Talk:Presta valve

Presta Threads

I just spent an hour in my shop to make an adapter, and figured out empirically that the Presta valve body thread is _not_ M6 x 1 (as suggested below), nor is it M6 x 0.75, as is suggested in several online threads. In fact, the correct thread has the ISO 4570 designation 6V1 as noted in this thread , and the spec is given here . As noted in the second reference, the thread diameter and pitch are 6 x 0.80, but the thread form is slightly different (rounded roots) than the standard metric thread form. TheoSmit (talk) 05:06, 8 November 2016 (UTC)

/sources http://www.sheldonbrown.com —Preceding unsigned comment added by 69.194.115.241 (talk) 02:23, March 19, 2006

Comment "In addition, the Presta valve has a much smaller diameter than the Schrader valve", but what diameter is the Presta valve? —Preceding unsigned comment added by 217.154.240.18 (talk) 12:17, March 29, 2007 at Wikipedia talk:WikiProject Cycling/to do

I believe that the thread on a Presta valve is standard M6thread, so that would be 6 mm.

The Schrader has an O.D. of .3125", 5/16"; or about about 8 mm. The Presta is 6mm, and, there are three standard 6mm thread pitches. The 6mm x 1.0 on Presta valves is considered medium-fine, and probably the most common 6mm pitch.68.231.184.217 (talk) 23:13, 21 June 2011 (UTC)

References

Advantages / Disadvantages

I'd like to see what advantages there are to these valves. After having used them along with Schrader valves, I certainly can't think of any, other than lighter weight or something. 99.246.143.181 (talk) 01:01, 6 June 2009 (UTC)

The article already says: "has a narrower diameter than the Schrader valve, which helps strengthen narrow rims because the weakest point of a bicycle rim is usually the valve hole." -AndrewDressel (talk) 03:39, 6 June 2009 (UTC)

Presta's only advantage is that there is no return spring in the valve, so they are "theoretically" easier to hand-inflate.

The line above is not entirely true since the spring in a Schrader valve is depressed by the little nub in the pump head when it is placed on the valve. Therefore the spring valve actually does nothing to inhibit pumping air through the valve. There is only the slight restriction of flow in the design of the check vave and spring, which I consider negligible. Prestas work on back pressure to seal them, so no air is lost when connecting to the pump. Again, the slight loss on connecting up a Scrader is negligible. Of course the pump must have a check valve to work properly with Schrader valves so pumps made for Presta only could be simpler. But most pumps include the necessary check valve anyway.

Other than that, I think they are a pain as you always need remember an adapter, and my air chuck always leaks even with the adapter, making it nearly impossible to read the pressure. And, you need remember to unscrew/rescrew the check valve each time on a Presta, not just shoot-and-go.

It is Possible the smaller Presta is a bit better in a very thin rim, as stated. With a clincher rather than sewup tire on such; this space is at an extreme premium. See the link at bottom of article. But, I think the disadvantages outweigh these small advantages.

Any opinion of them being "better" in higher pressures is sheer Fallacy...big Truck (lorry) tires often have high pressure (100 PSI) in them, and use Schraeders. The high side of a compressor in A/C systems use Schraders; they work at a high pressure, too. I've seen Prestas in only 45 PSI max tires.

Also, Prestas have a metal-to-metal surface which can leak faster than the rubber seal in a Schraeder. If Schraeders ever leak, well, a new core is only a few pennies (pence, centimes, pfennig); you don't have to buy a whole new tube. And, it goes in in a jiffy. But a Presta valved tube will only be at a specialty shop, not the nearby toy/hardware store. And, most cores are unreplaceable. Have to buy a new tube. So, best to keep spares if you prefer Presta.

Also, no adapter need be put on a Presta to put it in the hole in a rim that a Schraeder came out of to "prevents cuts", as Prestas are all metal. Schraeders are often rubber at the base and can be cut easily by a rough rim hole or a low tube rubbing against the hole while riding. (I always add adapters, though; they are $4 the pair; a bit too high.)

These points should be inserted into the main body of the text.68.231.189.108 (talk) 18:38, 17 December 2009 (UTC)

In the 2009 discussion an anonymous source repeatedly overstates the advantage of a 6mm hole vs an 8mm hole and is simply factually in error in re: installing a presta valve tube in an 8mm hole. (The related changes made to the article cited a reference that no longer exists and the internet archive version has been linked instead.) While its true than in an otherwise uniform shape the inflator hole is the weakest point the hole's diameter is unimportant because the rim profile is a C channel. A C channel concentrates stress on the two inward facing tips of the channel, not the web that connects the legs. Except for where it transfers force to the spokes, the web, the flat band pierced by the inflation valve is a spacer to keep the legs, the rim walls, apart. Away from the spokes it really only needs to be stiffer than the rubber tube and tire. Citing engineering sources about which part of the rim carries the forces and keeps it round probably won't inform a general audience discussion. Perhaps the observation that a flat strip of metal is easily deformed in the direction that it is thin is sufficient.

According to the manufacturer this valve's advantages are limited to a smaller piercing hole and weighing 4-5 grams less than other valves while it has a number of shortcomings relative to the Schraeder valve used on automobiles. Their comments include; "Before inflating, the knurled nut must be loosened. First time users frequently have some problems. Also the thin top pin can be easily bent when attaching and removing the pump connector. Caution: Be aware that using Sclaverand valve tubes on rims with larger valve holes often leads to a valve tear off when the sharp metal edges around the valve hole cut the valve stem off the tube." "The Auto/Car valve can be inflated very easily at a filling station and is pleasantly unproblematic."

The "points inserted in the main body of the text" in 2009 should be reviewed and revised to remove what appears to be a bias even the product's manufacturer can't provide meaningful support for. PolychromePlatypus 21:00, 14 July 2017 (UTC)

References

Correction - needs to be reinstated

According to the manufacturer the anonymous 2009 comment that follows below is mistaken and the Presta valve does require reinforcement and careful installation in the 8mm hole used for other valve types. (see "What causes valve tear off?") The manufacturer also specifically discusses strategies to reduce the frequency of valve tear off with deceleration. To summarize; increase friction from higher inflation pressure, or use a special tube material with more friction, or abrade the rim to it has more friction, or switch to a tubeless design so that tire slip doesn't tend to shear the valve stem.

NB: The admiring tone of the Wikipedia article for this product is unjustified. The same reference from its manufacturer has a section "Which is the best valve". After prolonged discussion of various difficulties of the Presta valve design "The Auto/Car (Schraeder) valve can be inflated very easily at a filling station and is pleasantly unproblematic. Older, as well as simple bicycle pumps are not compatible with car valves." Being older living in the USA and having only used Schraeder valves on bicycles the Schwalbe comment about pumps isn't applicable in North America. Also I've never had even a wildly tilted valve base tear or leak. Presumably the smaller diameter Presta valve root concentrates the force on a smaller area increasing the likelihood of tear-off. PolychromePlatypus 20:02, 14 July 2017 (UTC)

Prestas will not be "cut by deceleration" on a rim hole for a Schraeder as they are all metal. Please eliminate this from text. Scraeders are often rubber at the base and can be cut by low tube pressure, etc. Also, add the comments about Advantage/Disadvantages, etc.68.231.189.108 (talk) 18:59, 17 December 2009 (UTC)

References

Article scope

It seems like the article is getting a little side-tracked. The section on tubeless systems comprises over a third of the length of the page.Bmunden (talk) 15:02, 3 October 2011 (UTC)

Good point. I've moved the wikilink from the section heading to the section body and cut out material already addressed in the linked article. -AndrewDressel (talk) 15:31, 3 October 2011 (UTC)