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My MAFAC cant's hit eBay...



 
 
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  #1  
Old October 9th 12, 07:07 PM posted to rec.bicycles.tech
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Default My MAFAC cant's hit eBay...

My venerable Ritchey road frame is set up for cantilevers. I went through many a set before settling on MAFAC's. In the course of trying to understand how to calculate MA, I measured the dimensions of the posts. The horizontal and vertical displacements relative to the rim are notably different front and back, and, in a spectacular math fail, I concluded they had been designed for MAFAC Touring cantilevers up front and the smaller Racers in back, and so set the bike up that way.

In truth they have served well. They look great polished up, aren't really fussy despite what some say, and modulated my speed well up and down my 1000' neighborhood. But when I reach the bottom of the hill, or swoop down to my driveway, I really wasn't getting that crunching roll back stop at any time. Having finally figured out cantilever MA, (the projection of the yoke cable onto the line through the posts will give the equivalent horizontal lever arm), I decided it was time to get some newer components and fiddle with yoke length.

Well, none of the threaded post models will fit the old-time dimensions, so by the process of elimination I found my way to Shimano's CT91's. Actually they are great! Nice polish and incredibly cheap, taking first place away from my Ultegra headset in the bang/buck contest. And in measuring the post to rim distance in order to calculate just exactly what was what, I discovered it was 30mm in front and 27mm in the rear...blush. So my Touring front was giving a 4:5 ratio and the rear a 2:3! Serviceable, but low. No wonder MAFAC's are legendary for mud clearance. They simply pull further away from the rim because they so lack leverage.

The 91's set up easy. Between the rack and the low hanger in the rear, there is only so much variation available. Setting up for minimal MA gives about 3:2 which is easily matched in front. The main concern was whether the spring in the yoke wire would cause the pads to drag when open, but Tektro's thick but slack cables seemed to do the trick. I took it out for a shakeout, started up in the driveway, and hit the brakes as my wife returned in her car at the moment. Wow! Yes you can certainly feel the difference and it's going to take some time to recalibrate the fingers!
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  #2  
Old October 11th 12, 12:55 AM posted to rec.bicycles.tech
Dan O
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Posts: 6,098
Default My MAFAC cant's hit eBay...

On Oct 9, 11:07 am, wrote:
My venerable Ritchey road frame is set up for cantilevers. I went through many a set before settling on MAFAC's. In the course of trying to understand how to calculate MA, I measured the dimensions of the posts. The horizontal and vertical displacements relative to the rim are notably different front and back, and, in a spectacular math fail, I concluded they had been designed for MAFAC Touring cantilevers up front and the smaller Racers in back, and so set the bike up that way.

In truth they have served well. They look great polished up, aren't really fussy despite what some say, and modulated my speed well up and down my 1000' neighborhood. But when I reach the bottom of the hill, or swoop down to my driveway, I really wasn't getting that crunching roll back stop at any time. Having finally figured out cantilever MA, (the projection of the yoke cable onto the line through the posts will give the equivalent horizontal lever arm), I decided it was time to get some newer components and fiddle with yoke length.

Well, none of the threaded post models will fit the old-time dimensions, so by the process of elimination I found my way to Shimano's CT91's. Actually they are great! Nice polish and incredibly cheap, taking first place away from my Ultegra headset in the bang/buck contest. And in measuring the post to rim distance in order to calculate just exactly what was what, I discovered it was 30mm in front and 27mm in the rear...blush. So my Touring front was giving a 4:5 ratio and the rear a 2:3! Serviceable, but low. No wonder MAFAC's are legendary for mud clearance. They simply pull further away from the rim because they so lack leverage.

The 91's set up easy. Between the rack and the low hanger in the rear, there is only so much variation available. Setting up for minimal MA gives about 3:2 which is easily matched in front. The main concern was whether the spring in the yoke wire would cause the pads to drag when open, but Tektro's thick but slack cables seemed to do the trick. I took it out for a shakeout, started up in the driveway, and hit the brakes as my wife returned in her car at the moment. Wow! Yes you can certainly feel the difference and it's going to take some time to recalibrate the fingers!


I appreciate this post. I have cantis on some of my bikes, and have
never made a point of really dialing them in (just try to make sure
they hit the rims straight and flat with a little toe-in and can lock
the wheels when I want to). Of course brakes have never been a real
priority for me :-), but your post has inspired me. I honestly would
like to eventually be an affable citizen and contributing tech guru in
some sense (not just the next Baka).

  #3  
Old October 11th 12, 02:06 PM posted to rec.bicycles.tech
landotter
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Posts: 6,336
Default My MAFAC cant's hit eBay...

On Oct 9, 1:07*pm, wrote:
[snip]

The 91's set up easy. *Between the rack and the low hanger in the rear, there is only so much variation available. *Setting up for minimal MA gives about 3:2 which is easily matched in front. *The main concern was whether the spring in the yoke wire would cause the pads to drag when open, but Tektro's thick but slack cables seemed to do the trick. *I took it out for a shakeout, started up in the driveway, and hit the brakes as my wife returned in her car at the moment. Wow! Yes you can certainly feel the difference and it's going to take some time to recalibrate the fingers!


Those brakes are one of the best values around. My SO has them set up
with big fat Ritchey/Koolstop pads and you can't ask for nicer feeling
rim brakes. I'd love to see them slightly redesigned to take threaded
shoes, but at the price, who cares.

 




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