Chainstays and tyre clearance - some newbie help please

[mayan42]

Frame number one is a lugged 'cross bike, which I'll use for winter roads, a bit of 'cross training but mostly a muddy commute down the canal.
The plan is to have clearance for 35mm cross tyres, so after fitting in the dropouts to the chainstays (bought as part of a kit from ceeway and pre-crimped) i measured up to check for clearance.

DSC_2633-web.jpg

The longer vertical pen mark to the right of the cable tie is the centre mark of the bb (cs length = 425mm c-c), the shorter pen mark to the left is the outside point of the lug. The distance between the outer lug points on the BB shell I measured to be 65mm, and I tightened the cable tie so the chainstays are at the distance they would be in the bb shell when I've cut them to length. Hope that makes sense!
Anway, the tyre is 35mm conti speed king (measured up at 34.5mm) and I'm getting about 1-2mm clearance each side -

DSC_2632-web.jpg

As I see it, my options are -
1) Live with it, dont ride in mud or stick with 30 - 32mm tyres.
2) Lengthen the chainstays...I tried messing with this and adding an extra 5mm or so to the chainstay doesnt give me much more than an extra 1mm each side.
3) Crimp the stays some more....bearing in mind this is my first build!!!

I'm leaning towards lengthening the chainstay by 0.5cm or more, bearing in mind that the dropouts are semi-horizontal -

DSC_2628-web.jpg

so I'm gonna need a far bit of room at the bb area to drop the wheel forward and out.
Any options I've missed? Any thoughts on how different the 425mm vs 430mm chainstays will be? (I'm guessing the ride difference will be pretty much negligble - there's probably gonna be so much other mis-alignment going on that the extra 5mm is the least of my worries !! )

thanks!

[progetto]

You can manipulate those suckers to suit, as Richard say's "show them who's boss".

[Will Outlaw]

If you're gonna dimple 'em, dimple 'em BEFORE you attach them into the BB. Ask me how I know this. :-)

(I did about 8 test dimples on some old chain stays I had, got a process I liked figured out then went ahead and dimpled the real things. The dimples were beautiful, the rear triangle alignment, which had been spot on, went all to hell. One of many lessons learned on #3.)

[Eric Estlund]

If you are using those drop outs, slide the wheel forward and reassess. Odds are you will run the wheel up front with a derailleur, but either way you want to make sure it drops out (and in) the frame.

Oval stays are also a nice way to get some room.

[mayan42]

Thanks,
So I guess there's really 2 options to modify the chainstays, the first is to try and continue the ovalisation a little further along the chainstay up towards the bottom bracket and the second to actually dimple with a indent running along the centre of the inside surface of the chainstay.
Any thoughts on which would be best / easiest / most likely to not ruin the tubes?

[echelon_john]

Look in some of the galleries for pictures of dimpling. In a nutshell, on a shoestring, get or make a tube block that fits the round section of the chainstay. Only use 1/2 of the block to support the outside of the chainstay, and make a piece of wood the size/shape of the dimple you want to press against the inside. Then go to your bench vise and go to town.

[Eric Estlund]

Any thoughts on which would be best / easiest / most likely to not ruin the tubes?

Not trying to bust on you, but if you want to make more of these things, don't worry about this bit. Assume you WILL mangle some tubing and the stays on to figuring this out. At this stage they are all just bits on the way to a bike frame.

[steve garro]

S-bends, man.
Also, why are the ends so close together?
Plus, you have the tire choked up into the round, not on the oval part - did you trim the small end?
- Garro.

[Rody]

Mayan...

My concern is similar to Steve's, before cutting either end, one must first have a systematic layout to determine the best use of the tubing for the application.

Here is a link to a post I did on a simple approach to laying out a rear end for a fellow builder, perhaps it will help you understand the process...

Groovy Cycleworks 330-988-0537: How to lay out a rear end...old school style

cheers,

rody

[mayan42]

Thanks for all the comments, no offence taken at any, all advice is welcome!! To answer a couple of querys....
The (bottom bracket) ends are so close together cos I havent cut them to length yet, the longer vertical mark on the chainstay you can see about an inch from the end is the c-c length of 425mm, so the ends wont be that close when trimmed - I estimate they'll end round about where the cable tie is in the piccy.
I cut less than 5mm off the dropout end to prep that end of the tube before cutting the slot for the dropout, the slot I cut is about 5mm deep.
And yep, I noticed the tyre sits beyond the ovalised section of the stays, hence me wondering if extending the ovalised section is an option.
Rody, thanks for the link, I did layout everything prior to cutting but I didnt draw it out....lesson learnt for number 2!!!

I think S-bends are beyond me at this stage, I think my best bet is a dimple in both stays, unless ovalising the tubes further up towards the bb is a realistic option?
again.....all comments are welcome, I really appreciate the input of you guys who know what you're doing (unlike me!!)

thanks

[mayan42]

OK,
with a bit of gentle persuasion, I squeezed the chainstays a little and ended up with this....

DSC_2638-web.jpg

which when compared to this...

DSC_2632-web.jpg

is quite an improvement.


I also noticed that the already ovalised section isnt quite in phase with the slot i cut in for the dropout, thus its not actually at its thinnest at that spot - lesson number 2 learnt - check the centre line and then check it again!!!

The photo dosent show it too well, but I think I have at least 4 or 5 mm either side, and I think if I run 32mm tyres then I should be OK for clearance.
My learning curve is pretty steep at the moment!!!

[echelon_john]

Nice. Brute force can be your friend; just make sure you're applying it in the right direction! ; )

It's amazing what you can accomplish when you start thinking less like a surgeon and more like a blacksmith.

OK,
with a bit of gentle persuasion, I squeezed the chainstays a little and ended up with this....

DSC_2638-web.jpg

which when compared to this...

DSC_2632-web.jpg

is quite an improvement.


I also noticed that the already ovalised section isnt quite in phase with the slot i cut in for the dropout, thus its not actually at its thinnest at that spot - lesson number 2 learnt - check the centre line and then check it again!!!

The photo dosent show it too well, but I think I have at least 4 or 5 mm either side, and I think if I run 32mm tyres then I should be OK for clearance.
My learning curve is pretty steep at the moment!!!

[mayan42]

It's amazing what you can accomplish when you start thinking less like a surgeon and more like a blacksmith.

+1
you're right, its defo easy to get stuck in the theoreticals.....

[prolix21]

s-bends are sexy

IMG_4474.jpg

[suhacycles]

FWIW, if you're using a lugged BB shell, I've found that Pacenti and Eisho chainstay socket spacing is wider than the others. I managed to get at least 3mm of clearance on each side with 430mm CS's, 135mm hub spacing and ROR CS's with no squeezing or denting using 35c Ritchey CX tires.