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Old 06-26-10, 02:27 AM   #1
imi
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Same frame, 700c AND 26" wheels?

Hi!

Is my thinking way off here?

I'll be ordering a custom frame (≈58cm) later this year. The basic build would be the same as my present (old) bike, fine for paved touring in europe, the USA, Oz etc where I'll probably be for the most part in the future
  • 700c wheels on 135mm XT hubs
  • dual pivot caliper brakes
  • max 32mm tires
  • no fenders
  • threaded headset
Well so I got to thinking (always a risky moment)... why not get the frame set up for Asia, Africa, S. America AS WELL?!!!
  • 26" wheels
  • cantilever brakes
  • wider tires
  • fenders

This would mean:
  • cantilever bosses lower on the fork and seat stays
  • wide fork crown and chainstay
To make the transition would mean changing:

wheels
brakes and brake levers
...and putting on fenders

all in all, shippable amounts of stuff if I wanted to swap in mid (round-the-world) tour.

With a threaded-to-threadless stem adapter it would be easier to change set ups (maybe even two ready-to-go handlebars)

So... anything I'm missing? Is this silly trying to make a "jack-of-all-trades"? - or pure genius?

Thanks for any input

p.s I guess if I got 132.5mm rear spacing I could even put 130mm wheels with 23mm tires on for randonneuring when at home

Last edited by imi; 06-26-10 at 03:50 AM.
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Old 06-26-10, 10:31 AM   #2
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People sometimes have this idea when they get a 700C or 29er disk brake bike, and realize that there's technically nothing stopping them from using a 26" wheel on there. But apparently it's not without its complications: A bike is made with a given geometry assuming the wheels will be a certain size. If you put 26" wheels on a bike made for 700C then this will lower the bottom bracket, which will probably cause strike issues with the pedals (especially cornering or approaching curbs etc). The handling may also be negatively impacted in ways that are hard to predict. Then there's fenders - they will end up very far away from your 26" tires, if the bike is made for 700C.

When I asked Salsa about putting 700C tires on my 29er Fargo, for example, they advised against using anything much smaller than 50mm, since it would apparently change the ride. So that's not even 26" - just smaller 700C tires! There are obviously issues there. Framebuilding geometry is a very subtle business, small changes can have big impacts. So you can try it, but it's not a slam dunk with no consequences... why don't you talk to the custom builder you're going with, I'm sure they will be able to fill you in on what the potential problems would be. Possibly an ace framebuilder could design a bike that would work from scratch with either wheel size, but I think what you'd end up with is a bike that isn't really optimized for either. Jack of all trades, master of none syndrome. I'd say it's better to just build a 26" expedition tourer, if this is a "round the world" type bike - do it right for that wheel size, and be done with it.

Neil
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Old 06-26-10, 11:14 AM   #3
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Thank you for your insights Neil! The BB issue crossed my mind after I'd posted this... something I'll definitely consider when I get to the UK to get fitted and discuss the build. Fenders not so important to me, but handling would be...

In the first instance I'm going for a 700c bike... the 26" idea is more for a somewhat more distant future, but by then I may well go for a fully fledged expedition bike...

Anyone one know how Surly have solved these issues with the LHT in larger sizes for both 700c or 26" wheels... same frame dimensions or different?

Last edited by imi; 06-26-10 at 11:20 AM.
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Old 06-26-10, 06:29 PM   #4
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better to pick one size. if you try to do both, neither one will be great... it would be a shame for a custom.
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Old 06-26-10, 08:15 PM   #5
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If it has a high enough BB, I would just get disc break mounts on the frame and fork and use those. Seems like it'd be easier to switch between the two and make a cleaner-looking frame.
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Old 06-27-10, 06:25 AM   #6
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The larger Surly LHT frames are for 26 inch or 700c wheels, the frames are not designed to allow both sizes of wheels. Their website lists geometry, you can check the numbers there.

