gthomson

A neighbour of mine who see's me tinkering with my bikes asked if I could look at an old bike she has to get it in rideable shape again. I had to point out I am in no way mechanic but would see what I could do.

The tires were toast, new innertube, put one of my seats on and had to replace the rear brake cable which was not working. I cleaned it up and it looks pretty good but for some reason the brakes are not performing well. I got them so the pull and release fine and the pads are fully connected with the rim but they barely stop the wheel.

Is there something obvious I've overlooked here? I'm assuming it would all be original so are the brake pads too old? They don't look too worn down but I'm not very familiar with mountain bikes. Any help would be appreciated before I go to the LBS.

davester

Primary reasons for poor performance (in approximate order of importance) are:

1. Old, hardened brake pads. Replace with Kool Stop salmon pads.
2. Too much friction in cable housing. Replace cables and housing with Jagwire or Shimano lined housing.
3. Brake pivots corroded or dirty, resulting in high friction. Take apart, clean, grease if appropriate and reassemble.
4. Dirty rims. I use one of these to clean all the rubber off the rim braking surfaces: https://www.amazon.com/Swiss-Stop-Al.../dp/B00EN1UOU8
5. Straddle cables incorrectly adjusted, resulting in poor leverage. Several youtube videos can be found regarding how to adjust this.

There are other possibilities but I think these are the main ones.

RustyJames 

If’n twer me, I would start with 1 and 4 from above.

gthomson

thank you sirs, very sound advice. I didn't think to clean the rims when washing the bike, seniors moment. I'm sure the brake pads are original so another easy win. Will try both of these right away.

madpogue 

Re. # 5 above, the close-up shot is a little too close up to be sure, but the straddle cable angle does look pretty "steep" to me. A slightly wider shot showing the whole straddle, up to where the main cable connects, would help.

And seeing the overall crud factor, # 2 and 3 are both worth a look, just for good measure. Even pulling out and lubricating the cables could help.

randyjawa 

Make sure that the front of the pad(s) contact the rim first. This will result in better brake function and, pretty much, eliminate brake squeal. I try to set my pads up with the front just touching and the rear the thickness of a match book cover away. This might not seem like a big deal but it really is important. In the OP's picture, it looks like the back might be touching first.

tricky 

I assumed (know what they say...) that pic was taken with the brake lever pulled and the calipers fully clamped down on the rim. @gthomson is that pic with the brakes lever pulled or not? That's too close to the rim if that is how they are at rest and you should revisit your straddle cable angle/height. #1 and 4 are still definite first steps here, but 5 is a maybe depending on your answer to the question.

ClydeClydeson

Mentioned above, if the brakes are set so the straddle cable is at a more shallow angle (lower 'triangle' of cable above the brake) then there will be more leverage pulling the brake arms in for the same amount of force at the brake lever. You can accomplish this by letting some slack through the cable at the pinch bolt on the brake arm, then adjusting the pads so they are sticking out further from the arms.

gthomson

Regarding brakes pulled, no this is with them released. When I had them further away from the rim it didn't brake at all. I'll check the straddle cable angle/height and see if that needs adjusting. See pic's below if that tells you anything more.

Front brake


Rear brake

tricky 

Those brakes need some adjustment. Definitely get new brake pads and clean the rims, but also check out this video to help you setup your cantilevers.

nlerner

Any chance you reversed the front and rear straddles? They seem to be different lengths.

Otherwise, I’d ditch those Shimano saddles, use a cable hanger, and adjust the length of the straddle according to the video linked above.

degan

So are are you able to get good solid pressure on the rim from the brakes and it's just pushing through them or is it not getting the clamping power needed to squeeze the rim? If it's the former then there isn't enough friction between the rim and pad. Lots of answers for that here already, but I'd just add that using a file to remove a MM or so from the brakes pad surface is oftentimes enough to get rid of the slick, dried out layer that forms over long periods of non-use. If it's the latter then it means it's out of adjustment or something is broken. If you can't dial it in and the rim and pad is fine, I'd look for something broken or flexes badly when you grab the brake. Sometimes even just a cable housing can fail in such a way that allows it to compress way too much. With the info given, though, I'd guess it's a rim/pad issue.

gthomson

Watched a bunch of videos on setting up cantilever brakes, and never knew they were so diverse. As mentioned above, it looks like the adjustment of the hanger and the angle on the brake pads to the hanger are super important along with having mushy brake levers. The bike above clearly has issues with location of that triangle hanger piece and the brake levers are too tight. I also have the brake shoes too close to the rim. Regarding the front and rear straddles reversed? Not sure, as mentioned above, not my bike so it's possible someone was playing around with it before it was brought to me.

Great choice to post, Path Less Traveled, as I've really been enjoying his videos as of late.

52telecaster

This probably isn't your issue but if the brake levers have been changed they might be the wrong pull ratio. If they are made for linear pull brakes it will never stop well. Also some levers had options for canti and linear pull. Make sure they are right

Andy_K 

With Shimano Z-link cables, you can't really change the straddle cable length and height. The idea with them was that you just use the Z-link and you don't have to worry about that. The thing is, the Z-link comes in several sizes and getting one that sits lower makes a huge difference.

