's Forum Archives - Components

Archive Home >> Components(1 2 3 4 5 6 7 8 9 10 )

Crank Length & Cassette Size(12 posts)

Crank Length & Cassette Sizemaryb
Apr 3, 2002 8:11 AM
Newbie here! Need advice on crank length & cassette size. Here's my background. Just over 33in inseam (72.6 cm). I never mash big gears and hills are my biggest challenge. For a girl, I'd like to say I'm pretty tough, but I'm not a pro. I ride about 80 miles/week (on an old triple) but I have a new bike I'm building and will keep increasing mileage over the summer to about 120-140 miles/week.

Here's what I'm thinking. Ultegra double - 170 crank?

You guys take it from there... any suggestions?
Some thoughts...Pedal Jockey
Apr 3, 2002 10:27 AM
First of all, something is not correct with your inseam measurement. A 33" inseam converts to 83.82cm. If 33" is correct then you must be a tall female to have such a long inseam. I have an 87cm inseam, and I use 180mm cranks. 170mm crank arms will help your spin, but I might advise on 172.5mm or 175mm lengths. Remember, with each 2.5mm of crank length, you gain 15.7mm of length in the revolution.

See if an LBS will let you try different crank lengths, and choose the one most comfortable.

As far as the cassette goes, if you are not a strong climber, but will be working on your climbing skills, then get a cassette with a 25t large cog. If you are going to avoid the hills at all costs, then a 23t max cog will suit you just fine.

Append...Pedal Jockey
Apr 3, 2002 10:33 AM
There is not a rule in sizing that says x length of inseam needs to go with y length of crank arm. If you want to promote your spin, choose shorter cranks. If you want to mash (although mash really is not the right word) then go with longer arms. With my 180mm cranks, I spin very comfortably, and I climb well with them.

Zinn had a very good tech article in Velonews on this subject. See if you can find it and read up.

Thanks PJmaryb
Apr 3, 2002 10:38 AM
Is it really that hard to believe... a chic with long legs?
Thanks for your advice, especially on going to the lbs to try out cranks. I've got a bunch of back issues of Velonews, so I'll check that out too.
Here is some more information...Pedal Jockey
Apr 3, 2002 10:53 AM
This website had some good advise about crank arm length sizing:

Zinn's articles in Velonews were in May and July 1996. Here is another website for you to reference on the subject, and this one talks about Zinn's study.

long inseamsimstress
Apr 3, 2002 10:55 AM
If 33" is correct then you must be a tall female to have such a long inseam.

Not necessarily. Women tend to have longer legs and shorter torsos relative to men. For example, my legs are as long as my boyfriend's, yet he is several inches taller than I.
ditto to simstressmaryb
Apr 3, 2002 11:12 AM
I agree with you on that one! All my height is in my legs, and I have just about the same inseam as my boyfriend who is also 1/2 foot taller than I am. Even with the inseam length, due to shorter torso, I actually ride a 53 Lemond Maillot Jaune.

While I have a female in tow... I have some questions for you. I've been trying to find decent road shoes but am frustrated by the lack of available kinds. Have you or any friends tried mens?
I like my Carnacs...dsc
Apr 3, 2002 1:08 PM
not simstress here, but as another long-legged female (34"!)
I thought I'd chime in:

at my height (5' 10"), I've got the size 42 feet to match, so I can almost never find a decent selection of women-specific gear. I tried out several pairs of shoes, and eventually went with a pair of Carnac Comets. I like the wide toebox, as my feet tend to swell slightly about 4 hours or so into the ride. Tried the Sidis (men's AND women's model; LBS actually had my size!) but they felt just the tinest bit snug. Might have been OK, but didn't want to chance it. Also tried on some Northwaves that felt good.

Anyway, my 0.02. Hope it helps.
Good luck!

Apr 3, 2002 10:20 PM
My sister uses unisex Sidi Genius 3. She loves them so much better than the women's Diadoras they replaced.

I am using Lake shoes right now. They are comfortable for rides as long as centuries, even multi-day events. I have women's Sidi Toscanas for MTB and Spinning. They are less comfy than the Lakes, but that may be due to the SPD's they are used with.

I am considering both unisex and women's Sidi Genius 4's for my next shoes. I am, however, willing to consider any other shoe that has a good fit, comes with a buckle, and takes Speedplay cleats without big adaptors.

Good luck finding your shoes!
re: Crank Length & Cassette Sizemaryb
Apr 3, 2002 10:34 AM
Sorry! Correction 33" = 83 +/- cm inseam.
Correction! 33" = 83cm (sorry!)maryb
Apr 3, 2002 10:44 AM
my personal experiencesjw25
Apr 6, 2002 12:43 PM
I'm a fairly new road rider, coming over from the dirty side a couple years back. My first bike had a 170mm double (39/53) with a 12-23 cassette.
Compared to 175mm cranks on the mtb, the 170's felt pretty strange, and with the gearing, I seemed to be caught between the "spinny" cranks and the "mashy" gearing. Being a newby didn't help, either. My inseam's 33" or about 84cm, so pretty close to yours.
I swapped up to 172.5mm cranks, after reading somewhere that road should run 2.5mm less than mtb. That's probably not that accurate, since the gold standard for mtb is 175, but that's what I tried.
Even though it's only a 5mm increase total, it definitely felt better to me, and gave more leverage on the hills. I'm not really a spinner by nature, so I haven't noticed much difference there, but after mounting a computer with cadence, I see I can spin 110 - 120 rpm pretty comfortably.
In back, I went to a 12-25 cassette, and again, found it to suit me a lot better. I don't mind the larger gaps between gears, and I like having a 25 to spin on when things get climby.
The TT bike (really my first road frame, with some new parts) has 172.5's with a 12-23, but I'm wanting some 175 cranks there, to see if it helps on the hills.
So, if you made it this far, I'd start with 172.5's and see how they feel. Most of the women in my club, racers and non, ride doubles, so I'd stick with 2 rings, but maybe a bigger cassette, like a 12-25 or even the 12-27. You might also want to swap the 53 for a 52 up front, if you never mash. Me, I like mashing, but to each their own.
If hills are your problem, practice, practice. I do a ride about once a week with lots of climbing, mostly 2 big grinders, but with lots of smaller rollers, too (central PA isn't flat). With a HRM, you can watch your effort in different gears, and more importantly, pace yourself to crest the top strongly.