Monday, February 04, 2013

McCalla 4 - Done

Here's the frame, in a composition I call "still life with stool, tomato ladder, and super fun short chainstay long travel 29er"

For other posts on this frame, click here to read part 1, part 2, or part 3.

Now, geometry info and discussion/incoherent rambling:

-120mm travel front and rear. With a swap of rockers, you can get 140mm rear travel, and if you want to use a 2.25" stroke shock as well, you can get all the way up to about 160mm. I don't think McCalla will ever want that much. The frame will clear a 2.5" tire at 160mm travel/full bottom out, though, if it ever comes to that.
-69.5 head tube angle and 67.5cm front center. I did my best to talk him into going a little slacker but this is what we eventually settled on. Takes a tapered steerer fork, of course.
-73 degree (effective) seat tube angle, 49cm seat tube, 32" standover (yeah, pretty high)
-43cm (actual, 42.7cm effective) chainstay length and 13.3" BB height (unsprung). He's running 170 cranks and wanted a pretty low BB. I would normally probably go higher for a bike with this much travel, but like anything it's a matter of preference and making tradeoffs.
-110.2cm/43.4" wheelbase.
-For 1x (XX1 in this case) only. You could not fit a front derailleur on this bike, no way, no how. I could put a direct mount on it but the chainstays would hit the derailleur at full compression so there's really no point. But thanks to XX1, it's moot, because McCalla will have plenty of gear for anything he wants to ride.
-Tubing is a mix of straightgauge OX Platinum (seat tube), heat treated 4130 (head tube, downtube) and Supertherm (toptube). All the small bits (ie pivot mounts and such) are 4130. This bike is arguably pretty overbuilt but McCalla is one of only a handful of people I have ever met who rides as fast as I do on the downhills so I know it's going to get the snot beaten out of it. You could pretty easily take 150-200 grams off with lighter gauge tubing for a smaller rider or for XC/shorter travel applications (like I did with my own FS bike).
-Frame weight is 3000g even (but it doesn't have the powdercoat on yet, that'll add a little bit) including the shock and all the hardware.


Mike said...

Does snow hold air pollution down like rain? Honestly curious...

Feldy said...

I'm shocked that stool made it all the way to SLC.

Walt said...

That is the brother of the really crappy stool. The really crappy stool got thrown away. This one is only sort of crappy.

onlyontwo said...

Sounds like a hoot to ride. Just curious...On a 100-110mm bike, how short could you get those stays?

Can't wait to see it built...


Walt said...

Hey Only2 -

This is about the practical limit using the Ventana rear end/low single pivot design. I could imagine going shorter with a high single pivot but that's a completely different animal.

Keep in mind that 43cm is pretty normal for a 26" wheel FS bike.

If you really, really must go shorter, 41cm would be doable with a 650b rear wheel. I'd love to do one like that at some point.