Tire pressures

[Feejer/Weejer man]

Wow! I just thought the moisture in the air inside the tire expanded with heat. Thats why some use nitrogen. More stable and makes the pressures hot/cold more constant. But I damn near failed physics so what do I know.

 

[Bearly Flying]

Thats why some use nitrogen.

Uhmmmmm...... I'm thinking EVERYBODY uses nitrogen in their tires. Being as how the air is 78% nitrogen.

 

[scmagna]

Doesn't altitude also effect tire air pressures?

No. The pressure is the same inside the tire, it changes on the outside.

Dr. Science of Blues and tire pressure presents; FJR Forum online physics class. :goatee:

Your bag of chips you bought at sea level has X pressure in it. The sea level atmospheric pressure keeps the bag deflated (so to speak) by the outside pressure pushing against the bag-O-chips. At say 7K feet, the outside pressure is less so the bag inside pressure is able to push out and inflate...so to speak. No inside pressure change, just the outside.

Test next Tuesday on, Why women think we're all crazy. This is a pass or fail exam. Please make sure Bust and odot get the proper tutoring before the test. :graduated:

You're right - but you're also wrong. Altitude does affect tire pressure because tire pressure is measured in psig, not psia. What matters with respect to tire handling and other characteristics is psig. As ambient pressure decreases with increased altitude, the tire psig will increase. The tire will be stiffer on top of Mount Everest than at sea level if the amount of air inside the tire is not changed.

 

[War Machine]

I just read the previous 22 posts without stopping.

My brain hurts so much I couldn't even focus on a tire guage now!

 

[zorkler]

stradas front 36 rear 40

 

[arefog]

An FJR on the top of Mt. Everest.............now THAT would be cool! But which color..................................?

**** Fogg

 

[northern rider]

An FJR on the top of Mt. Everest.............now THAT would be cool! But which color..................................?
**** Fogg

if using notrogen, at what pressure would one set their tires at? 41-42 psi with air, but one must also consider the 8% ish increase from cold to hot; so that air inflated tire will be at 44.25. hot (41 cold) and 45.4 hot (42 cold) , something that you wont get with nitrogen.

so should the tires be inflated with nitrogen to the HOT value?

btw, i have contacted both goodyear and dunlop for feedback but have not received any yet

 

[FJRAust]

[quote

btw, i have contacted both goodyear and dunlop for feedback but have not received any yet

I doubt you will.

 

[chrisflock]

but one must also consider the 8% ish increase from cold to hot; so that air inflated tire will be at 44.25. hot (41 cold) and 45.4 hot (42 cold), something that you wont get with nitrogen.so should the tires be inflated with nitrogen to the HOT value?

Incorrect, you will still get a different in pressure from cold to hot with nitrogen. Regardless of what gas you use, pV = nRT.

 

[johnny80s]

Ken
A low cold tyre pressure makes it flex more which generates heat raising the running pressure. Higher cold pressure reduces the flexing and will run cooler. Check the pressure on a cold tyre. I run my Storms at 42 front and 44 rear - 230 lb solo rider, 25 lbs luggage. When I used the pressure stated in the manual the front tyre cupped and I had a wobble around 45 mph. With the higher pressure and proper balancing (dynamic with no center weights, not static) the wobble went away.

Just my observation, your mileage may vary.

Brodie

Brodie,

What is Dynamic Balancing and how does it work?

 

[Jonozz]

all depends on how good your pressure guage is as well, i don't trust the ones at the garages(Fuel stops) as they get abused to hell.,thrown dropped etc....

 

[northern rider]

but one must also consider the 8% ish increase from cold to hot; so that air inflated tire will be at 44.25. hot (41 cold) and 45.4 hot (42 cold), something that you wont get with nitrogen.so should the tires be inflated with nitrogen to the HOT value?

Incorrect, you will still get a different in pressure from cold to hot with nitrogen. Regardless of what gas you use, pV = nRT.

You are right!!! did some test runs with my tires inflated to 40psig front and rear with nitrogen (released the air, install a vacuum pump to purge the tires without unseating the beads). ambient temp is 72F as were the tires (sitting for the last 4 hours) took it on a 45min run, included some hghway and city and took imediate temp and psi readings

front and rear are at 44psig hot. rear tire was at 102F and the front tire at 104F.

so now my question is;

the benefits of nitrogen

A. less likely to seep through rubber

B.will not deteriorate rubber

C.

