Tire Pressures?

[Whoops]

I saw a reference to this video elsewhere that said this man is on crack with his tire pressure mumbo jumbo. After watching it though, I kind of feel like he might be smarter about tire pressure than most.

Does anyone else do this?

 

[jimgl3_imp]

at the track, yes. on the street, no.

 

[LakeWylieJoe_imp]

The way we measure tire pressure is called gauge pressure; it's the difference between the pressure in the tires and the ambient (outside) air pressure. If the amount of air molecules were fixed (no leaks), the gauge pressure varies with altitude, temperature, barometric changes, etc.

A quick example. If you pump your front tire up to a reading of 36psi at sea level at standard temp and barometric pressure, then take it to the moon, the reading there will be 36psi + 14.7psi (50.7psi) because there isn't any ambient pressure pressing back on the outer surface of the tire. There was 14.7psi pushing on the outside of the tire at sea level. And yes, the tire will be hard as a rock on the moon with that amount of air in it and wouldn't have a proper contact patch even if the gravity there put the proper amount of weight on the tire. Also, a flat tire at sea level will magically have 14.7psi in it in space, assuming it doesn't leak...

All that being said, the 36 & 42 psi pressures are a good compromise for a given load within the CB1100 carrying capacity specs at any temp, barometric pressure, altitude, etc. as long as you properly set the pressures before riding. I'm sure there is a perfect pressure for each load on the bike, but figuring all that out and constantly monitoring and adjusting the pressure as the temperature changes during the day isn't practical.

A tire with a gauge pressure of 36psi in Qatar will have less air in it than a tire with a gauge pressure of 36psi in Iceland on the same day. This is a good thing. Both give a good contact patch and wear characteristics and that's why we go with a fixed gauge pressure wherever you happen to be.

I used to be a physicist. :-\

 

[GoldOxide_imp]

The way we measure tire pressure is called gauge pressure; it's the difference between the pressure in the tires and the ambient (outside) air pressure. If the amount of air molecules were fixed (no leaks), the gauge pressure varies with altitude, temperature, barometric changes, etc.

A quick example. If you pump your front tire up to a reading of 36psi at sea level at standard temp and barometric pressure, then take it to the moon, the reading there will be 36psi + 14.7psi (50.7psi) because there isn't any ambient pressure pressing back on the outer surface of the tire. There was 14.7psi pushing on the outside of the tire at sea level. And yes, the tire will be hard as a rock on the moon with that amount of air in it and wouldn't have a proper contact patch even if the gravity there put the proper amount of weight on the tire. Also, a flat tire at sea level will magically have 14.7psi in it in space, assuming it doesn't leak...

All that being said, the 36 & 42 psi pressures are a good compromise for a given load within the CB1100 carrying capacity specs at any temp, barometric pressure, altitude, etc. as long as you properly set the pressures before riding. I'm sure there is a perfect pressure for each load on the bike, but figuring all that out and constantly monitoring and adjusting the pressure as the temperature changes during the day isn't practical.

A tire with a gauge pressure of 36psi in Qatar will have less air in it than a tire with a gauge pressure of 36psi in Iceland on the same day. This is a good thing. Both give a good contact patch and wear characteristics and that's why we go with a fixed gauge pressure wherever you happen to be.

I used to be a physicist. :-\

Thanks Joe. Um, what are you now?

 

[the Ferret]

Dave Moss is a track specialist and sets up suspensions and tires to suit racing enthusiasts

 

[LakeWylieJoe_imp]

FBI Agent...

The way we measure tire pressure is called gauge pressure; it's the difference between the pressure in the tires and the ambient (outside) air pressure. If the amount of air molecules were fixed (no leaks), the gauge pressure varies with altitude, temperature, barometric changes, etc.

A quick example. If you pump your front tire up to a reading of 36psi at sea level at standard temp and barometric pressure, then take it to the moon, the reading there will be 36psi + 14.7psi (50.7psi) because there isn't any ambient pressure pressing back on the outer surface of the tire. There was 14.7psi pushing on the outside of the tire at sea level. And yes, the tire will be hard as a rock on the moon with that amount of air in it and wouldn't have a proper contact patch even if the gravity there put the proper amount of weight on the tire. Also, a flat tire at sea level will magically have 14.7psi in it in space, assuming it doesn't leak...

All that being said, the 36 & 42 psi pressures are a good compromise for a given load within the CB1100 carrying capacity specs at any temp, barometric pressure, altitude, etc. as long as you properly set the pressures before riding. I'm sure there is a perfect pressure for each load on the bike, but figuring all that out and constantly monitoring and adjusting the pressure as the temperature changes during the day isn't practical.

A tire with a gauge pressure of 36psi in Qatar will have less air in it than a tire with a gauge pressure of 36psi in Iceland on the same day. This is a good thing. Both give a good contact patch and wear characteristics and that's why we go with a fixed gauge pressure wherever you happen to be.

I used to be a physicist. :-\

Thanks Joe. Um, what are you now?

Thanks Joe. Um, what are you now?

 

[GoldOxide_imp]

FBI Agent...

The way we measure tire pressure is called gauge pressure; it's the difference between the pressure in the tires and the ambient (outside) air pressure. If the amount of air molecules were fixed (no leaks), the gauge pressure varies with altitude, temperature, barometric changes, etc.

