Crank Length

I have always considered crank length to be something meaningless
depending, of course, on not being extreme. For example, I have ridden
with 170mm cranks on road bikes for years and years and as long as
174mm on mountain bikes, and never noticed any difference between the
lengths. Added to this the charts that I have found tell me that, with
my height, I should be riding something like 165mm cranks.

However :-)

I have two bikes, in Bangkok, both essentially the same. Same frame
measurements, same seat height, same distance from the saddle to the
handle bars, same gearing and weights within about a kilogram. the
older bike - frame and forks - weighs 3.2 Kg. the newer 2.5 Kg.

While I don't make a fetish about it I did notice that the last time I
rode the older bike on my usual Wednesday loop I seemed a bit faster
for the same apparent effort. I checked the sprockets and I was riding
one cog higher gear ratio on the older heavier bike. I would usually
ride in a 58" gear and that day I was using a 61" gear.

When I got home I did some checking and found that the New BKK Bike
has 170mm cranks and the Old BKK Bike has 172.5mm cranks.

Given that the usual recommendation for a guy my height is a 165mm
crank but in practice I am finding a 172.5mm crank seems faster than
the shorter crank, for the same effort, is the formula wrong? My usual
pedal RPM for any crank is 80 - 100 rpm.

Any comments or enlightenment?
--
cheers,

John B.

On Thursday, October 20, 2016 at 7:42:53 PM UTC-7, John B. wrote:
I have always considered crank length to be something meaningless
depending, of course, on not being extreme. For example, I have ridden
with 170mm cranks on road bikes for years and years and as long as
174mm on mountain bikes, and never noticed any difference between the
lengths. Added to this the charts that I have found tell me that, with
my height, I should be riding something like 165mm cranks.

However :-)

I have two bikes, in Bangkok, both essentially the same. Same frame
measurements, same seat height, same distance from the saddle to the
handle bars, same gearing and weights within about a kilogram. the
older bike - frame and forks - weighs 3.2 Kg. the newer 2.5 Kg.

While I don't make a fetish about it I did notice that the last time I
rode the older bike on my usual Wednesday loop I seemed a bit faster
for the same apparent effort. I checked the sprockets and I was riding
one cog higher gear ratio on the older heavier bike. I would usually
ride in a 58" gear and that day I was using a 61" gear.

When I got home I did some checking and found that the New BKK Bike
has 170mm cranks and the Old BKK Bike has 172.5mm cranks.

Given that the usual recommendation for a guy my height is a 165mm
crank but in practice I am finding a 172.5mm crank seems faster than
the shorter crank, for the same effort, is the formula wrong? My usual
pedal RPM for any crank is 80 - 100 rpm.

Any comments or enlightenment?

How old are you?

On Thu, 20 Oct 2016 23:05:30 -0700 (PDT), Doug Landau
wrote:

On Thursday, October 20, 2016 at 7:42:53 PM UTC-7, John B. wrote:
I have always considered crank length to be something meaningless
depending, of course, on not being extreme. For example, I have ridden
with 170mm cranks on road bikes for years and years and as long as
174mm on mountain bikes, and never noticed any difference between the
lengths. Added to this the charts that I have found tell me that, with
my height, I should be riding something like 165mm cranks.

However :-)

I have two bikes, in Bangkok, both essentially the same. Same frame
measurements, same seat height, same distance from the saddle to the
handle bars, same gearing and weights within about a kilogram. the
older bike - frame and forks - weighs 3.2 Kg. the newer 2.5 Kg.

While I don't make a fetish about it I did notice that the last time I
rode the older bike on my usual Wednesday loop I seemed a bit faster
for the same apparent effort. I checked the sprockets and I was riding
one cog higher gear ratio on the older heavier bike. I would usually
ride in a 58" gear and that day I was using a 61" gear.

When I got home I did some checking and found that the New BKK Bike
has 170mm cranks and the Old BKK Bike has 172.5mm cranks.

Given that the usual recommendation for a guy my height is a 165mm
crank but in practice I am finding a 172.5mm crank seems faster than
the shorter crank, for the same effort, is the formula wrong? My usual
pedal RPM for any crank is 80 - 100 rpm.

Any comments or enlightenment?

How old are you?

84.
--
cheers,

John B.

Same make and model of tires and same tire pressure on both bikes? 58 to 61 gear inches is about a 5% difference which could be easily accounted for by something other than the difference in crank length. Tires and tire pressure are the first thing that came to mind but for a single ride, there could be other variables at work.

On Fri, 21 Oct 2016 03:49:03 -0700 (PDT), wrote:

Same make and model of tires and same tire pressure on both bikes? 58 to 61 gear inches is about a 5% difference which could be easily accounted for by something other than the difference in crank length. Tires and tire pressure are the first thing that came to mind but for a single ride, there could be other variables at work.

Yup, same tires and pressures. And no, a 5% difference isn't much.
But from what I read about crank length a person of my height and leg
length should be riding 165mm cranks which would make one think that
increasing the length over what was all ready considered as too long a
crank would decrease efficiency.
--
cheers,

John B.

