Tuesday, October 16, 2012

Quickbeam Update/Bike Fit Musings: Is smaller better?

First, a quick Quickbeam update: 

Quickbeam updates

Got a Selle Anatomica Titanico X saddle, and mounted that.  The X is their new saddle designed with extra laminates to prevent sagging under big riders.  Also switched out the Nitto Bullmoose Bars for Civia Aldrich 70 degree bars.  At first, I tried the bars with Nitto Technomic (aluminum) and Dynamic 37 (tigged steel) quill stems, but neither had enough clamping force for the amount of leverage I could put on these swept-back bars.  After scratching up the bars in failed attempts to get enough clamping force through beer can shims, I went for a Civia Midtown 4-bolt faceplate stem, mounted via a Zoom-branded quill-to-threadless adapter. 

Civia Aldrich 70 degree bars and Midtown 120mm stem

Riding around on this setup, I’ve been thinking a lot the past couple of days about bike fit. Part of it is feeling like I'm still not dialed with this setup.  This rumination is also fueled by riding a Yuba Mundo longtail cargo bike at work for some test rides, and loving the feel of its cockpit.  It has a one-size-fits-all frame, with a 580mm top tube, a pretty short (for me) head tube, and angles listed at 71 degrees parallel.  Bars are North-Road style on a short (80 or 90mm) stem.  Part of the reason for the slack seat tube is that it helps the sizing be more flexible for a wide range of rider sizes, since the cockpit gets longer as you raise the seat to accommodate taller riders. 

Curious as to why I liked the feel of the Yuba so much, at lunch on Saturday I measured the setback, which is a fit variable I’ve been focusing on a lot in my recent bike fit experiments, on both bikes.  I measured horizontally from BB center to a plumb line below the seating area (widest point of saddle, basically) on both the Yuba (with the saddle set at my height) and the Quickbeam.  The Quickbeam has more setback, if anything (I measured ~34cm on it vs ~33cm on the Yuba), but it is possible that the SAA saddle doesn't let me ride as far back as the generic plasticky foamy one on the Yuba—this is my main complaint about most of the leather saddles I’ve tried so far. But, the negligible difference in setback got me thinking that there might be more to this all than overall setback. 

If anything, the Yuba could be said to be "too small" for me, especially by Rivendell standards, but it reminds me of many other frames that were "too small" for me, that nonetheless felt pretty good in the times that I rode them—my old beater that I described in the Quickbeam post is one.  It was something like 62cm with a 56cm top tube! My Takara with the original 100mm Technomic and Nitto 115 bars, set really low, was another one. The Specialized Secteur--pretty sure it was a 58--that I rode for my birthday ride this year, when the Casseroll was undergoing its gearie makeover, was another.  I also loved the feel of a smallish K2 MTB I did a townie bar retrofit on a few weeks back.  

In any case, I think that the next step, moving beyond thinking mainly about setback—only reading the "seat tube angle" column of geometry charts—is to think about TT length and saddle-bar drop(!). Combining my now-established preference for way-back seating, with the acknowledgement that even with a way-back CG position, during times of low pedaling force, the arms and torso must take the load of holding up the upper body, which is otherwise suspended by countering pedaling forces (see Keith Bontrager’s seminal piece “The Myth of KOPS,” hosted on the late Sheldon Brown’s site).  It could be that by lowering my upper body some, by lowering the bars (while keeping a short TT in order to reduce angle between upper torso and arms) brings some of my torso muscles into play to help support that weight during these times.  I think I feel better when I’m supporting myself through my torso rather than on the arms.  Maybe I would actually be more comfortable on shorter bikes. 

I’m trying to save up money for possible future framebuilding pursuits, so in order to explore this possibility, I’m going to try these things with my existing bikes:

One: rebuild the Trek in the manner of original 2005 Fixed/SS (re)build, but with gears. So: On-One Midge bars on Delta hi-rise stem, set low on the short steerer tube with no stem extender. Saddle way back. Will free up my Nitto 115's. 

Two: Nitto 115's go back onto Takara (which will be donating it's rear rack, and perhaps its fenders, to the QB) with 100mm technomic, and it may get its gears back (half step plus granny!) to reproduce the original configuration that felt so good. May try a few longer road rides on this thing to be able to compare better to my Casseroll. 

Looking at the QB, i may want to try the bars a bit lower. But that is hard--the quill adapter I've got pushes the stem about 3/4" above the top nut with its taper. I also have an inch or so of spacers between the top nut and threaded cup in the headset. So maybe if i cut down the fork (heresy on a Rivendell, i know!) and find a lower-profile quill adapter, I can get them somewhere around 2 inches lower. Or, the nuclear solution is do a complete threadless conversion--probably a new fork-- and slam that stem!

All of this will give me a lot more data to crunch on, maybe something to try to go for in my first custom frames. 

What do you think?  The Rivendell sizing philosophy is generally "bigger is better," but I think I may be an exception to that.  What have you found?  Have smaller bikes (in any particular dimension) sometimes felt better to you?

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