Andrew R Stewart 

Why not just replace the bosses entirely, instead of trying to fit M8 nuts and then welding them in/on? Have you dry fitted the cantis you'll use with the wheel you'll use yet? The reason I ask this is that canti boss locations have evolved over the decades with Asian cantis pretty much taking over the market in the 1980s. It would be a shame to do the M8 work only to find later that the boss really should be slightly this way or that way to better allow a brake pad positioning WRT the rim in use. Andy

Krov9

I see what you mean, and I'm also aware that older cantis used to come with a different spacing.

I'm trying to avoid having to buy and braze on entirely new bosses since it would cost more and also damage the paint.

I was able to score a set of Mafac cantis, model Criterium I think, that should be both period correct and from the same country, so I'm hoping they won't require moving the bosses. On the other hand as far as I know Mafac used a post standard all of their own, so that might require some fiddling? Many open questions about compatibility here

Andrew R Stewart 

Were I to build a canti equiped frame (and I have, just rode my touring bike on an overnight camping tour) that was to be ridden (and not hung on the wall) I would want to take advantage of the 40+ years of canti designs and not be stuck to a canti that lacks adjustability or uses uncommon bosses. I include the Mafac cantis in my view of what is best just looked at. This is coming from someone who has ridden/serviced dozens and built with a few Mafac cantis.

As to paint damage- welding on M8 nuts will burn paint too. That you would be doing something very few others have done (none that I know of) likely means you'll be redoing some aspects of the project after starting. I suggest just choosing what you know will work, and likely use cantis that allow for slight positioning tolerances.

If you need some current design canti bosses PM me. Andy

Krov9

In order not to sideline and hijack this topic entirely, here's a link to a list of stuff that used M6 brake bosses: BrakeSTUFF - Bremsscheiben und Cantisockel für das Mountainbike: Cantisockel für V-Brake und U-Brakes

" M6[x1.0] → Magura (Durin, Quake, Ronin), RockShox Mag 21, Easton EC90X, Hooger Booger und Van Tuyl Marzocchi: Bomber Z1, Z3 (Canti-Pin BAM), Z3 Flylight 100, DH3

M6x0.75 → Marzocchi: Z1 Wedge, Z2 (Canti Pin M-Arch)"

Now to Andy's comment:

Thanks for the insight. Just to make sure, do you refer to the positioning of the bosses on the frame, or the pad in the brake arm?

I am a bit suprised to hear someone suggesting against Mafac cantis, because I've understood they are highly regarded for their era. I chose them because I scored a set for cheap, and they are period correct for my frame.

I don't know much about other cantis, except that the Shimano Altus ones and similar supposedly break their plastic spring covers because they are incorrectly designed as load bearing. On the other hand, I know someone who has a set of those on his 40's-50's french constructeur rando bike without the plastic spring covers, so I guess they can't be all that bad?

Which cantis would you suggest? Some might require replacing and -spacing of the bosses, but I've understood the said Altus ones are among the few of modern offerings that work with pre-80's stud spacing...

Andrew R Stewart 

"do you refer to the positioning of the bosses on the frame, or the pad in the brake arm"

Pad on arm. Most modern cantis have a vertical slot to better position the pad WRT the rim. The smooth pad post allows in and outward adjustment already.

I know I am bucking the fashion of thinking retro/classic stuff is better than current stuff. In real use this is usually not the case. I am a simi active member of the Classic Rendezvous Google group and there classic stuff is the goal and all that is allowed to be talked about (we also require one's name and location on each post, so refreshing to know who you are talking with). For a collector keeping the components "on topic" (as CR people refer to this) is very important. But for a rider I have zero need to suffer with the poor performance the classic parts have, compared to more modern stuff.

I still ride steel frames, cable operated controls and tube type tires but also run Speedplays, Ergo controls with 9 cog systems and either modern dual pivot side pulls or Shimano BR-MT62 cantis (my personal favorite series).

As to what canti works best with which boss spacings? There's more to the set up than the boss c-c dimension that wants to be right. The rim/boss dimensions, from the axle is also real important and the rim width is directly a part of that boss c-c dimension too. A friend has a mid1980s Bridgestone (and we all know the cult status this brand has these days) that has very different boss c-c dimensions between the front and the rear brakes. The fronts have aprox 70mm of c-c and the rears closer to 80mm. It takes two different brands/types of cantis to have better performance than the really short armed Dia Comps that were stock. It took quite a few dry fittings to end up with this combo, IIRC I tried 6 or 7 different models of cantis to find this out. Andy

Krov9

I see what you mean. Here on BF I'm mostly lurking the C&V section. I think it's not entirely false to say that lots of mid tier stuff, at least, was made better than now back in the day. Components were more robust and aside of Simplex, Modolo etc. often feature less plastics that would turn fragile over time.

