Registered: Sep 2006
Location: Dahlgren VA
Posts: 13

Well, I decided to buy a set of rotor cranks. While looking through this forum, there was alot of discussion about the good/bad of short crank lengths. I decided that it looked interesting and decided to buy ones with 155mm cranks.

Got the cranks installed today. One thing I didn't anticipate was that by making the cranks shorter by 2 centameters, now pedals were 2 centameters closer to my seat. I had already pushed my seat most of the way back, so I didn't have alot of extra room for expansion.

I ended up pushing my seat back right to the very edge of the large hole. Going to have to see if that is good enough. Next time I am going to have to buy the next size larger bicycle I think.

Last edited by Midnmax on 06-16-2007 at 02:14 AM

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Registered: Jan 2004
Location: oklahoma
Posts: 243

Shorter cranks would mean you are now needing to move the seat closer to the pedals. A possible need for a bigger bicycle comes from adding to crank length not making them shorter. Did you say what you wanted to say in the above .
Keith

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Registered: Nov 2002
Location: Ga, for now
Posts: 502

The original poster had it right. With the crank arm being shorter on its farthest stretch from the bottom bracket/spindle, you now need to move the seat back to give full extension. The good news though is that your foot doesnt have to come up near as far to hit the closest point to you. I'm beginning to think crank length can be just as critical as the overall sizing of the bike, particularly for those who have had range of movement issues in their legs.

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Registered: Jan 2004
Location: oklahoma
Posts: 243

Thanks, I see now what I earlier did not. I have never shortened my crank. Live and learn.

Keith

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Registered: Sep 2006
Location: Dahlgren VA
Posts: 13

Well, took the bike out today. Even after moving the seat back as far as humanly possible, it was too short for my legs. Who would have imagined 2 cm would have made such a difference.

However, I was able to loosen up the bottom cording in my coolback seat and allow a larger curve in the webbing. This moved me back just barely far enough to fix the problem. I better not grow any, cause there's now no room to go. Of course, since I'm 31, thats not a huge risk.

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Registered: Nov 2002
Location: San Francisco, CA USA
Posts: 466

You can also theoretically get more leg extenstion by raising the seat. You would need longer bolts, and some kind of block or something to put under the seat to raise it up.

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Registered: Nov 2002
Location: NJ
Posts: 138

my bike is probably at the limit for my ex seam. A few years ago Gargner told me to get roughly 4 by 6 inch piece of 1 inch plywood, get longer carriage bolts, and it would provide little more distance to the pedals.
It is a lot cheaper and easier than getting a bigger frame or longer cranks.
alan

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Alan Mushnick

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