Drivetrain suggestions?

[ratz]

Yep Larry I do believe you are on the key points. And Charles is correct it's a very personal thing as even you pedaling style is going to influence your preference.

I think it comes down to Length of thigh versus femur and the angle that you like your foot at.

A vertical pointed toe brings the knee further forward; and a toe pointed forward is going to bring the knee back. I tend to point my toes forward and I notice in the videos; that Larry has his toe vertical. So even if we where twins we might like different crank lengths.

Physically if your femur is long or your thighs are short you will probably favor shorter cranks and if your femur is short or the thing is long then longer cranks. In the very end the Length your crank will dictate home much "throw" forward and back you have in your hips. The longer the crank the more potential throw as it goes threw the rotations as your femur thigh combination have to move from the max forward and leeward positions. Lots of throw makes pedaling uncomfortable and inefficient; if you don't change the crank length; then the only way to fix too much "outbound motion" which is basically not ridable is to pull the BB closer which we all know then gives too much knee bend and by by knees if you push hard.

Now if it wasn't so expensive to experiment with different crank lengths. Too bad there 's no profit is making a more sophisticated version of this: http://www.recumbents.com/wisil/misc/crank_angle.asp

 

[Rick Youngblood]

Some info on short cranks:

Recumbent Crank Length Calculator

Sheldon Brown

 

[MrSteve]

Crank length is a very personal thing. I agree that there are standard sizes for a given leg length, but if you are used to riding something different, that's just what you might prefer...

What Mr. Plager said.

My short crank arms were driving me nuts; my longer crank arms are comfy.

Everyone is different... even you.

 

[Rick Youngblood]

Everyone is different... even you.

I totally agree, short cranks may not the fix for knee pain, but like Bob said it would be nice to experiment with different lengths. However if you have knee problems, short cranks may be one of many areas to explore. It's just trying to figure out what's the source or culprit, shoes, pedals, boom too short or to long, IT band too tight, the list goes on. There's tons of info, and the same goes for controversy.

 

[DuncanWatson]

I have a lot of trouble adjusting the cleats on my shoes. So much so that swapping cleats or shoes gives me anxiety. I miss my old shimano mtb shoes they were perfect, now discontinued.

 

[Eric Winn]

I have 170mm cranks on my Vendetta and 155mm cranks (I think) on my velomobile and the loaner Quest had 155mm cranks of course .

So far I'm most comfortable with the the Vendetta for whatever reason. Personally I think the greater recline tends to make the longer cranks on the Vendetta work better for me.

I'm somewhere between 5'-6" and 5'-7" and currently around 192 pounds.

 

[Alan W Dolbeer]

Before asking the CB folks directly, I thought I would ask here as you guys seem very up on the the V. The full build for the V20 is it 10 or 11speed? No mention of crank arm length either but I would be interested in 165 or 170mm. My Silvio 1.5 has 155mm Ultegra which works fine but I think I would prefer a bit more length on the cranks.

 

[Rick Youngblood]

Before asking the CB folks directly, I thought I would ask here as you guys seem very up on the the V. The full build for the V20 is it 10 or 11speed? No mention of crank arm length either but I would be interested in 165 or 170mm. My Silvio 1.5 has 155mm Ultegra which works fine but I think I would prefer a bit more length on the cranks.

The standard build is 10 speed, and I believe 165mm crank arms are standard. But I think you can have it custom built up also.

FSA SLK Cranks
FSA SLK Calipers
SRAM Rival Shifters
SRAM 11-32 Cassette
SRAM Rival Front Derailleur
SRAM X9 Type 2 Rear Derailleur
Aero 67 700c Wheels
Panaracer Type A 25c Tires

Nice looking S 1.5 I might add!

 

[Alan W Dolbeer]

Does CB do a custom build?
Thanks for complement Rick on the Silvio 1.5. I only dress it up with the carbon wheelset when my fitness is high. At the moment the alloy wheelset is mounted. Planning 50 miles in the morning.

 

[Wannabe]

I am wondering how the length of the crank arms effects inputs on our FWD MBB machines? Would shorter cranks cause less deviations from straight ahead?

 

[Rick Youngblood]

Does CB do a custom build?

Alan, best bet is to email Robert using the Contact Form, I know he would be glad to answer all of your questions in detail.

 

[MrSteve]

I am wondering how the length of the crank arms effects inputs on our FWD MBB machines? Would shorter cranks cause less deviations from straight ahead?

The short answer of crank length and MBB FWD stability is: You.

And my longwinded opinion on crank length is still all about you.
As one of you, here's my experience:

Imagine that you are spinning short cranks.
Right?
Lots of inputs... and you are steering, making lots of little corrections, because of how quickly your legs are spinning the cranks.
Anyway, you're making lots of little steering corrections
-with your head -it weighs five pounds and it's all the way up there at the top-
-with your shoulders and arms
-with your hips and
-with your legs.

Now, imagine that you are spinning longer cranks.
Right?
Not so many inputs needed per minute as you needed for the short crank arms,
but the longer crank arms need the same steering inputs per revolution as the
shorter crank arms did.

The only other difference between long arms and short is that your legs have both a longer
lever and a longer interval per revolution when they spin the longer crank arms.
The longer arms take less steering effort from the legs less frequently.
Why?
Leverage: Longer arms = more leverage which means less steering effort.

