Monday, December 17, 2012

And that's probably the limit... Absurdium pt. 3

Couple shots of the new silly project (yes, it's for me). This is a pretty small tire (just what I had sitting around, it's a Specialized something or other 2.0") and it's only got 15mm of space to the bottom bracket shell. Note the generous side knob clearance - this sucker can't go any shorter without running into trouble with bigger (ie 2.3+) tires and clearance to the bottom bracket shell - because it has 400mm (that's 15.7" for the metric-challenged) chainstays. Heck, the effective (ie level with the ground) chainstays are 39.4cm/15.5"!

Gadzooks, you say, why? Well, because I'm a silly, silly person and I want to see how it'll ride. I was dubious about the original , but I ended up loving why not keep pushing the envelope? I love experimenting on myself, hence the various curved tubes, prototype dropouts (there will be more about those once I get the go-ahead from the manufacturer), offset rear end, etc, etc.

Geometry numbers for the curious folks:
-29" wheels, of course
-69 HTA, 97mm trail, 65.8cm front center
-73 effective seat tube angle
-59cm/23.2" effective toptube
-42.3" wheelbase. Yikes.
-For a 100mm tapered steerer fork
-305mm/12" BB height
-40cm/15.7" actual and 39.4cm/15.5" effective chainstays
-5mm offset rear end (requires a custom zero-dish geared rear wheel and 56mm outboard chainline), standard 73mm english shell
-Clearance for a 2.4" tire (but not a Knard, sorry)
-1x only - no front derailleurs allowed
-My usual long head tube and seat tube
-Way more curves than are necessary
-4.4#, give or take a few grams.


greg said...

just commit and do a 83mm shell and buzz the bb with a 2.4...

Walt said...

Well, a 2.4 is going to be quite a bit less than 10mm from the shell as it is, which in my book is pretty much "buzzing" anyway. So no, I don't think I'll do any shorter (cutout BB shell?)

Anonymous said...

How's the shifting? Can you use SRAM 1x11?

Walt said...

The shifting will probably be mediocre - chainline is great but the stays are so short that on the high/low gears the chain angle is going to be gnarly. Might end up being a situation where you can run 8 or 9 of 10 cogs on a 10 speed cassette.

SRAM 1x11 will not work on this frame, unfortunately, unless someone starts making an aftermarket chainring that will fit on a 104 bcd crank.

Dan Yoo said...

very interested in how this rides, i love short stays

Walt said...

Hi Dan -

I am guessing the ride will be very similar to my older shortish stay frame (links in the post). I loved that bike, I'm guessing I will love this one - if the trails ever dry out here!

Chris LaSalle said...

Is that a 29.8 seat tube with the lugged collar?

Anonymous said...

What are those chainstays and are you doing any extra shaping to them or do they come like that?

Walt said...

Chris -

It's for a 27.2 post. 31.8 OD on the collar. So pretty thick up top but I like it that way.

Anon -

They are a new Deda "29er s-bend" chainstay that came out recently. Call Bringheli and ask him about them if you're curious - not sure of the part number off the top of my head. I did some dimpling and added a little more bend but it's not major. Minor axis is probably still in the ~13mm range at it's thinnest. We'll see how that does for stiffness.

Chris LaSalle said...

I like that better than the curved 31.8 tube with the internal shim. Maybe for the next bike...

Walt said...

Chris -

This seat tube is probably not meant to be curved (it's .6mm in the center section) so I would probably not offer it to customers like this. From a mechanical/strength standpoint yours is much, much better.


Meriwether said...

new chainstays? so what's better about Dedaccai vs. True Temper's chainstays of the same style (other than a little lower cost)? Just curious since I've only used the TT ones.
Interested to hear what you think on the ride. I dig the offset rear and un-dished wheel. That short in the stay is like a unicycle with a front wheel! Do you notice a harsher ride while sitting and pedaling vs. a longer chainstay frame?

Walt said...

Hey Whit -

I have not ridden it yet, so no thoughts on compliance. I have never noticed any difference in hardtail compliance regardless of chainstay length or material, though, so I'm probably the wrong guy to ask.

The Dedas have a pretty radical bend (these ones especially) and are in general super cool. If you ever get time to call I'll give you the DL....


Paul Shin said...

I need to stop by and check this thing out. Hey, if you need dry trails, St. George is only 4 hrs away!