Crank Arm Length

[cycl...@gmail.com]

We've probably argued about this before but since I can't remember crap I can get clean opinions.

I presently ride 175 mm length crank arms. I have problems spinning and watching the Tour this year what was clear was that there are no more luggers in the peleton. This suggests that spinning is the way to go.

So: Has anyone experimented with different crank arm lengths and have they been able to tell the difference between one size different in length?

[John B.]

Years ago I conducted a personal test of spinning versus lugging (as
you call it) I rode 50km out, on a 100 km route, lugging and the
returning 50 km spinning. The second half was definitely faster.
Terrain in that case was pretty much the same in the two parts of the
test.

Currently I keep, on Phuket Island where the above test was conducted,
a road bike, currently with 170mm cranks, and a utility" bike with
175mm cranks. While most of the utility rides are in the local area I
do a 20km ride on it, usually once a week.

I can't tell the difference between 170 and 175mm cranks. In fact the
road bike originally had a mountain bike triple chain wheel set with
175mm cranks. When I changed it to a road bike triple with 170mm
cranks I never noticed the difference.

On the other hand spinning is probably not instinctive and lugging (I
prefer the verb "Mashing :-) probably is so you need to work at it a
little before it becomes instinctive.

The Pros spin at pretty high rates, Froome was said to be spinning
nearly 100rpm going up hill, but that probably isn't practical for the
average rider.

Initially, try riding, on level ground, and spinning at say 90 rpm, in
a lower gear ratio. When spinning begins to feel natural up the spin
to 100 rpm. I think that you will find it becoming natural after a
while.

Initially the secret is to use a lower gear ratio. 80 rpm in a 50 - 18
gear results in ~27 kph. 100 rpm in a 50 - 23 gear results in ~27 kph.

--
Cheers,

John B.

[cycl...@gmail.com]

I think that I would like a 50-11 top gear and a 34-28 bottom. This should give me everything I have with the triple except the bottom 2 gears which I never use (well, once up a 30% grade - how common are those?)

[cycl...@gmail.com]

By the way John - thanks for the information and I'll be sure and let you know the results of the experiment.

[John B.]

Depending on terrain the difference between gears sometimes is a bit
iffy with the (what do they call them, Compact?) gear sets. I find
riding in Bangkok which is essentially flat that sometime what I want
would amount to a 18-1/2 tooth gear on the back :-) which is
aggravated with the big, big chain ring and small, small ring setups.

I saw that ebay has/had 50/34 chain rings, 110 BCD, for as low as $30
a set.

--
Cheers,

John B.

[John B.]

I might mention that when I first tried spinning that I seemed to
bounce in the saddle. It takes a little practice.
--
Cheers,

John B.

[Doug Landau]

On Saturday, August 5, 2017 at 11:57:22 AM UTC-7, cycl...@gmail.com wrote:
> We've probably argued about this before but since I can't remember crap I can get clean opinions.
>
> I presently ride 175 mm length crank arms. I have problems spinning and watching the Tour this year what was clear was that there are no more luggers in the peleton. This suggests that spinning is the way to go.
>
> So: Has anyone experimented with different crank arm lengths

Yes
>Have they been able to tell the difference between one size different in length?
Yes

My roadbikes before I started paying attention all had 172.5s, I conclude, because 175 is too bouncy and 170 feels like too much strain on the knees.
My 5'10" body with 30" inseam likes 172.5s, and I think the change to 170 or 175 makes a big difference.

[cycl...@gmail.com]

I got some cheap replacements for my standard double and they were made of almost pure aluminum and were throwing grit off of them within 100 miles.

There are some compact rings that are 52 teeth. A 52/34 sounds good to me.

[cycl...@gmail.com]

I pedal circles so I don't bounce.

