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I've noticed that my mountain bike tire looses air, not because of a leak, etc., but just naturally as time progresses.

Does anybody know the average psi loss over time for a mountain bike tire and tube?

Just the average for a 29" wheel.

  • Depends on the tube, and, of course, on the pressure. With my road bike I figure to pump up my tires every 3-5 days (depending on how fussy I'm being). But some road tubes leak down substantially in 24 hours. Mtn bike tires should last a bit longer, because they're lower pressure and larger volume. – Daniel R Hicks May 10 at 1:46
  • It would be nice if a tire or tube manufacturer provided some technical info. online about average psi reduction for a healthy tire. Would keep the guess work out of a slow leak vs. natural loss. – J.M. May 10 at 1:57
  • Too highly variable, plus the fast leakers don't want to admit it. – Daniel R Hicks May 10 at 2:00
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    Varies quite a bit - not sure why but sometimes I am surprise how soft the tires have gone in a short time, other times (same bike, same wheels, same tires, same tubes) they seem to last months and are till good to ride. With a family I have 5 bikes to maintain, sometimes it feels seems I spend more timeadding air tires than riding..... If you are worried, change tubes to a different brand - stay away from light weight ones. – mattnz May 10 at 3:29
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    @Carel - The Presta valve should not be screwed TOO tight. Just to where the fingers feel some resistance. If you over-tighten you deform the gasket and it's more likely to leak eventually. – Daniel R Hicks May 10 at 11:57
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Continental tire ( they make tubes as well ) states that their tubes loose about 5 psi per week and suggests topping them off on a weekly basis.

This information is not published but they will tell you as much on their support line if you speak German.

For a tube and tire combination, the tube is designed to hold the air in, not the tire and is the point of loss to consider.

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