It might be possible, but would be a super tight squeeze. Probably would have to back out the set screws, and then have 1mm of space at the chain stays. I'd go 23mm especially since it's in the back and doesn't matter that much.

Thanks for the reply.

defeats the purpose somewhat though of using the wide rim wheel. Interesting that you state ' its in the back and doesn't matter that much ' I always thought wider on the rear was more aero. Cancellara rode the world TT one year on a 28mm rear and a 25mm front.

Although I do not know for certain and I'm sure there are people on here who know much more than I do... my understanding of using a 25mm tire on the rear would be more a comfort/grip/rolling-resistance factor rather than an aerodynamic factor given how dirty the air is by the time it reaches the rear wheel/tire-interface.

Given that more body weight is distributed over your rear wheel I would assume that using a wider tire (25mm) would mean less tire deflection and therefore a lower rolling resistance, not to mention increased grip and cushioning.

just my 2c.

I have no idea if that wheel-tire combo will fit in your frame

Interesting points.

I do remember reading on here somewhere that the older P3/P4 was actually designed to be fastest with a skinny flat disc in the back...like the Zipp 900.

I wonder was that anything to do with the fact it was designed before the 'fat' disc was ?!

Probably...but maybe I should have put it this way...I remember seeing that those frames ARE faster with the skinny flat disc versus a wider rimmed disc.

https://forum.slowtwitch.com/...s_P3095831/#p3095835

Cheers, thats an interesting thread. A guy there used a Super 9 on his P3 and it had more clearance than the Sub 9.