Rudomanski

I've recently been building a touring bike for a cross country trip this summer, I just finished building the wheels, and when I went to install the cantilever brakes, I found that the pads did not reach far enough down to the rim, they hit the tire.

When I looked further in this problem, I found out it may be an issue of wheel size. the frame I'm using is a 1987 Trek 520 Cirrus which comes with boss fittings for the brakes. After reviewing vintage-trek.com I realized I misidentified the frame as a 1985 before I built the wheels. The 85 came standard 700c wheels, while the 87 had 27". So the wheels I built are 700c, a bit shorter than the 27" the frame came standard with.

The funny thing is though, when I took a 27" wheel off of my commuter bike and put it on the frame, the new cantilever brakes I bought (Tektro Oryx) still did not reach down to the rim and hit the tire.

Do new cantilever brakes extend longer from the boss than the older ones? I would really like to use cantilever brakes on this bike. Is there any canti's out there that have a shorter boss - brake pad length? Is there any modifications I can do to make this work?

Thanks for your help!
Zach

FBinNY 

The difference between 27" and 700c shouldn't be enough to be a problem, so something else is wrong. I don't know anything about changes in brake design but it's possible.

Put the wheel back in and measure the vertical and horizontal distance from the center of rim to the boss. It should be in the 30mm range, but let's check. I have a bunch of NOS brakes from that era and if I know the measurement, I'll check if any will help.

DannoXYZ 

Can you post a picture of the brakes? Most cantilevers allow rotation of the arm that holds the brake-posts. This lets you vertically adjust the spot where the pads touch. The minor 4mm difference between 700c vs. 27" rims can easily be accomomdated by a brake-adjustment.


btw - the straddle cable on this picture is way too tall, you want it just barely skimming the tyre for maximum braking-force.

Here's how you adjust the rotation of the holder of the brake-posts:


From Park Tool - Cantilever Brake Service, near the bottom of the page.

une_vitesse

+1
i'm wondering if the bosses are set too close to each other for the oryx's.

velo-orange

Tektro Oryx brakes and many modern cantilever brake pads sit higher above the canti pivot studs than older cantis. Trek prolly speced Dia Compe cantis on that bike, which require the canti studs to sit slightly higher with a smaller tolerance range. Oryx won't work, neither will most modern low profile cantis (Shimano, Paul) and 'high profile' cantis (spooky, VO, Paul, and others).

You never mentioned why you are using the Tektro brakes in the first place. Your options may be limited to using the original canti brakes speced on the bike and upgrade the pads to something with a better compound. Koolstop salmon is a favorite around here. We (VO) have pads with adjustable toe in and are more forgiving to canti studs that sit higher on older frames too.

Rudomanski

Thanks for all the responses.
I measured the distance from the center of the rim to the center of the boss and got a vertical measurement of about 20mm, and a horizontal of 30mm.

Here is a picture of the brake on the front wheel.


The shoes on this brake are adjusted via sliding up and down. The shoe is in the farthest down position in the photo.

velo-orange - I've never used canti's before and was not aware that there was this much variation in the length between the shoes and bosses.

What is my best bet in terms of brakes that will fit the 20mm vertical masurement?

fuzz2050

Quick request, can you measure the distance between the two studs? That should let us all know if the reason you are having trouble is because of the cantilever stud spacing or the wheel size change.

velo-orange

The distance between studs may not matter in this case. 20mm from brake track to canti stud center sounds about right. I've measured 15mm for certain dia compe brakes. newer canti and V brakes like the oryx, shimano, paul, etc. are all going to need 25mm from brake track to canti stud center.

These measurements are going from memory though. so I may be off.

shimano really made an impact with standardization of frame spec to work with their components. They may catch hell for re-inventing stuff that doesn't need re-inventing, but in this case, the adjustment and compatibility range really opened up options for everyone.

Rudomanski

About 62mm between the studs.

Any ideas which dia compe (or other) brakes I could look at with the 15mm reach, and where I might find them?

Thanks!

velo-orange

dia compe 981, 982, 983 brakes are what I'm thinking. swap meets, e-bay, junk bins at old bike shops. it's going to take a bit of scavenging.

anyone else wanna put some more info down?

