Kawasaki VN750 Forum banner

1 - 18 of 18 Posts

·
Registered
Joined
·
66 Posts
Discussion Starter #1
A newbie question - factory tire pressures (28psi front, 30 or 32psi rear) drop some as the temperature drops. As you drive, doesn't that warm the tires up to the factory specs, or is it necessary to further inflate them back up to factory specs. Thank you in advance.
 

·
Registered
Joined
·
140 Posts
A newbie question - factory tire pressures (28psi front, 30 or 32psi rear) drop some as the temperature drops. As you drive, doesn't that warm the tires up to the factory specs, or is it necessary to further inflate them back up to factory specs. Thank you in advance.
yes, inflate your tires before you ride. otherwise you will possibly have tire failure due to excess heat caused by friction of your tire. they will build heat, pressure, but that is NOT good.
 

·
85 VN 700
Joined
·
1,033 Posts
I think the question is - if I filled the tires when it was 80 degrees out and want to ride when it's 40, do I have to adjust for the temperature difference?

Right?

While you should check your tire pressure before every ride, the pressure difference is negligable with the range of temperatures a sane person would ride in.
Quick chemistry lesson...

PV=NRT (T is in kelvins) - P is pressure, V is volume, N is number of molecules (in moles) and T is temperature in Kelvins. Simple algebra will change the formula to P=T/V

30 degrees farenheit = 272 kelvin
100 degrees farenheit = 310 kelvin

I don't feel like working the math, but at 32 psi that gives a pressure drop of about 4 psi (many gauges are only accurate to 2 or 3) and most people don't ride in that wide a temperature range.

All that to say - it's a good idea to check your tire pressure before each ride, but the change in pressure due to temperature is generally negligible. (and yes, the tires will heat up some during a ride making same difference even more negligible).

Ok... gotta run to work...
 

·
85 VN 700
Joined
·
1,033 Posts
You DO fill your tires when they are cold... but I think the original question was about temperature (weather) change and it's effect on tire pressure...
 

·
Registered
Joined
·
185 Posts
Its been cold here. And my front tire was definately mushy!
 

·
Old Truck Junkie
Joined
·
4,133 Posts
Also everything shrinks with the cold, you might get leaks through the valve stem, so tighten it. Also one might get a little leak around the sealing bead of the tire. Like mentioned above check tire pressure often.
 

·
Registered
Joined
·
66 Posts
Discussion Starter #8
Thank you...

gentlemen, for your replies. Curtis, thank you for your in-depth explanation. I check the pressure before every ride, and only recently have we had cold (30's) temps, and that's when I noticed the pressure drop.

niterider, good observation! I didn't pay much attention to the top of my valve stem cap until I noticed a 2 lb drop overnight. Turned out that as I was trying to get my tire guage on the valve stem, I loosened the threaded part of the valve stem, and the air leaked out. THAT's when I realized why the top of the valve cover was notched. DOH *G*
 

·
Premium Member
Joined
·
1,766 Posts
I think the question is - if I filled the tires when it was 80 degrees out and want to ride when it's 40, do I have to adjust for the temperature difference?

Right?

While you should check your tire pressure before every ride, the pressure difference is negligable with the range of temperatures a sane person would ride in.
Quick chemistry lesson...

PV=NRT (T is in kelvins) - P is pressure, V is volume, N is number of molecules (in moles) and T is temperature in Kelvins. Simple algebra will change the formula to P=T/V

30 degrees farenheit = 272 kelvin
100 degrees farenheit = 310 kelvin

I don't feel like working the math, but at 32 psi that gives a pressure drop of about 4 psi (many gauges are only accurate to 2 or 3) and most people don't ride in that wide a temperature range.

All that to say - it's a good idea to check your tire pressure before each ride, but the change in pressure due to temperature is generally negligible. (and yes, the tires will heat up some during a ride making same difference even more negligible).

Ok... gotta run to work...
Using 100F @ 35psi, 10L for vol, .93 moles, calucating for 30F, all other variables remain the same yields 30.6 psi, that is a significant change, worth correcting.

Jon
 

·
Search Goddess
Joined
·
2,002 Posts
gentlemen, for your replies. Curtis, thank you for your in-depth explanation. I check the pressure before every ride, and only recently have we had cold (30's) temps, and that's when I noticed the pressure drop.

niterider, good observation! I didn't pay much attention to the top of my valve stem cap until I noticed a 2 lb drop overnight. Turned out that as I was trying to get my tire guage on the valve stem, I loosened the threaded part of the valve stem, and the air leaked out. THAT's when I realized why the top of the valve cover was notched. DOH *G*
Ok, so you are saying you psssst'd out 2 lbs of air

(Sorry, couldn't resist!)
 

·
Premium Member
Joined
·
580 Posts
Just had a flat fixed on my car this mroning and, while waiting, I read a Michelin brochure about this. It had a rule of thumb stating the pressure in a tire will drop about 1 psi for every change in 10 degrees F.
 

·
Undercover Sportbiker
Joined
·
1,097 Posts
Your tire pressure should be set to factory spec (at a minimum depending on your weight and riding style) regardless of outside temp. It shouldalso always be checked when the tires are "cold" or have not been ridden on for a minimum of 3 - 4 hours (IIRC). Any rise in pressure from heat caused by riding is not relevant.
 

·
Headbanger/Popes of Hell
Joined
·
6,751 Posts
Your tire pressure should be set to factory spec (at a minimum depending on your weight and riding style) regardless of outside temp. It shouldalso always be checked when the tires are "cold" or have not been ridden on for a minimum of 3 - 4 hours (IIRC). Any rise in pressure from heat caused by riding is not relevant.
factory spec of what?.....the tire factory spec the psi on the side of the tire or kaw's bike manual psi, factory spec for the bike? sometimes they're not the same. so which one to use?
 

·
Registered
Joined
·
140 Posts
factory spec of what?.....the tire factory spec the psi on the side of the tire or kaw's bike manual psi, factory spec for the bike? sometimes they're not the same. so which one to use?
if you have changed from oem tires, then you should use the tires for your guide, considering your riding style, load etc. imho:motorcycl
 

·
Super Moderator
Joined
·
11,970 Posts
Most tire makers have a reccomended tire pressure that is figured for our bike...this can be hard to find sometimes.

If you still have stock tires, go by the owners manual. If you bought aftermarket tires for it..check the makers website for info..or post your question here as many here have tried various tires and may know the reccomended pressure.

The pressure on the tire itself is usualy the MAXIMUM PSI the tire can hold, and it not usualy the pressure you should fill them to.

KM
 

·
Premium Member
Joined
·
1,766 Posts

·
Registered
Joined
·
135 Posts
1 - 18 of 18 Posts
Top