30K miles on it and said the Phil brakes worked better than any cantilever or drum brakes he had on other tandems. I think for now I will add a dual pivot to the front and see about having a modern disc added to the rear in the future.


Good plan here. Just as long as you follow thru on the idea of the rear disc.
I know I have put things off, longer than I should have, and paid a bigger price for it than I should have.

BTW; I really do like the look of the bike!

[ultraman6970]

I believe i saw like a clamp thingy that goes into the seatstays and can hold a rear caliper.

[4Rings6Stars]

I believe i saw like a clamp thingy that goes into the seatstays and can hold a rear caliper.

I did some searching but haven't been able to turn anything up. Any idea what it's called or where you might have seen it?

[bambam]

I did some searching but haven't been able to turn anything up. Any idea what it's called or where you might have seen it?

I saw something like this as well at the 2009 NAHBS. I believe the intention was for adding brakes to track bikes. Not sure if its the best bet for a tandem.

[DRZRM]

I don't think I still have them, but Moots used to make "Moots Mount" strap on calipers. I replaced the U-brake that mounted under the chain stays on my first Fat Chance around 1986 with them in order to mount Magura hydraulics (I know, how f**king cool am I?). They may be somewhere, I'll look. I bet someone else around here still has a pair. They should allow you to run modern V-brakes or mini-Vs with a road lever...if you could find them.

Here's a pic.

http://forums.mtbr.com/attachments/vintage-retro-classic/326673d1200306229-moots-mounts-found-moots-mount2.jpg

And here is the strap on rear Dia Comp brake caliper, which is pretty cheap, but there is no way I would trust that to slow down a tandem unless I was riding with my imaginary friend on back...but I've never used one, maybe others have experience.

Dia Comp clamp on rear brake (http://www.tracksupermarket.com/index.php?main_page=product_info&cPath=72&products_id=582&zenid=6vs3j4mtonbohdl0tv3cmas6j5)

[forrestw]

My preferred two options would be to either:

Braze a larger fitting into the middle of the bridge and drill that to accommodate your side-pull brake.

Braze cantilever bosses to the seat stays.

Either way you'd be looking at a fair amount of re-paint / touchup and if you don't know how to do the work yourself the cost is likely to mount up to the same as replacing the disc.

[ultraman6970]

Here is something similar...

http://bmxmuseum.com/forums/viewtopic.php?id=315539

[ultraman6970]

In my country guys used to do something like this with 2 small pieces of rims, since they have the wholes already they need to be cut to the right size, but if you have access to some aluminum windows pieces or maybe in a hobby shop that sales big planes they might have some pieces of aluminum, just cut them as this guy did and you should be ready to go.

http://i48.photobucket.com/albums/f217/gbarchus/3Rensho1.jpg

[cnighbor1]

I rode a tandem with only rims brakes and no back up brakes. it works but if really moving out at over 30 mph than add another brake option.
With non drive frame at rear design it might take a disc brake
Or maybe add two rim brakes at front like trikes do One in front of fork and one on back side

[4Rings6Stars]

Thanks for all the comments.

Looking into all options. I want this to be safe, first and foremost, then inexpensive, then decent looking. I think most of the "clamp on" options only pass one of those tests...

I'm going to ask around to see what it would cost (and if it's feasible) to have a modern disc tab added to the rear and/or modify the bridge to safely accept a caliper. Then I'm going to look into repaint options--I would likely be doing it myself for $ reasons.

[4Rings6Stars]

I rode a tandem with only rims brakes and no back up brakes. it works but if really moving out at over 30 mph than add another brake option.
With non drive frame at rear design it might take a disc brake
Or maybe add two rim brakes at front like trikes do One in front of fork and one on back side

I'm not sure what you mean by that middle sentence. Could you explain/elaborate?

[Ralph]

What does the Phil Wood Company say? I would ask their advice first.

[Tandem Rider]

Our road race tandem has dual pivots only, front and rear. Adding a dual pivot with good pads in the front will probably be more stopping power than you will ever need. The disc brakes will work as great drag brakes if you are ever hauling lots of weight down large descents and need to control your speed.

The front brake is the workhorse on a tandem. The limiting factor to the front brake on a single is flipping over when the front tire hooks up after skidding under very hard braking. I can't imagine the forces necessary to flip a tandem. The trick for long hills on dry pavement is to get on the brakes like you mean it, no feathering. Then get off and let them cool, alternate front and rear until you can let it roll.

[DfCas]

If the chainstays were not designed for a IS disc brake, you might find that the rotor hits the chainstay, or you may find that you can only use a small rotor as opposed to the 203mm or bigger that is preferred for tandem use.

As far as going heavy on a front rim brake, no thanks. I'm afraid of heat blowing the tire off, and I'd much prefer that to happen on the rear of a tandem, as a front blowoff means going down for sure.

I've had some front flats on our tandem and its completely different than a single.