canti/linear pull advice for wide bosses and narrow rims

[nash]

i have an older mountain bike with brake bosses that are on the wider side, 90mm front and 85mm rear (or the other way around, i cant remember)

the rims i have on the bike are quite narrow, like 19mm i think.

obviously an option would be to rebuild the wheels with wider rims. but i'd rather solve the problem with brake choice.

i'm open to vbrake or canti. any suggestions of known brakes that have a particularly wide stance i guess? i have tried shimano v brakes, deore, and, with the wider spacer on the brake pad post towards the rim, they were still way too wide.

i've searched and read of people mostly having the opposite problem, narrow spaced bosses and how they made it all work together, but no specific models that work the other way.

also i havent been able to find any info from manufacturers about ideal brake boss spacing for their brakes, a range, etc.

i believe 80mm is relatively standard for modern frames.

[nash]

i have some avid trialign cantis on it now but they are hard to set up without being noisy and still feel good and have good power. its really giving me practice on setting up cantis and getting a feel for all the angles. only having been a mechanic for the past 3 years, i have missed out what must have been a wonderful time of mountain bikes with cantis. oy vey.

[donevwil]

Definitely cantilevers with post mount pads.

Tri-aligns hold the post pretty far away from the pad if I remember correctly. I've had years of happiness with some old Suntour XC-Pro cantis, internal springs and infinitely adjustable. Very nice cantis. Not mini-V's, but great brakes. Combine that with some fat, not thinline, pads like Yokozuna Mathausers or Kool Stop Eagle 2s and you should have all the width you need.

[SignatureJustin]

i have an older mountain bike with brake bosses that are on the wider side, 90mm front and 85mm rear (or the other way around, i cant remember)

the rims i have on the bike are quite narrow, like 19mm i think.

obviously an option would be to rebuild the wheels with wider rims. but i'd rather solve the problem with brake choice.

i'm open to vbrake or canti. any suggestions of known brakes that have a particularly wide stance i guess? i have tried shimano v brakes, deore, and, with the wider spacer on the brake pad post towards the rim, they were still way too wide.

i've searched and read of people mostly having the opposite problem, narrow spaced bosses and how they made it all work together, but no specific models that work the other way.

also i havent been able to find any info from manufacturers about ideal brake boss spacing for their brakes, a range, etc.

i believe 80mm is relatively standard for modern frames.

You should be able to move the brake post washers around on a V-Brake to take up that difference. Should work fine with a Shimano/Avid brake of your choice.

[nash]

nah, like i said, the washers dont make up enough of the difference. i already tried it. i guess i was hoping someone would chime in, 'oh yeah, had that problem, get this brake, it'll work'

with the smooth posts setup with the pads way in, there is a lot of brake post hanging out between the brake arm and the pad, this is where the squealing is coming from i suppose.

i'll have to just find a balance between keeping the pads close enough to the arms to keep them quiet, far enough to hit the rim, keep the straddle cable low enough to for power, high enough for modulation. it also seems the lower the angle of the brake arms are, the more leverage i get out of them. i dont really want to raise them by shortening the amount of brake post showing.

its a little ragamuffin of a bike, i like it a lot, but i dont want to spend money on it. total parts box bike.

[donevwil]

What pads are you using ? The XC-Pros with Mathauser pads I previously mentioned were originally run on a frame with 88mm front and 79mm back spacing, no sqeal. Height will also play a part, but we'll ignore that for now.

I used a Suntour Power Hanger with the XC-Pros which allowed me to run the arms more vertically and really improved braking as a bonus. I've used that set-up on for the last 14 years. Just last week I replaced them with Mini Motos. Jury is still out.

[nash]

hmm the power hanger is an idea

[rmplum]

/Thread revival - what did you settle on?

Dealing with this on my 2001 Poprad right now. My tape says rear spacing is 85mm (fronts at 75mm). Tektro Mini-Vs not even close to working out back (yes, large spacers are inboard). XTR M900 cantilevers work, but I'm using almost all of the post on the brake pads to get them there. The posts also may be in the low range, as both brakes (XTR and Tektro) want the pads very close to the top of their adjustment slots as well.

