Is Chrissie Slowtwitch approved?
Chrissie can ride the heck out of that Slice, can she not? But, does she ride that well in spite of position coordinates that vary from the norm, or do her fit coordinates inform her power?
I interviewed Chrissie some months back, after she switched to Cannondale, and asked for her fit coordinates. She didn't have them at the ready for us, but upon a renewal of this request she quickly provided them.
They are printed here, and a few stand out, in particular if you juxtapose her coordinates with what we've devised for a static fit system.
COCKPIT
She's got a saddle height of 72.3 cm, and a cockpit distance of 72.5 cm. In this case "cockpit" denotes the distance from the saddle's nose to the extension's end, through the bolt where the bar-end shifter passes. You'll note in our "static tri-fit system" that we're noticing an almost one-to-one relationship between saddle height and cockpit. This assumes a lot, most notably even proportions leg-to-torso. It's not a metric we advocate using to set up a bike, rather one that we like to use as a double-check.
In this case, we note that Chrissie's "A" and "C" are almost identical.
The other metric related to cockpit is the saddle-to-armrest measure. Again, this is a gauge, not a hard and fast rule, but, our static system expects to find this distance as a function of cockpit:
F = .58C
We would expect, then for Chrissie to ride with a saddle-to-armrest of 42 cm based on this formula, in fact she rides with 41 cm. Close enough.
SEAT ANGLE
She rides with a saddle nose 3.5 cm in front of her bottom bracket axle. I went out to the workshop and set up a fit bike with this config, specifically 72.3 cm of saddle height and her chosen saddle fore/aft. This equates to 79.5° of seat angle through the center of the saddle's rails. This was with a saddle that had a typical distance between the center of the rail's straight section and the saddle nose.
You'll note this comment in our static bike fit article: "If you measure seat angle through the bottom bracket and the center of the saddle's rails, the median seat angle preferred by those whom I optimize at a range of angles is 79.5°. This, after some thousands of trials. So, there you go. That's the angle."
This is not to say that every pro, or every good pro, or every top pro, rides this way. Chris McCormack was positioned here at our compound at 78° of seat angle. Others ride at 80°. But 79.5° is the average for fit, trim, experienced triathletes, pro and age group alike. Chrissie falls right on the norm.
ARMREST DROP
Using our rather famous (infamous) armrest drop formula, we would expect precisely 12.5 cm of drop, assuming her seat height and her seat angle, or 11.0 cm of drop if we're talking a typical age-group rider. Instead we find 9.0 cm, and that's a slightly higher aerobar set up than we would typically expect. Is this what we would consider her appropriate amount of drop? It depends on the more sure measure of hip angle, which you would measure with a goniometer while she's aboard her bike, or better yet a Retul or similar motion capture system while she's riding her bike (on a trainer).
Never would we dare to call Chrissie Wellington average, but, confined to the narrow circumscription of tri bike fit, she's got cheeseburger tastes (with the exception of aerobar drop). This means that her Cannondale Slice is a fine bike for her as far as fit and geometry. But wait, isn't the Cannondale a slight bit better for the leggy set? Yes. So, how can she be right in the middle of the fit curve?
Remember, her armrests are sitting about a centimeter back toward her saddle than we would've guessed, based on her cockpit distance. I rather think this measure, saddle-to-armrest, is her best metric of length. Note that she rides with the shifter not in her hand, but in front of her hand (in the pic above). Were I her mechanic, I'd probably cut the aerobar extensions down in length one or two centimeters. I suspect she is slightly leggy, explaining why her Cannondale fits her so nicely.
Then we'd have a cockpit distance slightly shorter than her seat height, which would be in line with a morphology slightly on the leggy side.
Chrissie Wellington's 2009 Kona bike
