Trek Multi Track 700 - JoeH builds Tootyred's for a friend.

[frkl]

Here is the thread with a discussion of how to deal with the issue safely:

https://www.retrobike.co.uk/threads/muddy-fox-courier-comp.441785/#post-3220614

But in my honest opinion, these brazed on cable tubes are such wonderful features that purpose-built the frame for cantis. I own two frames with them and think the detail is a wonder. It is a shame, in my opinion, to try to undo them for Vs. the bike was made for cantilever brakes. It should be embraced.

 

[frkl]

What element would you expect to fail?

If the nylon liner tube thru the braze-on crumples because the compressive strength is surpassed, the brake will have nothing to push against and it will loose any tension. This would happen if you pull too hard on the brake, ie, exactly when you need max braking power, the brake will fail.

 

[frkl]

What element would you expect to fail?

V brakes have nothing to push against to gain their braking power but the cable housing. Cantilever brakes usually pull with the house held in place by some sort of frame mounted stopper. But Vs go directly from flexible housing to actuated device (the brake itself). This mrans the house has to be able to transfer the entire braking force to the next frame mounted stop without compressing too much. A normal helical brake housing can take this because it is designed to take it. A new fangled linear brake housing can too. But an indexing housing or a non-metalic plastic tube cannot necessarily take it. It might be able to handle most situations, but when you really need it--car pulls in front of you while you are pulling a trailer full of whatever, it will suddenly fail.

Edit, sorry to answer the direct question, the part with the weakest compressional strength will fail, so the little tube between the braze on and the noodle.

 

[frkl]

Noice! I thought it was a bit controversial but fine for tootling around and the shifters were dirt cheap

There are nice historical examples of this, so it's ok early Suntour thumbies had steel bands that could go around brop bar diameters and I see these every now and then.

A tip if you want better shifting than the really cheap thumbies--Deore and lower Shimano thumbies from way back when use steel brackets, which can be bent and filed to fit around drop bar diameter tubes with a longer bolt. So from 22.2 to 23.8mm.

i have considered reaming the aluminum Shimano clamps but i read somewhere that they are actually heavier than the steel ones.

Anyway, most Shimano thumbie clamps use the same shifter interfaces, meaning you can put an XT shifter on a Deore or lower mount, like a 200 GS. i just had some 1989 Exage County stuff in my hands today, so really bottom of the barrel, and noticed that an XT unit would fit on the bracket! So you can find a cheap thumbie for the bracket, then swap the shifter for an XT.

 

[JoeH]

If the nylon liner tube thru the braze-on crumples because the compressive strength is surpassed,

The Nylon line tube does not resist any compression force as it has a free end (cyan mark).
I added the nylon tube to help the cable slide through the S shape, that's the only reason it's there.
Hence it feels a friction/sliding force not a compressive force

the brake will have nothing to push against and it will loose any tension. This would happen if you pull too hard on the brake, ie, exactly when you need max braking power, the brake will fail.

The brake is pulled together by levering from the mounting screw (white mark) against/through the noodle and to the front top tube braze on (black mark).
The noodle, nylon tube and 's shaped braze on' all direct the brake cable.

This design is unorthodox, and did from a test ride result in a softer rear brake, as the front braze on is much further away from the rear brake than a normal stop.

The brake will only loose tension if: mounting screw fails, noodle fails or front braze on fails. As none experience higher force than an orthodox setup I disagree that this setup is dangerous.

I do however if time and circumstances permit plan to add a stepped ferull as suggested earlier. This could be a neater way than running outer all the way.

 

[foz]

It's a V brake. The cable is only clamped on one arm, unlike with a canti. The other arm (where the noodle attaches) needs the outer cable to push against, otherwise it will have no force from the cable directed through it at all. Without the outer cable, when the inner is pulled you are only applying force to the side where the inner is clamped. Vs do not work in the same way as cantis, which do require only the inner cable from the last frame stop. You are wrong, the brake setup is wrong, and dangerous. I'm not the only one telling you this. If I'm not wrong you are also building the bike for someone else? If that is the case then I can only hope that the brake does not fail while they are riding the bike.

 

[frkl]

It's a V brake. The cable is only clamped on one arm, unlike with a canti. The other arm (where the noodle attaches) needs the outer cable to push against, otherwise it will have no force from the cable directed through it at all. Without the outer cable, when the inner is pulled you are only applying force to the side where the inner is clamped. Vs do not work in the same way as cantis, which do require only the inner cable from the last frame stop. You are wrong, the brake setup is wrong, and dangerous. I'm not the only one telling you this. If I'm not wrong you are also building the bike for someone else? If that is the case then I can only hope that the brake does not fail while they are riding the bike.

Second.

V brakes have nothing to push against to gain their braking power but the cable housing. Cantilever brakes usually pull with the house held in place by some sort of frame mounted stopper. But Vs go directly from flexible housing to actuated device (the brake itself). This mrans the house has to be able to transfer the entire braking force to the next frame mounted stop

Sheldon Brown explains it as follows:

"Traditional cantilever brakes used two cables, a main cable running down the centerline of the bike, and a second, "transverse" cable connecting the cantilever units on each side of the wheel. The main cable would pull upward on the middle of the transverse cable, causing the cantilever units to rotate inward.

"The "direct pull" cantilever, also commonly known under its Shimano trademark name "V-Brake" is a simpler design, using only a single cable. The cable housing connects to one arm, and the inner cable runs across the top of the tire to the opposite arm. When the brake is applied, the housing pushes on one cantilever while the inner cable pulls the other."

From
https://www.sheldonbrown.com/canti-direct.html
Edit, a V brake is in principle the same as a side pull caliper--the cable passes thru one arm and is fixed to the other. Just as a side pull needs housing all the way to the non fixed arm, so too a V

If this bike is for a friend, please have it looked at by a mechanic.

 

[was8v]

absolutely that rear brake is dangerous

I did this.once in a similar situation

Chopped the brazed noodle to make a stop

I've regretted it since but the brake works well.

 

[frkl]

absolutely that rear brake is dangerous

I did this.once in a similar situation

Chopped the brazed noodle to make a stop

I've regretted it since but the brake works well.


View attachment 612596View attachment 612597

Just a thought, I wonder if you could use a down tube cable housing stopper, filed flat, and mounted through the seat post binder bolt flush against the clamp braze on.


You would need to find a way to really stop it from rotating, though, something like a tooth lock washer. Or better yet, the interface on these things is square, so you could use an extra long M5 bolt from the drive side, tighten up an appropriately sized square or hex nut to the clamp braze on (this nut would handle the seat post clamping duties), slot the housing stopper on, and seal the deal with an M5 acorn nut. It still might rotate some, but not much and in the tightening direction--so self-stopping.

But more realistically, one of these ferrules placed into the routing tube would probably eliminate the need for the zip tie: