27.5 and 700c on the same frame

[JackT]

Saw this "Unbeaten Path" bike on the web just now:

http://www.bikerumor.com/2015/04/17/soc ... avel-bike/

Quite a lot interesting about it, but what interests me most is the idea of a single frame that'll work in two modes, depending on whether you use 27.5 wheels with fairly fat tyres (2.1) or something slimmer and more cross/touring (33mm on a 700c wheel). If the diameter of tyre plus wheel is about the same for each combination, then you have a very adaptable bike for off-road bikepacking and road touring or general tooling about.

Anyone else seen this elsewhere, or done it themselves? I am guessing the biggest challenge is the extra width required in the fork and stays to accommodate the 27.5 / 2.1 option.

Jack

[Bearbonesnorm]

I'm thinking the majority of 'off the shelf' rigid 29ers.

Mode 1 - 29" wheels with 2" or bigger off road tyres.

Mode 2 - 29" wheels with 28c - 38c cross / road / touring tyres.

Mode 3 - 650b wheels with 2.3" - 2.8" off road tyres.

[JackT]

I should have added that I see this as a drop bar bike.
And i think the differences between your mode 1 and mode 2 would be quite noticeable in terms of handling and geometry as that's a lot less wheel in there. I dunno, though, never tried it.

[Bearbonesnorm]

And i think the differences between your mode 1 and mode 2 would be quite noticeable in terms of handling and geometry as that's a lot less wheel in there. I dunno, though, never tried it.

Jack, I've tried running 38c cross tyres on my SS mountain bike and it was okay. You do lose a little ground clearance but nothing to upset it ... although I've never tried anything like 28c.

I should have added that I see this as a drop bar bike.

Mine's got drops on

[Gari]

I do like that, and am in the process of building a bike for the same usage. Trying to decide 700c or 650b, same widths as article. A few of my fave tyres are now available on 650 and I am just at the bottom of fitting a 29/700c comfortably. Bit pricey for me though.
I would probably get tired of the " off the beaten path" gags every time I fell off mind!!

[johnnystorm]

This mag has been full of that sort of thing for yonks!
http://www.bikequarterly.com

I should add not necessarily in fluro carbon...

[JackT]

I thought the BQ frowns on disc brakes - which is what makes it possible to swap out wheel sizes in a bike like this.

[johnnystorm]

I thought the BQ frowns on disc brakes - which is what makes it possible to swap out wheel sizes in a bike like this.

Yeah, you're probably right. No shortage of 650b you're, no wait overland....erm....Rough road bikes.

[JackT]

Thinking about it, a drop bar rigid 27.5 MTB with disc brakes would probably fit the bill, if the assumption that diameter of the wheel + tyre is about the same as a 700c with 30mm isn tyres is correct. The market doesn't seem exactly flooded with those at the minute.

[Fat tyre kicker]

I'm in the process of just finishing a 700c wheel set on 135/170 hubs
For my Mukluk,I'll be running 700x 38 tyres....some may wonder why
But it's to give me touring/towpath capability on one hand and winter
fat bike ability on the other....I'd love a different bike for each but this
Allows me to spec one frame much higher/set up well for me

[johnnystorm]

I'm in the process of just finishing a 700c wheel set on 135/170 hubs
For my Mukluk,I'll be running 700x 38 tyres....some may wonder why
But it's to give me touring/towpath capability on one hand and winter
fat bike ability on the other....I'd love a different bike for each but this
Allows me to spec one frame much higher/set up well for me

Yep. I've got the fat-not fat set for my fatty.Two weeks ago I took wee nipper off road and along the beach on 26x4 and last weekend fitted the halo twin rails and we did a road ride instead.

[jameso]

Anyone else seen this elsewhere, or done it themselves?

Been riding a bike like this for a while now, mainly on 650B but it's had the wheels from my Arkose (700x28 to 40C) on it also. The idea of wheel-swaps works out ok but there's more than outside diameter affecting things, the larger volume 650B tyres feel quite different to the 700Cs and throw some luggage into the mix and it can be tricky to get good steering handling. On my 3rd frame and fork combo and getting close to what I think it should be for the 650Bs. Also arrived at the conclusion that there's not much point putting really big tyres on a CX-type bike, it loses a lot of that faster road bike feel and still can't handle the downhills in the way that a nice light 29er can. It's really comfy over long rolling dirt-road routes though. I prefer the 35-40C CX wheels in the mud.

Last weekend along the Ridgeway
WP_20150418_032 by james*o, on Flickr

[JackT]

Interesting jameso, is that a production frame or a secret squirrel prototype? While you're there I did email you a little while ago about coming onto The Bike Show podcast (that I present) to talk about adventure road, innovation in design. but no reply.

[jameso]

Hi Jack (link made!) - I replied but was in Taiwan so maybe it didn't go through? Just re-sent it now .. sorry about that. It's an experiment bike, not sure where it's headed tbh, I just wanted to try something along those lines with slightly different geometry that's more biased towards the 650B tyres. I think any minor handling negatives of a bigger, lower pressure tyre are only really noticed on tarmac though, off-road it mostly dissapears among trail chatter and all that stuff.