All right, I know I'm probably going to get flamed for this post but I've done my searching and have read a ton of threads about it.

There seems to be mixed sentiment about using a rubber/metal grommet or just putting in a Presta tube and not worrying about it. None of my LBS seem to carry the grommet to narrow the hole so I'm stuck either buying online without seeing it or going without one.

My question is which do you all recommend? The only reason I want to put Presta in my tires is because when I bought my bike (used), the previous owner had already put one Presta tube in the bike (with no grommet) and the front tube is still a Schrader. He also gave me a spare new Presta tube he had lying around.

Also, the only grommets I can find online are the ones on Nashbar. However, on the Amazon reviews one reviewer states that these metal grommets only fit the newer 700c Schrader rims and not the old 27 inch Schrader rims like I have. Here are the links to both Nashbar and Amazon (it's called wheels manufacturing presta saver)

https://www.nashbar.com/bikes/Product...2_208238_-1___

https://www.amazon.com/Wheels-Manufac...8417072&sr=8-1

I use a stainless steel washer I bought at the hardware store (I think it was a 1/4"). I ground down two sides and curved it so it fit the channel of the rim perfectly. I made a bunch of them at the same time taking about 1 minute each.

If that's too much, you can do a decent job by carefully de-burring the inside of the rim's valve hole, and sliding 2 of those fiber reinforcements school kids put on looseleaf notebook pages onto the tubes valve. Or use a paper hole punch on the middle of a small round patch, and bond it to the tube at the base of the valve.

It doesn't take a lot of complexity to adapt the valve and hole, so think creatively and improvise with what you have.

I really don't see why you couldn't use this type of grommet

You should be able to find them at a LHWS.

I used to use similar grommets but found them to be too thick on the inside, and making it harder to mount tires on my narrow rims. That's why I switched to the washers. If your rims are wider, and the tire fit isn't too tight these work fine. If the hardware store doesn't have them Radio Shack does (or at least used to).

Shadowman, those might not be bad if you could get them into the Schreader holes as designed instead of just using them as washers. But the size difference between the Schreader and Presta is much less than what such grommets are sized for. I know because I built and serviced electronics equipment for years that used such grommets. For example you'd need a 3/8 hole to mount a grommet of that type which would have a 1/4 inch hole to accept the Presta stem.

So some washers just for padding and to spread out the pressure is all the "grommet" that will fit or that is needed.

My dad-in-law is a machinist and his solution (which I thought was extravagant) was to make custom presta valve stem screws. He'd machine start with round bar stock, machine a smaller lip just a 1/2 mm high, that would fit inside the schrader hole but not exceed the thickness of the rim, then cut off the bar stock about 5mm above the recessed lip; drill and tap the center hole, then mill off flat on 6 sides at 60 deg. rotational intervals. Lots of labour for a small part, but in quantity, these could be cast instead of machined for pennies I think and bundled with standard presta tubes. Flip it to the flat end for normal rims. Turn it around for schrader holes. It would nicely center the stem in the hole and provide relief without cutting the tube at the base of the stem.

Gyozadude, trust a home shop machinist to over complicate the solution. And I say that with affinity and a smile since I'm one of "them" and have been known to similarly overthink solutions from time to time...

There's really no point in making and including such a part when either simply ignoring the issue or at most adding a padded soft washer punched from some fiber reinforced rubber sheet is all that is required.

LOL! I think home machinists love the machining part of doing things. I have some really nice aluminum fishing reel eddy current rings (machined by dad-in-law) which I epoxy to the non-drive side of the spool on conventional casting reels for salt water. Coupled with 4 small samarium-cobalt magnets epoxied inside the cover plate and voila, super-anti-backlash system for big water casting. Saves skin off the thumbs and, like indexed shifting on bikes, it allows the dilettantes of conventional casting to fish like the pros!

But I'm sure if I could find a supplier of the presta/schrader valve seat screw at a cost of $1 each in quantities over 1000, I could sell these at 100% margin to cyclists at $2 each and turn a small profit too. I wonder what the cost of coloured anodizing might add.... hmmm

Are we really that transparent?

You'd likely sell a few to some folks that obsess over such things. You know, the same ones that battle on incessantly over what is the optimum chain lube? But the SERIOUSLY OCD ones would simply bypass your product and go straight to the "replace rim with Presta size hole rim" rather than "compromise" with a screw on adapter. So you'd likely be stuck with around 955 of them in all the various colours of the rainbow left over.

Mind you if you could have them made from carbon fiber or titanium that may well be a whole other story....

You can given them free, with sufficient S&H charge ;-)

Thanks for the explanation. I'd never tried it, but it seemed a simple fix. Now I know why it's NOT so simple.

