determining canti boss offset???....
 

Hello,

I was on the web looking for frame parts.........canti bosses, in particular.....and noticed some sites were stating the offset of the boss. I can understand what they mean by that, but how is this determined? IOW, how does one know what they need? I've already run a few searches without much luck in answers. Maybe it's my choice of keywords..........I dunno. But, could someone help? I'd like to put some on my Lotus Elite 700c.

Thanks.

For most canti brakes you want the studs to be 80mm apart- the offset is based on where you have to put the stud to achieve this. For example, most mtb forks/seatstays are wider so the boss will have to be offset towards the rim while a road bike with narrower stays/blades will have to be offset away from the rim.

FWIW, as I make my own fork crowns and bend my own seatstays the bosses I use are blank so I can vary the offset accordingly.

Thank you. Would you mind sharing with me, then, a method and the type of tools you use to go about figuring boss placement on the stays/blades? There aren't any frame builders around here, so what I'd have to do is get the bosses all set up on the frame and fork with fixtures in there respective locations and take it somewhere to have them brazed or welded on. I don't have the tools or experience to do either myself.

Thanks, again.

where you at? There are framebuilders everywhere, they can probably place them better than you can.

Yeah, I can understand why you'd say that, but I've rebuilt two Toyota engines quite successfully without ever having done anything like that before. All I needed was a factory manual and a few tips from someone with experience. So, with a little help from an experienced frame builder via internet, I'm sure I'll do just fine. I gots skill, dude.

Anyway, no frame builders close enough to be practical around here. I'd have to drive two hours +, atleast. Ain't happenin'.

I guess I'll just do some web searching on google or other forums. Thanks.

I've rebuilt engines, and don't see that the skills translate. You didn't say where you are, there are framebuilders everywhere -- they didn't all move to portland yet. I don't know where you are going to find someone with the welding/brazing skills you need. Not that non-framebuilders with those skills don't exist, but they aren't common either. And I don't see brake bosses as the best place for a first bike frame brazing/welding experiment.

when I put on my first set of canti bosses, there were a vanishingly small number of people in the U.S. that had done that. No Internet to ask questions, nothing about cantis in books. And the only cantis you could get were Mafacs that are famous for how difficult they are to adjust. I used the brakes and a wheel to mock them up and make sure I could get them in the right place. Even if you have a dimension, you want to do this as a sanity check before brazing.

To hold them in place, you can use a flat plate with holes drilled in it. Unless you have a mill, it's probably best to make one of the holes a slot so you can get the spacing just right. Bolt the bosses to the plate with the brake mounting bolt holes. Probably should get some 5mm bolts and nuts and use them instead of the bolts that come with the brakes. Once you have the bosses mitered you can rotate the frame in a park stand and it will just sit in place. Many framebuilders use gravity to hold things for brazing. You can also use an axle and a rod going up to the flat plate and a couple of small c clamps to hold it all together.

yeah what he said

This is how I have done it on all my frames. It's slower than using the correct jigs, but significantly less expensive, and works fine. The OP would do well to avoid overcomplicating things.

Not to be flippant, but I guess all I was trying to say was how 'bout not underestimating me and my abilities without knowing me, first? I'll define my own limitations, thank you. I'm not some youngster hopping around on the internet chasing the latest trend. I simply want some canti's on my sport/touring build. ;)

Anyway, all I was asking for was how someone has done it before. I'm sure I'd be able to figure it out as it doesn't seem that it would be much different than some of the carpentry projects that I've done before (among other things of this nature), but it's just nice when you can take a charted route sometimes. So, thank you for the map. I've got all the materials you've suggested including some pieces of channel iron that would make needing a mill moot.

Also, I have a friend that is able to the do actual brazing or welding. He does have the skills and knowledge of the metals involved.

BTW, I'm in NW Arkansas. Trust me..........there are no actual frame builders in this area. From what I'm told by a local bike shop owner, I'd have to drive to Tulsa, OK. I just don't have that kind of time running an animal sanctuary.