The downsides to longer crank arms are:
- more fun going straight while you learn to keep the bike going straight.
This is one reason why Cruzbike shipped their original bikes with short crank arms.
-less room between your thighs and your handlebars, because the longer crank arm
spins your feet in a larger circle, which moves your knees closer to your chest.
-And, of course, with your feet pedaling in a bigger circle, that means you will
need to adjust the TFT (boom) in a little to compensate... which, in turn, moves
your thighs even closer to your handlebars.
This is another reason why Cruzbike shipped their original bikes with short crank arms.
Another reason why Cruzbike equipped their bikes with short cranks is, well,
that's generally how recumbents roll.

I like my long cranks.
So, apparently, does Ms. Parker, so it works for some of us.

 

[Wannabe]

Thanks Steve. As I read that, it made sense.

 

[hamishbarker]

Just sound this on the web and thought this was the best thread to post it in: short cranksets by Cobb Cycling 145, 155, 160 and 165mm

http://www.cobbcycling.com/shop/accessories/Crank-Set

and compacts also
http://www.cobbcycling.com/shop/accessories/compact-crank-sets

In aluminium.

 

[super slim]

Just sound this on the web and thought this was the best thread to post it in: short cranksets by Cobb Cycling 145, 155, 160 and 165mm

http://www.cobbcycling.com/shop/accessories/Crank-Set

and compacts also
http://www.cobbcycling.com/shop/accessories/compact-crank-sets

In aluminium.

http://www.bikesmithdesign.com/Short_Cranks/apex.html

Bike Smith Design cost for shortened 137.5 to 158 mm Sram APEX doubles is $220. but is a bit heavier at 890 grams (for a 175 mm crank) compared to 770 grams

 

[ratz]

Now if someone would make shorties with a removable spider

 

[jond]

hi

I ride 150's and love them.
To me it's all about how your legs are built too. The length of each section, etc.
On the out-stroke you don't want you leg to be over-extended, so for most a very slight bend in the knee is the best setup. Once you have that dialed in, then take a look at what you're knee angle is on the back-stroke.
If it is going past 90 degrees, then it is usually bad on the knees. (Plus there is now power on the out-stroke with you knee bent that far)
With my original 172.5mm cranks, my knees where at at 65 degrees on the back-stroke, and I had some mild pain, and also noticed it was harder to spin anything above 90rpm.
When I switched to 150mm, I had to obviously re-adjust my boom so my out-stoke was correct again, and them my back-stroke is really close to 90. Felt so much better.
A lot of people say they want the longest cranks they can get because longer is better leverage.
While that may be true in theory, I have found that I have not really noticed any loose of power going to the shorter cranks. I can spin faster, climb faster and I have no knee pain.
Actually most of my training and riding I am spinning at 100rpm or higher, and have even done some workout sets above 110rpm for extended periods.
It's a win-win-win for me.
I am actually going to experiment with 140's (and smaller this year) soon and see what kind of metrics I get when compared to the 150's I am riding now.
At really high rpm, the shorter cranks you have, the less your legs are having to go back and forth. That is a big deal when you are going around at 120-150rpm.

hi larry and everyone. i note your great success with shorter cranks and your extensive testing.

as stated it is personal for crank length. i have found that spinning is of course beneficial especially for climbing but my cadence is naturally lower. this may be as you say due to the crank length. i can readily understand it would be preferable to spin at 100rpm 150mm cranks than say my 170mm cranks

however i have noticed that my heart rate goes up with cadence over 90 an i lose form over 100 rpm.

this rise in heart rate is independent of power figures.

Larry i wonder if your personal high cadence actually results in a higher heart rate independent of power too.???? or is it something that over time your body can adjust too. on the trainer i tend to have higher cadence well higher everything actually....... and therefore would imagine you can adapt to the higher cadence. but where is the limit?
where do you lose form? there must be a limit where increasing gradient and it's overall length dictates a required length of crank. but of course that gradient would be few and far between......15% and above pinch points????

it seems to me that when i get my legs flying around my body and heart responds even if my power output is the same.

does anyone else note this as a factor??/

therefore for me with the 170mm cranks i am able to spin only at 90rpm before i see a performance deficit. i normally ride at 80 but when i fatigue it drops to 72 or so. i guess i need to experiment to get a definitive answer though i am very happy with 170mm. i ride with 175 mm on everything else trikes and df.

 

[mzweili]

however i have noticed that my heart rate goes up with cadence over 90 an i lose form over 100 rpm.

this rise in heart rate is independent of power figures.

interesting observation, I feel the same

 

[MrSteve]

This afternoon, after shortening the TFT/boom on my new-to-me Vendetta V1.5, my thighs were starting to make intermittent
hard contact with the bars.
The bars are already closer to me than I'd like... so I decided to install my shorter cranks.

The simple, one hour job took all afternoon.
It was a pretty afternoon.
Bicyclists kept trickling by.
And my road bike was in pieces.

When I pulled the crank out, my fingers told me that the crunchy drive-side bearing was toast.
So, I replaced the Sram Force bottom bracket, cranks and rings with my Sram Rival rings, shorter crank arms and bottom bracket.
New bearings = ahhh.

While I was at it, I replaced the chain -which had some life left in it- but was now too short for my new, bigger rings.
And, since everything was apart anyway, I replaced the cassette, because, why not.

Now my legs fit.
And it shifts like new... because it is.

Tomorrow, perhaps, a ride?

Oh yeah, the reason this is posted here:
Shorter crank arms for opening up the cockpit a little!