A quick example. If you pump your front tire up to a reading of 36psi at sea level at standard temp and barometric pressure, then take it to the moon, the reading there will be 36psi + 14.7psi (50.7psi) because there isn't any ambient pressure pressing back on the outer surface of the tire. There was 14.7psi pushing on the outside of the tire at sea level. And yes, the tire will be hard as a rock on the moon with that amount of air in it and wouldn't have a proper contact patch even if the gravity there put the proper amount of weight on the tire. Also, a flat tire at sea level will magically have 14.7psi in it in space, assuming it doesn't leak...

All that being said, the 36 & 42 psi pressures are a good compromise for a given load within the CB1100 carrying capacity specs at any temp, barometric pressure, altitude, etc. as long as you properly set the pressures before riding. I'm sure there is a perfect pressure for each load on the bike, but figuring all that out and constantly monitoring and adjusting the pressure as the temperature changes during the day isn't practical.

A tire with a gauge pressure of 36psi in Qatar will have less air in it than a tire with a gauge pressure of 36psi in Iceland on the same day. This is a good thing. Both give a good contact patch and wear characteristics and that's why we go with a fixed gauge pressure wherever you happen to be.

I used to be a physicist. :-\

Thanks Joe. Um, what are you now?

Thanks Joe. Um, what are you now?

Thanks Joe. Um, what are you now?

 

[michael1954]

The way we measure tire pressure is called gauge pressure; it's the difference between the pressure in the tires and the ambient (outside) air pressure. If the amount of air molecules were fixed (no leaks), the gauge pressure varies with altitude, temperature, barometric changes, etc.

A quick example. If you pump your front tire up to a reading of 36psi at sea level at standard temp and barometric pressure, then take it to the moon, the reading there will be 36psi + 14.7psi (50.7psi) because there isn't any ambient pressure pressing back on the outer surface of the tire. There was 14.7psi pushing on the outside of the tire at sea level. And yes, the tire will be hard as a rock on the moon with that amount of air in it and wouldn't have a proper contact patch even if the gravity there put the proper amount of weight on the tire. Also, a flat tire at sea level will magically have 14.7psi in it in space, assuming it doesn't leak...

All that being said, the 36 & 42 psi pressures are a good compromise for a given load within the CB1100 carrying capacity specs at any temp, barometric pressure, altitude, etc. as long as you properly set the pressures before riding. I'm sure there is a perfect pressure for each load on the bike, but figuring all that out and constantly monitoring and adjusting the pressure as the temperature changes during the day isn't practical.

A tire with a gauge pressure of 36psi in Qatar will have less air in it than a tire with a gauge pressure of 36psi in Iceland on the same day. This is a good thing. Both give a good contact patch and wear characteristics and that's why we go with a fixed gauge pressure wherever you happen to be.

I used to be a physicist. :-\

I taught Physics/Chemistry...once a Physicist, always a Physicist!
I have always adjusted my tires for temperature, being so dang hot down here. It only makes sense.

 

[Mixagon_imp]

It won't be long before the TPMS systems advance to be able to inflate & deflate a tyre to a suitable pressure for the temperature, speed and road conditions then we can just ride ride and ride until it goes faulty.
Until then I'll stick at 36/42 and stay legal.

 

[GoldOxide_imp]

It won't be long before the TPMS systems advance to be able to inflate & deflate a tyre to a suitable pressure for the temperature, speed and road conditions then we can just ride ride and ride until it goes faulty.
Until then I'll stick at 36/42 and stay legal.

Hopefully the decades long "airless tires" for most vehicles would have been perfected by then. :-/

 

[Rocky_imp]

As much as I respect his views, which seem to make good sense, that's bit too elaborate for me.

 

[Tev62]

My mother drove a Mini Cooper well into her 80's, it had run flat tyres, they made the ride quite firm. You couldn't tell visually that they were punctured without the TPMS because the tyre walls were so stiff.

 

[michael1954]

As much as I respect his views, which seem to make good sense, that's bit too elaborate for me.

What do you think of the 42psi in the front tire cold? I have never put the same amount of air in both tires, putting more air in the rear due to the increased weight & stress.

 

[Mixagon_imp]

As much as I respect his views, which seem to make good sense, that's bit too elaborate for me.

What do you think of the 42psi in the front tire cold? I have never put the same amount of air in both tires, putting more air in the rear due to the increased weight & stress.

What do you think of the 42psi in the front tire cold? I have never put the same amount of air in both tires, putting more air in the rear due to the increased weight & stress.
My worry would be the legal side of ignoring the values of the recommended pressures as the police do check tyre pressures at times.
Also in the event of an accident and insurance claim I'm sure the loss adjuster would be delighted to find the wrong pressures in the tyres and void or reduce the claim as that being a possible factor in the accident.
They would only doing their job along with checking for any mods they have not been informed about.

 

[Cormanus]

Unless there was clear evidence of actual tyre pressure at or very near the of an accident, how would a loss adjuster know?

 

[GoldOxide_imp]

Unless there was clear evidence of actual tyre pressure at or very near the of an accident, how would a loss adjuster know?

Good point Cormanus. This would be especially true should the wheel be a part of any damaged components.

I suppose if the tire flung off the rim 300 m prior to the accident, yeah, then maybe there is something to talk about.