Thanks, again.

http://jamie-online.com/random-jamz/...6/facepalm.jpg

...

fellow BF'er meech151 is in Mountain Home Arkansas and you would probably be better off with him doing the job.

You'll have to forgive me if I think framebuilding requires a certain amount of skill that isn't just a matter of having above average mechanical abilities.

Okay........I'll take an older frame and try it out first. Sound good?

go for it and have fun. I recommend you order brass and flux from Henry James unless you can get the gasflux stuff locally. You can either get the bosses from them or you can actually by a big pile of them from Quality Bicycle Parts.

:lol: Couldn't have "said" it better!!!!!
(and to think unterhausen continues to be civil AND helpful):rolleyes:

What is this? The brown nose party? Sam's is having a sale on charmin. Unbelievably soft, you know?

Late replying, but it's been winter. Tends to keep one busy trying to stay warm, eh. Hope you're freezing Dr. Beltron.

I don't know what you guys make a such a big deal of. Like it requires some uber special skill that can only handed down from the golden throne of the gods. Just file things down right and make sure it's all going to work right before you tack it down. This is basic welders skills. Geometry. My friend that did the job (that builds aircraft) had to laugh at your comments. There's guys out there all over the place that are "nonframebuilders" that could do this stuff. Whatever, though. If it makes you feel better about yourself. Being helpful is one thing. Being smug and assuming is another. Sure.....I guess I'm being the forum drama llama, but what do you expect? Obviously I'm not part of the little clique around here, but then I don't want to be either. I mean, you do have each other. I guess that counts.

Yeah, I'm not too sure why you got jumped on either. It really is just "glorified pipe fitting" -- and adding canti bosses is one of the easier processes. Sorry you received such a nasty introduction to the forum.

Well, thank you, Six jours. I'm not really sure why, either. No matter, though. It's a pretty common way of interaction having seen it a lot on Toyota (and other) forums. You get some guys that know a lot (which is much appreciated), form a bond (which is just fine), and then a new guy comes around that doesn't quite know the terrain and from out of nowhere this snobbery kicks in. Not like I've never been guilty of this or even catch it in myself sometimes. But, I'm atleast aware of it, know it doesn't feel good, and make some effort to tweek my own attitude. Plus, it's just plain rude to assume someone's potential/ability without even knowing them. :notamused:

About the canti boss thing, though. (Or even frame building in general, for that matter.) A while back when I was enthusiastically inspired to build a beautiful bicycle for myself, I'd decided I'd build a bamboo bike.(Moot now. I have more lugged, steel bicycles than I almost know what to do with.) It was really a decision based on financial considerations at the time, I only had this Univega GT that was just too small, and the fact I like to do a lot of things myself. I'm not afraid to appreciate the fact or admit I do have a mechanical genius. I use those words only because I'm not sure how else to really say it. I can look at something and figure out how to make it work. Anyway, so bamboo bike. I designed my own jig before I realized there were others out there doing it already. That would have helpful to know and so that's why I figured I'd come here and ask about it the canti boss thing. In the end, I designed this scissoring type jig for the canti's that mounts at the fork crown. It sits out far enough from the fork so that the bosses and the brake pads clear the fork legs enough and allows me to adjust height, offset, and everything else. I blew off the accepted convention that brazing was the only acceptable form of attachment and my friend used stainless steel to weld. (Afterall, it's aircraft tubing!) Oh, thing is, I decided to take my best bike (an '82 Trek 614) to start with. I may not even put canti's on the Lotus at this point. I only wanted to because the unicrown only allows for so much clearance on 700c's. A 32c is a tight squeeze for sidepulls and adding fenders. I did consider 650B's, but that's cost prohibitive and kinda unnessary I think. I'm just going to use sidepulls and cut on the fender so the center bolt of the calipers are somewhat submerged. 32c's will fit just fine, then. A good 1/4" clearance........which is good enough for me.

