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Female bike sizes
May 12, 2010 5:09 PM   Subscribe

5'4" to 5'7" female bicyclists, what size frame / gear ratio do you ride?

I'm going to build a single speed for a friend of mine. It's a surprise so I can't get her on a frame to size out. She's about 5'6". I know there isn't a perfect formula due to leg and torso length, etc, so am looking for a collection of data on what size frames women who are 5' 4" - 5' 7" ride. I'm not interested in mountain bike data. Also not interested in brand recommendations (I'm into bikes and I know what I like). List your height, frame size and whatever other info you feel is pertinent (gear ratio if applicable). She's in shape but isn't a "bike person" so doesn't need to spin a monster gear.

Here is some more info about the bike I plan to build:

- Vintage steel men's road frame, probably something Italian, built as a single speed.
- 700c wheels.
- 170mm cranks.
- something like a 17 degree stem, nothing particularly long.
- Seat post and saddle TBD.
- Gonna be ridden in a flat city. Was thinking 42x17 to start.

Thanks!
posted by nathancaswell to Sports, Hobbies, & Recreation (18 answers total) 3 users marked this as a favorite
 
Oh, and I was thinking slight riser bars.
posted by nathancaswell at 5:17 PM on May 12, 2010


Is there a bike shop near you? This can be a very good resource for you.
posted by cestmoi15 at 5:30 PM on May 12, 2010


51-53 cm (5'6" f here)
posted by slidell at 5:54 PM on May 12, 2010


Actually, my bike is a 54 cm, but when I test ride other bikes, 51-53 is my normal range.
posted by slidell at 5:55 PM on May 12, 2010


I'm a bit under 5'5", and ended up buying a 48 cm (in one of those "Women Specific Design models). When test riding, the bike shops put me on 51 cm models, which seemed fine for stand-over height. However, I felt much too stretched out while trying to reach the handlebars, so the smaller frame worked better.
posted by weathergal at 6:02 PM on May 12, 2010


Mrs. Advicepig is 5' 6" and owns a 50cm in men's Trek but might prefer a 48cm. When she was test riding, she liked a 54cm in a Specialized women's bike the most.
posted by advicepig at 6:12 PM on May 12, 2010


I work in a roadie bike shop.

Leg length is easy to compensate for by dropping / raising the seatpost. You need to prioritize matching torso length to top tube (virtual, if actual is sloping) + stem length. The rule of thumb is that if you were to stand, feet flat on the ground, and you lifted the bike up and balanced it on its rear wheel, the saddle should line up to your crotch and the handlebars should line up to your shoulders.

If you steal some of her clothes (long sleeve pants and long sleeve top) and take them into the shop, an experienced bike fit technician should easily figure out her bike size.
posted by randomstriker at 6:27 PM on May 12, 2010


My girlfriend is 5'4" and rides a 49 cm road frame (not women's specific). She has a triple, I think 50/39/30 and 12/25 in the back.
posted by ghharr at 7:02 PM on May 12, 2010


49cm. Smaller is lightly easier to correct for than bigger.
posted by bensherman at 7:25 PM on May 12, 2010


52 should be a good fit. Top tube length should likely be 53cm. Older Italian bikes can be measured differently. The standard is center to center but still be sure to measure the top tube.

44 17 sounds fine

The cranks could go shorter to 165mm. If she ever goes fixed, then she can pedal through the corners. Italian steel bikes tend to have low bottom brackets and then she can have higher cadence along with better clearance.
posted by sciencegeek at 8:15 PM on May 12, 2010


I'm 5'5" and ride a 44cm Surly Crosscheck.
posted by firstdrop at 8:56 PM on May 12, 2010


I'd be stunned if that 170mm crank doesn't give significant toe overlap with the front wheel on a bike for someone so short, especially on a vintage frame.

The frame sizes offered are useless, imo. I have a custom-built Marinoni and it's 50.5, but my previous bike was a 53 Iro and was not too big. Every manufacturer is gonna measure differently. When buying used, I've found standover height a more useful metric, though of course the top tube length is equally important.
posted by dobbs at 9:24 PM on May 12, 2010


My 5'4" wife rides a 48cm Surly Crosscheck Cross bike and a 52 cm Specialized Ruby (womens version of the Roubaix) road bike. Both fit her well.

