I've got a 700c bike. I'm sure the cross over angles are more of a problem on the 650s since the stays would be shorter yet and the chainrings would be bigger. I've never had any major problems, but I tend to avoid the big crossover gears.

I've never had any concerns about anything accumulating in the cutout. I think that's a non-issue unless you're planning on going off-road (and I'm sure you're not.)

When I first got my bike, I had planned to build it up with a Mektronic system, but I had to abandon that idea when I found out that my right heel would not clear the rear derailer. Of course, I've got big feet and 180mm cranks, so I'm sure it might work for some. It just didn't work out for me because of the extremely short stays.

Conveniently, I rode my P3 through a patch of wet sand on Monday. The sand did rub on the frame for about two revolutions of the back wheel, then there was no more friction after that.

My new P3 (650C) has handled much better on decents than my old 1988 Cernturion Ironman Expert.

I never ride in cross-over gears, so my only comment will be that I have no chain rubbing issues.

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Mr Ed
Triathlete with one horsepower

The P3 is a pure bred, died in the wool race machine. I wouldn't (and I don't think you should) ride it in the crossover gears. Do you think you could change your gearing to avoid that? Really, on a standard raod bike or a touring bike maybe crossover gears should be tolerated, but this is a Formula 1 car we're talking about- it's for racing. I don't think you should spend much (if any) time in the 39/11.The wet sand thing? well, the bike is certainly not optimized for an environment where wet sand is present. These bikes are (IMHO) masterpieces, they are perfectly adapted for what they do, and they aren't much good for anything else. That is not a negative statement- if anything, it is an acknowledgement of how refined these bikes are. They are a pure bred.

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Tom Demerly
The Tri Shop.com

I have a 51 cm 650 P3 and can answer most of your questions pretty well. You can use all the gears if you really want, but I never use the most extreme crossover gears and I stay away from the one next to that unless it is for a short period of time. Even the 39/12 in your example will give a small amount of chain rub inside the cassette between the chain and the adjacent cog. This should not be a problem in a time trial or triathlon since you have plenty of time to select a gear intelligently. Learn to do this. Being in a crit or peleton might be a very different story. Wouldn't know since I don't do that.

I have never had a problem with sand build up but I did get scared by an occasional scrape when I had the bike initially. It took a while to figure out, but it was caused by having just the right sized pebble stick to the tire and get jammed up through the cutout. It got my attention first when riding on some recently paved roads. It had lots of sticky pebbles just the right size. If you take the rear wheel off and look at my cutout, the paint is scrapped away where this happened.

The first solution was to not mount the wheel overly aggressively relative to the cutout. Give it a bit of a gap. The second solution is to know what it is and just deal with it. A pebble will scrape for one or two revolutions at most and then be ejected.

I can't answer about handling since I handle my bike like a limo. One day it may be at the level of a minivan.

A couple of notes:

The short chainstay has nothing to do with tucking the rear wheel in. With this chainstay length and the corresponding front-center, it allows you to have a good weight distribution between the front and rear wheel (the basic concept is, your body moves forward on a tri bike, so the wheels should shift forward too to keep the balance). On steep descents, the opposite of what you think will happen actually occurs. On a descent, the bike is tilted forward, moving your weight even more forward. So with a long chainstay that can cause a problem, not with a short chainstay.

We can make a P3 with any kind of chainstay length, we chose what we chose because of that weight distribution. Note they are also no shorter than what we used to do on the Eyre Tri seven years ago, which didn't have a rear wheel cutout. It's just what we feel is the right dimension.

To prove that point, you will notice that a 51cm 650c P3 has the exact same chainstay length as a 52cm 700c P3, even though the wheelsize is obviously a lot different. Then when you compare a 52cm 700c P3 to a 61cm 700c P3, you will see they have different chainstay lengths even though the wheelsize is the same. And for all these frames, the cutout spacing is the same.

The same goes for the P2K, even if wheelsizes are different we can create the same chainstay length AND create the same seattube cutout clearance for the rear wheel.

As for stuff getting stuck in the cutout, you control this yourself. If you keep the tire clearance UCI Legal (i.e. you can stick a credit card between seattube and tire), nothing will get stuck. If you tuck the wheel in as deep as you can and leave almost no room, then stuff will get stuck on rough roads. I had this happen in one race when I went off the road into the ditch, and I had my rear wheel set very tight (this was in 2000, we had little experience with the P3). So it took a few revolutions for the cutout to clean out. But if you allow just a little bit of light between tire and seattube and stay on the road, it won't be a problem.

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Gerard Vroomen
3T.bike
OPEN cycle