I'm racing the Tour of California. This, assuming the organization doesn't recognize that they might be making a mistake inviting me.

I'm not entered in all the stages. Just the time trial. I'm an invited guest, along with Chris McCormack, Chrissie Wellington, and somebody else. Probably another actual athlete (like Chris and Chrissie).

Here's the proviso: I'm to be aboard a Cannondale Slice. This doesn't bother me. I don't own a Slice presently, but, I've ridden that bike and I like it a lot. Those who've taken our F.I.S.T. Workshops know in what high regard I hold that bike, both as a bike per se, and as a value for end users.

But I did have a condition. I don't want to just hop aboard the Slice the day of, as if it was just demo day. No. I'm Chrissie's "minute man," see, so I could set a record for how quickly a guy could get chicked in a TT. I don't know what the record is, but I'm pretty sure I could threaten it.

Therefore, I've asked Cannondale if I could have a little time with the Slice. They've agreed in theory. The problem is laying my hands on one. The bike has been a hot seller this year, and they're out of stock. But there must be one somewhere! Or so I hope.

This, because I am picky (as you all know by now) about how my bikes are set up. There are what we in the game call "position coordinates." The distance your saddle sits from the bottom bracket is an example. Your saddle height doesn't change if you move from a Colnago to a Pinarello, does it? There are five major position coordinates in triathlon: saddle height; saddle setback (or set forward); saddle nose to aerobar pads; saddle nose to extension shifter bolt; armrest elevation drop from top of saddle.

These are immutable. If you looked at my chromosomes under a microscope, you'd find these numbers one one of my genes.

In Maine they have a saying: "You can't get there from here." If the imperative was posed to a bike shop, "I've got a P3 in size 58, I have to reproduce my fit coordinates on a 58cm Slice," I've little doubt you can't get there from here would be the end result, after the retailer had fiddle-farted around for a couple of hours. Nevertheless, it is often possible to get there (a Slice) from here (a P3) and, I'm going to show you how.

Furthermore, I'm not going to have to resort to any fiddle-farting. I can figure this out pretty easily just sitting at my computer.

Which I will do, in the coming days and weeks, leading up to the race. But I'll take this opportunity to introduce you to a way of thinking about your equipment. It's an approach that not only end users should consider, but, that bike designers, engineers and product managers would do well to keep in mind. The approach is to determine, in advance, what's important to you—what's mandatory—in a construct or a system.

So, let's consider these two bikes in question here, a Cervelo P3 that I now ride; and a Cannondale Slice on which, in a month, I will be racing. That P3 was purchased by me for this reason: I wanted to road test a 3T Ventus bar. I wrote about this process (links below). In this case, The Ventus was an "input." This was the mandatory element in the "system" (A complete bicycle is, for this exercise, a "system").

I set a Ventus aerobar on my fit bike, and I adjusted the fit bike to my fit coordinates. These coordinates are also inputs. They're mandatory, non-negotiable elements to the system. Then I looked on my fit bike, read the stack and reach of the frame that would fit this aerobar, with its geometry, given my fit coordinates. There were a few frames that would work, and, these frames were the "output." (The output as the set of negotiable items.) The P3 was one such frame.

In the case of this time trial coming up, what are my inputs? Well, again, my fit coordinates are inputs. No changing these. And, the frame is an input. I'm to ride a Cannondale Slice. I'm quite sure 58cm is the size of Slice yielding me the best result, given my fit coordinates. These are the non-negotiables.

What is the output? It's a compendium of all the elements that lead from the frame to the aerobar pads and extension ends: stem length, stem pitch, spacers under the stem, headset top cap, and, of course, the aerobars.

My P3 is mounted with a 15mm headset top cap, and no other spacers. Atop that is a 3T Ventus with an integrated stem that, as well as I can measure, is about 90mm long pointed at a -6° angle (up 12° from horizontal).

The head tube of the slice sits 13mm higher than the P3's head tube, for fitting purposes. In point of fact, each bike—the P3 and the Slice in 58cm—have 145mm head tubes, so, on paper you would assume they'd be the same height. But the P3 has 60mm of bottom bracket drop compared to 72mm of drop in the Slice, so, the Slice fits taller.

One way to "normalize" for this height difference is to place on the Slice a low profile headset top cap. Most bikes come with tallish top caps, but Cane Creek, FSA and other headset makers almost all manufacture a low profile top cap. Were I to stick a 5mm-tall top cap on the Slice, that gets rid of 9mm of the 10mm difference (it doesn't lower the bike the full 10mm, because the top cap sits on a 72° bias).

If I place a -8° stem on the Slice, I've probably gotten myself most of the other 4mm of "lowness" I'm looking for.

But that stem needs to be longer than the 90mm stem built onto the Ventus bar. The bigger difference between these two bikes is in length. The P3 is 2.8cm longer than the Slice. Now, the Slice has crept a little closer in length to the Slice through the choice of top cap. The P3's 15mm top cap has pitched the bike back about 4mm in length—remember, spacers, top caps, etc., occur up and down this 72° angle, so, when I add that taller top cap it "narrows" the bike.

Now I have to find that other 2.4cm, but not quite that much, because, remember that the P3's Ventus had a built in -6° stem. The 90mm of stem pitched slightly higher means that the forward protrusion of that stem is slightly less than 90mm. So let's round down and say I'm looking for about 20mm of extra length. If I replace the 90mm stem with a 110mm stem, I'll pretty much have it.

If I'm off by 3mm or less in any axis, I'm not going to get hinky about that. The human body—at least my human body—can distinguish 3mm in saddle height, but not in cockpit distance or armrest elevation.

This all assumes that I'm not changing aerobars. Were I to change to a different aerobar, all bets are off (as you all know by now). Aerobars have their own geometries. Of course I do have to change bars, because the Ventus comes with a built in stem. But 3T's Brezza, or its new Aura, features the same spatial relationships between armrest and handlebar clamp—they share a geometry similar to the Ventus. They don't share the same armrest. But the armrests are interchangeable between all these bars, and interchange them I will do.

My preference is to use a slightly shorter stem than the 11cm stem I'll use on the Slice, because I think tri bikes ought to be ridden with shorter stems than come on any rider's corresponding road bike. About 2cm or 2.5cm shorter. I ride a 12cm stem on my road bike, and, this means a 9.5cm or 10cm stem on a tri bike. The Slice also has 20mm less front/center, which means more weight will be on the Slice front wheel than on the P3 front wheel.

An 11cm stem on a bike that—if ridden with a steep seat angle—has a shortish front/center is not ideal. Countering that, however, is a slight bit more trail on the Slice—62mm—which makes this bike handle a bit slower, a bit more stable. So all in all I should be fine on the Slice.

I'm evenly proportioned or, perhaps, slightly longish in the torso. And I ride steep, with a fair amount of armrest elevation drop. This makes the P3 a closer match to me than the Slice. It doesn't make the P3 a better geometry, any more than a Sidi is a better cycling shoe than the Specialized. We recognize that morphology determines fit, and, it's no sin if a Sidi fits you better than a Specialized cycling shoe fits you. The P3 is a slightly better fit for me than the Slice. But, the Slice is not that far off, and, this is a rational method for moving from one geometric style to another.

Will this help me hold Chrissie off for another minute or two? I sure hope so!