Or you can ditch the Z-link and get a proper yoke and staddle cable. It takes a bit more thought to setup correctly but you have much better control over the result. I had a dispute with one of the senior mechanics at my LBS over this about 10 years ago. I went in looking for the shorter Z-link cables. The sales people didn't know what I was talking about so they referred me to the mechanic. He told me I needed a proper yoke and straddle cable. I left feeling miffed and bought the Z-link on the internet. Eventually I realized the mechanic was right.

Soody

It's traditional to set up a rear brake with a longer straddle cable (less mechanical advantage), and shimano stock link wire lengths reflect this.
(my) Reasoning is less mechanical advantage allows the brake pads to be set further away from the rim, as a rear rim is more likely to be or go out of true and will flex more climbing/sprinting.
The rear brake also has far less braking to do because of weight transfer, and will just skid while the front is still stopping you. It's more useful for scrubbing speed especially in corners and less mechanical advantage gives better modulation.

I think the shimano link wires are good and fine tuning mechanical advantage is rarely the real issue with poor cantis. The advantages they have over traditional straddle cables is they already have the wire pulled taunt, so they brake immediately, while traditional straddle cables take some lever travel to pull the straddle cable into the v-shape. And, the reason they exist is they catch a broken brake cable so they are safer unless you run a doodad (not really relevant unless you're underbiking).

I am just rambling and you simply need new pads.

Soody

Kool stop eagles as mentioned are amazing and worth it, but the other thing you can do is run the brake pads along a file or sand block to get to fresh rubber (easy to feel with a fingernail, and see, what is soft or not). That helps a lot if you don't have new pads.

Also clean rims -really- well with isopropyl after soap/water.

PatTheSlat 

Lots of discussion in this thread and some good tips on fine-tuning cantilever brake setup, but considering those are ~25-30 year old Shimano brake pads, I guarantee you they are about as soft as concrete and replacing them with even cheap replacement pads will solve 95% of your problem.

79pmooney

+1 I hate those Z-link cables. I always use a regular cable, yoke and straddle cable appropriate for that particular brake. I love the brakes that anchor the straddle with a screw on one side (like yours). Leave both the brake cable and straddle long with your first set-up. Now ride the bike, try the brakes and adjust cable lengths to suit. Don't cut anything until you have braking you like.

t2p

Kool Stop cantilever brake pads are great

Installed the dual compound pads (black/salmon) and they immediately made a significant difference (despite less than ideal cantilever set-up)

gthomson

Thanks all for the input, a friend of mine told me cantilever brakes are finicky and most people don't like them, and I'm seeing where he was going with that statement. That being said, after watching the videos, I think they probably take getting used to but are then loved.

I'm going to start with new pads and this just makes sense since they are 30+ years old as mentioned above. The owner will not be doing any mountain biking so won't need performance quality stopping but just to make them safe. I really like the bike and if the opportunity is there, will probably offer to buy it from them.

Mr. 66

Nice Trek, made in the USA. Those have a little cult to them, the Volkswagen Jetta bike came as a package with the car. A Jetta geek would like that bike on top of the car for show, just like the showroom. For a MTB of the time they have a shorter wheel base than most of its type bitd. Definitely shorter than the 800 and 900 series lines.

Those tires must be funk ride, I've never seen that tread.

masi61

The rim sidewalls in the 1st photo look beyond dirty into more of deep gouges. I would purchase that Schwalbe eraser pictured or even use some silicon carbide wet/dry sandpaper on a block of wood and spin the rim slowly 360 degrees forward and back several times with like 240 or 320 grit. Then you could switch to aluminum mag wheel polish on a folded up little square of cloth and again apply the compound around the full 360 degrees to the whole sidewall (use valve stem as a reference) then reverse. Let the compound dry a bit then spin the wheel with a clean bit of cloth - this combined with new pads, toe the pads in slightly and make sure the cables and housings are stainless steel, the housing isn’t too flexy and what the others have said about the straddle cable adjustment - should be able to make braking very good.

John E

Personal experience tells me that Shimano brake pads, even when new, are dreadful. Yes, replace immediately with KoolStops.

Andy_K 

This is not my experience. Cyclocross racers liked them for a while before disc brakes took over because they don't actually want to stop anyway and cantis give you freedom to adjust for mud clearance. Touring riders like them because they leave a lot of room for fenders and they're easy to fix on the road if necessary. When adjusted properly they stop well, but I don't know if I'd say you'll ever love them.

Looking at the bike, another possible issue is the cable pull on the brake levers. Those look like long pull brake levers. That means they pull more cable, but they don't pull it as hard (per unit of hand force) as short pull levers. Cantilever brakes are extremely adjustable, and so you can adapt them to either sort of cable pull, but you'll need to set the pads closer to the rim than you would with short pull levers. If they are long pull levers, the absolute best upgrade you could make, IMO, is switching to V-brakes. You can get a set of used Avid Single Digits for around $35, or maybe $20 for knock off brands. These will give you a response that's much closer to something like a dual pivot caliper brake, which is great for people who don't like to have to use a lot of hand strength to stop the bike.