Picked up a really nice 26" Mavica X517 rear wheel, only problem is its a presta where all three of my bikes are Schraeder.

Is it possible just to drill out the valve stem opening? If so, what size drill bit would I need?

Thanks,

Mike

Yes, it's possible to drill the rim (assuming it's aluminum), but before you do so, make sure the rim is wide enough to handle the width of the valve + two thicknesses of the tire bead. Looking at the rim (picture) I suspect it'll be very borderline. Width considerations are a major reason that bicycles use Presta valves.

I suggest you simply stick with Presta valves and simply leave O-ring adapters on them full time.

As for the drill size, I believe it's 5/16" but measure a valve to be sure.

I agree that to reduce your tube inventory in the future, convert the current rims to Presta by using either reducing grommets or the aluminum insert bushings. Any bike shop should have these and they are cheap.

absolutely! get a drill bit set and size it up - try a few in an old wheel hole and pick the bit that just fits. use a metal bit, meaning a bit designed for metal. also get 2 files a round file and a flat file. these for cleaning up the burrs outside and inside the rim and smoothing the actual hole after drilling. also get some black (if you have black wheels) model paint and a small brush so you can cover the fresh metal. this will reduce abrasion and prevent rust (if it's a metal that rusts). I've done it a bunch of times and don't let anyone scare you that the wheel strength will be diminished. the amount of metal that is removed is miniscule.

21/64" is the size.
Don't know why you want to convert though and possibly ruin a rim by drilling.
These are a much safer solution, if you have a Schraeder only pump.

https://www.jensonusa.com/!mYP5QroTv5...FbFxQgodXwwAkw

Your LBS should carry them and you only need one.
I keep one on my key chain so i can use gas station air if I get a "slower" leak, to get back home.

adapters like that don't work on cheap coin-op gas station type pumps

I don't know why everyone's so eager to reach for the power tools. All it takes is a couple twists with this:



Tapered reamers are very handy in general; no shop should be without one.

And I'm so sure you can explain why?

I'm with JDT, though my Hozan tapered hand reamer, is likely cheaper than what he shows..

My LBS gets $5 each for those. I don't consider that cheap. I paid it because I needed them right away, but never again.

An old cycling teammate of mine always drills out his MTB rims to accept Schaeder valves, but then he runs presta tubes with the adapter. This is not the filler adapter, this is sort of a grommet that fits in the Schraeder hole and shims it down to presta-sized. That way if he gets caught with a flat and no tube, so long as he can find someone to bum a spare off of, it doesn't matter which they're riding. I carry a pair of the adapters in my MTB tool kit in case I find another rider stranded with a flay who has Schraeder rims.

The gas station air hose only works when used on a valve with a spring-loaded central needle, like a Schaeder. The screw-on Shraeder filler adapter is hollow so there's no needle, nothing to depress the button in the air chuck, which is what turns on the air flow.

Gas station hoses work fine with PV adapters, but it depends on the adapter. If the adapter is short enough that the PV stem reaches close to the top, it works just like an Shrader valve. Or the ID of the adapter at the upper edge can be small enough, that it opens the chuck by engaging the conical valve depressor.

Lets face it, PV avapters are made for the express purpose of using with the ball chucks at gas stations. If they couldn't do that they wouldn't exist.

A Schraeder valve wouldn't be using a Schraeder to Presta adapter in the first place!

My Presta pump doesn't depress the pin on my Presta valve either!
If I don't manually "burp" it, the air pressure won't overcome the "stickiness" of the pin.

Apparently you have a different "understanding" of air chucks. There isn't a "pin" in the AIR CHUCK that gets depressed!

The compressor regulator setting is an individual choice, by the compressor owner

Cars dont need as high a pressure , as bike tires do , so they, in the gas station, may be set lower.

A lot of truck tires run much higher pressure.

IME, 90 PSI seems to be about the norm for the 2 places I've used.

I drilled my Swiss DT rim using a hand drill. I'm not sure I would let rip with an electric drill for such a small amount of metal. Clean and finish up the sharp edges as advised earlier.

no I can't actually. I just know it didn't work when I really needed it to. and I tried 3 machines one desperate day. so never again will I rely on outdated technology for which there is no need. Schrader valves rule and that's my opinion!

if there is no pin to push against the gas station chuck what allows the air to leave the gas station pump/hose/chuck to fill the tire??? doesn't it have to be valve pin against pump chuck pin?

Operator error? Did you have the presta valve open?
All of the air hoses at the shop I volunteer at have "gas station" type air chucks(we get them for cheap at Harbor Frieght). Of course they work great for schrader valves. For a presta, we screw on a standard adapter, and fill em up. Never a problem.

yes, of course, that's how I pumped it with my mini pump. maybe I need pictures ...

but why use an adapter when you can just use the real thing ...?

hey check this out - using a dust cap as an adapter.

https://www.youtube.com/watch?v=cZja_8crIEI

but see, the pin sticks up to activate the pin in the chuck.

as seen at the end of this video, after the adapter is screwed on there is no pin to activate the pin at the gas station. it's too deep inside the adapter and doesn't reach out far enough to hit the pin at the gas station chuck. anyway, that's what was happening to me.

https://www.youtube.com/watch?v=9Ux08bz43qY

Differential air pressure opens and closes presta valves.

Did I say that right?

yes, you said it right. PV's are simple check valves that open and close so air can enter the tube, but not flow back out.

EXCEPT

That sometime between when the Italians and French made them, and when it all went to Taiwan and China, they messed up on the gasket material so now the valves stick closed over time, and have to be unstuck by manually letting a bit of air out (burping) before they'll work right when you pump.

but something needs to actuate the cheap coin-op gas station chuck to let air flow, once the adapter is on the PV, the PV doesn't stick up high enough to mate up with the pin in the cheap gas station type chuck

Is it safe to use a Presta valve tube in a Schraeder rim WITHOUT the adaptor? I'm doing that right now, Presta in the rear tire and Schraeder in the front tire . I though it was probably ok since the entire Presta valve stem is metal. I'm converting to Presta so that my spare tubes will work with the other bikes I ride with.

This is ONLY true if the adapter is too long. The right length adapter will have the top of the valve stem just below the lip of the adapter, the same way the pin on an SV is. Since adapters are brass, or aluminum, they're easy enough to file, so everyone can solve this problem (if they have it) themselves.

I drilled out my rims, not particularly for pump compatibility, but to increase the chances of finding a tube if I ever need one in some out-of-the-way place. Schraeder tubes just seem to be more widely available.