Too wide presta valve?
 

Hi,
I'm finally getting around to putting together a bike from parts actually made in this century as the funds and parts become available. My question has to do with the width of the presta valve (the bottom part that's inside the tube.) I have Weinman DP18 rims, Michelin ProRace 700X23 foldable tires and Kenda 700X23/25C F/V 48mm tubes. When I put it all together, the rim is not wide enough to accomodate the two tire beads and the valve. After a bit of playing, i found that I could push the valve down further inside the tire, which allowed me to seat the tire beads, and then pull the presta valve back up and inflate, but I am concerned that the hard edge of the presta valve inside the tube may be rubbing against the inside of the tube and eventually wear thru as I ride. Any suggestions, or experience with this? Oh and by the way, the presta valves are the smooth outside type, not threaded. Hope I explained this clearly enough. Thanks.

No worries. That's the proper way to seat the bead on a narrow rim.

What you experienced is fairly normal as regards pushing the valve up into the tire to allow seating of the bead into the rim. There should not be a problem - prestas work in worse rim situations than yours.

+1 on what those folks said. Pushing the valve back into the tire, seating the beads and then pumping up pushings the bead into the hooked walls of the rim and helps prevent blowouts at the valve. So it sounds like you're doing it just fine. Same technique works for schrader valves too.

Thanks for the quick answers. Feel better about it now.

But carry a spare tube just in case. Andy.

Just to add, once the bead is pushed inside the hooked walls, there will be enough room for the presta valve to seat as before so there will be no hard edges...

As long as the base of the valve is just a thicker bit of rubber that tapers away, you're fine.

But if it's the type that has a hard washer embedded in it, the tube might puncture in front and behind the washer, if it can't seat all the way down in the rim..

Or 2. Flats happen

There is one concern. If the base around the stem doesn't sit flush down against the rim, the adjacent portion of the tube can bulge into the space between the rim and the valve base and fail.

+1, the wider base flange of the older design PVs didn't allow the valve to settle low enough leaving a gap that the tube ballooned into often splitting or overexpanding and leaking.

The tubes sold today, have a redesigned, bonded in valve with virtually no base flange. They were designed to solve the problem caused by the narrow 700x rims in vogue today.

So go ahead and try your tubes, and you might be OK, but is you develop leaks near the the valve, you know why and need to buy a more modern tube.