current concepts in crankarm length

[stackie]

So what's the consensus on longer crankarms these days. I know Zinn wants all of us tall dudes on 200mm plus cranks. I'm not sure I'm on board with that.

I'm running a 91 cm inseam (barefoot to top of one inch book pressed too firmly into taint region). I've been using 177.5 Dura Ace 7700 cranks on the road. I think I may have arsed up the left crankarm. I'm going to try to salvage it with some industrial loctite, but am not too hopeful. I can't get another 177.5 7700 crankarm, so I'm thinking of switching out to a 175 crank since I think I can get my mitts on that crankset.

What are other peeps with longish inseams using for crank lengths? Any reasons other than gut feeling? Am I just making a mountain out of 2.5 mm?

Thanks,

Jon

[dannyg1]

Ever since I mounted a 165mm crank on my favorite bike (I'm 5'9") I've been annoyed by longer lengths. The 165's seem to spin up faster and give the whole bike a tighter, more racy feel. I have 175's on one of my favorite riders and I'm definitely going to be replacing it soon. I really cant stand the way it makes my left leg feel especially.

[gregclimbs]

Am I just making a mountain out of 2.5 mm?

Pretty much...

g

[Waldo]

My inseam is about the same as yours, and I'm running 190mm cranks with Rotor chainrings. Have been on them for about 3 years now -- love the cranks and rings dearly. Your experience may vary.

[regularguy412]

I was on 170s for the first 8 years, when I got my first 'good' bicycle. That's the size that came on that bike. And, of course, that bike 'had ' to fit, because the stand-over height was right. :p

Fast forward to 1996. I finally got my first 'real' fit from the proprietor of the shop where I purchased my CSI. I felt like I couldn't get good leverage on those 170s. That Saturday morning, I spent 4 hours on the Serotta Size cycle. So together with a complete position change (more aft) and a slightly longer crank 172.5, I became both more comfortable on the bike AND I finally felt like I could get more power to the pedal circle.

I guess you could say that I tried to be a 'spinner' for those 8 years (more forward position, shorter crank), but discovered that I was more efficient and powerful turning slightly slower and using a slightly longer crank. IMHO, I think a lot of crank length preference comes down to what type of pedaler a person is and what type of muscle (fast vs. slow twitch) one has.

Mike in AR:beer:

[Ken Robb]

first let me say that 5mm is pretty darn small but I can say feel the difference between 170 and 175 cranks because I ride bikes with both. When I got my Legend it had 180mm cranks and that was a first for me. I was amazed at my ability to muscle up hills in taller gears. After a few weeks though I got some discomfort under my patella. This might have been (I love giving my medical guesses to an M.D.) due to the longer cranks causing increased flexing of my knee. OTOH, it might have been because I was muscling up hills just because I could.
I replaced the 53-39 180mm cranks with 175mm and 50-34 rings and used more rpm and less leverage to climb the same hills. No more knee pain.

At this time I also had 172.5mm cranks on another bike. I couldn't detect any difference between 175 and 172.5mm.

You are much bigger than I am but my PBH is 89cm measured the same way. As I said, we are discussing pretty small differences--princess and the pea-like--but some riders are sensitive to these amounts. Don't forget that your saddle height may have to be raised with shorter cranks to get the same leg extension.

It's just nice to know a guy your age can still ride. :)

[wildboar]

Like Regularguy says, it's going to come down to personal preference, fast twitch/slow twitch. I haven't measured my inseam in quite a while but it can't be much more than 82cm and I never felt right on 170cm cranks. Going to 175 gave me the leverage that felt right and I've never had any knee problems.

[jlwdm]

I have a 90.7 cm inseam and run 175s.

Jeff

[RaleighComp]

My fastest bike is my Spectrum Ti with 175mm Ultegra SL compact crankset. My most comfortable bike is my '74 Raleigh Competition with 170mm TA 42/52 crankset. At 49 years old and 150 miles per week I feel a speed difference, a leverage difference, but not much of a comfort difference. My guess is that at my height (5' 10") with maybe a slightly longish inseam (I forget) you can go either way and the topography and turn characteristics of your ride will determine the micro advantage/disadvantage. No knee problems ever(knock wood).

[pbjbike]

It's all in the femur/lever length...I've seen the new Zinn cranks and they are beautiful! Pay the $$ for a good sizing and upgrade to what fits you.

Cheers

[flickwet]

34 " inseam and my cadence remains the same on 175's or 180's so I always ride 180's cuz I like to think the greater leverage at the same cadence means I'm pushing a larger gear, that is its faster...for me, everyone else will have a different opinion, also FWIW, I'm 52, my knees are average, never get pain from the legnth and my flexibility is good

[Louis]

I've found that for me there was little difference between a 170 and a 172.5 (my first bike came with a 170 and I was too much of a noob to realize that that was too short for me) but there was a significant difference between 172.5 and 175. It was noticeably easier to stay in a given gear and maintain higher RPMs on rolling hills with the 175. I've been meaning to try 177.5 but haven't gotten around to it yet.

Data gathered from a survey I did on the forum a while back:

http://forums.thepaceline.net/attachment.php?attachmentid=4132&stc=1

[stackie]

Wow, Louis! What an answer. Thanks for the scientific response. Actually, thanks to everyone for chiming in.

Jon

[Tobias]

Data gathered from a survey I did on the forum a while back:

http://forums.thepaceline.net/attachment.php?attachmentid=4132&stc=1
Nice data Louis. Confirms the very high bias towards tall riders using shorter cranks for their size compared to short riders. Taken to the extreme, does it mean a person of "zero" size would use 107 MM cranks? :rolleyes: That would be hard to spin, right? :beer: