Tire Pressure

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Jimmydreams

Well-known member
Joined
Apr 23, 2010
Messages
1,500
Location
Oceanside, Ca.
I felt my range was dropping just a bit lately (although I HAVE been using my heater in the morning a lot).....so tonight I decided to check the tire pressure:

Door-jamb label calls for 36psi all the way around.

All my tires were at 33psi.

I filled them up to 40psi (max pressure is 44psi as listed on the tire).

I'm guessing I see a noticeable bump in range tomorrow. I wonder what the delivered pressure was?!? Check your tire pressure, folks!!
 
Jimmydreams said:
I felt my range was dropping just a bit lately (although I HAVE been using my heater in the morning a lot).....so tonight I decided to check the tire pressure:

Door-jamb label calls for 36psi all the way around.

All my tires were at 33psi.

I filled them up to 40psi (max pressure is 44psi as listed on the tire).

I'm guessing I see a noticeable bump in range tomorrow. I wonder what the delivered pressure was?!? Check your tire pressure, folks!!

Even tho' it will ride a bit harsher, I would run with 44psi cold on all 4 tires. It makes a difference of about 3-4mpg on my Prius, due to lower rolling resistance.
 
prberg said:
Thanks for the reminder to check the tire pressure. How low does it have to get before the TPMS will give us a warning on the dashboard?

-Peter

My wife's car's low pressure light comes on at about 28, but with these LRTs, I read on the tire website (someone had posted a link a few months ago) that they take higher pressures than regular tires. I found the link: http://www.tirerack.com/tires/tires.jsp?tireMake=Bridgestone&tireModel=Ecopia+EP422
 
The maximum pressure you should pump them up to will be listed on the sidewall, note this is measured when the tire is cold. Many people routinely exceed that pressure, some up to 100psi, but you risk a blow out.
 
the max pressure on the sidewall is for ultimate safety margins. u can, under "normal" circumstances, easily exceed the rating by 50% with minimal compromise to your safety.

now, we cant always predict that driving conditions will be normal and a sudden pothole may be unavoidable.

i put my tires to 42 PSI all the way around on day 2 of ownership. i have no doubt that it makes a difference. on my Prius, i am guessing that i am getting 2 mpg increase from the standard 35/33 to 42/40 F/R
 
so TPMS is not adaptive? i am kinda sorta sure that the Prius is...since it does have a reset button.

that is a bummer. if i set my PSI at 42, i want to be alerted when the tire hits 36 PSI at worst.
 
And you read this where? And by that, I mean from an actual tire manufacturer or other respected authority.

This is from the DOT's website:

Maximum Permissible Inflation Pressure:
This number is the greatest amount of air pressure that should ever be put in the tire under normal driving conditions.


DaveinOlyWA said:
the max pressure on the sidewall is for ultimate safety margins. u can, under "normal" circumstances, easily exceed the rating by 50% with minimal compromise to your safety.
 
mogur said:
And you read this where? And by that, I mean from an actual tire manufacturer or other respected authority.

This is from the DOT's website:

Maximum Permissible Inflation Pressure:
This number is the greatest amount of air pressure that should ever be put in the tire under normal driving conditions.


DaveinOlyWA said:
the max pressure on the sidewall is for ultimate safety margins. u can, under "normal" circumstances, easily exceed the rating by 50% with minimal compromise to your safety.

a true and reasonable max tire pressure cannot be advertised due to inaccuracies measuring the pressure coupled with the limited common sense of the person filling the tire so therefore the max rating has a VERY comfortable margin of safety built in
 
Again, where is this written? I am an engineer; I know about designing with safety margins and worst possible case scenarios. I also know that that number was not taken from thin air (no pun intended) and is based on sound engineering and science. Exceeding it is like prodding the tiger and if your tolerances happen to line up in the wrong direction - and you will have no way to know that in advance - you are risking a possibly catastrophic failure. I'm sorry, but in my eyes it is a fool's errand and I have to strongly recommend against it.


DaveinOlyWA said:
mogur said:
And you read this where? And by that, I mean from an actual tire manufacturer or other respected authority.

This is from the DOT's website:

Maximum Permissible Inflation Pressure:
This number is the greatest amount of air pressure that should ever be put in the tire under normal driving conditions.


DaveinOlyWA said:
the max pressure on the sidewall is for ultimate safety margins. u can, under "normal" circumstances, easily exceed the rating by 50% with minimal compromise to your safety.

a true and reasonable max tire pressure cannot be advertised due to inaccuracies measuring the pressure coupled with the limited common sense of the person filling the tire so therefore the max rating has a VERY comfortable margin of safety built in
 
If you grossly overinflate your tires to try to save a few kWh, you might also want to try slamming on the brakes to assess the tradeoff you're making in stopping distance.
 
I also run my Prius tires a bit on the high side - but always got the impression that the return of better mileage for high tire pressure strongly diminished as the tire pressure hit the 40-42 psi range. Over that I never noticed a reasonable enough increase in the mileage to warrant any higher pressures.

Are your experiences similar to that?

(Seems like the kind of experiment that Bob Wilson would have run - with lots of charts and graphs to go along with it)
 
i guess we missed the part when i said i set mine to 42 PSI. hypermilers set their Priuses to 60 PSI and have been doing it for years.

i am not suggesting that anyone here do the same and i question the benefit of going much over 44 PSI on modern tires anyway.
 
DeaneG said:
If you grossly overinflate your tires to try to save a few kWh, you might also want to try slamming on the brakes to assess the tradeoff you're making in stopping distance.
Yes - risk is in breaking, as much as in a blow out.

BTW, with regen - does it still matter ?
 
evnow said:
DeaneG said:
If you grossly overinflate your tires to try to save a few kWh, you might also want to try slamming on the brakes to assess the tradeoff you're making in stopping distance.
Yes - risk is in breaking, as much as in a blow out.

Add to that uneven and premature tire wear.


Not too economical.

Tire%20-%20overinflation.jpg
 
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