Rims are cxp-30 - but I'm not sure that even one of the wider rims out now would get the rear mini V's in workable range. The front mini-V's just barely work.

rp

[Gattonero]

I fit lots of TRP Euro CX, never really happened to deal with frames different from the classic 80mm spacing between the studs, but almost always on 20-21mm rims and the post is always 1/2 in.
So I reckon that with a 90mm spacing you may have to get most of the pads post out, but still with a safe grip.
What I like about them, is that the post has a small 4mm allen key to adjust the toe-in. They've a nifty adjuster on the cable end, too

[newellbt]

I have the opposite problem. My RB-T has less than 80mm spacing, the front is less than the rear. I had purchased Paul cantilever brakes, and I can JUST barely set them up by having the pad leave at a maxed out angle.

I believe my solution will be the same for you. As mentioned above, Post Mount Cantilever Brakes. The additional adjustment of the pad in or out will take up the space.

[Gattonero]

Of course, having a big amount of post in or out, does modify the angle that the brake arm will work with the straddle wire.
It may end in a position that is not favourable, so with the straddle not being very close to the "90º rule" to get the best leverage.
With more post out, make the straddle longer; with less post out, make the straddle shorter

[nash]

i settled on my avid trialigns. they are a little bit of a pain to get right, but not really. and they feel fine once i got them right. so yeah, post mount cantis seem to be the deal.

/Thread revival - what did you settle on?

Dealing with this on my 2001 Poprad right now. My tape says rear spacing is 85mm (fronts at 75mm). Tektro Mini-Vs not even close to working out back (yes, large spacers are inboard). XTR M900 cantilevers work, but I'm using almost all of the post on the brake pads to get them there. The posts also may be in the low range, as both brakes (XTR and Tektro) want the pads very close to the top of their adjustment slots as well.

Rims are cxp-30 - but I'm not sure that even one of the wider rims out now would get the rear mini V's in workable range. The front mini-V's just barely work.

rp

[rmplum]

Of course, having a big amount of post in or out, does modify the angle that the brake arm will work with the straddle wire.
It may end in a position that is not favourable, so with the straddle not being very close to the "90º rule" to get the best leverage.
With more post out, make the straddle longer; with less post out, make the straddle shorter

Here is where I'm at. Just using the cheater Shimano linky thing, but if it's good enough for Page, it's good enough for my weak ass. Plus it's easy to use when trying a bunch of different setups (I have them in multiple lengths) and I'm pretty close to 90deg.



Biggest problem with my shown setup is that those XTR pads are pretty ancient and need a good cleaning, or some Kool Stop salmons. And the OCD part of me needs to balance the posts side to side.

[GrayJay]

Of course, having a big amount of post in or out, does modify the angle that the brake arm will work with the straddle wire.
It may end in a position that is not favourable, so with the straddle not being very close to the "90º rule" to get the best leverage.
With more post out, make the straddle longer; with less post out, make the straddle shorter

Definitly good advice for narrow and medium angle cantilevers. One exception to point out however is that if you are are setting up wide angle mafac style cantilevers (TRP EuroCX, spooky, frogleggs etc) and you have them setup so that as the pads strike the rim, if the saddle cable anchor ends are on the same horizontal line through the frames 2 cantilever bosses , then the saddle hangar height and angle of the saddle cable do not effect the mechanical advantage of the brakes. You can largely ignore tha 90° cable angle rule for wide angle brakes. If the cantilever bosses were so wide (or the pad post pushed max outboard) such that the cable anchors are well above horizontal line through the frame boss then wide angle brakes gradually start to behave more like medium angle brakes and cable angle does come into play.
Also note that for medium and narrow angle cantilevers, a lower hangar placement (so long as hangardoes not hit the tire) will always result in higher mechanical advantage of the brakes. Problem is that the mechanical advantage can be so high that you either have insufficient clearance between open pads and the rim, and/or too much lever travel is needed to move the pads to make contact. THe 90° rule is just a good general starting rule for matching the mechanical advantage of average levers to the mechanical advantage of the arms, if you had levers with unusually high or low mechanical advantage, it would be fine to deviate from 90° saddle angle to re-ballance the overall system.

[Gattonero]

That's why in the '90s with super-flexy front suspension forks 3 hands were needed to setup the brakes :-\

[Human Epic Jolt]

That's why in the '90s with super-flexy front suspension forks 3 hands were needed to setup the brakes :-\

someone needs a lesson.

[Gattonero]

someone needs a lesson.

?