Have fun!
posted by cccorlew at 10:46 PM on May 12, 2010


yea what randomstriker said. I'm 5'4", female and ride a 49cm in what's now called "standard" geometry (non-sloping top tube). I've been racing bikes for over 20 years and do my own coaching and fitting for beginners.

The magic component for my fit is that it has to be a 51 or 51.5cm top tube length. My cyclocross bike is actually closer to a 53 in seat tube length, and I have very little seatpost showing on it, but the top tube is the correct length, so I'm fine.

If any given frame runs longer in the TT then it means the reach is off, which throws off my fore/aft balance. Yes, you can compromise by shortening the stem length, but I'm picky about that since it affects how the bike handles.

Fore-aft balance is key. Ideally the rider's weight should be centred over the cranks, not too far forward or aft, with not too much weight on either the hands or the saddle (bar height / drop will also factor in there). Get properly measured by someone who knows what they're doing. Seat tube length is only about 20% of the equation in bike fit, especially since every manufacturer under the sun measures their seat tube at a different spot in the geometrical equation, and this can further be complicated by stuff like "compact" geometry where the top tube slopes downward towards the seat tube.

As far as gear ratios, you don't want to run what I do on my fixie, which is a 48x16 (track gearing). Like I said, I'm a bike racer, thus I'm pretty strong. Depending on whether you plan to run it fixed or free, you can play a bit with ratios (fixed you can get away with running a little taller gearing because the bike "helps" you along a bit) but I'd recommend starting with a 42x16 or 17, both of which are classic "street" gears for single use.

dobbs, I've ridden small fixies with 170s for about a million years (or since 1987, whichever came first), and toe overlap is only as big a deal as you want to make it. It can make it somewhat harder to learn how to trackstand, true, but for 99.99% of daily riding manouevres it never even comes into play. The bigger issue would be cornering clearance when riding fixed, and there you just have to be aware of it, and it's not even clear that the OP is considering running the bike fixed anyhow. In fact, a lot of the truly vintage (road, and especially touring) frames one sees these days have tons of fork rake and will actually have less overlap than the rash of early 90s "crit" style frames and/or track frames that you maybe thinking of.
posted by lonefrontranger at 11:31 PM on May 12, 2010 [3 favorites]


I'm 5'6" but I have short legs and a long torso, so while my old bike was a 52cm my new bike is 49cm. I much prefer the 49.
posted by mlo at 11:41 AM on May 13, 2010


5'4" here w/ short torso, long legs, and the 49cm frame I'm on now is my perfect size.
posted by mochilove at 1:48 PM on May 13, 2010


Leg length matters more than height for this purpose; I'm 5'5" with stumpy little legs. My road bike fits me really well, with a 50.5 cm top tube and a 47.0 cm seat tube. SO height is 28.1".

I'm with the group that says that using shorter cranks might be a good idea, but I don't think it's super-essential either. Especially since shorter cranks can be a PITA to get ahold of. I have no intention of ever riding a fixie (hell, I can barely get around town on a geared bike as it is), though...

My gear ratio isn't going to be too helpful for you because I live in a super-hilly city so I opted for the triple (and I STILL can't make it up some of these damn hills...)
posted by kataclysm at 4:17 PM on May 13, 2010


Leg length matters more than height for this purpose

No.

Torso length. Torso length. Torso length. Torso length. Torso length. Torso length.

Have you noticed how almost every bike sold these days has a sloping or semi-sloping top tube? Have you also noticed how bikes only come in 5 or 6 sizes now (XS,S,M,L,XL), versus a dozen (46,48,50,52,54,56,58,60,62) a decade ago? These two facts are interrelated.

The semi-sloping top tube is one of the greatest innovations in cycling, not for stiffness, handling or any other bullshit "technical" reason. The semi-sloping top tube makes leg-length and standover height non-issues for sizing a bike correctly.

The only real factor now is matching torso length to virtual top tube length, rather than matching a difficult combination of leg and torso length to standover height and reach.

Thus, in one fell swoop, bicycle manufacturers have been able to cut in half the number of sizes they have to produce, which has simplified inventory management, which has led to lower costs for everyone including the consumer.

Case in point: Colnago is one of the few makers that offers non-custom frames in "traditional" (horizontal top tube) shape. But this is only true for their top-of-the-line, high margin models. And these "traditional" frames are still offered in at least a dozen sizes, because they're harder to size correctly.
posted by randomstriker at 3:20 PM on May 14, 2010 [1 favorite]


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