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 Post subject: Crank length - track
PostPosted: Tue Nov 30, 2010 12:22 pm 
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Joined: Wed Dec 15, 2004 10:54 am
Posts: 1411
Location: Melbourne, Australia
Interested in your views on crank length for track events. General suggestion I've seen is shorter for sprints and longer for pursuits. Curious if this is based on science or tradition! :noidea:

Specifically wondering if there is any benefit going from 170's to 175's for the pursuit, in particular starts? Currently I'm racing 170's for all track events and 175's on both the road and TT (UCI legal position) bikes. Interested to know if it would be worthwhile to source some 175mm arms for my track bike just for the pursuit and kilo.

Thanks

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Last edited by Dalai on Tue Nov 30, 2010 1:12 pm, edited 1 time in total.

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 Post subject: Crank length - track
Posted: Tue Nov 30, 2010 12:22 pm 


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 Post subject: Re: Crank length - track
PostPosted: Tue Nov 30, 2010 12:47 pm 
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Joined: Thu May 03, 2007 10:39 am
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Well I'll refer to Jim Martin's study on crank length here as the study looked at peak power production. It seems that peak power is largely unaffected by crank length. That being said the kilo is not just about peak power. The ability to sustain a high power output seems to boil down to maintaining a high cadence. Now the question is, can YOU maintain 150rpm on a 175mm? Unless you feel some sort of limitation with the 170s I would stick with them. But you are right to some degrees that much of track cycling is dictated by tradition. But given how long it's been around sometimes that is for a reason ;)

FWIW, I run 170 for everything on the track.

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 Post subject: Re: Crank length - track
PostPosted: Tue Nov 30, 2010 1:11 pm 
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Joined: Wed Dec 15, 2004 10:54 am
Posts: 1411
Location: Melbourne, Australia
Tapeworm wrote:
Unless you feel some sort of limitation with the 170s I would stick with them. But you are right to some degrees that much of track cycling is dictated by tradition. But given how long it's been around sometimes that is for a reason ;)


Thanks Tapeworm. Not feeling a limitation, just looking at all options. :wink:

I'm currently trying to hunt down an elusive set of older 4 bolt SRM track crank arms (or can also use 3 bolt octalink road arms) to test. And since I've still no luck sourcing second hand, I thought I'd ask before dropping $300 for a new set of arms for what is realistically only four pursuits a year (club, State individual and Omnium and lastly Nationals).

Peak power may not be affected, what about the additional leverage of the longer crank and starts then?

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 Post subject: Re: Crank length - track
PostPosted: Tue Nov 30, 2010 2:41 pm 
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Joined: Wed Oct 06, 2004 6:55 pm
Posts: 1921
Location: Vienna, AUT
You might want to consider your track too.
If you are indoors on a steep track, then you should consider clearance - perhaps not so much for pursuit though.
Sprinters are pulling some crazy moves on the boards and therefore probably tend toward shorter cranks as opposed to the pursuiters who are not contending with traffic.
If you track bike has a lower BB then that also plays a role in your decision.
I also run 175 on the road and have used 170 and 167.5 on the track. I could not really tell the difference (after fiddling with the track fit to get it right)
But I was comforted psychologically with the knowledge that the cranks would not bottom out as fast as with 175's.
I say stick with the 170's and use the money saved on some rocking fast track tubulars...


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 Post subject: Re: Crank length - track
PostPosted: Tue Nov 30, 2010 5:29 pm 
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Location: New York
Track frames by design always have a higher BB.

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 Post subject: Re: Crank length - track
PostPosted: Wed Dec 01, 2010 1:08 am 
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Joined: Thu Nov 18, 2010 1:44 am
Posts: 121
Location: Melbourne
Dalai the track SRM I have has crank arms from a set of Sugino cranks, ground down, tapped / threaded and fixed via 4 bolts. It's a fair bit of work (I bought them from someone like that), but thought I'd mention it as it is another option. From memory SRM crank arms are a tad soft? Not to disparage them but they are also damn ugly ;-)

Did you ask the same Q on FGF?

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 Post subject: Re: Crank length - track
PostPosted: Wed Dec 01, 2010 2:40 am 
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Joined: Wed Dec 15, 2004 10:54 am
Posts: 1411
Location: Melbourne, Australia
Cheers MrAK. I haven't had any issues with SRM arms, but I also am not punching out huge numbers... Your set up sounds pretty involved, happy enough to use the standrad SRM arms as I'd only swap then for specific events and I don't mind how they look either. :wink:

I've searched on FGF but haven't asked the question yet.