Rudomanski

I spoke with someone from harris cyclery via email and he said an old pair of ritchey logics should work with the measurements I listed. I'm going to try and see how those work. Thanks for everyone's help on this, I'm looking forward to getting out on the road.

-Zach

helicomatic

Just for posterity:

The more recent cantilever brakes I found that have the shortest pivot to braking surface distance are old Ritchey Logics, made by Dia Compe. I'm not sure what the Dia Compe equivalent is, the forging and pad hardware looks similar to the 986, but it uses normal springs instead of the "U brake" style that the 986 used.

The minimum pivot to rim vertical distance on these is 19mm with pads horizontal, you could angle them down just a bit to get a little lower. The maximum distance is about 30mm. The box specifically says "Longer slot allows for greater vertical pad adjustment" and they mean it.

I sold the last set of these to Rudomanski. We don't have any more, but they're out there.

32x24T

Ok, well to pick this thread back up, I have a Bridgestone T700 that has a vertical measurement of 15mm with 700c rims. Do you think I'm out of luck? I was hoping you could tell me if you came across anything with that sort of clearance. I'm half-tempted to email Grant Petersen over at rivbike.com just to see if I can get to the bottom of the thinking behind this.

Rudomanski

the logics I put on there just barely cleared at 20mm. I'm afraid these probably wouldn't work at 15. If you're not set on cantis, you may be able to go with a set of long reach calipers.

Drakonchik

There are two fancy variants of the Dia-Compe cantis I know of which feature an eccentric bushing. One is a variant of the 983 model, and the other is model (or variant?) NGC982.

These bushings have an off-center hole, this is the hole that the stud slides into. By varying the orientation of the bushing, one can change the vertical position of the entire brake by about 4mm. (Actually one can vary several parameters relevant to brake set-up simultaneously by simply rotating the bushing).

These fancy variants tend to come on a rare few vintage higher-end 1980s mtn bikes that typically have U-brakes on the rear and said variant cantis on the front. They are very hard to find. In five years of full-time bike salvage I have only come across a total of 3 individual brakes.

These models do not allow any vertical adjustment at the pad post, only at the bushing.

Drakonchik

I have a Dia-Compe NGC982 canti brake on my desk right now. With the eccentric bushing set so that the pad can sit as low as possible, there is a vertical distance of about 23mm from the center of the stud to the center of the bolt which fastens the pad post.

Drakonchik

Got a set of Dia-Compe 986 ("Coda" Cannondale branded) on my desk. Vertical reach on these is also 23mm at lowest setting.

bikemig 

I just ran into this problem. I was installing tektro 720s on a 1992 bridgestone XO-2 and they're not going to work on the front wheel. I set the cantis as low as they can go and they are still a bit high. Plus the movement on the cantilever isn't quite right; I think the spacing between the canti posts is a bit close by modern standards. Sigh, lol. I could go with 650b wheels I guess (the bike was originally spec'd with 26inch wheels but I don't want to build/buy new wheels. It looks like I'll be scrounging around for old cantis to try to find a pair that works.

drisee

Been researching this topic and wanted to raise it again to see if anyone else has solved this in recent years.

I have a mid-80s touring bike running on 27" wheels. The canti brakes i have are dia compe 980s from 1986. They don't work great, are impossible to toe-in and in general would love a vintage upgrade.

If i were to updgrade to a later version of the 980, would the sizing remain the same in terms of working with my 27" wheels? Thank you everyone.

Rick

Paul makes V brakes that will solve the reach problem. They are pricy though.

70sSanO

I'm running XTR M900 cantilevers. They have the same toe-in setup as other cantis, but with Koolstop pads there is no braking issues.

These Dia Compe cantilevers look to use a linear style brake pad and are probably easier to setup, and still vintage looking. Have no idea how well they stop but I'd use Koolstops.

DC980 | Diacompe

John

drisee

Thx. While not sure about the V brakes, i did reach out to Paul regarding the two canti options they have on their site and they let me know that neither one would work for me. Bummer as i love their product.

Also trying to keep the look of the canti brakes for this one. Thx.

drisee

Thanks John. Yes, the link you sent are the ones i'm looking at, the newer version of the 980. I believe they should work and i can see the pads have a vertical adjustment. Hopefully they figured out some good improvements. Has the look i'm going for and i appreciate they don't have a double barrel straddle cable, which is a pain IMO. Thx.