Tuesday, March 5, 2013

Get the most out of your canti brake...

With all the focus on disc brakes and getting the most out of mechanical discs, I thought I'd address the good old cantilever brake.  Maybe folks' dissatisfaction with them is simply because they aren't set up properly.  

I see a lot of canti brakes during my day in the shop since my own cross frames are built around cantis and I work on a lot of old bikes with cantis.  There are several things that affect cantilever brake performance and they are all easily addressed and fixed.  The first one is the actual brake pad itself.  A thick brake pad, like the one used on Shimano canti brakes during the hey day of cantilever equipped mountain bikes is the worst choice for good performance (and maybe this is where the root of cantilever hatred lies).  A thick brake pad may last a long time, but you don't want a pad that lasts a long time because as the pad wears, it starts to dive under the rim.  This is simply due to the point where a canti brake pivots - below the rim.  Conversely, a roller-cam or u-brake pivot is above the rim and when these pads wear, they start cutting into the tire. 

Pad thickness:  Thick vs. thin
Thick pads are squishy.  When you apply the brakes on a bike with thick pads by squeezing the lever, the pad hits the rim and as you squeeze, you might feel mush.  Part of that is the pad compressing.  To solve this issue, thin brake pads are immensely helpful.  The KoolStop Thinline pad works great.  Very little flex/compression going on at the brake pad if you are running Thinline pads.  Probably the main reason Paul Components supplies their brakes with these pads.  But the thin pads will wear out faster.  So what.  This simply means that the brake adjustment - the pad to rim contact - will be optimal longer.  You're not going to have the pads wearing at an angle as you would with thick pads and the chances of the pad diving under the rim are greatly reduced.  

Pad positioning on the arm
By this, I mean where is the arm in relation to the pivot when the pad hits the rim?  With threaded pads, I try to make the pad to arm junction as close to 90 degrees as possible when the pad hits the rim.  What does this mean?  Hard to describe.  Threaded pads have a series of washers that fit on both sides of the brake arm.  The spot where the pads fit on the arms is slotted for up and down adjustment.  I try to make this slotted part of the arm be perpendicular to the brake pad post when the pad contacts the rim.  Why?  Because this lets the pad hit the rim as squarely as possible.  Too far past 90 degrees and the brake loses power (especially true with v-brakes) and when the arm is past 90 degrees, it's on its way to promoting the pad diving under the rim.  Square up the arm/pad/rim geometry.  This is easy to do by making sure the concave/convex washers are on the proper side of the arm.  The Thinline pads also have another 1mm thin washer to further fine-tune this aspect.  On canti brakes with eye bolts, it's easy to move the pad to its desired position. 

Straddle cable and yoke position
To get the most out of your canti brake, it's crucial to get the straddle cable carrier (yoke) installed in the right position based on the type of brakes you are running.  Simply put, you want to try to achieve a 90 degree angle between the pivot bolt/cable anchor/straddle cable.  The angle formed if you drew a line from the pivot bolt to the cable anchor on the arm and along the straddle cable should be around 90 degrees.  This gives you a good combination of modulation and power.  It's possible to alter this angle to get more power, giving up modulation.  A rough rule of thumb is low-profile brakes require a low straddle cable carrier position, wide profile brakes require a high straddle cable carrier position.  Going even lower on a low-profile brake will give you more power, but the modulation will be lower and the brake pads will need to be set closer to the rim.  This position also will feel a little mushy at the lever.  Most lower profile canti brakes I see have the straddle carrier set too high.  This might feel good at the lever; solid feeling, you might say, but when you need to hit the brakes you won't have the power needed to stop. 

Other overlooked details
It's easy to talk geometry and mechanical advantage because there are quantifiable formulas to determine the end result.  This 6-page piece on mechanical advantage of cantilever brakes is good and easy to read.   There is one thing that no one talks about when setting up cantilever brakes:  cable flex and cable line.  You've just tightened the bolt securing your straddle cable and you think you're done.  After all, the brake pads are adjusted.  The straddle cable carrier is positioned just so.  The lever works.  The pads close and open.  However, chances are, you are not done.  There's one more trick you can do to get the most out of your canti brakes.  Straighten the straddle cable.  If your straddle cable has any kind of curve to it between the brake arm and the carrier yoke, when you apply the brake lever, some of that lever movement is taken up in straightening the cable.  By physically bending the cable over the yoke and where it's anchored, you'll get a straight line and all of the lever movement will go into applying brake pressure to the rim. 

Now you're ready to fully embrace the cantilever brake.  It's pretty awesome when it's set up properly.  Here's some photos illustrating (hopefully) cantilever brakes.

Canti 2
Notice the curve in the straddle cable.  This is before straightening it.

Canti 3
After straightening.  Simply bend the straddle cable with your fingers where it comes off the yoke.  Easy.

Avid Ultimate
Avid Ultimate.

IMG_0004
The right arm has the pad set up properly with the thick washer on the inside.  The left arm has the thin washer on the inside and the arm is past the perpendicular position to the rim.

IMG_0005
1980s Shimano cantilever, a mid-profile design (not wide like the Mafac and not narrow like the Paul Touring Canti above).  This straddle carrier is bit too high, but I installed this long ago when I ran fenders on this bike.  The carrier is also a wide version.  I like these when used with drop bars (that this bike has) because it shortens the straddle cable and gives a more positive feel at the lever.

IMG_0006
Wide style Mafac canti brake. 

IMG_0007
Low-profile Dia-Compe 996 - one of my favorite canti brakes.

IMG_0008
Low profile Shimano.  I probably would have set these up with the arms a touch wider by sliding the pad inboard a bit in the eye-bolt. 