At some point, I'll be adding canti's to my 1970's Dawes Galaxy. Then, I'll have two rides capable of loaded touring (one in case a friend would like to come along......and, just having the fun of options) and the Lotus more or less relegated to light touring and sporting around. I'm half-stepping all them, too. Seems to be the logical thing, in my mind. I already have an understanding of gearing from my exposure to the Toyota 4x4 thing. Gear it low enough in logical enough steps and you make any vehicle a lot more capable of a variety of applications. Fun stuff, eh.:D

there was some inappropriate posting at the end of this thread. But the next guy that comes in here, acts clueless, and wants an easy way to install canti posts is probably going to get greeted with suspicion and guarded answers from practicing framebuilders. As you say, thook, the techniques and equipment needed are obvious to someone who is capable of doing the job.

There aren't a lot of people that read this forum that have any experience. I try to help people out, maybe I shouldn't. I am not going to give someone advice if there is any doubt in my mind that they might use that as license to hurt themselves.

As far as the negative reactions you see on various forums, that's probably due to the tone that you take. And tell your airplane welder friend that I can build airplanes just as well as he can because I replaced the main bearings in my Taurus.

FWIW, unterhausen, I think your responses were perfectly appropriate. I don't understand the point of Webb's post, nor of Deltron's. C'est la Vie.

Also, I've built frames, so I can replace the main bearings in a Taurus as well as you can. :lol:

Okay, I think your taking things a little far, unterhausen. But, whatever. We're obviously on the wrong foot of understanding one another. I don't live in your world and you don't live in mine. No reason we can't relax and find something to agree on.......stop the pointless back and forth already.

I do appreciate the tips. What I didn't mention in my last post was your idea did inspire the way in which I set things up. I've got two other frames I'd like canti's and this will work well. I get them set up and take them to my friend. I'll mention what you said, but he's one of those dead pan kinda people. Probably just light a cigarette and "hmph".

Anyway, and thanks for the tips on quality parts. Better price than the LBS could do.

Oh, and what's wrong with looking for an easy way if there is one? I split my firewood every winter with a handsplitter. If I had a hydraulic splitter (and, could afford one) I'd use that. So, I find the easiest way I can to get the job done. Wouldn't you?

I agree that it's basically a misunderstanding. At this point your feelings have been hurt (mine would have been too), and we're pretty much talking past each other. You're better off being as forthcoming as you can up front. In a forum like this where busy people with expertise may not check in every day, it's best to be a little patient. I think in the future I will refrain from answering a question where my best answer is "find a framebuilder." I think canti posts are the second most dangerous things a beginner can attempt, right after fork crowns.

Just to get this back on-topic, Henry James and Anvil both make very nice canti boss/brake bridge tools. I'm sure there are others. And you can check Alex Wetmore's site for a home-made version.

not going to read the rest of the posts, but pipe in here. When you use terms like "basic welder skills" it makes you sound a bit ignorant. First off, welding something like a brake boss is a silly options. You want to braze it, and pref with silver. Why would you want to take a presumably unstressed frame and add potentially hundreds of pounds of stress to it by welding on it at a very fragile point? Anyways, take it to someone that can do brass or silver cromo brazing at the least, this however should be harder to find than a local framebuilder. This is all said presuming this is a quality made and materialized frame, if it's something you got a walmart, by all means break out the torch and steel filler rod, get a plate with holes drill 80mm apart, bolt posts to that, carve posts for ss incidence , tack, release fixture, and weld. You will probably relieve it of stress!

Why do you say welding is a "silly" option, and why do you say silver is preferable?

I see nothing wrong with tig welding canti posts on a steel frame. Silver should only be used if it can build a fillet, which 56% is not capable of doing. I use brass. If I ever build a stainless frame with canti posts, I'll probably try to get the local framebuilder that tigs to do it for me.