# Chain stays. Argh - what stock tubing to use if not using a standard offering?



## yomattyo (Dec 20, 2007)

Hey all,

Been lurking for a while. 2 years ago I started pursuing this dream of building some bikes, but due to some crazy life circumstances had to put it on the shelf for a while. Anyway - I'm back to it. 

I'm in the process of drawing up my first frame. I'm going for an All-mountain style 29er, with more aggressive geometry than the a traditional 29er XC frame. It's the style of frame I was planning on purchasing next, so figure it'd be a good choice to just build it instead.

I'm having some struggles with the integration around the crank/BB mainly with chainring clearance. I want to keep clearance for at least a 2.3 rear tire, but have some pretty short stays drawn in (420mm). I'm designing around a 1x11 crankset with a max 36 tooth chain ring (dims pulled from SRAMs GX specs). I'm also using the paragon poly dropout setup as i want to have a 142 x 12 rear end with a 140mm disc brake.

My question comes down to the fact that given this geometry and hopes, I can't seem to make a standard true temper or nova chainstay tube fit, while maintaining the clearance I need, and keeping the weld area for the drop outs on the correct portion of the tube. I've also looked at chopping the front off a standard tube to weld to a machined "yoke" that connects to the BB, but then its a really weird portion of the tube.

All that being said - is there a standard non butted tube out there you'd recommend for building my own custom stays that need to fit between to machined elements (dropouts and a yoke piece to the bb)? I'm going to need to put a pretty decent S-curve in it to maintain clearance to the Chainring, Crank arm, and then hook back out to the poly drop. 

I attached a few pics of the current design that shows my initial ideas/thoughts with a modified True Temper Stay, but i don't have enough clearance for the Crank arm, and I don't really like the shape of the yoke piece as its currently shown. The poly drops also extend really far forward as well, which make the bend issue even worse, I'm thinking that if I want to keep the clearance and geometry, I might have to look for a different drop out solution that doesn't force the chainstay attachment so far forward.

Thoughts and ideas are much appreciated!

P.S. i know the ST/DT/BB junction looks a little wonky in the pics - I intend to put a gusset of sorts to back that joint of the seat tube up, or potentially put a bend in the tube. I just need the ST moved further forward for the tire clearance.


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## afwalker (Apr 26, 2012)

Well if the [URL=http://www.cycle-frames.com/bicycle-frame-tubing/NOVA-MTB-29R-S-BEND-24mm-OVAL-x-450mm-NOV_COCS_SBND_29R.html]NOVA MTB 29W S-BEND 25.4mm OVAL x 450mm :: S-BEND :: MTB CHAINSTAYS :: CHAINSTAYS :: TUBES STEEL :: Nova Cycles Supply Inc. and the Deda 29r+ http://www.bringheli.com/PDF/DEDACCIAIsteel.pdf won't fit, then bend it!
Even just the Harbor Freight bender will work, fill with sand, go slowly a bit at a time and sneak up on it. Compact Bender
andy walker


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## wizzer16 (Sep 9, 2010)

A few things.

I love the 1x11. I am sold entirely for anything other than a touring rig. With that in mind, a 36 tooth chainring would require either flatter ground or stronger legs than I have got. Are you sure you need to go so big?

Have you thought about embracing the boost 148 spacing? 6mm added between flanges which can give tire clearance (think 27.5+) as well as a boost crank which has an extra 3mm on the chain line.

I like using tube wherever possible. Aesthetically it suites me more than a plate.


Just a few things to consider as you plan it out. Good luck.


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## yomattyo (Dec 20, 2007)

Thanks for the inputs! I'm gonna check out that first tube option you posted Andy, I hadn't seen that one. I assumed I'll be figuring out some sort of tube bender, be it that HF option, or something else.

