Tire Pressure Issue

[Mr. Bloom]

I'm no scientist or anything.

Shouldn't there come a point when the tube is under pressure that the interstitial spaces are too small for air molecules to go through?

Karen: Such big words! Are you sure you're not a scientist?

ehirsch: My tires are 100 psi. bikeleague training says not to overfill, so I don't (although I used to...)

The bikeleague training also says to check air pressure before each ride. I do since I'm alone during the week and don't have many to call for help if I get a flat and get stuck out past dark.

[kiwi girl]

I'm only riding my road bike on the weekends at the moment. My tires seem to go down from 120 to 80 or even less over the course of a week - but I agree with the slowing down of the rate of loss theory - after a couple of months they haven't got much below 50.

Note to self - pump up the tires on the commuter.

[sundial]

Mr. Silver, is there a chance you have a bad batch of tubes? Our LBS had cyclists coming in by droves with flats. I believe the bad batch of tubes were Specialized. They switched to Bontrager and it reduced the incidents of flats.

I had something weird happen not long ago. I purchased new Specialized Captain tubeless tires and it would go completely flat over night. The bike mechanic took soapy water to it and air bubbles developed all along the sidewalls. Needless to say I switched tires.

[redrhodie]

Am I the only one who pumps before every ride? It's part of my pre-ride ritual. If I didn't do it, I think I'd feel like I forgotten to brush my teeth.

Okay, I admit it, I'm a little like Monk.

[sundial]

I do. But then I've been accused of OCD.

[bmccasland]

Don't forget the laws of physics involving air pressure also includes ambient temperature. So when my bike sits in my car all day on a sunny day, I rarely have to pump the tires before my afternoon ride. But on cool mornings when I head out from the house, I need to add air.

More fun with air pressure - when I used to live and work at 7000 ft elevation, and we'd get an order of lab supplies, the boxes would be almost bursting open. All our pipets, tubes, and other such plasticware would be packed in sealed plastic bags, the difference in elevation change from the factory site (sea level) to the lab would make the sealed plastic bags expand. This also happens with air splints, so if you have an air splint and go up elevation - more pressure on your broken limb. Air splint going down elevation, loss of pressure, loss of splint function.

So Mr. Sliver - are you checking your air pressure the same time / every day? Has it been warmer or cooler than the day before? You could have all kinds of road trip fun checking pressure at various temperatures and elevations.

[OakLeaf]

Even more fun with air pressure:

if you bring a flexible water bottle with a straw onto an airplane, then before takeoff, take a big drink and re-close the bottle WITHOUT letting air enter (so the bottle is slightly concave.

If you don't do this - or if you have a rigid bottle without a bite valve - then before you open the bottle during flight, warn your seatmate of the impending geyser.

DAMHIK.

[parity]

Am I the only one who pumps before every ride? It's part of my pre-ride ritual. If I didn't do it, I think I'd feel like I forgotten to brush my teeth.

I do this as well before every ride. I first let a little air out to avoid over inflating and then pump my tires to 110 PSI. I've also heard latex tubes will leak more air then butyl tubes. I guess its also possible ultralight butyl tubes will leak air faster then a heavier butyl tube. I use Michelin Aircomp Ultralight tubes and overnight they will lose around 5-10PSI.

[VeloVT]

I give them a "pinch-test" before every ride . If I'm riding every day, I pump up probably every other ride, maybe every 3rd if some of the rides are very short (under 25 miles). If the bike is sitting around longer between rides, I might have to pump up every ride. I pump to 120 front and rear. I think my tires are rated to 145 but I've never tried riding them at such high pressure (not to mention that I'm not sure I'm strong enough to pump that much air into the tire).

[Mr. Bloom]

Yes, I check before every ride. I've made the bikeleague mantra my routine:

A - Air
B - Brakes
C - Chain/Chrank
Quick Release.

I think what I'll do is check before and after each ride to see what a difference that makes.