Tire Inflation/Deflation

[SiamJim]

How long does it take for tires to lose pressure under normal circumstances i.e., how often to you check and find you have to top up the pressure? I feel like my rear tire loses pressure too quickly but I cant find a leak in it.

 

Also, how much do you compensate for when your tires are hot. For example, the owners manual says to put 36lbs in the rear for one-up riding w/o luggage. What should the pressure be when tires are hot?

[ChrisE]

A standard rule the pressure increases with heat 10% front and 20% for the rear.

 

As regards loosing air, it shouldn't. Might want to check the valve stem core is tight, but don't over tighten. If that doesn't make any difference, change the valve core.

 

Failing that and you could do this first, mix up some dish washing liquid and place around the stem and see if you get any bubbles. Failing that, fill up a bath tub and remove the wheel and look for the leak.

[ShovelStrokeEd]

10% increase from cold is what most racers look for. The street will tend to flex the tires more and thus actually heat them more. What happens at the tread in terms of tire temperature actually has very little to do with the resulting temperature of the air inside the tire. Almost all the heating comes from carcass flex.

 

You won't be too far off following what the racers do. 10% increase from cold to hot on both front and rear. Unless you seriously underinflate the rear, you'll never see, nor would you want, a 20% increase.

[JayW]

It is my understanding and experience that tires DO lose pressure "normally" over time. It varies with the pressure at baseline, but a pound or 2 per month is not unexpected. The ultimate proof of this is the temporary spare tires in most cars. They are inflated at the factory to 60PSI, and nearly all of them are WAY low when needed, because the owner never tops them up.

 

Also, don't forget that the tire pressure will drop up to several pounds just due to any decrease in temperature over the winter months.

 

Jay

[ShovelStrokeEd]

Assuming dry air inside, if you inflated your tire to 40 psig at 70 degrees F and then measured the pressure at 0 degrees F, you would have found the pressure to have dropped to 34.7 psig assuming the barometer didn't change and no leaks.

 

Most of the pressure loss can be attributed to leaks. For some reason unknown to me, the more you ride, the less the tires leak.

[ClearwaterBMW]

Ed,

what is your opinion of Nitrogen tire inflation for motorcycles....

 

that is one link about it

 

http://www.wcpo.com/wcpo/localshows/dontwasteyourmoney/3aa5047d.html

 

i was going to have that done to my GS on saturday

 

any thoughts from you?

thanks in advance

greg

[Ken H.]

Ed,

what is your opinion of Nitrogen tire inflation for motorcycles....

I'm not Ed, and I don't play him on TV, but I do have an opinion (imagine that), air is about 80% nitrogen already, so what can 100% possibly accomplish for us mere street mortals?

 

It's all a marketing gimmick IMHO.

[ShovelStrokeEd]

Greg,

It is basically B.S.

The only advantage would accrue if your air source was so full of water as to make it humid inside your tire to a huge degree. Then, as Mitch pointed out much better than I could, N2 as a source of dry gas, offers some advantage. Do a search on +Nitrogen, +tire with Mitch Patrie as the poster name and you should learn all you need to know.

 

My warehouse is not plumbed for compressor use and the air in my neck of the woods is pretty humid. In fact, my compressor has been broken for 2 years. I have one of those tall (about 5'5") Nitrogen cylinders that I use for inflating tires and occasional air tool use. It is a superb source of dry propellent and only costs about 11 bucks to fill. Do your own tires and amaze your friends.

[ClearwaterBMW]

Thanks Ed

 

greg

[Bob Palin]

Fill them with hydrogen, less unsprung weight and it makes leaks really easy to find with a match, and the problem is instantly solved!

[ShovelStrokeEd]

"Oh, the humanity!!!"