Please forgive my ignorance, but I just purchased a pari of Zipp 808 deep dish wheels and I can't figure out how to close the valve on the presta valve after inflation as it is burried in the deep dish. I used a valve extension to inflate the tube, but should I leave that on after the inflation process. No matter what I do, it seems like I'll never be able to close the presta valve. Will that hurt performance or lead to the tire deflating during a race? I've had disc and tri spoke wheels before, but they always had a cut out for the valve where you could have easy access to it. Just wondering if there are techniques out there that I don't yet no about. Thanks.

If you are using the Zipp extension (or similar) where the valve core remains on the tube, you leave it open. It will not harm anything and you will not lose any air from the valve. It is standard operating procedure.

-Eric

The air pressure in a presta valve will keep air from leaking out. The other option you can use it to buy tubes with removeable valve cores such as continental. Problem solvers has extensions that then screws on that extends the presta valve another 60mm so you can get to your valve screw.