Another "crank-length" thread!

[CarlosContreros]

Hey Y'all........
Could I get some help in regards to changing crank length??

1).If you install a longer crank?....should you move your
saddle forwards to maintain that whole "KOPS" thing?

2).Should you also change saddle height?..becase if you lower
it to account for the newly enhanced length?...now at the top
of the stroke your leg will now have a reduced bend at the top?

3).And....maybe not related to crank-length...but can your "cycling
style" be dictated by your saddle-height??..eg..if you have a very
high saddle height you might become "toes-down" because your
legs can't reach far enough to be "heel-down"?
thnks!

[Dave]

I really don't think there is a "correct" answer, just a lot of opinions. The answer might also vary depending on your saddle height.

Someone with their saddle jacked up real high might immediately notice an increase in crank length and feel the need to lower the saddle, while someone with a more moderate height might not.

I'm just starting a KOP experiment myself. After riding for about 1-1/2 years of mountainous terrain with my knee at least 2cm behind the pedal spindle, I made a large change, moving the saddle forward 2cm (and up about 6mm). My resaon for having the saddle further back was to enhance my ability to apply torque to the cranks, or so I thought. This might be important for folks who only carry a 39/25 low gear into the mountains. Since I use a triple and have a 28/25 (39/35) low gear, it dawned on me that applying lots of torque really wasn't necessary. Even though I've always used a relatively high cadence when climbing (75-90), maybe an even higher cadence would work better (like it does for Lance).

Right now, it's too early in the experiment to draw any sound conclusions. I have noticed some reduction in my ability to apply torque on a climb. I find myself needing to spin a 39/25 a little faster instead mashing on a 39/23 on certain sections of my climb. This affect may change as my muscles adapt to the new position.

The KOP change hasn't bothered my knees, my average cadence is higher and the additional weight on the front does seem to make the bike feel more stable when carving turns at 40mph on the descent.

As for changes in my power output, I don't have a power meter, so I have no relaible gage. I do time myself over the 10 mile climb on my regular ride, but I've seen no significant improvement yet. On a 10-mile climb, wind conditions and how much effort is put into the climb can make a large difference in the time. Separating these variables from a difference in power output is just not possible.

[boulder_courier]

When you change the length of your crank you should,at the very least, maintain the distance from the pedal to the top of the saddle (longer cranks = lower saddle height and vice-versa).

I raced for years with 180mm cranks, but always switched to a 172.5 cranks for criteriums for obvious reasons. So I would raise my saddle height .75cm in order to maintain the length from pedal to saddle top. I never bothered with adjusting the saddle positon. I just optimized it for the cranks I used the most (180) and I would adjust my positon on the saddle to whatever felt comfortable when using the 172.5.

[Too Tall]

Dave, where are your cleats now? Direct under the ball of your foot? I made the same change last winter and needed to pay particular attention to self-massage of my lower leg and added additional stretching for achilles and IT. The impact was not immediate or apparent, the additional power was.

[Dave]

I always place the pedal spindle directly under the ball of my foot. I've been using the same Speedplay/Sidi setup for a long time.

How did you verify an immediate improvement in power?

The only thing I have noticed is my left hamstring nearly cramping a couple of times. Don't know what that's about. Other than that I've had no ill effects.

I just checked my KOP and even with the saddle 2cm further forward, my knee is still well behind the pedal spindle, at least 1cm.

I'm using a bit different method to check KOP. Eyeballing a plumb bob over the top of your shoe is extremely inaccurate, IMO. I use a small square held against the TT. I hang the plumb line over the edge of the square, to the spindle centerline. Then I mark this position on the top tube, with masking tape. I mount the bike and hold sqaure against the top tube to project the spindle centerline across to the knee. Seems much easier to eyeball the distance from the front of my knee to the square.

[Too Tall]

That's how I mark the spindle also when I am alone. When I do this as an observer I mark the riders shoe with tape and use a sharpie to mark spindle. Got this method from SmileyYoda. Than I measure the inside of the shoe from inside surface of heel cup forward and match that to the "bump" on metatarsal which I use as a landmark for "ball" of foot. (use a trace of the foot or ruler or both)...this gives me reassurance I am locating the ctr. of the cleat over ctr. of ball ON the shoe measured from the heel cup.

Dave, I have daily watts readings over nearly 3 yrs. I won't get beat up on semantics (again) and will only observe that I pedaled with more power during tests of 3/5/20 mins. It appeares to be a more powerful setup for me. It's not what I'd pedal across the USA with as the stress is greater, no question for me anyway. I was a 2+ cm behind spindle kinda guy for many yrs. of Ultra-racing...Smiley can tell you...I was well back and with plenty of saddle setback. Call me easy rider or whatever. Training and racing USCF morphed my position to someting quite different. It was trial and error to find this out.

[Dave]

I wasn't disputing your contention of more power, just wondered if you had a way to measure it. I've never owned a power measuring device myself. There are "experts" who contend that KOP makes no difference in power output, but they never have any data to back up that contention. Sure would simplify fitting a bike. I've always noticed a lower cadence and higher torque approach to pedaling with the saddle far back.

So far, all I know is that my average cadence is faster, which might make more power, if torque is not reduced. I was also a bit surprised that my knee is still behind the pedal spindle, after moving the saddle forward 2cm. I guess I have short femurs, even though I have long legs for my height.