sillypuppy

Hi, I'm new to winter riding and new to this forum. I've been having trouble keeping my tires inflated (they lose alot of pressure) when temps get below about 12 degrees F. Any suggestions? Are there special tires or tubes I should be looking for?

Thanks.

Hezz

I would bet the problem is the valve stems. Try a new pair of higher quality tubes. In winter it's nice to go with puncture resistant tubes even though they are heavier since changing a flat in winter is really unpleasant. It's possible that you have some very small punctures in the tubes that leak slowly but if you replace the tubes this should solve this problem.

Before changing the tubes make sure to very thoroughly inspect the tires to make sure that there are no small thorns or wires left that will reflat your tires.

!!Comatoa$ted

As the air temperature drops in your inner-tubes so does the space that it (air) occupies, and this may be causing you tires to deflate somewhat.

If you can, try measuring the pressure to see how much you loose. Or let the tires warm up after they are outside and see if they increase in pressure. Check this out, it will give you an idea of how much compressed air is affected by temperature.

rajman

Another problem is that if you heat and cool your bike (i.e. store in a heated area, ride in cold, heat up again), the valves are leaking air because the seals don't work very well when the temperature changes. My summer bikes are generally flat after winter...

bike2math

I've found (roughly) that if I inflate my tires inside (while changing a flat or putting on the studded tires) then the next day they will be badly in need of air. I think filling them with 68 degree air and then chilling them to 10 degrees loses a noticeable percentage of the pressure: You know, adiabatic gas law and all that.

jaysea

yes... and the reverse is even worse: i once saw two tires (friend's bike) explode (!) in our over-heated indoor garage... (tires were inflated outside) i do not remember what was the T at the time but it sure was below freezing... the front tire exploded in less than an hour (we though it was badly installed) but then the rear tire exploded in something like 4 hours...
and then we knew that it was `pV= nRT` fault...

jaysea

anybody tried nitrogen? there's a garage close to where i live that is equipped to inflate car tires with it... they do a lot of advertisement saying `better reacts to T change` `molecules are `bigger` and therefore less leaking`, ........ one day i'll try it. not sure what is the max pressure of their equipment...

i personally check my tires every couple days (just by hand or jumping on the bike (you can fell it)) and refill them when needed... maybe once per two weeks... nothing special. well, i always use new tubes each winter (might be a superstition. i dont care. (just afraid of flats in cold T) and my tires are special to non-winter bikers because, well, they're studded... (hakka w106)...

2manybikes

You should check your tire pressure before every ride. Even in the summer. All year round. It's just part of cycling. You could spend your life analyizing potential reasons for deflation. Forget it.

sillypuppy

Thanks for the ideas everyone. I have been moving my bike in and out of the cold regularly (riding, then keeping it inside). It must have something to do with the basic physics of air expansion and contraction; when the tires warm up, the pressure goes back to normal. As an odd twist, I think the problem was made worse by my using "fix-a-flat" in the front tire. The front tire has especially been losing lots of pressure, but then fine when it warms up. My theory is that the liquid from the "fix-a-flat" condenses along with the air causing the tube to draw in and collapse, forcing the tire to go flat. When it warms up, the fluid expands along with the air, re-inflating the tire. Kind of funny, but in an interesting, not amusing way.

Hezz

Temperature expansion can only account for a certain amount of change in the tire. THe liquid fix flat stuff you have is most likely the problem. THis stuff probably doesn't work well when cold and you may have multiple punctures in the tube.

I know for a fact that when the tires and tubes are properly maintained and inflated the air loss due to temp change is minimal. Also, if you are only inflating the tires by feel instead of using a gage you probably aren't putting adequate air pressure in them so a small loss in pressure can make them really low. And the valves rely on the inner pressure to keep the valve closed.

The fix a flat stuff is meant as a temporary fix. It doesn't work well for a long term repair.

jaysea

i personally would not go very far on a fixed-a-flat tire these days... well, any day as a mater of fact. interesting to know that it works to a certain point at low temps...