September 23, 2014 Login  


Sizing Conundrum
Last Post 08/20/2014 04:40 PM by ed custer. 35 Replies.
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Jimmy

Posts:27

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06/22/2014 12:39 PM
Yesterday, my wife indicated she'd like to get a road bike. The first issue is trying to figure out the right size. We are exactly the same height at about half inch shy of six feet. However, proportionately, we are polar opposites. I have a very long torso, so I am always looking for bikes with a long top tube and front end. So I ride a 56cm bike, generally with a 56-57cm top tube and long stem. My wife's legs are in the neighborhood of 4" longer than mine, and has a proportionately short upper body. Further, being new to cycling, a long and low position is not going to work for her, sort of a bummer because I am selling my road bike right now, but I don't think I can get it to fit her correctly. I am assuming I need to look for a 58-60cm bike with a tall head tube and short top tube. Given her normal female proportions, but a very tall height, does anyone have any suggestions or recommendations?
zootracer

Posts:292

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06/22/2014 01:47 PM
You should look at a women's specific bike...they have shorter top tubes.....
smokey52

Posts:80

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06/22/2014 10:20 PM
Zoot, the issue with WSDs is that they generally use 650 instead of 700 wheels and are targeted for women shorter than around 5'2".
Jimmy, I would look for a more relaxed-fit bike. Rivendell has some. What price range are you looking at? You could consider a fitting session at a reliable shop. Sometimes they roll the price of the fitting into the cost of the bike. Depending on the brand, a touring bike can be more upright than a road bike.
You can also consider renting bikes to check the geometry out on an extended ride. I used to ride a triple-crank, but after renting a compact during a business trip, I bought a bike with one.
sappie66

Posts:10

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06/22/2014 10:34 PM
Smokey's advice is good. The "Plush" bike is now a well-established category now -- just see any "buyer's guide" issue in many bike magazines. These are the taller headtube designs like Giant's Defy line, Cannondale Synapse series, etc. Also, see Cervelo's view on WSDs -- they essentially say its bullshyte. Their sizing philosophy has always been their own rather than conventional -- worth a google.

BTW - my wife and I are also close in height, but considerably shorter than you guys.  My main bike is a 49cm Cervelo SLC and my wife rides a 51cm Spec Amira Expert.  I can ride it just fine, but the position is considerably more upright and the bar is closer in.  Her legs are longer than mine too.
jmdirt

Posts:700

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06/22/2014 11:45 PM
Jim, how much extra steer tube do you have? After I dinged my C5, I went from a 110 mm, -6 degree stem to a 90 mm, +6 degree stem, and raised it 1 cm on the steer. It made my position on the bike more comfortable, and it didn't change the handling enough to even discuss. My neck is better, but I'm keeping the position. As you know though, I only ride my road bike when the trails are wet. Anyway, that might make your bike work for your bride, or at least give you a good reference if it doesn't.
Cosmic Kid

Posts:1109

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06/23/2014 10:00 AM
Zoot, the issue with WSDs is that they generally use 650 instead of 700 wheels and are targeted for women shorter than around 5'2".


That's not quite accurate, smokey. Very few actually use 650c wheels, maybe a few of the smallest sizes, but even then it is not automatic. I don't think the Trek WSD bikes have any 650c wheels.

All the women's bike lines offer a full size range, as well. Some of the trek models go up to 62cm and the Specialized Ruby Sport has options at 57cm.

I would definitely look at some women's specific models, but the "endurance / gran fondo" style bikes would also be a good option.

Just say "NO!" to WCP!!!!
Keith Richards

Posts:735

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06/23/2014 10:51 AM
I agree with CK in that there are a wide variety of frames from her to choose from.

She should look at both women's and men's sizes appropriate for her. And as always, stem and bars to finalize position. When I worked at a shop a stem and or bar swap would do wonders, especially for taller female riders.
----- It is his word versus ours. We like our word. We like where we stand and we like our credibility."--Lance Armstrong.
Master50

Posts:230

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06/23/2014 10:59 AM
Since your wife is tall she does have more options than many women. In general you need to adjust bike size for Top Tube length and in most cases you need a smaller frame size for your wife than you do with a long torso. My wife rides a bike 2 cm smaller than a man of the same height to ensure her stem is not less than 10 cm. I picked that stem length to ensure goo balance. If drop from the seat to the bars is a problem for her you may need to look at bikes with a taller head tube as the smaller frame size will make this issue worse because of the longer seat post she needs.
Obviously a lot of really good bikes are available in women specific builds and you can even get a top level bike like a Colnago in custom size but I expect that option is over the top in this case?
smokey52

Posts:80

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06/23/2014 07:24 PM
Cosmic,
I guess things have changed in the last decade. When I searched for a bike for my daughter's college graduation a few years ago (11), all the WSDs had 650s.
Jimmy,
Another way to check on sizing would be to extend the seat post up to comfort height and rotate the bars up (or down) to simulate a change in stem length/angle. Take the measurements and find a frame/stem that replicates.
jookey

Posts:139

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06/23/2014 08:27 PM
I always tell my wife size doesn't matter.
THE SKINNY

Posts:395

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06/23/2014 08:29 PM
you might spring for a professional fit. they are pricey but sometimes they take that out of the price of a new bike. plus that puts the burden of getting a comfortable fit on the shop and not on you. sadly, now women specific bikes come in much nicer colors than men's bikes. those dark flat charcoal and glossy magentas do it for me.
How we spend our days is, of course, how we spend our lives.
Oldfart

Posts:472

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06/24/2014 02:11 PM
Master50, what is wrong with a stem under 100mm? By balance you mean?
79pmooney

Posts:1115

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06/24/2014 04:22 PM
I have heard for years that bikes with stems shorter than about 10 cm tend to be very quick steering and that if the front end geometry isn't designed to compensate, the bike can require undo attention to ride safely. I have never ridden shorter that 11 cm (at least not since I was riding my UO-8 with it's steel rims and very slow steering) so I cannot comment first hand but I have pushed the other extreme, to super long stems. I want the bike under a 180 stem to be too quick for normal use.

The thoughts that have been around for dedicated are that longer stems have more inertia so a sudden bump to one side of the handlebar has less effect and that handlebars on longer stems move more to make a course adjust; this in effect "desensitizes the steering. That first thought, inertia, makes a lot of sense to me. Rotational inertia is a function of the mass of the system times the square of the radius. Since the system includes the handlebars, brakes, tape, etc. the radius is affected a lot by a change in stem length. (Comparing a 100 to a 130: 130^2/100/2 = 1.69 or a 130 stem and bar has almost 70% more inertia than a 100.)

Now, you can make the bike behave as I said before with proper geometry. There are millions of proper handling bikes with very short stems. Even stems pointing back.. But you will notice the fork and headtube angles don't look racy, certainly not anything you would put a friend on. (Witness all the third world cargo bikes.)

Ben
SideBySide

Posts:170

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06/24/2014 07:32 PM
Wouldn't the vast majority of inertia be in the spinning wheel? I would think the stem length would be relatively less important, especially at speed.

Note: My last physics class was in high school, a long time ago.
79pmooney

Posts:1115

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06/24/2014 09:28 PM
At speed, yes. But at slower speeds, wheel inertia doesn't stabilize steering much. (And the inertia we are talking about here is gyroscopic. It isn't very hard to turn a light spinning wheel held by the axle. You can put your SO on a bike with heavy wheels and tell her it is for her safety, but I will leave the premises before you start.)

I haven't run the numbers and don't plan to. But as I said above, I have noticed real changes when I increased stem lengths.

Ben
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