Presta Valve?

Forums Mountain Bike Forum Presta Valve?

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    • #76366

      What are the pros and cons with Presta Valves? I bought some tubes and have no idea how im going to put air in them, thinking about just returning them. Thanks for the help. .

    • #76367

      Im not really sure what the deal is with presta, I think its a weight saving issue as standard schrader tubes are on the heavy side. Most down hillers and free riders use the schrader tubes because weight isnt as big an issue and the extra protection is worth while. You need a presta to schrader adapter to inflate a presta tube, you usually get one included when you buy a bicycle tire pump. keep in mind, the valve stem hole in some rims are smaller and will only accomodate the presta valve, (you’d have to drill out the hole to put a larger stem tube into it..)

    • #76368

      cjm

      Presta is supposed to hold air for a longer period time. I have not tested this. The perk of Schrader is that it can be filled at the gas station. This is a super bonus when you break your pump right before a ride.

      Schrader valves can be a bitch to get inflated, because they don’t always poke cleanly through valve hole in the rim. Presta valves have the nut that over comes this problem. Some Schrader valves have the nut, but it’s not a common thing.

      Personally I stick with Schrader because of the gas station thing. I have also broken a Presta Valves on the trail.

      Goose, which shock is using Presta?

    • #76369

      All I can say is that since I got my new bike which came with presta valves, I have to top of my tire a lot less often than on my old schrader valves.

    • #76370

      In addition to the comments above:

      Presta valves are sealed with air pressure from the inner tube side, Schrader uses a spring

      Presta means a smaller hole through the rim, leaving more rim material intact. In the late 70’s and early 80’s road rims this was important.

      Presta is the traditional valve used on Sew-up type (sorta like tubeless but not) racing road bike tires. Sew-ups were the only decent tires to race on until the early 1990’s when clincher technology finally became worth a hoot.

      Presta is way faster to let the air out of if you have a slow leak and need to change it quickly.

      Most presta rims can be drilled out to schrader with no problems (but it will void whatever warranty you had).

      You can special order "Rim Saver" inserts from most local bike shops [url:39a79wbm]https://www.bikeparts.com/search_results.asp?ID=BPC305723[/url:39a79wbm] so you can put presta valves in a schrader rim.

      Schrader is easier to fine tune pressure, generally the air path is held open with the pump chuck – the pressure gauge on your pump is reading exactly what is in the shock/fork/tire. With presta usually there is a pressure build up on the pump side before the valve breaks free.

      Presta is not-so-great under 20psi. Schrader really sucks over 90psi.

      In my opinion the weight difference is almost zero and not worth talking about especially when said valve is on a 800+ gram tire.

      In my opinion both valve technologies have lasted in cycling because they each have distinct advantages and disadvantages. If either were truly superior the other would have died out like the woods valve.

      Personally I prefer Presta, but mostly so I can have the same on my road bikes and mountain bikes.

    • #76371

      cjm

      Mongoose; Oh man, I shouldn’t have asked. My wallet has done so well this year beating down the "bike geek" 😀

    • #76372

      cjm

      Feet;

      I am really curios about this statement "Schrader really sucks over 90psi." I have seen similar made before, but I have yet to hear it explained. When I first installed my DHX5 there was a lot chatter about the boost valve leaking air. It was explained to my bike wrench by Fox that the shock wasn’t leaking air. But, when you commit a large percentage of your air volume to fill the hose on your shock pump, you will lose a crap load of air pressure. I ride 120psi in the boost valve. It didn’t matter when I checked the air, either six seconds or 6 months later, it would always be the same roughly 20psi lost. I found a similar behavior with my Marz ATA (130psi). I never checked the air on my swinger air because the sag always stayed at 30%, but I believe it was at 110psi. The only thing I have seen with Schrader valves is that over time the valve core seal will lose its ability to hold air, that however is regardless of air pressure. I have never seen this on a bike, I saw it on old cars.

    • #76373

      It has to do with how the valve is held open with the pump chuck. Lots of pumps you push the chuck onto the valve then flip a lever, twist the head or whatever to get the air seal around the valve. Above about 90psi lots and lots of air escapes during those seconds. Some air while you put it on, some air while you take it off. What a pain. I suppose my statement in the previous post is inaccurate, I should have said "Schrader [i:198j3d1o]pumps[/i:198j3d1o] really suck over 90psi"

      Ever notice how different the connection on your high pressure schrader shock pump is constructed/operated? Shock pumps make the air seal first, then engage the valve core to hold it open. If you get a cheap one that works the opposite it is a disaster.

      With presta the valve is already closed when you pull off the pump head, the big rush of air you hear when you pull off the pump head is air in the hose that was still at 110psi.

    • #76374

      cjm

      Feet;

      I just got a new shock pump (soaked my old ones in brake fluid) that illustrates your statement. I has two moving parts in the chuck. The first screws to the valve body. After you have that tight, you twist down a plunger that open the actual valve. You could probably get more accurate pressure checks by getting some pressure in the hose, before twisting the plunger to open the valve, too.

      You are first the one to mention the pump. I am more educated person now. It’s been a good day.

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