 

[northern rider]

but one must also consider the 8% ish increase from cold to hot; so that air inflated tire will be at 44.25. hot (41 cold) and 45.4 hot (42 cold), something that you wont get with nitrogen.so should the tires be inflated with nitrogen to the HOT value?

Incorrect, you will still get a different in pressure from cold to hot with nitrogen. Regardless of what gas you use, pV = nRT.

You are right!!! did some test runs with my tires inflated to 40psig front and rear with nitrogen (released the air, install a vacuum pump to purge the tires without unseating the beads). ambient temp is 66F as were the tires (sitting for the last 4 hours) took it on a 45min run, included some highway and city and took immediate temp and psi readings

front and rear are at 44psig hot. rear tire was at 102F and the front tire at 104F.

therefore the benefits of nitrogen

A. less likely to seep through rubber

B. will not deteriorate rubber

C. will not oxidize rims

D. if all air is vacuumed out, air includes moisture, pressures rise from cold to hot more predictably

but it is not a set it and forget fix

 

[Fred W]

The main benefit of nitrogen is a financial one to the purveyors.

 

[Wannabe_4x4]

Hi,
Just replaced both sets of tires with the new Dunlop Roadstar Sportmax (here in AUS)

My last set of tires suffered bad cuping even after looking after the pressures on a regular basis.

When I arrived at the store I was direcred straight to the changing bays and the tire pressures were

checked hot. Both were about 7 PSI above the recommendations that I normally run and it occured to

me the reason for the cupping, the tires normal hot running pressure of about 49PSI.

I was told to drop the cold pressure 5-7 PSI, ie front 34 rear 36.

What would be the general consensus ???

Regards

Ken

Ken, kind of funny, but I'm having the same problem with my brand new Metzler E 880 tires. I was told by a mechanic to drop the pressure to 32 PSI in the front, and 36 PSI in the rear tire. Ironically, I also opened the rebound dampner to 18 clicks in both the forks and the rear shock. Bike runs smooth as glass now... no cupping, and no center wear.

Let me know what happened in your case. I'm too lazy to read through all the replies on this thread

 

[jjsC6]

Hi,
Just replaced both sets of tires with the new Dunlop Roadstar Sportmax (here in AUS)

My last set of tires suffered bad cuping even after looking after the pressures on a regular basis.

When I arrived at the store I was direcred straight to the changing bays and the tire pressures were

checked hot. Both were about 7 PSI above the recommendations that I normally run and it occured to

me the reason for the cupping, the tires normal hot running pressure of about 49PSI.

I was told to drop the cold pressure 5-7 PSI, ie front 34 rear 36.

What would be the general consensus ???

Regards

Ken

Ken, kind of funny, but I'm having the same problem with my brand new Metzler E 880 tires. I was told by a mechanic to drop the pressure to 32 PSI in the front, and 36 PSI in the rear tire. Ironically, I also opened the rebound dampner to 18 clicks in both the forks and the rear shock. Bike runs smooth as glass now... no cupping, and no center wear.

Let me know what happened in your case. I'm too lazy to read through all the replies on this thread

What does "no center wear" mean? How is this possible?

 

[Wannabe_4x4]

What does "no center wear" mean? How is this possible?

I'm back in suspension nirvana, well sorta. I went to 40 psi in both the front and rear tire. Most of the bounciness is gone, but still get an occasional hard hit over a series of bumps. I opened up the rebound to 20 clicks in the back with a Penske aftermarket shock.

Just curious from the guys who run 40 front, 42 psi in the rear tire... is your ride bouncy or a bit hard at times going over ripples? Or does your suspension absorb everything?

 

[Fred W]

What does "no center wear" mean? How is this possible?

Well, duh... It means there is no wear in the center (of the tire, no doubt).

Which would only likely occur if one never goes in a straight line, thereby subjecting the center of their tires to the ravaging roughness of the road surface. This might be the case if one has a severe case of the palsy and is continuously weaving about left and right in their travel lane.

 

[Wee Willy]

40.247 psi front (dry nitrogen) with cold tires at 72.5 deg F ambient OUT OF THE SUN (this is critical!!!)

41.447 psi rear (dry CO2) with cold tires at 73.7 deg F ambient IN THE SHADE.

This setting will provide you with maximum lateral G's at the limit when cornering WITHOUT BAGS.

YMMV

Cheers,

W2

 

[Sir Price]

I run 40 psi front and 42 psi rear. Cold as per manual

, I was always taught to check tyres cold car bike truck whatever.

Why cold you ask? because grasshopper there is only one cold ( within reason) the same as engineering measurements are all taken at 20deg C

EG valve clearances same all done cold .