For me, older technology is what I can afford, because it's easy to thrift. Many parts I can usually fix myself with simple tools. I'm now building up an older steel frame with a 7 speed cassette with a 34t large cog, SunTour V GT Luxe RD & Vx FD with SunTour PowerRatchet shift levers.

I could have gone with Shimano Altus or Tourney (ones with the huge pulley) with some thumb shifters for even more range and gotten indexing for the same price, but I chose the retro approach for reasons a great deal of which were undeniably aesthetic. We'll see if I'll end up modernizing in the long run.

I was first considering Weinmann centerpulls for brakes, because I find them efficient, easy to adjust and having great modulation, but then I found the placing of the stud bosses was intended for cantis.

Just curious, what combination did your friends' Bridgestone end up with?

Andrew R Stewart 

The XO-1 got one Tektro 720, in the rear IIRC. My notes don't list the other brake. It turns out I did this for him about 9 years ago.

I do agree with your point about material grades being better, or at least w/ less plastics (Simplex excepted). During the later 1970s and on I noticed greater chain and tooth wear on many Asian equipped bikes than I remembered for those that were 1970s bikes with Euro parts. I concluded this was because of three factors. First was that teeth and chain contact surfaces got less as more gears got crammed into the same apace, so stuff became thinner. Second and less understood is to make the cogs and rings with stamped features (Twist tooth, W cut, shift gates, ramps and now pins) in the volume that low cost bikes need softer materials were used for all but the top levels. These softer steels and alloys just wear at a faster rate, all else being equal.

I am also a fan of Weinmann 999 (610 or 750) calipers. When I built up my 1975 Fuji Finest I chose the 610s over the Asian copies (Dia Comp). This bike shows how I choose to balance the OEM/classic/on topic against having a rider. I retained the sew ups but used a pair of Ukai non foam filled rims that had double eyeletted spoke holes. Modern Aero brake levers buy SunTour bar ends (non indexed). I run a 13-32 7 cog SACHS fw with a Mighty Comp 47/42 ring crank. Rear der is a SunTour XC LTD, front is a Cyclone. Concor Light saddle with Speedplay Xs. One can see I tried to keep to the basic theme of the era's technology but with rider contact points exceptions and use what I had on hand. Ironic that I have only ridden it a few times over the 8 or so years I've had it. Andy

Krov9

Interesting to hear your thoughts! I agree with much of what you said.

Btw. I was finally able to identify what ever weird bosses were on my frame - never seen anything similar

Turns out they're MAFAC "Jacky" bosses!
https://www.flickr.com/photos/431553...57677101234090

https://flic.kr/p/ZXXz4K

Andrew R Stewart 

Mafac Jacky- I have heard of them and now remember they were a "kids" version of their cantis (according to another forum's discussions). But I had not seen their boss and bolt design and had thought they would use the same full boss that the more common typed did. The bolt with the "post" section is what many call a shoulder bolt, quite common in industrial machines. Andy

boneshaker78

This was an interesting learning experience for me. I can’t express enough how much I love this community and the help everyone provides for me. I’m a hands on learner, I have difficulty with abstract concepts and comprehension. Once I can get my hands on something and experience mechanics in my own way I learn quite a bit. I realized after reading through this again that Grumpus had suggested that the bosses were cut off from the start, I missed it, thank you for your help Grumpus. A special thank you to Andrew Stewart… you’re a wealth of knowledge and a very important contributor to the forum.

I finally got around to finishing up the Jamis and thought I’d share some pics. The brake boss solution worked flawlessly, not even a hint of brake squeal and the stopping power was more than adequate. I took my time, researched the issue thoroughly with the help of this forum and couldn’t be happier with the results. I was fearful of attempting to fix this issue, but once I got going at it and put the pieces together, I realized it wasn’t too much to handle. I get a great sense of accomplishment when learning new things about bikes, it helps me with my self-esteem and allows me to be more self-sufficient. Thank you to everyone here… this community is an invaluable resource.

masi61

I’’m pretty sure that my Trek Multitrack frame cantilever bosses take an M6 x 1.0 bolt. I have a problem with trying to tension the canti spring on my SunTour “XC” cantilevers that I want to use (these are not XC Pro, just XC). The stud is too long! This caliper has a strange design where a tension nut located in the rear is snugged up against the back of the caliper to preload the spring tension. On mine, since the stud is too long, the M6 bolt and the backing nut are both tightened down all the way and there is still play in the caliper arm and insufficient spring tension. I had considered grinding the post down some since these posts are not the swappable type. But I don’t want to damage these posts really and I figure someone must remember these SUNTour XC cantilever calipers and their odd mounting procedure. Thanks for any help to get my project back from being mothballed.