Thursday, October 24, 2013

29+ thoughts for the bored and/or curious

I built Gal a 29+ (ie, Knard tire compatible) frame and fork this week and I'd thought I'd share some thoughts. Keep in mind:
1) I have only limited time myself on this tire (on a Surly, natch) on dirt.
2) This is the first one I've built (though I've built lots of 26" fatbikes which have some of the same issues)
3) I had to re-do like 4 things because lots of things about these tires aren't intuitive if you spend a lot of time doing skinnier (ie conventional mountain bikes) or fatter (full fatbikes) frames.

Damn you, photobombing leaf.


Here's my take:

-If you want a 73mm BB shell and conventional drivetrain, your lower limit for chainstay length is around 45cm, just like the Krampus. Surly has basically squeezed all the tire into the space that you can at that length, there's not much you can do trick-wise to go shorter. I only mention this because it's the first question everyone will ask me.

-If you throw the "conventional drivetrain" part out the window by either using a wider shell (83mm or 100mm would both work here) or offset rear hub/wide chainline, you can get down to about 43.5cm (which is what Gal's frame is). If you really go crazy, the tires are 390mm radius so I guess in theory you could do 42cm and have 10mm of space at the BB shell but it would require a 100mm BB and super wide chainline.

-Big tires are not the same as suspension. They do great on small obstacles and low speeds. The faster you go and the bigger the stuff you hit, the more the lack of damping will hurt you. That's my experience, anyway - YMMV. As as aside, it's "damping", not "dampening". Your suspension doesn't need to be moisturized.

-Toe overlap may be a problem for you even if you have never had it on any other 29er. There's basically 20mm of extra tire sticking out in both directions from the hub so even folks in the 6 foot/average American male range will have to keep toe overlap in mind.

-If you're worried about cutting the sidewalls of your tires, use the 27 tpi Knards. The 120tpi are way thinner, scary thin, even.

-If you mainly want to ride on snow, just go 26xhuge. The Knards are in no way competitive with really fat tires on snow.

-The Knard will (sort of, warranty violation, blah blah blah) fit in some suspension forks so unless you have handlebar height problems with a long fork it's nice to do a suspension corrected frame in the event that you get old and fragile like me and want some cush. The shortest fork I can easily build (rigid fork, that is) will be around 43cm.

-Bikes are fun, I loved building this bike even though I wanted to punch myself in the face a couple of times because I messed up easy things, and I think my 2014 bike (Sarah and I have an agreement: I can build myself 1 bike a year) will be at least Knard-front capable if not front/rear.


Hassan said...

I resent your 6ft, average American comment. I am not an elf!

Chris said...

Hey Walt,

Any thoughts on a 29+ FS??

Walt said...

29+ FS? Doable, sure. Desireable? I'd guess not really but opinions vary. I'd be excited to try a project like that, certainly, but it would have to be for the right rider.


Jackson said...

Any thoughts on running 29+ as a winter setup on a regular frame/fork?

Walt said...

If you have a frame/fork that will clear the tires, it sounds great. Not a lot of those out there, though.

Jackson said...

Well, you're building the frame sometimes this winter/spring, so that's doable. As for the fork, well... I'll have to do some research.