Thursday, November 19, 2009

2 x 9 chainring insanity

30t/40t 2 x 9 xt 737 crankset

i don't really work anymore. i don't do housework, either. i don't really do much anymore. except...

except think of ways to get the exact gearing i want on my mountain bike.

not exactly true, but i have spent an inordinate amount of time thinking about it for the last year. putting myself onto bigger wheels has caused me much weeping and gnashing of teeth. i don't even know why. look at all of the fast single speeders and you'd think i was a pretty big fool for thinking more than a minute about my crankset and associated chainring choices.

i've always been a crank man, though. they've been the most fascinating bike part since i started riding bikes. so naturally i think about what ring sizes are on them. and, q-factor as well as aesthetics play a big part. today's cranks just don't allow for much tinkering.

over the past 6 months or so, i scrounged around on ebay and found a couple of square taper, low profile 58/94 bcd xt cranks. the 94 bolt circle allows for as low as a 29t middle ring, any number of big chainring sizes, and there are still a ton of good rings out there. little chainring choices are pretty much irrelevant to me. salsa makes a bunch of rings for the 94 bolt circle, so i've been using a 30/42 combo most of the year. just yesterday, i picked up a couple more 30 tooth rings for spares and finally scored the 40t big ring that i've been wanting. i would probably do well to use a 29t for my low, but they're harder to find and the chain actually rests on the spider arms instead of nestling down completely on the teeth, so i can live with a 30t. i ground down the little chainring bosses to allow me to keep the crank in as far as possible, as well as avoid any nasty chainsuck issues. let's face it: if i am using a little chainring, i'm off the back.

probably considered the low point of the whole deal is the square taper spindles. it's only a low point because they aren't quite as stiff as the current crop of overbuilt, integrated pipe designs we see now. the only low point for me is finding new or lightly used un72 or un91 shimano bb's. shimano hasn't made the high quality square tapers in a lot of years. but, they are almost indestructible and the wide variety of sizes is awesome. with the superfly, i can use a really short 110mm and keep things in really tight.

for the weight weenies, i'm sure the whole deal just gives them a bad case of whooping cough. cranks, rings, chainring bolts, un72 bb and crank bolts brings the grand total to 846 grams. heavy to the weight weenie, but about 10 grams lighter than the newest xt crank and bottom bracket. a inconsequential weight savings, but in immeasurable difference in versatility as far as i'm concerned.

if you're still with me at this point, you probably have some insane bike fetishes too.


Ethan said...

I'm still with ya

Jim Sullivan aka Johan said...

tim, old stuff is the NEW new stuff. it's still around, b'cause it was build to last in the first place. (just to make a vein pop in your head...) have you thought of running a single up front and use an internal hub in back?

Brian H. said...

Me too. But you probably knew that.

jeronimo said...

I've found some 29's for mine, but I've gone a new route lately. I found a 27t granny that I will run with a 42 big ring placed in the middle ring position (I want a 40).