# brazing fastback seat stays to the side of the seat tube



## Meriwether (Jul 26, 2007)

I did a search but couldn't find this covered. I probably just don't know what it's officially called. I know this isn't used a lot with MTB's anymore but am wanting to braze straight seat stays to the seat tube like you see on a road or cross frame. Here's a pic of my IF Planet Cross frame to see what I'm talking about.







What is the best way to do this? I tried it once already and had some "issues". The frames I see with these types of seat stays have very little fillet around the top of the stay and with a seat stay cap such as the one below...you apparently don't need that much? Do people tack ST/SS first then the SS/slotted dropouts 2nd? Is there any pinning involved with the capped stays like the below? 







thanks for any advice...

Whit


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## rbemiss (Nov 19, 2008)

in my world... using home made seat stay caps like you are showing or the occational slug type top i would brass braze s.s caps/ tops on. then slot to drops. then i would pin to rear drop and to seat tube and use silver from wade to braze s.s top to seat tube to achieve a nice silver fillet around that area where there isn't alot of material thickness to keep temps low and be as close to bomb proof as i can get. hope this makes sense... good luck


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## GrayJay (May 16, 2011)

The old Paterek manual contains a lot of good info on capped seatstay construction that would be usefull; download it from here; 
The NEW Paterek Manual


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## Feldybikes (Feb 17, 2004)

FWIW, I think brazing to the side and fastback are two contradictory concepts. Though I could be wrong here. The IF pictures is like a hybrid where only half of the stay is mitered to the 

Terminology aside, I've done this once. It was the first frame for which I build a normal rear triangle (priors were a full suspension and rebuilding a front triangle). I brazed onto the bike, then put on the cap. That was a big mistake. Would be much easier to do that cap first. But I think you already knew that. If I were to do it again. I'd braze on the cap, slot, then clamp/tape/whatever the stays in place (I'm sure pinning would be fine if you're into that), and braze everything up using brass. I can't say silver is a bad decision -- it might even be better -- it's just that I personally would be more comfortable with brass.

And, yeah, *apparently* you don't need that big of a fillet, but it sorta freaks me out, too.


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## Meriwether (Jul 26, 2007)

Feldybikes said:


> FWIW, I think brazing to the side and fastback are two contradictory concepts. Though I could be wrong here. The IF pictures is like a hybrid where only half of the stay is mitered to the
> 
> Terminology aside, I've done this once. It was the first frame for which I build a normal rear triangle (priors were a full suspension and rebuilding a front triangle). I brazed onto the bike, then put on the cap. That was a big mistake. Would be much easier to do that cap first. But I think you already knew that. If I were to do it again. I'd braze on the cap, slot, then clamp/tape/whatever the stays in place (I'm sure pinning would be fine if you're into that), and braze everything up using brass. I can't say silver is a bad decision -- it might even be better -- it's just that I personally would be more comfortable with brass.
> 
> And, yeah, *apparently* you don't need that big of a fillet, but it sorta freaks me out, too.


Thanks for the great responses.

I'm never using the term "fastback" again for these types of stays after spending WAY too long filing last night! I also managed to skewer my fingers a few times on the points which was awesome. There's nothing fast about their fabrication (for me at least). Nice not to have to bend them since I don't need more tire clearance but I'd say harder to miter by hand. I brazed on some caps and plan to brass braze them to the seat tube. I just can't imagine making enough of a fillet with the silver I have. Maybe it's best done with the Cycle Design wire but I don't have any.

I'm not comfortable pinning, never done it, so the toe-strap holding them to the side I hope will do the trick. But the last time I tried a similar thing, one of the stays migrated up the seat tube a bit while brazing and made the rear wheel sit a bit crooked. Any advice on pinning?

I see that Yipsan makes some sweet side-mounted seat stay MTB frames (if they're not fastback, what are they called?). You out there Yipsan?


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## Live Wire (Aug 27, 2007)

Check out ByStickel for a cool sidetack/fastback/wishbone(sort of) seatstay attachment.

"I'm not comfortable pinning, never done it, so the toe-strap holding them to the side I hope will do the trick."
File a groove/divot in each side of the st- it will hold the stays in place better and give you more surface area for a stronger connection.


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## Feldybikes (Feb 17, 2004)

Meriwether said:


> ...I also managed to skewer my fingers a few times on the points which was awesome....


HA! ( the prose, not he injury)



Live Wire said:


> File a groove/divot in each side of the st- it will hold the stays in place better and give you more surface area for a stronger connection.


I like it.


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## Meriwether (Jul 26, 2007)

*done!*

I finished the seat stays and it came out pretty good. I added a bit more brass up there than I needed to but it's definitely a solid connection. It was difficult (for me) to get the fillet close but not touching the TT/ST weld. 
I followed much of the advice given -- after hand mitering, I brazed the caps on, notched the seat tube where the stays were going to go (harder than it seems), used brass but I may have to try some Fillet Pro next time for this type job. I tacked the SS/ST in frame fixture the first, then at the dropouts (slotted), and took out of the fixture to finish brazing. I didn't get any SS creep even without pinning which was great so the rear alignment stayed put. thanks again for all the help!


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