After a couple hundred miles on gravel last summer with my 700cX37mm tires while touring with a friend who had 26X2.1 tires on his mountain bike, I decided that I needed wider tires. I tried some 42mm wide tires and had fender mount rubbing problems. With different fenders, I might have been able to keep the 42mm tires but I think that would have been my upper limit for tire width and I wanted wider than that.

Thus, I concluded that I needed a touring bike with 26 inch wheels. I could have gone with a 29er but decided to stick with the more common 26 inch for wider variety of tires. I now have a 700c LHT and a recently built Thorn Sherpa with 26 inch wheels. Regarding handlebars and other components, I use drop bars on both, same combination of gearing on both (road crank and mountain 8 speed rear), etc. The only significant difference in equipment is the wider rims, tires and fenders on the 26 inch bike.

If I could only have one touring bike it would be a 26 inch wheel bike. You can use wide tires for off pavement with that and also narrower tires (26X1.5) at higher pressure for pavement.

I am going to keep both bikes, the LHT for paved touring and the Sherpa for non-paved touring since I already have both. But, if the 700c bike was stolen, I don't think that I would replace it. Instead I would buy some narrower tires for the 26 inch bike.

Last edited by LHT in Madison; 06-27-10 at 06:28 AM. Reason: correction
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Old 06-27-10, 08:20 AM   #7
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If you use fat enough 26" tires and skinny enough 700c tires, the outer diameter is not that different. I'd say it could be done without fubaring the geometry too bad. Worth asking your framebuilder at least, instead of a bunch of yahoos on the internet that pretend to know about bike geometry.
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Old 06-27-10, 08:55 AM   #8
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hihi, I like your attitude jtgotsjets but thanks everyone for your comments... I'll see what the framebuilder says about this... in the end the only difference would be where the cantilever bosses would be on the frame...

uh what kind of word is "fubaring"... though I get your meaning
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Old 06-27-10, 08:56 AM   #9
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hihi I googled it... go wash your mouth out with soap young man!
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Old 06-27-10, 09:10 AM   #10
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Quote:
Originally Posted by imi View Post
in the end the only difference would be where the cantilever bosses would be on the frame...
I've actually often wondered if there was a place you could put your canti-posts such that you could use cantis for 700c (or maybe 27") wheels and U-brakes for 26" wheels. This might be veering too hard into the world of "what's the point?," but I thought it could be cool.
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Old 06-27-10, 10:11 AM   #11
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interesting thought... *scratches head* anyone know?
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Old 06-27-10, 12:00 PM   #12
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here's the thing: you're not the first to think of this idea. So look around and see how many real world examples of a touring bike for the two different wheel sizes you can find...

bueller?
bueller?

...crickets...

there is a reason these don't widely exist, and it aint that no-one has ever thought of it before now. But if you really want to go this route, find someone (if possible) who has actually made at least a few of them and talk to them about it. I htink Chas roberts in the UK would be a great place to start... they make amazing touring bikes, both 700c and expedition style 26- and they really know their stuff. they could give you a very informed opinion about why this might or might not be a good idea. Also, the U brake idea, if even possible, is a bad one... U brakes, aside from being very tough to find dont work particularly well, and (usually) have crappy mud clearance. youd be best off with disks, really, or two sets of canti-bosses (front of fork, back of fork, chainstay and seatstay) with one pair for each size.

Pay someone enough money and they'll make you whatever you ask for... that doesnt necessarily mean it will be a good design. I would be interested in what you end up with, but if I were spending my hard-earned, I would pick one (26")
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Old 06-27-10, 12:37 PM   #13
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I hear you positron... it was just an idea, that I threw out here, as I hadn't heard of it before (probably because it isn't such a good idea)... no sweat

oh and thanks for pointing me in the direction of Chas Roberts! I'd never heard of them... checked their website out and see that they're based in the town where I grew up!

Last edited by imi; 06-27-10 at 12:51 PM.
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