John B. considered Sat, 22 Oct 2016 07:26:25
+0700 the perfect time to write:

On Fri, 21 Oct 2016 03:49:03 -0700 (PDT), wrote:

Same make and model of tires and same tire pressure on both bikes? 58 to 61 gear inches is about a 5% difference which could be easily accounted for by something other than the difference in crank length. Tires and tire pressure are the first thing that came to mind but for a single ride, there could be other variables at work.

Yup, same tires and pressures. And no, a 5% difference isn't much.
But from what I read about crank length a person of my height and leg
length should be riding 165mm cranks which would make one think that
increasing the length over what was all ready considered as too long a
crank would decrease efficiency.

Yes but:
You can become used to almost anything, so overlength cranks (i.e.
most of them) only really become a problem when you blow your knees
out.
I'm about 172cm tall, and found 152mm cranks a bit longer than I would
have preferred - we don't bend the knees much in walking or running,
so our knees are best at transmitting force when not any more bent
than when walking up a moderate slope.

On Thursday, October 20, 2016 at 7:42:53 PM UTC-7, John B. wrote:
I have always considered crank length to be something meaningless
depending, of course, on not being extreme. For example, I have ridden
with 170mm cranks on road bikes for years and years and as long as
174mm on mountain bikes, and never noticed any difference between the
lengths. Added to this the charts that I have found tell me that, with
my height, I should be riding something like 165mm cranks.

However :-)

I have two bikes, in Bangkok, both essentially the same. Same frame
measurements, same seat height, same distance from the saddle to the
handle bars, same gearing and weights within about a kilogram. the
older bike - frame and forks - weighs 3.2 Kg. the newer 2.5 Kg.

While I don't make a fetish about it I did notice that the last time I
rode the older bike on my usual Wednesday loop I seemed a bit faster
for the same apparent effort. I checked the sprockets and I was riding
one cog higher gear ratio on the older heavier bike. I would usually
ride in a 58" gear and that day I was using a 61" gear.

When I got home I did some checking and found that the New BKK Bike
has 170mm cranks and the Old BKK Bike has 172.5mm cranks.

Given that the usual recommendation for a guy my height is a 165mm
crank but in practice I am finding a 172.5mm crank seems faster than
the shorter crank, for the same effort, is the formula wrong? My usual
pedal RPM for any crank is 80 - 100 rpm.

Any comments or enlightenment?
--
cheers,

John B.

What is the frame materials? After dumping my carbon and aluminum bikes and going back to steel I am much faster everywhere but steep climbs. Steel rides SO much more comfortably that I think a lot less of dodging pot holes and more about riding.

On Sat, 22 Oct 2016 09:29:36 -0700 (PDT), wrote:

On Thursday, October 20, 2016 at 7:42:53 PM UTC-7, John B. wrote:
I have always considered crank length to be something meaningless
depending, of course, on not being extreme. For example, I have ridden
with 170mm cranks on road bikes for years and years and as long as
174mm on mountain bikes, and never noticed any difference between the
lengths. Added to this the charts that I have found tell me that, with
my height, I should be riding something like 165mm cranks.

However :-)

I have two bikes, in Bangkok, both essentially the same. Same frame
measurements, same seat height, same distance from the saddle to the
handle bars, same gearing and weights within about a kilogram. the
older bike - frame and forks - weighs 3.2 Kg. the newer 2.5 Kg.

While I don't make a fetish about it I did notice that the last time I
rode the older bike on my usual Wednesday loop I seemed a bit faster
for the same apparent effort. I checked the sprockets and I was riding
one cog higher gear ratio on the older heavier bike. I would usually
ride in a 58" gear and that day I was using a 61" gear.

When I got home I did some checking and found that the New BKK Bike
has 170mm cranks and the Old BKK Bike has 172.5mm cranks.

Given that the usual recommendation for a guy my height is a 165mm
crank but in practice I am finding a 172.5mm crank seems faster than
the shorter crank, for the same effort, is the formula wrong? My usual
pedal RPM for any crank is 80 - 100 rpm.

Any comments or enlightenment?
--
cheers,

John B.

What is the frame materials? After dumping my carbon and aluminum bikes and going back to steel I am much faster everywhere but steep climbs. Steel rides SO much more comfortably that I think a lot less of dodging pot holes and more about riding.

Both steel. and as I said the "Old" bike bare frame and forks weighed
3.2 kg the "new" weighed 2.5.

As for the difference between steel and other materials, yes and no.
Certainly a single speed, two top tube, Flying Pidgin bike is pretty
rough riding compared to a more modern design super light weight steel
road bike.

The only aluminum bike I have ridden for any time at all is a hard
tail mountain bike that eventually died and I resurrected by replacing
the forks with solid, aluminum, and a new drive train and it is a
pretty rough ride compared with a light weight steel bike.

Interestingly, the aluminum bike fame and fork is significantly
heavier than a frame I built using Columbus SL tubing :-)
--
cheers,

John B.