What tire pressure do you run on winter/snow tires? - MustangForums.com



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Old 12-10-2016, 08:41 PM   #1
99GTvert
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Default What tire pressure do you run on winter/snow tires?

Mine after being in storage are at about 25 psi cold. I don't remember if these were higher before but I want to say I should air these up to about 30 or 35. They're skinnier, taller tires at I think 215/65/R17.
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Old 12-10-2016, 10:14 PM   #2
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Check the manufacturer recommendation. Running them too high or too low will compromise performance.
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Old 12-11-2016, 07:55 AM   #3
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Use the psi listed on your door data plate.
This info is independent of size & or type of tire.
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Old 12-11-2016, 10:49 AM   #4
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Tires lose pressure over time and temperature, just set them at the manufactures recommended pressure on the door and you will be fine.
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Old 12-12-2016, 07:33 AM   #5
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Quote:
Originally Posted by 1 Alibi 2 View Post
Use the psi listed on your door data plate.
This info is independent of size .
.
Not true.

Proper inflation pressure is a function of the load vs inflation tables, and a larger tire does not need to be inflated quite as much. Conversely, a slightly smaller tire can sometimes be "crutched" up to meet your car's load requirements with a little more than door plate pressure.

Larger here means Load Index number and whether the tire is designated Standard Load, eXtra Load, or some other description (Light Load, P-metric, maybe more). There is an official procedure for adjusting pressures to suit different size tires, buried in the text that accompanies the load vs inflation pressure tables.

I have a copy of the SL and XL tables and some of the P-metric information . . . and a little home-grown spreadsheet app to do exactly the sort of pressure adjustment you need for size changes involving the SL and XL tables.


FWIW, I do set the same pressures year round for my street driving, but they differ a little from the sticker number for handling behavior that's a little less understeerish. The track driving gets still different pressures (and are measured hot instead of cold).


Norm

Last edited by Norm Peterson; 12-12-2016 at 07:40 AM.
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Old 12-12-2016, 07:48 AM   #6
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Quote:
Originally Posted by 99GTvert View Post
Mine after being in storage are at about 25 psi cold. I don't remember if these were higher before but I want to say I should air these up to about 30 or 35. They're skinnier, taller tires at I think 215/65/R17.
If you give me what your snow tire size is - preferably the Load Index number (guessing 98 or 99) and the service designation (probably SL), the same information for the tires that your car came with, and the door sticker pressure recommendation . . . I can give you a pressure for your winter tires that will match your car's original load requirement.


Norm
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Old 12-12-2016, 08:53 AM   #7
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I run my tires at just slightly less pressure in the winter, I have no science behind this other than as the air gets colder the tires lose a little pressure then when it warms up, the pressure comes back. and this way i don't need to adjust pressure. it's just automatically ok all year. it's kinda like not washing my car. I just make sure there's enough pressure to avoid overnight flatspots. the other advantage of this is, when your tires freeze to the ground, and they will up here, you just inflate them a bit to pop the ice and presto, you can drive now.
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Old 12-13-2016, 10:24 AM   #8
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Quote:
Originally Posted by Norm Peterson View Post
Not true.

Proper inflation pressure is a function of the load vs inflation tables, and a larger tire does not need to be inflated quite as much. Conversely, a slightly smaller tire can sometimes be "crutched" up to meet your car's load requirements with a little more than door plate pressure.

Larger here means Load Index number and whether the tire is designated Standard Load, eXtra Load, or some other description (Light Load, P-metric, maybe more). There is an official procedure for adjusting pressures to suit different size tires, buried in the text that accompanies the load vs inflation pressure tables.
I have a copy of the SL and XL tables and some of the P-metric information . . . and a little home-grown spreadsheet app to do exactly the sort of pressure adjustment you need for size changes involving the SL and XL tables.
FWIW, I do set the same pressures year round for my street driving, but they differ a little from the sticker number for handling behavior that's a little less understeerish. The track driving gets still different pressures (and are measured hot instead of cold).
Norm
.
Interesting:
.
When I bought tires for my 14, larger size & different mfg., both TireRack & Pirelli said to use the inflation info on the door sill from the mfg. !
One would think people in the tire business would know this stuff..
.
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Old 12-13-2016, 12:49 PM   #9
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People on the engineering side would know that (and a few other things), but people on the marketing and sales sides might very well be unaware.

It still comes down to being a 'starting point' if you're fussy about pressures for any reason. I don't even count the OE sticker pressure numbers for more than that, as they generally have a built-in bias toward understeer and possibly softer cornering response and precision.


Norm

Last edited by Norm Peterson; 12-13-2016 at 12:52 PM.
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