Based on the specs - 25.4mm 33.5/15 Oval Profile x 0.9mm/0.6mm wall thickness x 450mm

That's referring to a 33.5 x 15 mm Oval at the BB side, but what does that go down to? Also trying to get a good idea of the dimensions to each bend and each bend angle. Also, it has a .9/.6 wall listing, but I can't quite tell where the butt lengths are. Using the paragon drops, i'm going to have to cut off a good portion of the back end of the stay, is that okay to do and still weld on?

One of the reasons i went to the TT tubes is that henry james has a spec sheet drawing for each one, so it makes it really easy for me to draw them up in my model - anyone know if Nova offers that?

I wonder if going to a more traditional dropout like these would be a better option: MODULAR 142/12 DROPOUT IN STEEL-RockShox MAXLE SPEC :: MTB DROPOUTS :: STEEL DROPOUTS :: DROPOUTS :: Nova Cycles Supply Inc.

Anyone else out there have any input on the poly drops?

BTW - I plan on this being a Tig Welded frame FWIW.


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## yomattyo (Dec 20, 2007)

I actually did go back down to 34.... I currently run a 32 on my 1x10 setup, and just wanted to make sure I had a little room later if I decided to go up with it.

I'm just learning about the boost spacing. I think it was just a bit out of my comfort zone mainly due to requiring specific hubs and being a little less "compatible" with the more common standards. But, it might make sense to do if I'm building this out specifically how I want and plan to do it. I'll def look into it!



wizzer16 said:


> A few things.
> 
> I love the 1x11. I am sold entirely for anything other than a touring rig. With that in mind, a 36 tooth chainring would require either flatter ground or stronger legs than I have got. Are you sure you need to go so big?
> 
> ...


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## dr.welby (Jan 6, 2004)

Another approach is to press the stay into a better shape. It will crimp the stay narrower and increase the bend angle. It doesn't take any fancy tooling.

New and improved chainstay dimpler by Kelpie Cycles, on Flickr


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## yomattyo (Dec 20, 2007)

Yeah, thats a good point. I actually have a second model that has a dimple in the chainstay, but wasn't sure how much is "allowed" before you compromise that tube too much - any thoughts?


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## shirk (Mar 24, 2004)

https://instagram.com/mattercycles/

Check out Collin's solutions. 5mm plate for a yoke with the long low mount dropouts and likely straight gauge for the chainstays. Go back a few weeks to see better shots of the yoke.

That should give you some inspiration on how to get it done.


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## yomattyo (Dec 20, 2007)

What/where do you guys recommend for straight gauge tubing for stays?


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## shirk (Mar 24, 2004)

Aircraft Spruce.

http://forums.mtbr.com/frame-building/round-mtb-stays-758875.html

Search function has some great previous discussions on round stock for stays.


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## G-reg (Jan 12, 2004)

83mm bb and a "boost" rear hub would be a nice mix with big wheels and short chainstays. Been looking at exactly that for a "play-bike."


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## briderdt (Dec 14, 2012)

I've used both 1"x and 7/8"x.035 for road chainstays recently. Not as much manipulation needed to clear 25mm tires, though.


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## Feldybikes (Feb 17, 2004)

yomattyo said:


> ...it has a .9/.6 wall listing, but I can't quite tell where the butt lengths are. Using the paragon drops, i'm going to have to cut off a good portion of the back end of the stay, is that okay to do and still weld on?


Generally, the thickness for butted stays that's quoted is the thickness the tube started out with when it was still a straight tube. When the thin end is swagged down, the wall thickness goes up. In the end, what's listed as 0.6 actually ends up thicker than then 0.9 side because the O.D. is reduced so much. It *probably* never gets thiner than 0.9, at least not that Nova tube, but if it did, it would likely be right in the middle of the tube and you'd be doing something really weird (like cutting all the way past on the of the bends) if you ever got close to it.


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## yomattyo (Dec 20, 2007)

Thanks everyone for your responses - been out of town with fam on vacation for the last week so haven't had a chance to check back in. I'll checkout the offerings from Spruce and play with the round tube shapes for the stays and keep you guys posted!

I need to play with/get more familiar with bike CAD I think to help layout the rear triangle.


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