The tolerances are extremely tight on the new Cervelo P4 and the new S3. Manufacturing of carbon fiber bike frames does not have the tolerances of steel machined products. There are slight variations with carbon fiber frames coming off an assembly line. What works with one Cervelo P4 frame, may not work another and vice versa. If it is tight Cervelo recommends trying the wheel with the frame before making your purchase. Also wheels deflect under load which is a function of rider weight and riding style. Undoubtedly Cervelo cut the tolerances too tight on the new P4 and S4 for rear wheels and some cranks, i.e. Campy. Cervelo has information on the web site plus you can contact Cervelo customer service.
I was thinking about purchasing a P4. However I am now leaning toward a P3 and getting a P4 when the kinks are worked out in the 2010 model.
I bought the P4 and have a set of 1080s I have been riding on it and they work fine, no rub.
I am 153lbs and have a relatively low cadence / high gear approach (80-86RPM).
I think this whole conversation (not just here, online generally) is largely about ride weight and power. I can see that a heavier rider with a big watt approach may have flex issues.
Chris Stephenson
You will have to try the wheel on your specific frame. The “slight variations” in chain stay width that others have mentioned are actually up to 2-3mm per stay, which means that your particular distance between stays could be 6 mm different from another bike, which is quite a lot.
Also, some others have mentioned about the wheel possible rubbing when it flexes under power. This shows a basic misunderstanding of how a wheel flexes. When a wheel flexes, the axis of rotation is actually in line with the chain stays, so the relative movement of the wheel inside the stays is virtually zero. However, when power is applied, the chainstays of the bike do flex, and can sometimes created wheel rub. Rub from wheel flex is most often noticed at the brake caliper (when it is mounted on the seat stays, not on the chainstays like the P4), not at the chainstays.
On the 3 P4s I have tried the 1080 on, I have found 2 it would not fit, less than 1mm clearance, and one with about 3 mm, which in my opinion was also too close, but could probably have been ridden. The Sub9 was a similar situation. The 808 was also very tight, plenty of room for a 404.
Why do you say a Sub9 is not a good idea? Because of fit issues or for other reasons?? Gerard has already hinted in a previous post that he didn’t think a Sub9 was a good idea in a P3/P4 but didn’t elaborate.