Valves

July 13th, 2007 by Brad Quartuccio

There are two types of valves on bicycles. Presta and Schrader.

Schrader valves are used on automobile tires and lower-end bicycles. Presta valves are common on high end bicycles, mostly due to fashion but there is some semblance of truth to the smaller diameter leading to a stronger rim. And on road bikes, the larger Schrader valve just doesn’t sit into the narrow rim and tire very well.

You can run a Presta valve on a rim drilled for a Schrader, but not the other way around. Everyone gets caught at least once with a Schrader replacement tube for a Presta drilled bike, don’t feel bad. I once rode a few miles home on the rim, since I had two of the wrong tubes with me. If you’d like your Presta drilled rim to take old-faithful Schrader valves, pull out a 5/16″ bit and go to town. I’ve known some to drill all of their rims to the larger size, never to think about it again.

On the use of valve caps: Optional on Presta valves, but required with Schrader. Schrader valves have a small spring in their valve mechanism, and can become clogged with dirt if run without a cap. A good cap also provides a measure of protection against leakage - on high pressure Schrader valves like those on suspension forks the cap is functioning as a secondary seal.

On that little Presta valve washer: Use it, but don’t overtighten it or you risk tearing the tube. Just snug it up a bit to keep it from rattling, nothing more. It comes in handy pushing a pump head on and off.

5 Responses to “Valves”

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1 Captain Bob on Jul 14th, 2007 at 7:59 am

I thought presta valves were used mainly for speed in changing a flat. You can finish deflating a flat much quicker and change the tube and continue riding racing withouth giving up too much time.
2 John Wm. on Jul 14th, 2007 at 1:01 pm

Stupid Question:

Which side of the rim does the presta washer go? I’ve seen it on either side of the rim. I’ve also seen valves “Bolted In Place” with washers on BOTH sides of the rim.
3 Ghost Rider on Jul 14th, 2007 at 4:53 pm

The washer is optional, but if you have one on there, it must go on the OUTSIDE of the rim. Using two is a bad idea, as is just one on the inside (where the knurling will rub on the inflated tube — bad idea!!).
4 donutbiker on Jul 15th, 2007 at 12:34 pm

i prefer the schradar, as its more robust for trail riding. I find the presta too fragile and tears easier or breaks easier during trail fix while pumping with the mini pump.
5 Guitar Ted on Jul 15th, 2007 at 11:08 pm

Hmm……I might get flamed for this, but I think all Schrader valves should be banished to cars and suspension products. If you tear off a presta valve while pumping it up, you aren’t doing something right. Actually, I see more torn off Schrader valves by far, being a shop mechanic, than I do Presta valves. That’s because Schrader valves don’t have that washer, or more properly, “nut” that Presta valves do. Therefore Schrader valves can be shifted during hard braking cusing cut valve stem bases as the valve hole of the rim chafes the tube.

Also worthy of note, a bigger hole in your rim for a Shrader valve makes a weaker spot in it. This is especially a problem with narrow road rims, not so much mtb’s, I’ll admit, but still it’s a concern.

Finally, the Shrader valve is more prone to leaking, as pointed out in the post. It not only can be impacted with debris if the cap is missing, but the valve seat inside the stem can get fouled and leak down more quickly. Presta valves are a manual closure, not relying upon a spring to hold air pressure, so this is much less a problem with Presta valves.

Valves

5 Responses to “Valves”

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