Most Presta (a.k.a. French) valve stems are externally threaded (6V1, which measures 8 x 0.80 mm). Inner tubes equipped with this type of valve stem typically come with a small knurled nut, which is at the heart of one of the most heated debates in the history of cycling: Keep it, or chuck it?
At BIKETUBE, we believe what you do with your nuts is a very personal decision, but we’d like to offer up a few opinionated points, in hopes of making your choice a little less agonizing.
FIRST, A BRIEF DISCUSSION OF THE ACTUAL ADVANTAGES OF THE PRESTA JAM NUT
When inflating a deflated or nearly deflated tube, using the nut can prevent the valve from slipping down in to the tire when you attempt to attach a pump. However, simply pressing down on the tread of the tire can have the same effect. (If you’re using CO2, beware that compressing the tire like this could subject the tube to damage from cold.)
If you can’t get enough stem extension to attach a pump without a nut, try using a slightly longer valve stem. BIKETUBE offers a variety of lengths.
During initial inflation, tightening the nut after seating the tire bead on both sides of the valve can help keep the tire in place as you seat the rest of the bead. (You’ll want to loosen the nut a bit after fully seating the tire bead, but before fully inflating the tube.)
NEXT, THE IMAGINED ADVANTAGES OF THE PRESTA JAM NUT
The nut will give the valve side-to-side stability when using a mini or frame pump to inflate the tube. NO! Never put a side load on the valve. Correct pumping action involves holding the pump head in your fist, and loading the pressure between both hands. A clamped-down valve is more likely to break off.
The nut will keep the valve from making rattling noises on deep section rims. NO! Wrap a small amount of electrical tape around the valve stem if this is an issue for you.
The nut will allow you to use Presta valves (7mm hole for 6mm valve) on a rim drilled for Schrader valve (9mm hole for 8mm valve). NO! In general, it’s best to use Presta valves only on 7mm rim holes. There are grommets available to fill the gap if you choose to use Presta in a 9mm hole.
FINALLY, SEVERAL POTENTIAL DISADVANTAGES OF USING THE PRESTA JAM NUT
It adds extra, perhaps unnecessary, procedures during a tube change.
Over-tightening the nut can compromise the tube’s rubber section around the rim’s valve hole. Never use a tool to tighten this nut. Notice that it does not have wrench flats, but instead has knurling designed for use with fingers. (Further to this point, we recommend carefully de-burring the edges of the rim valve hole, using a file).
Over-tightening the nut can create a situation where you can’t get it off without a tool. Again, never use a tool to tighten this nut.
This nut weighs approximately one gram. Not a huge deal, but in a world where people are paying $36 to add weight to their carbon wheels to “balance” them, perhaps this matters to some.
Freds might smugly scoff at your nuts, because they don’t look “pro”.
In summary, from a practical standpoint, riders using large size tires and/or CO2 may benefit from using the nuts. It comes down to personal style and preference, but we believe every rider should always keep a couple of nuts in their bag anyway, just in case.