Canti post spacing?

[Tom_Bishop]

Have a custom ti cx frame with straight seat stays. Canti post spacing is giving me grief as I have to angle the pads (when new) on the most extreme angle in their range (EuroX or Paul's) even with narrow rims (Open Pro) in order to get them to flatly meet the sidewall. This is limiting me from going with wider rims and causing extra canti setup hassles.

The builder welded the canti studs on using the inside of the stay, so it's no surprise that they're close together. Conversely, you can see Sacha's Speedvagen posts (Paul specific) are pushed towards the outside of their shapely stays, so clearly Vanilla gets it. My questions for the cx frame builders here:

1) what do you use as the c-t-c for canti's spacing spec?

2) Has this spec changed with the new wider rims coming on the market?

3) Is there an eccentric, thread-in brake post option available that would widen the spacing?

4) Is there a canti brake that is likely offer better flexibility in this dept over Paul or TRP EuroX?

My humble thanks for any experience you can share.

[bellman]

3-1/4"ish or so

I've seen trimmed pads for fat carbon fork blade applications (sven nys), It allowed the brakes to open all the way without the back of the pad contacting the inside of the fork blade in the open position. You may be able to do something similar with the rear, all the stopping is done with the front anyway right? :-)

[Todd Mosley]

You might try an old style canti brake that uses a brake pad that has posts instead of a pad that bolts to the brake arm. You may be able to move the pads in enough to get the clearance you need.
f2f_shim_xtr.jpg

[steve garro]

65mm-73mm center-to-center.
- Garro.

[prolix21]

I found that most cx frames are based around 80mm c-t-c canti spacing. That's what the forks are and what the rear should generally be if you want to use anything from Paul, etc. I have a set of paul minimotos that wouldn't do a bike with 72mm spacing, neither would spookys (trp eurox's).

I found the Shimano BR-CX70 is the most flexible setup, handles anything from 65mm to 85mm post spacing with ease.

[echelon_john]

I've always used 80mm.

Garro, is your (skinnier) number geared toward much wider mtn rims? Lord knows you can do this stuff in your sleep; that number just sounds skinny.

???

[steve garro]

Garro, is your (skinnier) number geared toward much wider mtn rims? Lord knows you can do this stuff in your sleep; that number just sounds skinny.

???

Mostly just from building a few hundred bikes with canti/V-brake spigots.
70mm for shimano @ 253.5mm from axle center is money, with a 21mm outside width rim.
Paul brakes all run to their own standard. When using pauls I like to have them on hand, they run wider.
It's too bad Cantis don't have the sliding posts on the pads anymore, that sure made them work better.
YRMV and all components sure do.........
- Garro.

[Andrew R Stewart]

With mid 1990s Shimano cantis (before the "low profile" stuff) and rim widths of 22/24mms I find about 80mm post spacing gives a lot of adjustment flexibility. I tried to mount new Tektro 720s on a fork from a late 1980s Bridgstone MB that had about 65mm bosses and a 24mm rim. Would not work to my standards. I did have a used od set of the Shimanos previously mentioned and they JUST barely worked. Andy.

[Tom_Bishop]

Lots of good dialogue here. At 8cm spacing, I'm wondering if straight stays on 130mm spaced-bike could even be feasible, and if so, how would the builder would manage? Anyone done this? I'm just thinking my builder may have been a bit handcuffed on canti post width at the point he decided not to bend the stays on a 130mm bike.

I'm keen to keep std road cartridge pads in the mix. So far I"m using sand-paper remove some of the bottom edge off the pad and increase the contact area...of I can just run Thinline pads from Koolstop to help.

[prolix21]

On the cx frame i built with ~70mm spacing I used stays with a 'cx' bend to get some mud clearance. I should have offset the bosses, but didn't think about it at the time and ended up with closer spacing. Looking at the frame, if I had used straight stays I probably would have been closer to 80mm depending on how I attached the stays to the seat tube. The rest of the variance can be fixed by mitering the bosses to sit on the stay to meet whatever spacing you're shooting for. I learned all this the hard way.

[bellman]

canti 1.JPGcanti 2.JPG

Lots of good dialogue here. At 8cm spacing, I'm wondering if straight stays on 130mm spaced-bike could even be feasible, and if so, how would the builder would manage? Anyone done this? I'm just thinking my builder may have been a bit handcuffed on canti post width at the point he decided not to bend the stays on a 130mm bike.

I'm keen to keep std road cartridge pads in the mix. So far I"m using sand-paper remove some of the bottom edge off the pad and increase the contact area...of I can just run Thinline pads from Koolstop to help.

Side tacked stays are much wider than fastback stays........ the boss can be put anywhere on the stay itself. inside, center, outside. Heres how i miter mine and a shot of one centered on the stay.

[Andrew R Stewart]

One can also build up the boss base with larger tubing of even a cross tube. This is where being creative seperates the pros from the boys. Andy. (who sometimes is a big boy).

[steve garro]

One can also build up the boss base with larger tubing of even a cross tube. This is where being creative seperates the pros from the boys. Andy. (who sometimes is a big boy).

The "regular" old one piece 9mm offset canti bosses slip fit something like 5/8" x .049".......
- Garro.

[Tom_Bishop]

Can all this be done in Ti or are the options more limited on boss-type or where you can mount it?

[Andrew R Stewart]

Can all this be done in Ti or are the options more limited on boss-type or where you can mount it?

I would think this depends on your ability to fab Ti. Can you machine a one off part or addition for a pre made part? As many have said you design the bike to do what it needs to then pick/make the stuff to get that done. Andy.