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1985 Trek 620 Cantilever to V-brake conversion

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1985 Trek 620 Cantilever to V-brake conversion

Old 01-01-11, 08:48 AM
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1985 Trek 620 Cantilever to V-brake conversion

Any here with a 1985 Trek 620 or similar vintage Trek that converted their cantilever brakes to V-brakes?

The '85 Trek 620 had 27" wheels and cantilever. Right now I have 700c wheels which work fine with the original cantis. I'm more comfortable adjusting V-brakes than cantis and I like the stopping power of V-brakes better.

Anyone do this with success?

I know some of the earlier cantis bosses were not compatible with the V-brakes. Also V-brakes don't have as much wiggle run for adjustment and since this bike was originally designed for 27" wheels, I don't know if V-brakes will work.
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Old 01-01-11, 09:16 AM
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Cantilevers, if adjusted properly stop, as well as anything except a disc. With that said, You would have to check if V-brakes have enough adjustment to take a 700C wheelset. I think it's a try it and see kind of deal.
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Old 01-01-11, 09:24 AM
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I have an 85 620 that I converted to 700, using old Deore cantis because they had a very wide range of adjustment.

The bosses are narrower than more modern bosses, so they are not ideal for v-brakes. I have not tried it however.

Two thoughts:

-the conventional wisdom is that narrow bosses do not work with v-brakes. I think because you need more width so that the brake arms do not touch at the top.

-I really had to use a radical brake-pad angle to get my cantis to fit. I am very doubtful that any v-brakes would have that kind of adjustment range.

I am all for trying however. Hopefully you have a set in the parts-box to dry-run.

jim
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Old 01-01-11, 10:00 AM
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If the bosses are more narrow you can modify the V brakes by relocating the thick washer from the inside of the V brake (pad side) to the outside. I've had to make this change when updating some older MTBs to V's.
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Old 01-01-11, 10:19 AM
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Originally Posted by roccobike View Post
If the bosses are more narrow you can modify the V brakes by relocating the thick washer from the inside of the V brake (pad side) to the outside. I've had to make this change when updating some older MTBs to V's.

Definitely worth trying. But this case will be a little harder than the run of the mill conversion because he is not just fighting against the narrow bosses, but also the lost 4mm of the smaller rims.

jim
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Old 01-01-11, 10:31 AM
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Originally Posted by jgedwa View Post
Definitely worth trying. But this case will be a little harder than the run of the mill conversion because he is not just fighting against the narrow bosses, but also the lost 4mm of the smaller rims.

jim
I'd recommend some shimano v-brakes for this sort of conversion. #1, because i know they have the thick versus thin washer option for the narrow bosses (and, presumably, relatively narrow rims), and b/c both my lx and my xt v-brakes have <15mm of vertical adjustment for the pads.

i'd be stunned if you couldn't run it with 700c rims, at least in terms of brake-reach issues.

hth,
-rob
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Old 01-01-11, 07:19 PM
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https://www.paulcomp.com/motobmx.html

Maybe?
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Old 01-01-11, 07:38 PM
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If you want to use your road levers, you may need a Travel Agent to take up the extra cable required by V-brakes.
https://www.rivbike.com/products/show...l-agent/15-144
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Old 01-01-11, 07:55 PM
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If brake reach is an issue, they do have mini V brakes and BMX V brakes that might do the trick. YMMV. There are Tektros and an inexpensive 'Rockwerks' brand that are actually Tektros.
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Old 01-01-11, 09:16 PM
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With narrow bosses and smaller wheels, its not simply a brake pad reach issue, but more problematically a brake pad angle issue.

Finding some brake set up with sufficient reach is not very hard. Getting one that can accomodate the strange new angle is a problem. With cantis, I think this angle can only be accomodated with arms that take smooth post pads. Because those can be angled any way you want. Are there v-brake arms that will do this?

jim
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Old 07-21-21, 08:22 PM
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What did you end up doing? I'm facing this at the moment, and would appreciate any help you might have found.

They'll work, kinda.. but I want to stop dead in my tracks if need be and I am planning on loading it down with racks and gear which will only intensify the need..

Maybe my LBS can get them dialed in for me.
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Old 07-21-21, 08:36 PM
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OP hasn't posted to BF in eight years.... Hopefully someone else can help.
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Old 07-21-21, 10:39 PM
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I broke down and bought some 27's off of ebay until I can find another option, I'm still figuring out this platform, thanks for the heads up.
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Old 07-22-21, 01:05 AM
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Since this zombie thread has been Lazarus'ed, I will say, as a 1985 Trek 620 owner, for future readers of this thread, whenever you may be, that the rear spacing is ~77mm and height (from the axle) is acceptable (~287mm IIRC) to support V-brakes (or mini-Vs in my case). With standard 'old school' rims, (20.0mm max external width), the angle or splaying of the arms is alright. If running a wider modern rim (22.7mm external in my case), the splaying will be quite obvious and not, IMO, aesthetically pleasing. The front canti posts are spaced, CTC, at ~66mm with a height of about 294mm or so. 100% no go for V-brakes of any sort.

What I ended up doing is paying someone to position new posts at the spec'd height of 283mm and width of 80mm, which is what seems to work (and is spec'd) by many--though as always, please check with the company of the brakes you wish to run. In my case, a taller post height would have worked perfectly fine for my TRP CX 8.4 mini-V setup as the 283mm height puts the pads well into the middle of the slots, which can 'limit' vertical clearance. This is only a problem, potentially, if one wants to run large tires and fenders at the same time, and if those tires happen to be 38-40mm actual width. I am running 42mm nominal width Soma tires (Supple Vitesse EX) that measure 39.0-39.5 at 40-45 PSI, which my frame and fork clear by 3mm at least at the fork blades and chain stays.

I am running a post width of 82mm in the back and 79-80mm in front. The TRP brakes look good and the narrower-set fork blades aren't disrupted by the wider-than-the-center-line posts, which manage to stay mostly within the silhouette of the fork blades (when viewed front to back). A bonus of the new canti posts is the three holes for brake spring tension setting, versus the single hole originally. Additionally, I can throw in and take out fully-inflated 42s, which was not possible with the very narrow fronts.

PS: Frameset was powder coated and new decals were placed after the frameset was modified. It's not a cheap path to take, but in my case, the frame is fantastic, capable, stable, and fun, with crummy roads necessitating large tires for comfort and sanity. These are very special bikes/frames, and I have ridden many over the years!




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Old 07-22-21, 11:49 AM
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Man Riddle, I love seeing your bike.
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Old 07-22-21, 04:57 PM
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Originally Posted by Jasongrace313 View Post
Man Riddle, I love seeing your bike.
Thanks, man. Best part now, is that I FINALLY solved my howling brakes and shuddering fork issue. After trying all toeing in/out combos, I went back to toeing them in, just more aggressively than before (before would have been fine for a side pull caliper as there is no slop in that system, among other things). I still picked up Kool Stop salmon-colored pads. Initial brake bite is lessened a little as, naturally, less pad is making initial contact with the rim. Brake lever effort is still light, so I can still squeeze the levers harder (yet more easily? you know what I'm saying) to bring about the desired vice-like stopping power. So I suppose, in essence, I have gained modularity. The takeaway for other vintage canti-to-V convertors, is to work the pad toe angles. It can be vexing and discouraging, especially if you half built a bike around something like these TRPs and they don't cooperate right away. I should note that after redoing the toe-in, I took a rasp/file to the pads as they had glazed in parts due to heat buildup and vibration during their pretty extreme break-in period/introduction to Seattle topography. Brakes, like anything on a bike, are an ecosystem, and it can take a little bit to find the balance!
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