Crank length question

[MomOnBike]

Crank length is a HUGE issue in the recumbent community right now, with some 6-foot + men going down as low as 153.5's. All sorts of wonderful things are attributed to short cranks; elimination of knee issues, speed gains, whiter teeth, more sex appeal, you name it. Color me sceptical.

The most reasonable theory I've seen is that the crank should be some percentage of your femer length. I'm trying to say 20%. I don't think that's quite it, but that's the ball park.

It sounds to me that 175's are a bit too long for you. The dead spot being the giveaway. I don't know how tall you are, but you might consider going down to 170's or even 165's - especially if you are worried about your knees.

The problem is, of course, that the only real way to find out about these things is to spend the cash and try them on the bike. {sigh}

FWIW, I'm trying to talk DH and my budget into a really expensive new crankset with 165's. I'm looking forward to the increased sex appeal.

[jobob]

One of my bikes, which I bought used, has 175 mm crank arms. My other bike has 170 mm arms.

I looked up various charts, and the 175 mm arms are a bit on the long side for me (I'm 5'7" with a ~ 32" inseam).

Call me dim, but I really don't notice that much of a difference.

A few months back I was having a bit of an ache in one knee after 40+ miles, but I noticed that on both bikes. Come to find out the cleat angle on my shoe was a bit off, and adjusting the angle did the trick.

One of these days I'll probably change the crank on Dusty to 170 mm, the length I'm "supposed" to use, but I'm not in a hurry.

[nuthatch]

I'm looking forward to the increased sex appeal.

Oohh, me too! Maybe I'll get whiter teeth too...

Thanks guys. I'm mostly concerned with potential knee issues but I'm about 5'9" (inseam 31.5 - call me Popeye) so, while the 175 is probably too long, it's not outlandishly long. I know a new crank means $$$$$ and I hate to return the bike (I'm within the 30 day return period) because it seems to be perfect in every other way.

[bcipam]

Do a alittle research and maybe check with your LBS but 175 cranks are long for your height. You should be on 170's or at the longest 172.5. Yes it seems like the difference is so slight as to be unnoticeable but trust me there are differences and if doing longer rides, you will feel it both in leg fatigue and in performance. Now it's not unusual to have different cranks length on different bikes especially if the bikes are designed differently and used differently but you still need a crank that fits your size.

[Trekhawk]

I read somewhere that people often have longer cranks on their mountain bikes than their road bikes. Not sure if this is the case for most but after reading this I checked and I do. I have 170 on my road bike and 175 on my MTB and both feel just fine.

[nuthatch]

Interesting you should bring this up about mtn bike cranks. This bike is made by a company that is primarily famous for mountain bikes. They may have decided on 175s for this touring bike because that's what they had a big contract for with all their other models. Hmmmm.....it's a compact geometry frame, too, rather than the traditional frame most makers use with touring bikes.

[Trekhawk]

Hey Nuthatch
Here is where I saw the bit about cranks. Clink on link and then scroll down to the cranks part.

Hope this helps.

www.coloradocyclist.com/BikeFit/index.cfm

[doc]

Try these sites:

http://www.cranklength.info/cranks.htm

http://www.cptips.com/crnklth.htm

http://www.cranklength.info/
http://www.nettally.com/palmk/crankset.html
http://www.zinncycles.com/cranks.aspx
http://www.billbostoncycles.com/crank_length.htm