"Inflate snow tires 4 psi more than recommended tire pressure"

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In regards to the max speed, it's true that in a worst case scenario, winter tires tend to be Q-speed rated, good to about 99 mph. But, with the studdable and "high end studless", tires, if you have to do an emergency lane change, and you were doing say 90 mph at that time, slamming the brakes and performing evasive maneuvers may still lead to a crash, since the tread tends to be very squirmy due to the design of being more heavily siped for that snow and ice traction. Mazda's arbitrary recommendation is probably based on braking and cornering at the same time without killing yourself. If you have a "performance winter tire" that can be H or V-rated, you can drive a little faster, since the tradeoff for better dry road handling is worse snow & ice traction. But.. what if you're driving through say Utah and you're in a 80 mph zone on I-15? Drive slower and stay in the right lane unless you need to pass someone. It's a speed limit, not minimum speed. Some highways may have additional signage that indicates minimum speed, but that tends to be around 45 mph, if you're driving that slow, your hazards better be on.
 
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Originally Posted by CapriRacer
I think the reason why they wrote that is 2 fold: 1) A smaller footprint is more likely to penetrate the snow and get the tire in contact with the pavement - which always has more grip. 2) Because people don't like to adjust their tire pressures when it's really cold out there, this 4 psi more covers 40°F temperature drop - the tire will never be under inflated.
+1
 
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Originally Posted by ARCOgraphite
** I say close to nothing as I assume COLD is at Imperial Standard Temperature and Pressure. ( 60F 1 ATM)
Bad assumption. Tire manufacturers say that "Cold" means when the tire is at ambient temperature, regardless of what that temperature is. When to Check Inflation Pressure - Check inflation pressure when tires are cold, that is, when the vehicle has been parked for at least three hours or has been driven less than one mile at moderate speed. Significant changes in altitude or temperature at which a vehicle will regularly operate will result in changes in inflation pressure and will require an inflation pressure check and adjustment. - source USTMA (US Tire Manufacturers Association) Care and Service of Passenger Car and Light Truck Tires
 

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Seems logical … Pretty much what I have to do since I don't have an air conditioner where we park ! Far as I know the TPMS has no digital thermometer …
 
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Keep tires 3 > 4 p.s.i. higher during late fall to mid spring due to fluctuation of temps . 36 > 37 for 32 p.s.i. manufacturer recommendation .
 
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May 17, 2009
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Originally Posted by CapriRacer
Originally Posted by ARCOgraphite
** I say close to nothing as I assume COLD is at Imperial Standard Temperature and Pressure. ( 60F 1 ATM)
Bad assumption. Tire manufacturers say that "Cold" means when the tire is at ambient temperature, regardless of what that temperature is. When to Check Inflation Pressure - Check inflation pressure when tires are cold, that is, when the vehicle has been parked for at least three hours or has been driven less than one mile at moderate speed. Significant changes in altitude or temperature at which a vehicle will regularly operate will result in changes in inflation pressure and will require an inflation pressure check and adjustment. - source USTMA (US Tire Manufacturers Association) Care and Service of Passenger Car and Light Truck Tires
I think my problem is being in New England with the 30 deg temps swings, the tires are always at the wrong pressure for the commute. Under-inflated on the way in to work and over-inflated on the way home. The are just right for Lunch with the car just sitting there! I do understand for trucks hauling loads you have to have the pressures correct for the load no matter what the ambient starting temp is.
 
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I have a 2018 Mazda 3, I have 4 Altimax Arctic 12 on the car, I KEEP it inflated at 36 psi, as mentioned on the door jam. 4 psi more is for when temperature drops, a snow tire wont give you the same stability at higher speeds due to softer compound, mushy ride. I add air when it gets colder and check on a weekly basis.
 
Joined
May 8, 2003
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N. VA
Late so-called internet tire expert from what I've read from industry sources over 30 years; winter tires should have several more psi to round them out and narrow the contact patch to better cut through fresh snow and have more tread reach the pavement vs the opposite of lower psi and fatter patch riding on top, commonly the desired mud/sand flotation principle. That's why snow sets are usually spec'd at smaller section widths and wheel diameters for the higher profile look. Yes snow conditions vary to hard pack & ice but generally the thinking should be pizza cutter and not steam roller for winter tires. Cold psi should be before trip whatever the outside temp, otherwise 34 psi @ 60*F will be 27 psi @ -10*F; I tend to doubt that's what Mazda and others intended.
 
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Apr 13, 2014
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In very cold temps, tires do not heat up like they do on a warm summer day. Check you tires before / after a long drive in the summer, and your tires will 3-5 psi higher, or more, after the drive. Do the same on a cold winter day, and the tires psi often won't have changed at all.

Any race spec tire sets a HOT psi recommendation, after the tires have warmed up. The tire operates best in a narrow window of inflation pressure. Street tires approximate the hot pressure window by using a cold inflation pressure, with an expected psi increase from "normal" operating conditions. An average tire, driven in an average manner, will warm up a predictable amount, getting the tire into its optimal pressure range.

And, most winter tires tend to have less firm sidewalls and tall, flexible tread blocks, which can feel floaty or less precise on dry pavement. A few extra psi can help the tire feel SLIGHTLY less squirmy.
 
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Jun 15, 2003
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I had a valve stem jam ever so slightly open when I checked a tire during a -20F cold snap. I think a piece of ice condensation got in there and jammed it, leading to a flat tire. Bugs me because I try to inflate during periods of low absolute humidity.

Never again! I check my tires monthly-ish but never in a cold snap. A few extra PSI to keep from having problems in potentially life threatening weather works for me.
 
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Apr 3, 2017
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The higher the tire pressure means the higher the pressure/inch of the contact patch. Will give better traction in low grip environments. I actually know the guys who were largely responsible for creating the MPSF standard, and they recommend higher pressures in low grip situations. Inflate to say 36 PSI, and the tread will be exerting 36 PSI on the pavement.
 
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