Thursday, April 1, 2010

Feeling cranky and confused.

Cranky as in bicycle cranks and confused about recent and new revelations thereof.  Therein?  Thereout?

Anyway, I have been riding 180mm cranks since the dawn of time, at least 15 years now.  I am a diesel when it comes to sitting and pushing gears and I liked the extra uuummph at low RPMs.  It took some time to come to terms, muscle wise, with the bigger circle, but once adapted it was all happiness.  I have 180s sitting around all over the place going back to old 5 arm XTs, Top Lines, etc.  However, nowadays the selection of 180s is getting thin.  Most of the new crank sets from the manufacturers are not sold in that length.  XTR, XT, some dedicated SS stuff like Stylos and, of course, all the aftermarket stuff like Whites, Middleburn, etc. are made in 180mm lengths.

So naturally I transferred these over to the 29ers as they came along.  And, of course, the singlespeed got them too.  Many riders that run 175mm cranks on their geared bikes go to the 180s on the SS for the extra leverage.  It does make some sense that, if you have only one gear and the hills get steep, a bigger lever will allow some grace there and give you an edge in power.

“Give me a place to stand and with a lever I will move the whole world.” Archimedes, SS rider and all around smart guy.

Recently I have been riding a lot of test bikes for 29".com and none of them come set up with 180mm cranks.  At first I noticed the lack of torque and lamented the fact.  But the body has a way of adapting and after a while, it was normal.  Then, going back to my singlespeed with the 180s felt odd at first but that faded as well after some time on the bike.

Now, here comes along the Rockhopper SS with 175mm cranks, the first time had ridden a 29er SS with a shorter crank.  At first I missed the 180s but the Rockhopper was so darn snappy a climber, it was not really as significant as I expected it to be.  I just figured, "think how fast I would be if I had looong cranks on there?"

So then I get on my buddies Salsa Selma while he rides the Rockhopper.  The Selma is stiffer, lighter, and should be killer on the hills as it runs 180mm crank arms.  Oddly enough, the Selma felt like it was bogged down a bit and my legs felt tired, especially seated pedaling up a local singletrack.  I had just done 3.5 hours of riding in the same area on the 'Hopper 2 days ago with the 175s and that actually felt really good all day.  Was I just not used to pedaling the bigger circle now?  Or could the 175s actually have some advantages?

Oddly enough, Ed the Tall felt like the 'Hopper with the 175s felt very good on the hills and he actually thought it made the climbs easier.

So here we have two guys, both tall, that seem to be thinking that the shorter lever is felling pretty good on the SS.  How odd.  How can that be?  Is it possible that the shorter crank allows for 'getting over the top' of the pedal stroke in a more efficient manner?  If so, does the ability to get the crank around faster, offset the loss of torque in the last part of the downstroke?

I am not ready to ebay the 180s yet, but I am very intrigued.  Maybe I am wrong and it is just me having trouble adapting back and forth. Maybe.  More time is needed on this.  It would be interesting to see some numbers in a test lab on how this all works out, pedal stroke vs power vs effort, etc.

I may end up agreeing with Archimedes, except that I will be standing 5mm closer to the world than I used to.

1 comment:

Fonk said...

Well, in theory one can supposedly spin a slightly higher cadence naturally w/ a shorter crank, so maybe you're just experiencing the benefit of a higher cadence/smoother spin.

I've noticed a similar experience on one of my road bikes. I ride 175mm on pretty much everything I own (I could probably easily switch to 180's, too, but have never gone to the trouble). The exception is a new road bike I bought about a year-and-a-half ago. It came w/ 172.5mm cranks (the next size up came w/ 175, but I liked the slightly smaller frame on this model). I, too, figured I'd feel it to be a detriment on the climbs, but actually have not. Again, I think it might be because the smoother/faster cadence might be saving me some muscle power, thus the faster pedaling makes up for the less torque.

However, it does feel odd after I've spent a lot of time on my other bikes w/ the slightly longer cranks, and we're only talking about a 2.5mm difference here, not even the 5mm difference you're experiencing. I've purchased a 175mm to swap it out with. I think I might throw the 172.5s on through the winter for higher-cadence training, and then swap back to the 175s when the regular season hits again.