Repair/Replace rim brakes with bottom cable routing

Question

Ok people I need some knowledge around here. I'm working on fixing up my wife's bike. It's a wonderful classic Peugeot women's city bike. Mid 70s steel frame. I've run into the issue of the brakes. They lack for stopping power immensely. I swapped the cables and pads to no avail.

The brake mechanism themselves are simply north of 40 years old and the pivot as well as the bolt are losing integrity. Both front and back refuse to remain centered and the back in particular requires a very firm pull. I don't believe them to be so degraded as to be dangerous but certainly have seen better days.

While I'm planning to disassemble, clean and lube them, I really don't have my hopes up for great improvement. I will likely replace them both. Here's the rub (pun intended): the rear brake cable is routed through the center of the crossbar, which is a step through style with two parallel bars with two cable stops at each end for the inner cable to run through without the outer cable. It then follows down the seat stay and loops back upwards, entering the barrel and clamp from below as opposed to the more standard top down. This would be incompatible with most modern caliper brakes that I am familiar with as they typically have the barrel and release mech above the clamp.

Any ideas of where I could look to find a compatible set? Do I need to be searching for a specialty maker or a NOS route or is there a way to modify a modern (presumably superior) caliper. There is a very brief passage on Sheldon Brown's website about potentially modifying one but it mostly requires specialized tools and creating a new decidedly not standard part. The rear caliper is mounted on the seat stay bridge, so I wouldn't be able to switch to a direct pull mounted low on the seat stays.

Long story short... Help lol. Thanks again as always and sorry for the long post. I will try to upload a pic for clarification but I've been getting errors as it's too large.

Answer 1

It sounds like this bike has single pivot calipers, and that the rear brake has the cable entering from below and clamped on top - ie the cable mount part is upside down. Something like this:

Power The pictured brake has just as much mechanical advantage as if the cable entered from above and got pinch-clamped on the lower arm, (probably like the front caliper)

This setup looses some power due to the additional frictional losses involved with that large sweeping bend, and a little to the additional length.

If you have new modern inner cable with a coating, and outer housing with teflon liner, then you're as well-set up as you can reasonably get.

Centering Cable-operated brakes all use springs to pull the pads off the brake track. On an older bike, its totally possible for one side of a spring to lose tension at a different rate to the other side of the spring. Some calipers have little blocks that push the arm out, adding tension to try and keep them about the same. You can also try flipping the spring over.

Pads Traditional brake blocks were plain rubber. Modern brake pads tend to have much more technology in them, and even a simple one-for-one replacement with good new ones is an upgrade to braking. This may mean buying brake pads that have a permanent shoe and a consumable insert rather than the one-piece items we used to have (as pictured)

Wheels Does it have steel rims? If so, one excellent upgrade is Aluminium rims. The braking track has much more bite and simply works better. Downside is a rim will wear out faster than a steel rim, but that's still many ten-thousands of kilometres.

You might also find that modern rims are 622mm, whereas your older bike might have 630mm or 635mm rims. This will give a much wider selection of modern tyres, but the brakes have to reach further and therefore loose mechanical advantage.

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Personally I'd go for aluminium rims, with dual-pivot calipers, and kool-stop brand brake pads. If you can only replace one rim, make it the front wheel.

For calipers, there are "long reach" which will help you overcome the slightly smaller diameter of modern wheels, for example Tektro R559

Nobody seems to sell a cable-direction swapper adapter, so you might have to steal parts off the old caliper to make a new one work, or possibly put up with an S bend in the cable outer's path.
Another option is to use a brake "noodle" from a V brake to help turn the wire's path by 90 or 135 degrees, but this may need some finangling to work well.

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Expanding on a noodle:

The noodle is the silver tube seen here on a V brake that "turns" the pull of the inner cable by 90 or 135 degrees without the longer length needed by outer for the same turn.

I've used noodles at other points for the same purpose - pictured here is a folder with noodles allowing the gear and brake cables to take a relatively sharp turn. These happen to be flexible noodles but rigid ones would work the same here.

I don't own a mixte frame, but imagine the green line is the missing tube and is the highest path your brake cable can follow. The pink line is the cable outer's path, and I've clamped some parts to the rim as a mock-up.

Another shot of the mockup. Your challenge is to clamp the inner cable wire at the top arm, and put the outer cable-endstop in the lower arm. This may be possible with machine tools and fabrication, or you may be able to move parts from the existing caliper to a new one.

OTHER OPTIONS

• Refurb the current brake and be aware that it's kinda rubbish. Upgrade the front brake to a dual pivot and learn to brake more with that. If you can find a replacement fork with disk brake mounts, then a new front wheel with a brake rotor might be an option though this is getting pricy.

• Check the middle tubes and the chainstay area for another brake mounting hole. You might be able to relocate the rear brake caliper around the wheel a bit, permitting a straight-line entry for the cable.

• Perhaps a single noodle will allow you to mount a normal caliper, and still get the cable routed sufficiently well.

• There exist products like the Problem Solver's Cross Clamp which can turn a bare cable by any amount up to 180 degrees.
  
  although these have no way to terminate the outer housing.

• Also there are "travel adapters which work like a V brake noodle but use a pulley to change direction. These have an outer-cable stop and might work similarly to a noodle but again with more angular change. https://problemsolversbike.com/products/brakes/travel_agents_-_6416

• Apparently there exist old Weinmann calipers which are convertible from conventional top entry to bottom entry. However they're vintage, likely expensive, and probably still rubbish at braking.

I suggest a Dual pivot caliper for the front, and refurb the existing caliper as much as possible for the rear. It'll never be great, but two brakes makes it legal. Anything else has higher costs.

Answer 2

You don't mention if it's a steel or aluminum back rim. If it's steel, that's probably a lot of the problem by itself.

Step-through and mixte bikes with "upside-down" routing to a sidepull brake don't need special brakes or adaptors. They need a brake where the housing stop and cable anchor positions interchange, which is common on basic single-pivot sidepulls. Typically this will be a type where the housing stop looks like this:

And the cable anchor looks like this:

It can be hard to make out in the photos, but the part that passes through the brake arm on each is a flatted oval type shape. It's the same on both so they can interchange. This is a standard of sorts that's been around a long time, such that generic replacement parts like the pictured ones exist and are common shop items.

Single pivot sidepulls are some of the weakest of all rim brakes. There are some double pivot calipers that can have their position switched in the same way. You're basically looking for ones that have the kind of housing stop and cable anchor pictured. There are some in Dia-Compe's line. I think this could be a good place to look. Be careful that whatever you get has a pivot bolt that matches the needs of the frame. Specifically, this bike likely can't take a recessed nut brake, and some of what you'll find is recessed nut only, but you may be able to circumvent that by using a front in the rear or switching pivot bolts.

Upside-down routing always has the disadvantage of the housing being open to the elements in a way where gravity is working in favor of water/dirt ingress. There are various nosed ferrule and boot type products that have attempted to address this - see Brompton brakes for an example. Another approach is to just switch the routing to continuous, zip tie it up the seat tube and then back down, and use one of the various fancy compressionless housing options that will take the extra bends without adding a lot of friction. Then you could use whatever dual pivot brake you want of the appropriate reach and mounting type, which is likely the path to getting the most power you can in the application.