What is the deal with presta tubes in mountain bike tires? I have used at least three pairs and I've had problems with leaks. They are Kenda tubes, too. The last one doesn't inflate properly. It says that a 1.95" tire is in the range, but when I pump it and go to 165 pounds of pressure, which is well above the recommended of 80, the tire is still not tight. I can't figure it out. I think I will just stick with Schrader tubes in the future on the mountain bikes. Will hybrid rims fit Schrader valves? If so, maybe I will replace those down the road when the current tubes go bad on my hybrid.

What do you mean the tire isn't "tight". Do you mean it's still soft? or that the super high pressure didn't seat it.

I suspect that what's happening is that the valve is sticking and your pump is reading hose pressure, not tire pressure.

The possible causes are that you failed to back off the nut far enough, your pump head isn't pressed on far enough, or the valve is a bit sticky and you didn't press it before pumping to make sure it's free.

The last is usually only a problem when topping off tires that already have high pressure in them. I've been using Presta valves for over 40 years, and never ran into this until fairly recently. I suspect that the Taiwanese tube makers are using valves with a softer seats than those used by the Italians (but that's just a guess.

These days I can still top off my tubulars the way I always did, but have to "burp" the Presta valves in my commuter first.

FBinNY has the answer. If you were actually inflating the tube to 165psi it would have exploded and taken a fair bit of your hearing with it.

Can you tell us more about the problem with leaks? Do you mean they don't keep pressure very long? Do you mean they puncture easily?

Why would anyone need 165 psi in a mtb tire ? 65 psi is more than enough with Schrader valves.

Are you pumping into a stuck shut valve? tap on the end of the stem ,
once you unscrew the little nut,let a bit of air out,
then you know the valve will open ,
when the pump presses more Air pressure in.

I have no idea. MTB rims should be wide enough to safely drill out and use schraders.

You could be doing something wrong, but some presta tubes are just defective garbage. I have never seen a schrader valve fail.

I can only imagine the valve needs to be "burped" before pumping in this case. The 165 psi reading is more than likely just pressure in the pump itself not the actual innertube.

I think I've only had one bad presta valve in about 20 years. I've seen a handful of bad schraeders but I used to work in an automobile tire shop so I've probably seen more than the average bear.

If the tube pumped up properly, I would probably good with 50 psi. Something was wrong with the tube taking air. It certainly didn't have 165 psi, as the other poster noted, because it would have popped long before it. I must not have had it set properly.

I'll stick to scraders on my mountain bike forever. Thanks

Thanks for the info.-what do you mean by valve needing to be burped?

they didn't have 165, I heard one pop the week before b/c I think the valve stem was in crooked--it's very loud. I don't know why they leak. I've had two left in a garage for a week and they leaked air. Yes, they don't keep pressure long, say a max of 20 pounds and for some reason my pump shows it going up from there. I haven't had a puncture issue with these tubes.

One just needs practice. Yes you were pumping just the hose on the high pressure reading. Typically the pump head needs to be pushed on harder, to depress the presta valve more.

The tube isn't inflating properly. Maybe I didn't press the head far enough in or I need to make sure the valve is free. I still need these tubes for my hybrid tires. Do schraeders ever fit in hybrid rims?

Thanks for the info. I'll check it out next time with my hybrid. I didn't have problems topping off my hybrid tires this year.

Yes to pushing on the pump more and testing to see if the valve is stuck. Some hybrids are presta some are Schrader.

Presta valves became popular with mtb bikers because they let you bleed off pressure without a valve tool - and some terrain is easier to handle with lower pressure.

And professionals use them all over the world without issue so don`t blame the valve. There are junk presta tubes and junk schrader tubes and price is usually a good indicator.

Of course theres really no problem having your rims drilled out for schrader valves, but you can end up with exactly the same issue there if you don`t connect the pump correctly.