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-   -   Selecting crank length (http://www.bikeforums.net/track-cycling-velodrome-racing-training-area/881200-selecting-crank-length.html)

Dolamite02 04-02-13 10:56 AM

Selecting crank length
 
On my road bike, I'm running 172.5 cranks, while my stock Pista has 165's. I'm interested in swapping cranksets for DA before I start buying rings, but don't know the right length to go with. I've heard that shorter lengths help prevent pedal strike on the track, but I'm wondering a) if that's true, and b) either way, what's the common advice for crank sizing on the track?

theblackbullet 04-02-13 12:02 PM

a) yes, but that doesn't necessarily mean that you will have issues with a longer crank. I've ridden both the Dick Lane Velodrome (36 banking) and the Giordana Velodrome (42.5 banking) using 172.5 cranks without any issues.

b) Generally you will see shorter crank lengths at the velodrome. Most riders find the shorter crank length easier to spin at higher cadences. As mentioned earlier though, I use 172.5 cranks which is the same length that I use on my road bike. It's all personal preference. What I did was buy cheap used cranks to play around with length before investing in a set of cranks that I really wanted in the length that I preffered.

theblackbullet 04-02-13 12:03 PM

and assuming you stay with a true track crankset with a 144bcd, there isn't any reason you shouldn't be able to start investing in chainrings

Hermes 04-02-13 12:32 PM

I have used 172.5 at Velo Sports Center 45 Deg, Superdrome Frisco, TX, 45 deg and Anadia Portugal 42 deg banking with no problem. Generally, one is going fast enough that pedal strike is not a problem meaning one is perpendicular to the track in the turns. If one slows enough to strike a pedal, more than likely, one will slip down the track anyway. So for pursuit and mass start racing, 172.5 is fine. For match sprint competition, it can be a problem. If one uses sticky tires and the right technique, one can go slower in the turns.

For example, the Superdrome in Frisco, TX is a 250 track with 45 degree banking but has a rougher painted surface. So racers can go very slow in the turns. I watched 3 racers strike a pedal and slide down the track going too slow. I do not know what crank length they were using.

Traditional theory on crank length is sprinters use shorter cranks and pursuiters use longer cranks. Experimentation and testing is the best way to determine optimum crank length and gearing.

Dolamite02 04-02-13 01:14 PM

Thanks for the input, guys. As to the investment in cranks, unfortunately my Pista came stock with FSA F. Gimondi cranks which run 130BCD. I'd prefer to jump to a 144 crank early rather than replace rings later.

Jaytron 04-02-13 01:58 PM

It's hard to recommend crank length because a lot of it boils down to preference. What Hermes said:
Quote:

Traditional theory on crank length is sprinters use shorter cranks and pursuiters use longer cranks. Experimentation and testing is the best way to determine optimum crank length and gearing.
is generally true. I did a search for this answer a while back, and it seems that sprinters will go for about 5mm shorter than their road bike for crank arm length.

FWIW, I couldn't decide so I went in the middle. I have a 172.5 on my road bike and went with 170mm on my track bike. Can't really tell the difference, but I've been injured so I haven't been riding much.

Dalai 04-02-13 04:49 PM

I ride the length which came stock on my track bike which was 170mm. I have 175mm arms to swap over for pursuiting but haven't done so yet. Otherwise I ride a range of crank lengths - Road, TT and MTB 175mm, CX and commuter 172.5mm...

carleton 04-02-13 04:58 PM

Quote:

Originally Posted by Dolamite02 (Post 15459990)
On my road bike, I'm running 172.5 cranks, while my stock Pista has 165's. I'm interested in swapping cranksets for DA before I start buying rings, but don't know the right length to go with. I've heard that shorter lengths help prevent pedal strike on the track, but I'm wondering a) if that's true, and b) either way, what's the common advice for crank sizing on the track?

Let me confuse you:

1) The rule of thumb is to go 5mm shorter than your road cranks.

2) If you are over 6' use 170mm, under 5'8 or so use 165, in between use 167.5

3) If you are a pursuiter add 2.5mm. If you are sprinter subtract 2.5mm

4) Measure your femur.

5) If you mash, go longer. If you spin go shorter.

6) Do what feels good as one study has shown that self-selected length made the most power.


Soooo... basically you have to try several out to see what works. There is no magic formula or right answer.

I'd suggest buying 167.5mm which is in the middle of the most common 165, 167.5, and 170mm trio. It's really going to come down to trial and error. I've raced 165, 167.5, and 170...and you know what? It didn't make that much of a difference in my results. What I lost in torque I gained in leg speed and vice-versa.

So, how tall are you?

carleton 04-02-13 05:00 PM

I've read stories of elite athletes who change crank length based on the event, shorter for mass start and longer for pursuits.

Finding the right crank length is like finding the right saddle. It could be a short or long journey.

queerpunk 04-02-13 05:51 PM

To carleton's list, I'd add, "pick one and don't stress too much about it."

Dolamite02 04-03-13 10:27 AM

Quote:

Originally Posted by carleton (Post 15461577)
Let me confuse you:

1) The rule of thumb is to go 5mm shorter than your road cranks. 172.5-5=167.5

2) If you are over 6' use 170mm, under 5'8 or so use 165, in between use 167.5 I'm 6'1"

3) If you are a pursuiter add 2.5mm. If you are sprinter subtract 2.5mm Don't know the answer yet. This is only season 2 on the track.

4) Measure your femur. 20"

5) If you mash, go longer. If you spin go shorter.

6) Do what feels good as one study has shown that self-selected length made the most power. 10-4


Soooo... basically you have to try several out to see what works. There is no magic formula or right answer.

I'd suggest buying 167.5mm which is in the middle of the most common 165, 167.5, and 170mm trio. It's really going to come down to trial and error. I've raced 165, 167.5, and 170...and you know what? It didn't make that much of a difference in my results. What I lost in torque I gained in leg speed and vice-versa.

So, how tall are you? 6'1"

Bolded

carleton 04-03-13 10:53 AM

Quote:

Originally Posted by Dolamite02 (Post 15464293)
Bolded

I'm also 6'1" and I'm a spinner. I liked 167.5. I'd start there. You'll like it.

Dolamite02 04-03-13 11:11 AM

1 Attachment(s)
Sounds like a winner to me. Grassy ass, Carleton. In thanks, I offer the following photo.

https://sphotos-b.xx.fbcdn.net/hphot...35992808_n.jpg

carleton 04-03-13 11:42 AM

Thanks, bro :)

Profile updated.


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