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Discussion Starter #1
I was perusing Tire Rack articles and ran across the comment that the fed rules for TPMS is 30% down from recommended air pressure is were the system warns one of low tire pressure.
So the system is really stupid.
Folks rely on it instead of checking htier tires..
I had boosted my fronts to 44psi last week, and checked them and they were already down to 42. So I added some air. Went to 45 psi due to it is gettin cold outside.

Anyway, just though I would mention the 30% drop before the TPMS gives a warning anyway.
 

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GO Green
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I was perusing Tire Rack articles and ran across the comment that the fed rules for TPMS is 30% down from recommended air pressure is were the system warns one of low tire pressure.
So the system is really stupid.
Folks rely on it instead of checking htier tires..
I had boosted my fronts to 44psi last week, and checked them and they were already down to 42. So I added some air. Went to 45 psi due to it is gettin cold outside.

Anyway, just though I would mention the 30% drop before the TPMS gives a warning anyway.
Just remember, your psi changes throughout the day. Just driving down to the gas station to fill up your tires will change the psi 1lb. If you leave your car in the sun the psi will change. But its true, people should check their tires and not rely on tpms. Tpms imo is good for emergencies, like if you got a leak in your tire or get a flat. Thats most likely what it was designed for, not for maintaining tire pressure.
 

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30% drop from what exactly, since there's already a degree of acceptable psi.
 

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"Hey, tonight I'm going to make him get up at 3:00 in the morning and tell him to go check his tire pressure! Watch this... Pat, Pat, it's the Lord! I want you to go out and check your tire pressure."
-- Sam Kinison
 

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Sonic Mk3 Crew #03
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Tpms warning light comes on at 29 psi found out today in 50 degree weather. Had to go to ford to reset it cause I was right there. Apparently my bluepoint air gauge is way off because it was reading 40 but my tires were all at 29...
 

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30% drop from what exactly, since there's already a degree of acceptable psi.
30% is from the set point. thus if you inflate your tires to 40 psi, then put your cars computer into learning mode, and the relearn all the tires in the proper sequence, the cars TPMS system will indicate a fault either high or low of 30% of the set psi.

the tpms will now show fault on the cars at 28 psi or56 psi which is 30% either above or below the set and learned tire pressure of 40 psi.

now from what I have experienced in the past and informed from the maker of these tpms sensors is that they actually trip at 25% either high or low of set psi. I guess by law they cannot exceed 30% and the maker sets them at 25% to allow some manufacturing tolerance in production.

from my experience I always allowed an additional 2 psi for warm tires and note that for every 10 degree drop in temperature there is a 1 psi loss of pressure. I have also noted that in general tires loose 1 psi every month with the exception of hydrogen inflated tires which loose about 1 psi in pressure per year.

even if you do not change your wheels and tires every season, I think you would be wise to purchase the $32 ford reset tool to set your tires to your own desirable pressure, then have your vehicle relearn your desired tire pressure, and not the factory set limits in which your car came with.
 

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I was perusing Tire Rack articles and ran across the comment that the fed rules for TPMS is 30% down from recommended air pressure is were the system warns one of low tire pressure.
So the system is really stupid.
Folks rely on it instead of checking htier tires..
I had boosted my fronts to 44psi last week, and checked them and they were already down to 42. So I added some air. Went to 45 psi due to it is gettin cold outside.

Anyway, just though I would mention the 30% drop before the TPMS gives a warning anyway.
Wow 45 psi cold. That's about 49 psi warm.
My sticker recomends 31 psi (cold) for up to 3 passengers in the car and some luggage. What does your sticker recommend ?
I think that you will wear out the Center of the Tires pretty Quickly at that inflation.

http://www.dalcrosstyres.co.uk/?page=advice
 

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I think the psi is determined by the make/model and tire option. I thought the 195 tires were 32 psi, the 205 was 33 psi the 215 were 35 psi and I know the 235/40/18 is 39 psi, so with elizabeth running 44 psi if she has the 18" option is not too much out of spec.

I believe she is only running that on the fronts, and if I remember right the reason for tire rotation is because the fronts are always getting the sides worn down prematurily mainly because of the constant turning of the tires goes through durning normal driving.

I guess the 44psi will compensate with the side wear by also wearing down the center and hopefully will end in even tire wear across the whole tread.
 

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I think the psi is determined by the make/model and tire option. I thought the 195 tires were 32 psi, the 205 was 33 psi the 215 were 35 psi and I know the 235/40/18 is 39 psi, so with elizabeth running 44 psi if she has the 18" option is not too much out of spec.

I believe she is only running that on the fronts, and if I remember right the reason for tire rotation is because the fronts are always getting the sides worn down prematurily mainly because of the constant turning of the tires goes through durning normal driving.

I guess the 44psi will compensate with the side wear by also wearing down the center and hopefully will end in even tire wear across the whole tread.
Just Checked my sticker, it says 31 psi for all sizes up to 17 inch / 18 inch not listed.
I actually pump 33 in front and 31 rears, Even 33 feels too hard when the tires are hot. I've got 215/55/16 on Alloys. I coundn't imagine pumping 45.
45 is over 3 bars.
 

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Discussion Starter #11
I think the psi is determined by the make/model and tire option. I thought the 195 tires were 32 psi, the 205 was 33 psi the 215 were 35 psi and I know the 235/40/18 is 39 psi, so with elizabeth running 44 psi if she has the 18" option is not too much out of spec.

I believe she is only running that on the fronts, and if I remember right the reason for tire rotation is because the fronts are always getting the sides worn down prematurily mainly because of the constant turning of the tires goes through durning normal driving.

I guess the 44psi will compensate with the side wear by also wearing down the center and hopefully will end in even tire wear across the whole tread.
I discovered that the fronts would wear perfectly evenly across if i had the pressure up around 42psi to 44psi in my last car.
I never bothered to rotate (as it was only front to rear with directional tires) and just bought new tires for the rear every two years.
With the high psi front, the car was just better. So in the front, with the engine weight added, the front at high psi did not get worn at center tread at all, and in fact wore perfectly evenly across the tread. Through several sets of tires over 13 years.. I pretty mush just wore out the front, bought a pair and stuck the new pair on the back, and rotated the rear to the front. Every two years or so.. (I used Summer only Ultra High Performance tires all the time.. Winter too no problem.)
Rotation IMO is a waste of money if paid for, (It cost much more than it saves in tire wear!) and only if self done is even reasonable, For myself, i would never bother again to rotate tires. Keeping the fronts 7 to 8 psi over rears is all i do now.
And 45psi is just for the winter. In the Summer i would do 44psi, maybe down to 43psi if it is really hot out, like in the 90's all the time.
I have used this method for 13 years and am very satified with the results.

Also if one drives in a 'spirited' manner around corners, the higher front psi gives a lot better turn-in than stock on my 2012 Focus... Seems to make up for the flabby sidewalls a bit.
 
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