Sweetbike (.org)

I’m on a couple bike forums – on these forums is a common thread titled “what did you do to your bike today”.  This was today’s conversation with Fred and I.

ME:  Finished recabling the canti brakes on the XO with the new Cowbell 3 bars.  Spent most of last night mucking around with the brakes, using THIS SITE to get them to feel good/better:

http://www.circleacycles.com/cantilevers/canti-geometry.pdf
http://www.circleacycles.com/cantilevers/

I hate canti brakes.  Lot of work for crappy stop-not-good if you ask me.

BUT – me and Flickr are looovin these purple rims.  Ah vanity, you old fickle so-and-so.  So what’s the problem?  Well, to be perfectly honest I’ve never had a tremendous amount of satisfaction with cantilever brakes (they never seem to brake well enough) and the braking surface on these rims is un-machined which isn’t helping anything.  Using the most powerful canti brakes I could reasonably get ahold of (because canti’s suck bad enough, get good ones), using the softest grippiest extra biggiest salmon V-brake pads I could fit on there, in perfectly dry and badass conditions, Dolphin Dancer here still stops pretty badly.  If there’s any wet out there whatsoever, braking disappears entirely.

It scares me.  I’m a big dude.  Brakes are important.  A rain bike that does not stop in the rain does not make an awesome rain bike.  Since I was re-doing the cockpit with new handlebars, it seemed like a good time to revisit this topic.

There’s all kinds of crap to consider when you’re setting cantis up – yoke height, pad angle, straddle cable length, arm angle, leverage and compression and spring tension and cable pull and spacer placement – all manner of miscellanea that make these things just a joy to work on.  A real pleasure.  Yep.  And depending on your brake, all these factors are different for every brake on every bike.  And when you’re aalllll done with em, you have a brake that works fractionally as well as a dual pivot or centerpull brake.  The only reason we use them is because commercially they were the first brake to allow really wide tire clearance.  I hate these fucking things.  But I digress.

In an effort to mitigate the pain of these stupid things, I dropped a little cash on some of the nicer cantilever brakes I could find, hoping that quality construction and some attention to detail would yield at least tolerable results.  Thus I give you the Avid Shorty Ultimate.

Cool thing about the Shorty Ultimates is they can go wide profile or narrow profile with the adjustment of a couple screws.  I’ve had them in the wide-profile position to squeeze as much braking force out of them as possible, but it was suggested that I may get better by going to narrow profile.   I was out of things to try so gave it a shot even though it’d also mean ditching my V-brake pads for normal brake pads.

No joy.

I didn’t really expect it to work better but I can say I spent a couple honest hours giving it the benefit of the doubt.  Went back to the old wide-profile position with v-brake pads, and on a lark raised the placement of my straddle cable hanger to something like 4~6 inches above the tire horizon just to see what would happen.  To my surprise I got quite a bit more braking force out of them.  It’s pretty crazy high but fuckit – as long as it works better I’m game.  It’s a fredly fucking build anyhow – who am I going to impress with perfect flickr-fit straddle cable hanger height.  DNGAF.  Wrapped the bars, called it a night.

Todays ride in was pretty dope.  So far, so good.

FRED:

…The biggest problem is that at 60mm your canti posts are way narrower than modern spec (though not quite as ridiculous as old touring bikes)

I just modified a copy of the calculator to get it to allow OP values under 35: http://www.wabdo.com/fred/canti/

The important measurements for Scott’s setup are: OP=30, OD=26, PA=56. In the manual the brakes are shown with α at 25° narrow and 67° wide, but because the posts are so close on the XO the actual values are at 5-10° wider.

As you’ll quickly see Scott is pretty screwed in the narrow stance on these brakes with his premodern canti studs, with the straddle above 150mm he’s proper fucked, he probably can’t get low enough without hitting the fatty fender and even then they’d be bullshitty.

The wide stance likely really is better for him. A lower straddle cable will still always benefit but not by very much, since it doesn’t really get into the inflection point until the straddle is well below the tire surface.

Most curiously, the situation is completely reversed with the two options from Paul (remember to bump α by 5-10°). The Neo-Retro with it’s shorter arms basically has no hope of ever working at all, shit is nearly flatlining. The Paul Touring on the other hand with it’s longer arms gets pretty awesome especially if you can get the straddle lower than 150mm, orders of magnitude better than any of the other options under discussion.

These things could interesting too if the PA distance is even longer than the Paul Tourings: http://www.interlocracing.com/brake_canti.html

Bonus tip: with V-brake pads you can fuck with the washer placement to adjust α, for Scott in the wide stance he needs to minimize α and maximize it in the narrow stance.

Also note that none of that stuff about the Shorty Ultimates applies at all to modern cross bikes at proper spec.

With OP=40, OD=28, PA=56, α=25° the things would have rimcrushing mechanical advantage with the straddles low over a 35mm tire.

I’m glad you’re on my team Fred. Cuz you’d be scary as shit if you were the enemy.

WAT… don’t give me that look.  This blog can’t be all world news every day.  This is my blog afterall.  Day in the life, this is.

Onward