IMG_0009
An example of a thick brake pad that can potentially rob the brake of power.  Is it a coincidence that this brake arm shape, coupled with the thick pad, and that all of these brakes, at the time, were supplied with a one-piece straddle cable assembly that did not allow for proper straddle height came out in the hey-day of the mountain bike which means that the vast majority of people were simply set up with canti brakes that weren't optimal.  Could this be the impetus of cantilever disdain?

One last word
I'm not a big fan of the one-piece straddle cable carrier.  On my personal bikes, I prefer to set the straddle height where I want it for optimal performance.  Many cantilever brakes, today, are supplied with one-piece straddles in various lengths that can be used to get a proper straddle position.  It's just will the proper one be chosen?

IMG_0001

(What's playing:  Loretta Lynn Women's Prison)


12 comments:

Nick said...

No wonder I still haven't met a canti I liked. Thanks, Mike!

gypsybytrade said...

A well-tuned brake is always better than a poorly adjusted brake. Great article. I love cantilever brakes.

nicholas

Anonymous said...

As always great tips and looking forward to adjusting my canti's this weekend

ol'grumpy said...

Yay canti's!

I think that canti's could make a real comeback in the hearts of cyclists if people saw them as the artisan brake caliper. Maybe someone should make a nice video about the cottage industry of properly setting up a cantilever brakeset. You know, the blood, sweat, and artistry that goes into a properly set up caliper set. Beautiful and powerful stuff.

Disclaimer: 90% of my bikes have canti brakes. I even tried putting them on my track bike.
-Gabe

Anonymous said...

Some cantilevered thoughts in random order:

The wide straddle hanger basically allows one to get a particular (and crucial) straddle cable angle while physically having the hanger in a lower position. Think Mafacs on the rear (or front) of a small bike where a high straddle cable wouldn't be possible. IMO, the angle on that orange and blue rig is pretty close to ideal. The 90 angle needs to be looked at when the pads hit the rim, since that is when the braking takes place, not when the brakes are released.

Another critical piece to the canti puzzle is cable housing. It's got to be routed well and as short as possible. And of course lubed up. Squishy housing makes a decently set up brake feel bad.

Those thick old Shimano pads. Even to this day (probably drier now) I still like those. I hear ya on the issues they face when worn at an angle, but the remedy is just to replace them once they get all womperjawed... or file them back to flat. The firmness of these old XT pads does what you like about the thin pads. I've tried the thick soft pads like a Kool Stop and they're mushy, like you say, and seem to be much more howl-prone.

The one piece straddle carrier is nice if it's the right length because it makes the brake feel crisp. Even straightening out your straddle, as you mentioned, won't give as crisp a feel as the one piecer if done right.

The Bruce Gordon needs a lower straddle. One easy way to check that 90 degree angle is to hold an "L" key allen at the pivot and at the cable attachment point. Remember to check when the pads are making contact with rim rather than open.

Working in a bike shop in the 80s and early 90s gave me tons of chances to experiment with the set up of these brakes. Each repair and build I'd do I'd try to perfect better than the last. Canti's can work so well if everything is right, but that was their downfall I think; you can't really mess up a V brake if you tried. Shimano tried to simplify set up with the one-piece yoke and the color-coded templates they sent out in the late 80s, but they just sat in a box in the corner of the work area. :)

bubba said...

There are two details that a lot of canti-haters overlook:

1. The rim contributes just as much as the brake pad. Some rims are just not good braking rims.

2. The position of your canti-posts determine a lot of the geometry characteristics of your brakes. If the posts are a few mm high, your brakes automatically tend towards mushy. Too low, and it's harder to get the power.

Anonymous said...

Lower pad height actually gives the brake more mechanical leverage since it's closer to the fulcrum and therefore a mushier pad.

Fred Zeppelin said...

Late to the party, but I wanted to mention that as I understand it, the standards for how wide apart the posts are has changed over time. My understand is that with older touring and other "road" bikes the posts were narrower, then with wider rims and MTBs arriving, the post spacing got moved wider, too.

Mike, can you comment on this? Have I understood correctly or is my thinking off?

blackmountaincycles said...

Those are all great comments. Yes, those old Shimano pads with the alloy pad holder were good. The bad ones were the pads that came out in the late 80s (the ones on the Gordon). Never liked those and at that time the Aztek pads were the pad of choice.

Fred Zeppelin, there is actually a standard that is published by Shimano in graph form that does alter post height depending on rim width. But, yes, if you want to run a very wide rim (like the old Araya RM25) a slightly wider post spacing would have helped.

It does seem that the old pads with the smooth post were easier to adjust based on rim width. Modern threaded posts can't be adjusted as finely.

Anonymous said...

Fred Z. is right about the post spacing. Posts got wider when mountain bikes started becoming popular in the early 80's. The posts on touring bikes - for example my Schwinn Voyageur - are 60 to 65 mm apart. Mountain bikes are more like 80 to 85 mm, regardless of rim width. Modern brakes are all designed for the wider space. I think the Shimano standards are based on it too.

This can be a big problem if you need to replace brakes on the old bikes. The geometry gets goofy and sometimes can't be made to work well. Switching a 27" touring bike to 700c adds another layer of confusion to the whole mess.

Rich F.

saddle up said...

Thanks for the post Mike, it's times perfectly. I have to replace the pads on my Maruishi. Is there any difference in performance between the different colors of Thinline pads?, Salmon seems like a favourite.

blackmountaincycles said...

Saddle up, the salmon is a favorite because it seems to be more all-weather. Kool-Stop's website is lacking tech info on the different compounds, but I'm pretty sure the salmon pad is harder than the black pad. Can't go wrong with a little salmon in the diet.