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 Post subject: Re: Crank length - track
PostPosted: Wed Dec 01, 2010 4:36 am 
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Joined: Wed Dec 15, 2004 10:54 am
Posts: 1411
Location: Melbourne, Australia
I found the following topic on FGF - http://www.fixedgearfever.com/modules.p ... sc&start=0

Quote:
Gentlemen....just to add to the myth, if you can cast your minds back to the 2000 Sydney Olympic Games, and remember that the German Teams Pursuit were the first team to ever break 4 minutes. Then it was told that they all used 180mm cranks, and so we all tried to change. Subsequent revelations will suggest that it was something other than long cranks that won them the gold and set that time.

To add to this comical scenario, in the early 2000s NZ employed one of the most succesful endurance track coaches the world had seen, a man who took Australia to many many world and Olympic titles through the early 90s. When he came to NZ he would make the riders all train on the track with a certain length crank, and then on race day increase the crank length. This without any changes to position... well hello..if you have set the rider up in their optimal position...and then change something...its not optimal anymore!!!!!!!!!! Unfortunately when I inherited the NZ Team, there were still a couple of guys that would still do this...and they still do. When I asked why this was done to the respective coach...he couldnt give me a categoric answer.

With our Pursuiters, we have some big guys...and we tried all sorts of crank lengths from 170-180mm, and I have to tell you that most went better on 172.5mm.

But to add a little fuel to this firey debate... consider this..if your car gets a flat and you have to change the wheel..you get the jack out to lift the car...if you hold the handle close to the jack..its difficult to lift and push...but if you hold the handle right at the end where you have more leverage...it is far easier to use.

That is where the theory of a longer lever is easier.

So...this is my opinion for what it is worth...power is measured through the bottom bracket, or rear wheel and as such it doesnt measure the actual force on the pedals. It measures power output, but not specific power through the pedal. Even though the crank is longer and at the pedal is easier to turn at slow rates, the cadence doesnt alter irrespective of what crank length you use...but....your pedal speed does increase as the crank is lengthened... because it has further to travel through 1 rpm.

Therefore a longer crank should assist with acceleration to a given cadence, but then the reverse occurs..the faster the cadence the less efficient your pedalling becomes because of biomechanics, and of course he fact that with the longer crank the pedal speed is increased.

Maybe Im right..maybe Im wrong...

Terry Gyde
Champion Training Systems

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 Post subject: Re: Crank length - track
Posted: Wed Dec 01, 2010 4:36 am 


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 Post subject: Re: Crank length - track
PostPosted: Fri Dec 03, 2010 6:49 pm 
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Joined: Tue May 23, 2006 4:33 am
Posts: 737
It's important to realize that all these studies, including Martin's, look at one or two parameters in assessing the efficacy of different crankarm lengths. They don't address all the issues.

Consider, for example, that on the track you have to ride on the drops all the time (madisons excepted). While some rules are being bent for riding on the tops (the Cameron Meyer position), the rule books and most officials will call you for riding anywhere but in the drops. Certainly for most events you have to be in the drops. Now if you are, your abdomen and diaphragm are being compressed by the lower position. If your crank arms are longer, not only do your legs potentially extend farther, but they also rise farther up into your chest. This leads to further compression and restrictions on breathing. You may get more transient power, but you can't breath as well and survive in any event longer than a 200m. This is actually one of the most cogent reasons for sticking with shorter crankarms on the track. Also, most riders riding longer crankarms rotate their hips improperly to accommodate the range of motion required, and this is exacerbated with the more aggressive positions many riders take on track bikes. If you rotate your hips, your cadence and power are both limited. So despite whatever a laboratory study may say, unless you are quantifying everything on your own accurate powermeter, you may not be doing as well. Generally the top riders in the world have flexibility that the rest of us only dream about, as well as the body geometry to match. As a result, they can get away with more than we can. When I coach riders, I rarely recommend anything but a 165 track crankarm to begin with. Everyone blows smoke about power and snap and so on, but the real issues are more basic. You have to have your body in the right position at every degree of rotation of the crankarms or you are going to lose on the track. The speeds are higher and you don't have the option of changing hand position or doing lots of out of the saddle riding like a hill-climbing road rider might. So your position better be perfect. You do less harm to your position and your efficiency with 165's. Going longer, you may do fine, but test it first.

And by the way, almost any decent track bike on any steep track in the world, including the 50 degree Moscow indoor wood track, will do fine with 175 mm crankarms. As long as you don't have a really funky road fixie or a converted road bike, crankarm length isn't a contributor to hitting the pedal on the banking.


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