They sell metal ones on eBay for a couple bucks that work nicely.

Duct tape.

Mavic makes their own , plastic , split-slot , with a shoulder ,
it stays in the rim hole until removed with intention.

https://www.sjscycles.co.uk/mavic-rim...esta-prod3335/

And, Schwalbe presta tubes, have a shoulder in the ring nut , to center it
in the larger hole.

I used the aluminum ones I get from the LBS,
on my 349 , 16" wheel when the S/V tubes sell out at the Wholesale level, they still have P/V to ship..
so I adapted the rim...







....

A Google Shopping search brings up lots of options, each a little different but all serving the same purpose:
https://www.google.com/search?q=schra...A&ved=0CE4QrQQ

for a free option: if you have threaded presta stems get an extra two of those knurled little nuts that hold the stem in place so you have four total. thread one on all the way before pushing the presta stem through the schrader sized hole (inside the rim) install tube / tire normally. now thread on the extra knurled nut from the outside and the two of them effectively sandwich the valve tight on the rim.

i've done this with our two touring bikes and mountain bike and it works great. lots of miles on all of them and no problems so far. got tired of buying / carrying different tubes for all our different types of bikes. plus i can keep my portable lezyne pump set to presta and never worry about flipping the nozzle.

This shouldnt be a big deal. There is the special collar that fits in the shrader sized hole that allowes you to use presta tubes. My LBS carries them, and I would think that most good shops should carrry them.

BTW my RANS Stratus came with them, and I carry one just to make sure that if somehow I lost one on the road, I would have a spare. I actually think they are a good deal since the tube side of this aluminium gromet is curved inside so the stem is well supported rather than just a square hole for the stem.

I use these:

https://www.bikepartsusa.com/bikeparts/item/01-124360

This is a 3 year old thread but I was curious what others do running presta tubes in a rim drilled for a schrader tube. There were some small gizmos mentioned in this thread that I had never seen like this one from mavic, https://www.sjscycles.co.uk/mavic-rim...esta-prod3335/

I've always just used a washer underneath the threaded nut on the presta tube.

Sir, I'm sorry for this really late bump.
Google just wouldn't help me on this one.
What does LHWS stand for?

Local Hardware Store (True Value, Ace, etc)

Wheels Manufacturing makes an aluminum insert to take up the space between the rim and valve. It is called a "presta valve stem saver". I used them for a switch from schrader to presta a long time ago. Just be sure to keep track of the spacer when you change or patch a tube on the road.
$5.26 with free shipping on ebay https://www.ebay.com/itm/WHEELS-MANU...SgdQ:rk:1:pf:0
$6 on Amazon https://www.amazon.com/Wheels-Manufa...66451793&psc=1

Thanks for your quick response, guys. Again, sorry for thread necromancy. However, this topic is indeed in my hands right now. I bought this bike with a fine pair of 19x622 rims. However, the previous owner seems to have been in a some kind of situation where he needed a Schrader / Dunlop valve to go in, so he has drilled the rim hole a bit so that a Dunlop valve will just about go in. The hole is such a nearly fit so that I will have difficulties pulling the rubber part on a Schrader valve through. A Dunlop valve works though. However, even though I don't care that much about the practical aspects of different valve types, I suffer (true story) from some OCD eccentrics. In short, it's major key that I have symmetrics in everything in life, so now my mind bleeds every time I look on the bike with a Presta valve fitted on one wheel and a Dunlop valve on the other.

This might sound ridiculousness but it's the reality I live in. I've found that there are cheap rubber grommets that you can put inside a "big" hole to make it a air tight fit for a Presta valve. However, since this is a drilled hole (probably slightly smaller than the Schrader / Dunlop hole should be according to spec.) I'm thinking that such grommet may cause more harm than good. Also, someone suggested that you could put one Presta nut inside the rim, and one outside, sort of to hold it together tightly. I asked my LBS on this and he said that the one suggesting this must be out of his mind, it was the most stupid thing he had ever heard off. He suggested the grommet solution. Furthermore, some people seem to suggest just going with it, as it is. To be honest, this is what I've done so far. I simply put a Presta tube inside the drilled rim and screwed the (one!) Presta nut pretty tight.

What's the long time expectancy on this approach, would you guys think?
I could need some confidence here!

It probably depends more on how well the hole was drilled than what kind of grommet you use in there.
I've been running presta valves in Schrader holes for 5 years on my commute bike - no grommets, no stem nuts, zero problems.

Only arriving in time for the re-animation, but am I the only one amused by:
??? Maybe that's just typical Amazon , but by what manner of thinking could someone get the notion that the function of such a simple device would depend on the rim diameter?