A crankarm length question...

Discuss light weight issues concerning road bikes & parts.
veloflyte
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by veloflyte

To be honest, this is a question about your opinion of a special crankarmset that, while riding, you can alter the crank length of...
I've been an avid cyclist for many years now. I've always been rather picky about my crank length. For me, it seemed that I wanted a different length for each discipline...climbing, criterium racing, and general cycling over multiple terrain types. I've been toying with the idea of having a well made crankset that, with the push of a button mounted on the handlebar, you could alter the length of the arms. I've got a very solid idea as to how to produce such an item. It's weight and appearance would be quite pleasing.
So, if you can take a minute to ponder the thought, would you find it as interesting and perhaps useful to have such a crankset...?

by Weenie


latman
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by latman

no , actually

ghisallo2003
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by ghisallo2003

Not for everyday use. Happy with my length !

Maybe for bike fitting - power testing?

RussellS
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by RussellS

No. 175mm works fine for me for all types of riding. Touring, criterium racing when I did that, cyclocross bike, single speed bike. Although one single speed does have 172.5 cranks because that is what I had around to use. I think Look makes a crankset where you can change the length between 170, 172, and 175. It does this with the hole the pedal threads into. Its an insert that comes out and you can rotate this insert to one of three positions. I suppose if you carried a 6mm Allen wrench with you, you could make the change in the middle of a ride. But not with the push of a button on the handlebars.

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asphaltdude
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by asphaltdude

An adjustable crank for bike fittings would be nice (probably already exists) but I don't see a market for on-the-fly adjustability.

BTW, I'm under the impression that (finally) crank length is not that big of a deal anymore. It's not something magic.
Whow! That's a pretty damn nice garage door!

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euan
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by euan

165mm for everything. But especially cyclocross, you can get spinning sooner out of corners and it seems to have a quicker zip up to leg speed as well.
"Step forward the climber and all those who worship at the altar of lightness" - R. Millar

Frans
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by Frans

Agree for fittings or power testing but that's about it.

Basso tried to have an adjustable seatpost in the 2011 Giro. (a much simpler mechanism than this proposal) That caught on like a chocolate teapot.

Look already make adjustable cranks - there's a slot at the pedal hole which takes a wedge with the pedal threads cut into it. Depending on how you mount the wedge you can make them longer or shorter. http://road.cc/content/image/2298-look- ... ngth-crank" onclick="window.open(this.href);return false;

Next idea please?

Frans
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by Frans

http://www.lookcycle.com/en/us/route/ac ... zed-2.html

Looked a little harder. I mean these are smart for a variety of reasons, you can run them 130 and 110 as well:
- 110 if you're tired and want to have compact rings like 52 x 36 or 34 for touring.
- 130 for my fave CX gearing (46x38)

Ok, so maybe you're right in the people don't play with their crank arm lenghts enough to really explore what makes sense for them.

I got carried away with the Leonard Zinn crank lenght calculator (google it, it's easy to find) 3-4 years ago which resulted in me purchasing 180mm 7800s for my 89cm inseam. The 180s are excellent for long hilly sportives. They're NOT great for crit racing and sprinting b/c I simply cannot turn them over smoothly much above 110 rpms. Horses for courses.

User Name
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by User Name

Frans wrote:Basso tried to have an adjustable seatpost in the 2011 Giro. (a much simpler mechanism than this proposal) That caught on like a chocolate teapot.

Ha ha! I want one of those posts! :D To be fair to the company, I think it was something that Basso just wanted for himself, rather than a product that they really thought was gunna sell tons of.

I would pay hundreds of bucks for one. In search of one, I started a thread about them (here, I think), and even emailed FSA, but had no responses.

I'm one of those dudes who always adjusts his seat height, mostly because my lower back is a bit dodgy, and the difference between what feels comfortable on a good and bad day can vary up to 7mm! I also like to be a little lower for strong head and crosswinds.

Sorry to hijack the thread there for a moment.

The "changing crank length" is something I might be interested in, provided, of course, that it was 100% reliable, and without creaks, clicks or any perceived movement in the arm. I imagine extra weight and cost could be an issue. I like having longer cranks for off-the-saddle stomping, so I reckon it would great to flick a switch and have 185mm to sprint over to a breakaway. Seat height would also be an issue, because almost all people adjust the seat height for a different crank length
Last edited by User Name on Sun Jan 13, 2013 3:41 pm, edited 1 time in total.

Valbrona
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by Valbrona

Check out the Stronglight Adjustable Length System: http://www.stronglight.com/stronglight/ ... =fissionTI" onclick="window.open(this.href);return false; I use a Fission Triple.

I believe that Look also do adjustable length cranksets, as per a previous post.

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yourdaguy
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by yourdaguy

The problem with this idea is that most people take a period of time to adjust to a different crank length. Some even initially have knee problems because of the different angles of the knee with different lengths. Also, when you change crank length you must change the seat height, all things else being equal. So I see no market for cranks that can change on the run so to speak. The Look cranks are a great idea for someone that is not sure of their size, for dealers that don't want to stock 3 sizes of cranks, for people that share a bike, for a father that wants to give a bike to a child later, etc. but changing on the fly provides no benefit that I can see.
For certain parts stiffer is more important than lighter.

jano
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by jano

Aerozine also has a adjustable crank arm length system based on a wedge solution which allows the adjustment at 170, 172.5 and 175 mm lengths.

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asphaltdude
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by asphaltdude

I can't help being under the impression that these adjustable length cranks from Time and Aerozine have something to do with lower production costs :roll:
Whow! That's a pretty damn nice garage door!

jano
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by jano

asphaltdude wrote:I can't help being under the impression that these adjustable length cranks from Time and Aerozine have something to do with lower production costs :roll:


It is possible. The advantage would be especially that you will sell the cranks no matter what length the end user needs, so logistics are simplified as they only need to produce 2 different wedges, one for 170 and 175 mm lengths and one for the 172.5 length.
Personally I am curious how well the wedge system hold over time.

by Weenie


Geoff
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by Geoff

Well, you could get a Science SRM and test it. At least you'd have empirical data. Personally, I can't stand riding anything but 172.5's (I even have 172.5 track cranks). Everybody is different...

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