# Cantilever post spacing question (xpost)



## Entrenador (Oct 8, 2004)

Hi. I didn't get any replies in the brake time forum, but it's mostly tied up with disc brake questions. So any chance some cantilever brake wizards are reading?

I just put a set of Tektro Oyrx cantilevers on the front of my commuter Novara Corsa. They work a ton better than the Alivio/Ritchey pad set I removed, and were much easier to adjust. Then I tried to put a set of Oryx on the rear, but after struggling with the pad angle, I found that the rear bosses/posts are only 73mm apart. The fronts are 80mm, and it's the original fork, so I'm confused. I decided to measure my retro DB bosses, and they're set at ~77mm. Is this variation common amongst older frames? Am I stuck with the original cantilevers (beater shimano stuff) for the rear? Original post and photo are at the link below.

http://forums.roadbikereview.com/showthread.php?p=1490949#poststop

Thanks for useful suggestions.


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## shandcycles (Jan 15, 2008)

I always shoot for 80mm spacing. It should actually vary depending on rim width but no one builds for specific rims. Distance from the axle makes a difference too. Sweet spot is about 254mm (for 26")


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## ssmike (Jan 21, 2004)

I just installed a set of Tektro cantis on a cross bike today. They worked best with the thinner of the two spacer washers on the inside of the brake arm. The boss spacing was 75mm. Cross bike canti spacing will tend to be narrower than mountain bike (narrower rims, narrower spacing).


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## Entrenador (Oct 8, 2004)

*Axle to post measurement?*



shandcycles said:


> I always shoot for 80mm spacing. It should actually vary depending on rim width but no one builds for specific rims. Distance from the axle makes a difference too. Sweet spot is about 254mm (for 26")


Hey shandcycles, is that 254mm number the distance from the center of the dropout to the center of the boss? Is this measured along the seatstay or from the center of the axle to the center point between the two bosses? Lastly, any chance you'd know what the sweet spot is for 700c cross-type frames? I measured mine along the seatstay, and it's ~292mm from the LH dropout to the LH brake boss. Seems a bit long, as the boss is almost horizontal from the rim surface.

I swapped the spacers out so that the thinner ones are between the lever and the pads, but that only helped a little bit. I'm using Salsa Delgado rims. This is an older hybrid bike, and I don't think the Salsas are much wider than the original rims. I put the old Shimanos back on for now, but I'd like to get the Oryx working on this bike if possible.

Any ideas? 
Thanks for the insight.
105mm


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## Entrenador (Oct 8, 2004)

ssmike said:


> I just installed a set of Tektro cantis on a cross bike today. They worked best with the thinner of the two spacer washers on the inside of the brake arm. The boss spacing was 75mm. Cross bike canti spacing will tend to be narrower than mountain bike (narrower rims, narrower spacing).


SSmike, any chance you still have the Oryx boxes around? Can you check, or do you recall if they were marked as fronts and rears, or were they identical? My two boxes are exactly the same, but Universal Cycles shows a front and rear option, so I'm wondering if the rears are designed for a narrower rear post. No answer so far from Tektro.

Thanks again.


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## Entrenador (Oct 8, 2004)

*picture from the side*

Not sure if you can get any useful info from this, but here's a shot from the side.


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## ssmike (Jan 21, 2004)

105millimetersofpleasure said:


> SSmike, any chance you still have the Oryx boxes around? Can you check, or do you recall if they were marked as fronts and rears, or were they identical? My two boxes are exactly the same, but Universal Cycles shows a front and rear option, so I'm wondering if the rears are designed for a narrower rear post. No answer so far from Tektro.
> 
> Thanks again.


No boxes and the ones I installed were universal front or rear. If you have cartridge brake pads (the pad is in an aluminum holder), there are specific front and rear based on the orientation of how the pads slide into the holders (the opening has to point to the rear of the bike so the pad doesn't shoot out upon braking).

Delgado rims are a little on the fat side - especially if your post width is narrow. There is a range of acceptable brake boss location (height and width) based on rim width and other factors. It could simply be that your rim/brake boss width is not perfectly compatible with the Tektro brakes (I believe you would also experience the same with other canti brakes that use threaded post pads as opposed to the smooth post on your original brakes).

You probably won't get an answer from Tektro if your e-mail went to Taiwan.


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## ssmike (Jan 21, 2004)

here are Shimano's frame requirements for canti brakes. Tektro, Avid or any other canti brake would have the same requirements. This will give you an idea of the different parameters required for canti position/rim width...


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## shandcycles (Jan 15, 2008)

105millimetersofpleasure said:


> Hey shandcycles, is that 254mm number the distance from the center of the dropout to the center of the boss? Is this measured along the seatstay or from the center of the axle to the center point between the two bosses?


Imagine an axle in the dropouts and from the center-point of the axle measure out 254mm. From this point a perpendicular line across to touch the top of the boss should put the bosses 80mm apart. To be honest, if you take the measurement from the center of the dropout up the stay, you won't get much difference.



105millimetersofpleasure said:


> Lastly, any chance you'd know what the sweet spot is for 700c cross-type frames? I measured mine along the seatstay, and it's ~292mm from the LH dropout to the LH brake boss. Seems a bit long, as the boss is almost horizontal from the rim surface.


700c should be about 283mm. Although you can get away with a bit either side, 292 sounds a bit long.


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