Hi all,

I've been getting a bunch of flats on my commuter bike, and I believe the reason is the rim is drilled for schrader valves, but the tubes I use are all presta valve. I believe the "sharp edge: of the valve hole tends to "cut" into the tube at high pressures around the valve stem.

How do I solve this?

I have a bunch of those little "valve stem nuts" laying around that come with a lot of tubes, that I could apply to the valve stem on the inside of the rim? Would that prevent the rubber from getting "cut" if I put a nut on the bottom of the valve stem BEFORE putting it into the tire? Or would that lead to more problems?

Or should I use something like this: https://www.amazon.com/Wheels-Manufa..._&dpSrc=detail

Or this: https://www.amazon.com/Schrader-Pres..._&dpSrc=detail

Thanks!

Just out of curiosity... if the rims are drilled for Schrader valves, is there some reason you're avoiding using Schrader valved tubes?

I've personally never used either of the items listed... but I'd personally be more inclined to go with the Wheels Mfg. option first.

I've used tubes with Presta valves on rims drilled for Shrader valves and never gotten a flat. Did you look for any other reasons you are getting flats? Are your tubes leaking near the valve or somewhere else? Are there any sharp/foreign objects embedded in your tires? Did you inflate your tires to a proper pressure?

Shrader-presta

Use the Wheels AL reducing inserts. Place the flanged end inside the rim so the insert will be trapped in place when a tire/tube are mounted.


The most common reason presta valves fail at their stem base when used in a Schrader hole is from the wiggling about that the stem has without the support of the proper rim hole size. The stem tends to pull out/separate from the tube body right at the stem's bottom.


Another near the stem failure mode is when the valve base won't sit on the rim's bottom, usually held up by the tire's beads being too close together to allow the valve base to pass and contact the rim base. When the tire is inflated the tube stretches outward to fill the space inside the rim and tire. The large space next to the valve is where the tube will try to fill up and since the valve base is double thick (where the valve was bonded to the tube) the tube just beside this base will do the stretching instead. The tube wall gets too thin and it bursts, a small star shaped hole next to the valve base.


So use the Wheels, install smooth end out, take care to align the valve/tube so the valve is perpendicular and is long enough to still be able to fit your pump onto it. Really narrow rim bottoms might not let the insert's flange to sit flat, the flange can snag on the rim's bead seat base sides. You might have to file down the flange on two opposing sides to let it slip down flat. Andy

Use schrader tubes, or use an adapter/grommet to adapt the schrader hole to the presta valve stem.

Either of the adapters you linked above should work. My preference would be for the aluminum one made by Wheels Mfg., unless you have steel rims. In that case, go with with the rubber ones because aluminum left in contact with steel may develop galvanic corrosion.

My 26" wheel 'world tour' bike came that way .. adapter, in big hole and P/V stem tubes.. use either tube as needed..

did similar on my Bike Friday Tikit..Brompton sized wheels ..

I can get P/V tubes when the distributors to bike-shop have sold out of S/V tubes.




...

Thanks guys, I guess I will try that aluminum adapter. I believe the rim is aluminum.

Sure I could use schrader valve tubes, but my other bikes have presta valves, and I prefer to be able to buy 1 type of tube in bulk and use that on all my bikes.

Maybe use the proper tube and you wouldn't need to buy in bulk?

I use the rubber grommets on a heavy mountain tandem as well as a cargo bike. Never a problem however, the rubber grommets do make a bit of extra work getting the valve stem out when changing a tube.

The aluminum inserts look like they eliminate this problem, but add a small part to keep track of if it slips out of place during a trailside flat repair.

I've used both at various times. The rubber ones never get lost but it took me a while to get the first one installed. Once I did one, the second one was easy.

I wish I could remember the brand of inner tube that comes with a rim nut that doubles as a grommet for a Schrader drilled rim.

Okay mister smartypants.

when using the stem collar adapter; screw on the stem retaining nuts for preventative measures during tube air servicing.

This is a good example as to why paying attention to the exact failure mode is important.
You can have cutting/chafing flats, shear flats and straight tension flats. Cutting/chafing flats comes from burrs around the nipple valve. An adapter will fix those by covering the sharp edge. An adapter will also fix shear flats brought on by by an overly large diameter in the tubewards hole of a double-wall rim.
But an adapter won’t do squat for pure tension-type valve stem failures brought on by the tire sliding on the rim.
I’ve NEVER used adapters. At most I’ve poked kinda narrow holes in the rim tape when running Prestas in Schräder rims. Never had a valve stem flat reliably attributed to that.
If you think adapters are the thing for you, go ahead.
But remember they have to go into the tubewards layer of a double wall rim to work as intended.

Schwalbe does that. But the advantage is marginal-to-none WRT stem/tube failures.

What he said. Tubes are cheap.

Such silly questions on this forum sometimes.

You are the one posting about an inordinate amount of flats that you attribute to using the wrong tube.

Unless you are too lazy to patch a hole once in awhile, a tube should last MANY YEARS!
Buying "in bulk" should result in using tubes that already several years old before using.
I keep 1 spare for the 3 different sizes I use. When I need a tube, I use it and buy a new one at the LBS and help keep them in business. It also gives me an excuse to chat a couple minutes.

If you go the aluminum insert route, be aware that wet conditions can corrode the stem to the insert, making it difficult to remove. I would use plastic.

Install new rim strips. Use cloth tape instead of the rubber/plastic ones and make your own valve holes.

Switched to prestas when I rebuilt my vintage Bridgestone with it's 27" wheels.
I replaced the rubber rim strip with cloth tape, laying a 2" strip over the valve hole as reinforcement before I wrapped the rest of the wheel.
I used a small, sharp awl to punch through the tape, and pushed the valve through. It should be a snug fit.

I've been using presta tubes in my Shrader commuter rims for 4-years with no grommets and no punctures around the valve.



I suppose it's possible your "sharp edge" is sharper than mine, but I suspect your flat problem might lie elsewhere.
I've used those grommets before and determined them to be lots of hassle for no benefit.