The Problem with Women
Written by: Dan Empfield
Date: Tue Mar 05 2013
The problem is, of course, the constraints placed on bike design if you mandate that the bike be built with 700c wheels. I’ll end this with a wheel size anecdote, but, for now, let’s just stipulate that, at least for road race bikes, the wheel size is going to be 700c for all sizes. While the issues and problems are almost directly analogous when we talk tri bikes, today I’m writing in the context of road bikes, aka road race bikes, not tri bikes.
The problem is shoe overlap, which is not a problem in the course of normal riding, but it is when the wheel is turned sharply. This often occurs at low speeds, when the rider needs to execute an abrupt turn of the wheel in order to balance. Imagine a rider taking off from a dead stop, trying to clip into the pedal before reaching sufficient speed. Imagine a rider climbing a difficult hill, ascending without sufficient speed to keep balanced. “Learn how to ride better, and with appropriate gearing, and shoe overlap is not a problem,” you might say, but this is cold comfort to one who’s found out about shoe overlap the hard way.
The CPSC (Consumer Product Safety Commission) agrees. But it does not mandate a specific minimum front/center. Instead it says that the distance between the pedal spindle and the front tire can never be less than 9cm. Some companies are more conservative than others, and every company makes its own decision about the minimum front/center number. For most companies, it’s 57.5cm. But this depends on what crank length is spec’d on these small bikes, and of course this assumes 700c wheels. You could go down to a front/center of 55cm if you used 650c wheels.
Here’s the issue: fit coordinates are immutable. If you want to ride with your saddle 6cm behind the bottom bracket, that’s what you’re damned well going to do. As you should! If you hike your leg over the bike and sit yourself down on a bike that has a seat angle steeper than you like, you’ll simply push the saddle back on the rails—or trade the seat post in for one with more setback—in order to achieve your desired setback. Once you do this, you’ve turned your 74.5° seat angle bike into a “virtual” 73° seat angle bike, and your cockpit is now too long. You’re too stretched out.
The idea is to design a bike to fit properly while preserving its good handling. Fitting well means it should not just have good stand-over height (that’s easy if you build the bike with compact geometry, such as Specialized does with its Ruby). It means also building the bike in a seat angle a woman prefers (which is the seat angle a man prefers, more or less) while keeping the cockpit short enough so that she’s not too stretched out. If you’re bound and determined to make this bike with 700c wheels, there are two ways to do it right.
Note that you add offset when you shallow the head angle, and both these techniques push the front wheel in front of the bottom bracket. If you wanted to build a parallel 73 degree bike in 48cm, but you couldn’t because the front/center would be an unmanageably short 54.5cm, building this bike with 71 degrees of head angle and 55mm of fork offset gives you the 57cm of front/center you’ll need, and you can do this without lengthening the cockpit and without steepening the seat angle. The bike will fit properly, and it will still handle in a relatively sprightly fashion.
Building the bike in this fashion conspires to give these shorter-statured riders the 700c wheel size they want (whether or not they should want this wheel size); with the seat angles they want to ride at; the cockpit distances they need; and with handling characteristics that make sense.
Some bikes will conform to this motif, yet still employ (what I think is) an annoying habit of seat angles too steep. The Specialized women’s line (Amira and Ruby) features 70.5 degree head angles and 51mm fork offsets. So far, so good. However, they also have seat angles as steep as 76 degrees. That established, I’m less bothered by this because the top tubes are short on these bikes. If a rider moves the saddle back on the rails (which is very likely to happen) the bike is still going to fit well. Plus, Specialized specs a handlebar with 75mm of bar reach and 123mm of bar drop. All in all, Specialized did a really nice job with this bike.
Here’s the difference. The Reach of the 48cm Cervelo is 360mm, the reach of the 50cm H1 Trek geometry is 388mm. How long is that 388mm? Well, Trek’s more popular H2 geometry in size 56cm has a reach of 387mm.
Does this mean the H1 is a bad geometry? No. It’s a very good geometry for somebody—male or female—who’s very long in the torso and short in the legs and who needs that size bike. But that does not describe the fat of the bell curve. It should also be noted that H1 is probably Trek’s oldest geometry, and its newer geometries—H2 and H3—go a long way toward solving these problems. Let’s look at Trek’s H3 in size 44cm. Stack: 510mm; head angle: 70.3mm; fork offset: 53mm; Reach: 360mm.
I think this H3 geometry in this size might be a bit too shallow in the head angle—trail ends up at 66mm—but it’s a nice bike, and the thinking is in my view modern and correct.
Bottom line, women shorter than 5'6" regularly find that they need road bike Reaches to be less than 370mm, maybe 360mm, and even narrower. The Stack will vary depending on several factors, but it's not uncommon for some of these women's-specific geometries to have Stacks that are too tall versus that size's Reach. There are unfortunately too few fitters and bike sellers who really understand this. (We're working on it.)
About 650c in road race bikes, can I close by flying both the white flag in defeat, and the bird in defiance? I noted to Emma Pooley the odd quirk that some fast female time trialists started as triathletes. “No coincidence,” replied the then-reigning world time trial champion, when we talked at the Amgen Tour of California a couple of years ago. “Many of us did, and it’s because there’s no easy entre into bike racing for females. Many of us came through the door of triathlon because it is, as a sport, friendlier to women.”
I asked this as a preface to my next question. “Did Cervelo have to twist your arm to ride a dual 650c bike to your world championship victory?” “Convince me?!” she replied. “I’d choose these wheels in road racing as well, were I certain to receive spare wheel support during road races.”
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