[JQ]

I recently went from a 175 crank arm to 165, I did this because I have
severe degenerative arthritis in both knees. My pedal stroke seems to be
weakest and 3 to 6 but the top of the pedal stroke is the hardest on my
knees. With the shorter crank arm my power out put was a little better
on the power graph, the greatest benefit is to knee comfort especially
at the top of my pedal stroke. I can know actually ride in the drops
comfortably without my knees feeling like they are in my chest and
greater knee pains at the top. It is easier to spin at easier gearing
because the distance of pedal travel is shorter, now for the downside...
pedaling it is much harder takes more effort to turn the pedal using the
same gearing. You also feel like you don't get the same amount of power
and momentum per pedal stroke because of the shorter distance of the
pedal stroke circumference. Gear set up was 53/39 front and 11-23 rear
(my flat land and crit racing set up). What I noticed is to pedal with
similar effort I needed to drop down at least 2 gears (53/15 would need
to be 53/17). This doesn't sound like much of a difference but it is as
far as speed and power is concerned. I just changed my gearing set up on
my bike to 52/38 and 11-28 (to be able to climb hills). I even have a
12-30 for really steep hills. My original reason for changing out the
crank arms was for the arthritis of the knees, but I was hit by a high
speed car from the rear and was jacked up pretty good resulting in over
9 weeks in the hospital, over 22 broken bones through out my body
including neck, back and both legs, colostomy (after 1.5 years just had
it reversed!) and other injuries; in brief the shorter crank arms were
even more important because of the additional damage to my knees. I have
been on a long recovery and physical therapy to restrengthen my legs and
body. The recent change in gearing has made things easier but I have a
long ways to go to get back my strength, speed and power. I do like the
shorter crank arms for my knees but and being able to ride on the drops
but dislike that it takes more physical strength to pedal the same
gearing. Keep in mind the strength thing may have only been getting use
to the added resistance but adding the accident into the mix may not be
a fair comparison to an able body rider, other than I am able to pedal
without my knees feeling like they will lock up at the top of the pedal
stroke as they felt before I changed out the crank arms. oh few more
things that I need to mention; you will need to modify your bike fit by
raising the saddle height, your saddle position may need t move back or
forward, your bar height and stem length may need to be changed or at
least getting used to. I had already shorten up my stem and but have not
raised it which may be my next change as I am now in a very aggressive
forward lean, tough on the lower back, neck and arms which the accident
didn't help.

--
Ride fast, ride hard, ride for health and enjoyment... JQ Dancing on the
edge

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[cycl...@gmail.com]

How tall are you?

[JQ]

6' tall with 33.5" inseam

[JQ]

On 8/7/2017 4:52 PM, cycl...@gmail.com wrote:

6 foot and 33.5 inch inseam

[cycl...@gmail.com]

Since you're 4" shorter and with a 1/2" shorter inseam I don't suppose I'll have any problems.

[John B.]

You'd be surprised. Get a tachometer and see how high you can go
without bouncing :-)
--
Cheers,

John B.

[JQ]

being 4" taller 6'4" tall and 34" inseam and having longer legs will
mean you will have more radical changes than I did. If you were shorter
the shorter crank arms will may be more beneficial all the way around.
I am not sure I understand what you mean by not having any problems.
What problems were you thinking of?

[James]

Practise spinning by riding on rollers. You'll soon find out how fast
you can pedal smoothly.

--
JS

[cycl...@gmail.com]

Knee pain.

[cycl...@gmail.com]

Right now I'm just returning to condition but last year at this time I could accelerate through yellow lights up to 32 mph in third gear without bouncing. This was a 52/15. In a 52/12 I could ride for four or five miles at 28 mph.

In the first case that's 116 rpm without bouncing.

[Frank Krygowski]

There's a five-year-old in our extended family who's been riding a pedal
bike for about 15 months now. The bike is a tiny thing, nominal 12"
wheels and very low gearing.

While he was trying to go fast on a slight downhill, he was spinning at
an astonishing 175 rpm. I checked it with my watch, then confirmed it by
noting his speed and working out the bike's gear inches.

He did fall once when his feet suddenly couldn't keep up, so I advised
him to just coast when the downhill is steep enough. But he's coming
along nicely!

--
- Frank Krygowski

[James]

The crank length is shorter for Tom relative to his leg length. His
knees will undergo less articulation for the same length crank than yours.

--
JS

[Doug Landau]

How about gesticulation? Which length will result in Tom gesticulating less while he rides?

[cycl...@gmail.com]

Doug - at the moment I'm gesticulating at you. But only with one finger.

[Doug Landau]

https://www.google.com/search?q=marvin+the+martian&rlz=1C1GGRV_enUS751US751&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiT84Km2cjVAhUIi1QKHVkHBSkQ_AUICigB&biw=1258&bih=674#imgrc=_W4jOix93OUvzM:

[Radey Shouman]

Genuflection is that thing you do with your knee.

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