165mm Crank Arms, who rides them?

[carpediemracing]

I don't have hip or knee issues at this time, although I have very fragile knees. I think that's your biggest thing, to be able to work around your joint issues. However, on the performance side, it's "it depends on the rider".

I have very short legs (67 cm from top of saddle to BB center with Keo/similar pedals). I currently use 175mm cranks. I tried three years (different years - 2008, 2011, 2015) to return to 170mm cranks because of the whole "short crank arm" thing. However I had dismal results consistently with the 170s, even after almost a year on the cranks (2008, 2011). When I switched back to the 175s I immediately, and I mean within one race, saw differences with the longer cranks.

The "depends on the rider" thing is that I tend to do very short, very punchy efforts. I'm talking very short, like a quarter pedal revolution little punch to close a minor gap, literally a snappy half downstroke. Since my metric is "racing" and I'm pretty bad aerobically I have to be very efficient on the bike. The longer cranks make it possible for me to draft more efficiently because I'm a fast twitch kind of rider and the longer cranks let me coast a lot more because one little snap on the pedals can earn me shelter for many seconds. With shorter cranks I have to exert more power (albeit over a smaller distance) or do a couple efforts (two snappy downstrokes) which starts to tax my aerobic system.

I'm also faster in the sprint with longer cranks in my older age, although I was fastest with 167.5s overall. The 167.5s I used 30 years ago and I was unable to finish races consistently so I rarely got to use my sprint in anger - I was faster in training rides but mostly DNFed. When I went to 170 cranks I finished more races although I lost some top end speed. The 175s have earned me consistent top finishes and a slew of field sprint wins but I'm a solid 15-20% slower in maximum speed. There are years where I win almost every field sprint I contest on the 175s, and on the 170s I was struggling to finish the same races.

[gallant]

My bike fitter recommended I switch to 165 cranks during my last fit. So far so good. I tend to be more of a spinner than masher so I don’t mind having to spin more for the same effect.


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[marciero]

Originally Posted by carpediemracing

I don't have hip or knee issues at this time, although I have very fragile knees. I think that's your biggest thing, to be able to work around your joint issues. However, on the performance side, it's "it depends on the rider".

I have very short legs (67 cm from top of saddle to BB center with Keo/similar pedals). I currently use 175mm cranks. I tried three years (different years - 2008, 2011, 2015) to return to 170mm cranks because of the whole "short crank arm" thing. However I had dismal results consistently with the 170s, even after almost a year on the cranks (2008, 2011). When I switched back to the 175s I immediately, and I mean within one race, saw differences with the longer cranks.

The "depends on the rider" thing is that I tend to do very short, very punchy efforts. I'm talking very short, like a quarter pedal revolution little punch to close a minor gap, literally a snappy half downstroke. Since my metric is "racing" and I'm pretty bad aerobically I have to be very efficient on the bike. The longer cranks make it possible for me to draft more efficiently because I'm a fast twitch kind of rider and the longer cranks let me coast a lot more because one little snap on the pedals can earn me shelter for many seconds. With shorter cranks I have to exert more power (albeit over a smaller distance) or do a couple efforts (two snappy downstrokes) which starts to tax my aerobic system.

I'm also faster in the sprint with longer cranks in my older age, although I was fastest with 167.5s overall. The 167.5s I used 30 years ago and I was unable to finish races consistently so I rarely got to use my sprint in anger - I was faster in training rides but mostly DNFed. When I went to 170 cranks I finished more races although I lost some top end speed. The 175s have earned me consistent top finishes and a slew of field sprint wins but I'm a solid 15-20% slower in maximum speed. There are years where I win almost every field sprint I contest on the 175s, and on the 170s I was struggling to finish the same races.

You are certainly very tuned in to your biomechanics. So you are winning sprints on the 175s while at the same time having slower top speed... I assume this is due to your ability to jump and accellerate better? You must be winning these sprints while still accelerating, so at less than top speed. I'd be curious how you would do with a proper lead-out train!

[carpediemracing]

Originally Posted by marciero

You are certainly very tuned in to your biomechanics. So you are winning sprints on the 175s while at the same time having slower top speed... I assume this is due to your ability to jump and accelerate better? You must be winning these sprints while still accelerating, so at less than top speed. I'd be curious how you would do with a proper lead-out train!

Leadouts... someone said once that I'm like a glass vial of nitroglycerine. I'm very fragile, have to be babied up to the front, not put under too much stress, else I'll explode. But deliver me properly and I can do a good effort. The guy that said that leads me out here (he was on a different team but we're friends). You can see I eased a number of pedal strokes from the line as pedaling harder wouldn't accomplish anything:
https://www.youtube.com/watch?v=VRJrWJ09Mwc

Third person view of same sprint. I ease because the gap to the riders around me means that I won't catch Kyle and no one will catch me:
https://www.youtube.com/watch?v=opy_kecxZAI

And this is about the best leadout clip I'll ever get. Leadout was at about 35 mph into a headwind, I launched as early as I dared to try and catch the break riders ahead of us:
https://www.youtube.com/watch?v=dqrPW4FWyQg

As far as crank length, I learned a lot throughout the years. Has less to do with top speeds (although it helps a bit) and more to do with arriving at the finish with more in the tank.

The short punchy close-gaps thing I learned when I rode a tandem in a regular group ride. I realized I was expecting gaps to close with just a little downstroke punch, but with a 360+ lbs overall bike weight it felt like I was stamping my foot on a step, not on a pedal that moves down. We quickly got shelled as it took us 3-5 pedal strokes to close even smaller gaps. Back on my single/regular bike I noticed that, yes, I do these little stamps to close small gaps (like a few inches or a foot). I'm not strong aerobically so drafting closely is critical and the "pedal stamp" allows me to stay closer while not taxing me aerobically.

I think that stamp thing is why the 175s work better for me, because I can draft closer with less effort compared to the 170s. Less to do with the sprint.

I lost speed over the years. I think the longer cranks actually helped return some of that speed, but my top speed has gradually declined for about 20 years.

The longer cranks do help me overall, I think because it leverages my muscular system vs my aerobic system. If I was better aerobically it might be different.

For bike differences the crank experiments were well controlled since I only changed the arms (not the spider) and the saddle height. For the last three tries on the 170s I had the Cannondale SI cranks that I still have. For saddle height I dropped it 5mm for the 175s. I found that my peak power was about the same, my jump felt better with the short cranks (no proof it was actually better), top speed possibly a bit better on the 170s, but in practice, without isolating just the sprint, I felt much more taxed on the 170s during rides and races. I was closer to the edge, I'd get dropped quicker. My standard test was the local Tues Night races since the same riders show up and it's somewhat predictable. I'd get shelled every week on the 170s, put on the 175s, and literally the next race found myself vying for the win. For a couple of those experiments I put the 170s on over the winter, like Oct-Dec, and I only gave up on them mid summer the following year. I really wanted them to work as the 5mm higher saddle position is more comfortable for me, it felt better to sprint on the 170s, but the reality was that the 175s (and lower saddle position) worked better for me.

[marciero]

Wow-some awesome finales and racing in general. The subtitled commentary is great. Thanks for sharing. I recall linking to some of your videos a while back in a thread on race tactics-"tailgunning" I think. Good to see our own Shovelhead figuring at the pointy end of things. Incidentally, I've raced on that Ninigret course. I used to live just a few miles from there.