Black finish SunTour XC-Pro cantilevers with single spring adjustment at the rear of the arm
Champagne finish model with dual spring adjustment in front
Having recently set up two different versions of early 1990’s SunTour cantilevers, I thought it would be helpful to share my insights while they are still fresh in my mind. While each of these cantilever models is called by the same model name, they could not be more different. The champagne finish model pictured second has its adjusting springs and washers on top of each caliper, whereas the black finish model pictured first has only one caliper with an adjusting nut that sits below the caliper arm, but with two holes in the other caliper arm for additional spring tension adjustment.
The champagne finish model was more difficult to set up, which was counter-intuitive, given that each caliper arm could be dialed in for separate spring tension. The above photo shows one caliper arm of the dual spring model disassembled. SunTour provided a special cone wrench with each new XC-Pro Champagne finish brake set model sold (perhaps as a warning).
SunTour cantilever smooth post brake shoes
If you want a completely accurate engineering description of these brake calipers, you’ll find that at BikePro’s archived articles.
However, online guidance as to the particulars of setting up these brake arms is limited to the Sheldon Brown site, with its repellent advertising. So, I consulted my print materials including my collection vintage mechanic’s manuals. Oddly, the only really helpful print resource was Park Tools’ manual, which is also available online.
SunTour Model 59030334 Cantilever Instructions
Fortunately, both NOS brakesets I was installing included the manufacturer’s instructions. The dual spring adjustment champagne model, which was part of my Rivendell Appaloosa build, was my first attempt at setting these up. The instructions include a helpful cutout to measure your straddle cable angle. These dual spring XC-Pro brakes want a 90 degree angle. I got pretty close to that, and called it good. But, most illuminating about SunTour’s instructions for these cantilevers is the sequence of the steps, which doesn’t match my protocol about setting up brakes. SunTour advises positioning the brake shoes first, which in my experience is the very last step in any brake set-up. After that, SunTour advises how to install the straddle cable (very low) so that the cable angle is correct (90 degrees) and so that the brake pads sit very close to the rim. Then comes the spring tension adjustment. Let’s just say that things did not go as planned when I initially set up these brakes on my Rivendell Appaloosa. But, after some trial and error I finally arrived at the right spring tension adjustment, and the brakes are now performing well.
Spring tension 19mm nut under the brake arm
Only one arm has a spring tension nut.
Meanwhile, I set up a later version of these cantilevers on my Bridgestone MB3. This XC-Pro model has its spring tension adjustment on only one arm, adjusted with a 19mm wrench from behind the brake arm.
Above are scans of the single adjusting nut model of SunTour’s XC-Pro cantilever instructions. This model uses a spring adjustment nut (19 mm) on one arm, and which sits underneath the brake arm. These brakes allow for changing the spring tension by moving the spring from a low tension to high tension setting on the other brake arm, as shown in the scans above. Setting up these single spring adjustment brakes ended up being less time consuming than their dual adjusting nut siblings. The adjustment nut is only useful for centering the brake shoes, with spring tension controlled on the other arm with the hi-low setting. This model calls for a 96 degree straddle cable angle. I didn’t quite achieve that with the setup on my 1989 Bridgestone, but they are still working fine with a slightly lesser angle. I used the NOS SunTour brakepads (aka “bricks”) on the Bridgestone, after filing some material off their surface. Even though not well regarded as brake pads, they are working nicely, and have not squealed (yet).
Need an IPA?
Older vintage cantilevers do not have spring tension adjustment. So, if you needed to change the tension to improve brake performance you needed a 3 hole cantilever boss, or you needed to “strong arm” the spring to change its tension. While that’s where newer cantilevers can offer improved braking performance, setting up these cantilevers correctly is another thing altogether.
Trying to set up some Dia compe 980 canti’s on my 1987 Nishiki Cresta GT, so I feel your pain. Compared to todays brakes like say a Tektro 720 there isn’t a ton of adjustment but the canti studs up front are too narrowly spaced for something like the 720s. So I have set aside a quiet hour to fiddle with them and do a lot of manual adjustment’s.
So true. They work great when set up properly but can take a lot of trial and error to get there.
I interchanged mine with Shiman CX50 not using the original spacers but Koolstop Cross pads. Works perfekt when using the original Y link..
Just found this. Thanks.
I’ve some ’91 XCDs in grey that I cherish though I’m not sure why. Well used and I suppose now a lot of play in bearings compared to new. There seem to be so many ‘degrees of freedom’ when setting-up. Just the block has 3 ( rim proximity, height and toe-in) that all determine the contact plane. The main tightening bolt to the peg determines the relax position of the arm, then there is the tensioning spring, and finally the hanger and cable lengths. Is that it?
The most difficult outcome is to get the blocks to hit the rim at the same time when the brake is being pulled.
I start with a sequence protocol but frankly end-up with trial and error.
Fine adjustment of toe-in is very tricky as the block becomes loose and hard to hold in position as these adjustments are made. I find using a shim (feeler gauge or piece of card) at the trailing edge of the block as a spacer is good for toe-in set-up. Otherwise much squealing!
I am often resort to saying “it must be easier than this”. Of course it isn’t.
Rewarding to get it done, and some admiring comments when out and about, but you need ‘time on your hands’ to do this. It’s purgatory!
It is hellish sometimes to set up these cantis. But, once set up they perform so well that you almost forget the torture!
Just ordered set of theys there good breaks I reckon there safer than disc breaks I mean if its raining real bed my disc brake kept slipping once I. Got them am going to fit them disc OK but I trust break blocks more they stop quickly on the other hand why disc brakes slip pads have to be cleaned iv done this carbon dirt build up over time on disc shoe pads clean then then disc brakes stop properly but I still like theys brakes 👍
Theys brakes actually look cool I used to use years ago I just bought full kit set once got am going to fit the. Down hill test run
Nice to find such good descriptions of old brakes 🙂 In case anyone’s interested I’ve made some notes on my old DiaCompe 982 GC cantis, and (in a second post) possible replacements, given narrow boss spacing. https://crankular.wordpress.com/2018/11/23/dia-compe-ngc982-brakes/
Thanks, Ben! The narrow spacing issue is especially of interest.
I’ve just noticed that there are NOS Dia Compe 987s around for non-astronomical prices. One feature I like, though practically it may be quite minor: They don’t pivot directly on the boss, but like the 982s, have their own core that bolts onto the boss, and the arm rotates on this. Geometry-wise they look similar to the low-profile Shimanos (BR-CT91 in their current incarnation).
I’ve been using the champagne colored XC Pro’s on a bike for about 23 years now. The set-up never struck me as difficult, but I think Shimano’s arrangement with a simple Phillips screw adjustment is better. I’ve had issues with the springs breaking over the years. I’d bought a spare brake set, and only have one spare spring left. Of course, I just noticed that each side of the brakes has a unique spring, and it can be important to get the correct one in place! I can’t help but wonder if that was a factor in the broken springs. 🙁