It's cold - air up your tires.
12-07-2016, 07:51 PM
#1
AudiWorld Super User
Thread Starter
It's cold - air up your tires.
It was as warm as it's going to get for the next few months (41*F) today so I checked the air pressure in my tires. I put them on exactly two months ago and the pressures then were 38 psi fronts and 36 psi rear. They were all down six pounds each today.
Pumped them up an extra pound since it's forecast to be near freezing next week.
Pumped them up an extra pound since it's forecast to be near freezing next week.
12-07-2016, 08:53 PM
#2
AudiWorld Senior Member
Just checked my tire pressures before our first snow fall a few days ago. I normally pump in 39 PSI front / and 33 psi rear during warmer weather. Before the cold weather arrives, I pump in an extra pound.
12-08-2016, 01:19 AM
#4
AudiWorld Member
Not to hijack but just bought Michelin Pilot Sport A/S 3+, replacing A/S 3 installed when new car was delivered. Both sets 255-35-20 All Season.
I have been trying to get the 'correct pressure' #'s but no one seems to know. I'm at 42# all around and will add if down more than a pound for cold weather. The 42 comes from my decision to keep the tread flat across the treads, hopefully avoiding the outside wear that required replacement at 33,500.
Am I thinking correctly?
Fwiw, The dealer has been using 36# for customers' ride comfort and the manual is 39 fr 36 rr (not full load) which I used for most of the 3+ years I'd been driving on the originals.
I have been trying to get the 'correct pressure' #'s but no one seems to know. I'm at 42# all around and will add if down more than a pound for cold weather. The 42 comes from my decision to keep the tread flat across the treads, hopefully avoiding the outside wear that required replacement at 33,500.
Am I thinking correctly?
Fwiw, The dealer has been using 36# for customers' ride comfort and the manual is 39 fr 36 rr (not full load) which I used for most of the 3+ years I'd been driving on the originals.
12-08-2016, 02:23 AM
#5
AudiWorld Super User
Join Date: Apr 2001
Location: Northern NJ
Posts: 9,211
Likes: 0
Received 0 Likes
on
0 Posts
I have been trying to get the 'correct pressure' #'s but no one seems to know. I'm at 42# all around and will add if down more than a pound for cold weather. The 42 comes from my decision to keep the tread flat across the treads, hopefully avoiding the outside wear that required replacement at 33,500.
Am I thinking correctly?
Am I thinking correctly?
Additionally to all posting about topping off their tires (a good tip): don't forget the spare! you'll hopefully never need it, but if you do, it won't do much good if uninflated. Required pressure for the spare is 60 psi.
12-08-2016, 03:46 AM
#6
AudiWorld Senior Member
12-08-2016, 05:06 AM
#7
AudiWorld Super User
Tire Rack has this bit on their site:
Winter / Snow Tire Tech
Higher Tire Pressures for Winter Driving
Several vehicle manufacturer's owner's manuals recommend operating winter tires several psi (typically 3-5) higher than their recommended pressures for summer and all-season tires. While none of them actually provide the reason why, there are several scenarios that would support the practice.
First and foremost is that winter tires feature more aggressive tread designs, softer tread compounds and are often molded with deeper beginning tread depths than summer or all-season tires. While the combination of these design elements allows winter tires to remain more pliable in sub-freezing temperatures to provide more traction in snow and on ice, it often results in tires that have somewhat reduced responsiveness to driver input. The 3-5 psi higher recommended inflation pressures increase tire stability and help offset the reduction in responsiveness.
Additionally ambient air temperatures in winter typically range 40- to 50-degrees Fahrenheit colder than typical summer temperatures for the same location. The lower ambient temperatures allow tires to be more efficient at radiating heat and the tires will run cooler, building up less hot tire pressure. In this case, the 3-5 psi higher recommended inflation pressure increase helps offset the reduced hot tire pressures resulting from less heat buildup.
And finally, all tire pressures are intended to be measured cold, which means when the tires are at the same temperature as the air outside. Unfortunately, unless you park your vehicle outside or in an unheated, detached garage, and measure its tire pressures first thing on dark, cold mornings, the influence of attached garages or higher ambient air temperatures later in the day often means that drivers are actually measuring tires that are not completely cold. In this case the 3-5 psi higher recommended inflation pressure increase helps offset the reduced tire pressures associated with the conditions in which the tire pressures are typically measured.
You may also want to read "Air Pressure: When and How to Set"
I've noticed the low profile tires on these cars suffer from temp swings and low pressure, more so than I'm accustomed to seeing. OTOH, the huge volume of the SUV tire (Q5, for example) shows minimal change once the air temps plummet. It's good to check periodically and not rely upon a warning from the TPMS.
Mercedes used to show on the gas filler flap "+4 psi for snow tires". I recall their rationale was to minimize sidewall flexing and heat build up at autobahn speeds.
Originally Posted by Tire Rack
Winter / Snow Tire Tech
Higher Tire Pressures for Winter Driving
Several vehicle manufacturer's owner's manuals recommend operating winter tires several psi (typically 3-5) higher than their recommended pressures for summer and all-season tires. While none of them actually provide the reason why, there are several scenarios that would support the practice.
First and foremost is that winter tires feature more aggressive tread designs, softer tread compounds and are often molded with deeper beginning tread depths than summer or all-season tires. While the combination of these design elements allows winter tires to remain more pliable in sub-freezing temperatures to provide more traction in snow and on ice, it often results in tires that have somewhat reduced responsiveness to driver input. The 3-5 psi higher recommended inflation pressures increase tire stability and help offset the reduction in responsiveness.
Additionally ambient air temperatures in winter typically range 40- to 50-degrees Fahrenheit colder than typical summer temperatures for the same location. The lower ambient temperatures allow tires to be more efficient at radiating heat and the tires will run cooler, building up less hot tire pressure. In this case, the 3-5 psi higher recommended inflation pressure increase helps offset the reduced hot tire pressures resulting from less heat buildup.
And finally, all tire pressures are intended to be measured cold, which means when the tires are at the same temperature as the air outside. Unfortunately, unless you park your vehicle outside or in an unheated, detached garage, and measure its tire pressures first thing on dark, cold mornings, the influence of attached garages or higher ambient air temperatures later in the day often means that drivers are actually measuring tires that are not completely cold. In this case the 3-5 psi higher recommended inflation pressure increase helps offset the reduced tire pressures associated with the conditions in which the tire pressures are typically measured.
You may also want to read "Air Pressure: When and How to Set"
I've noticed the low profile tires on these cars suffer from temp swings and low pressure, more so than I'm accustomed to seeing. OTOH, the huge volume of the SUV tire (Q5, for example) shows minimal change once the air temps plummet. It's good to check periodically and not rely upon a warning from the TPMS.
Mercedes used to show on the gas filler flap "+4 psi for snow tires". I recall their rationale was to minimize sidewall flexing and heat build up at autobahn speeds.
Trending Topics
12-08-2016, 05:22 AM
#8
AudiWorld Member
The historic rule of thumb is to add 1psi for each drop of 10 degrees F. If you install tires which were stored indoors at about 70, and you expect to drive in about 30, for example, add 4 psi above spec during installation. The cold temp will bring them back down to the proper range. Same concept for anticipating a change in the weather for tires already on the car.
12-08-2016, 08:40 AM
#9
It could also be the result of vigorous driving/cornering. If on both inner and outer edges, it would take a lot of under inflation (like 28 PSI or less) to result in significant outer edge wear. Driving hard can do it more easily. No criticism of your driving intended - just my take on what causes tire wear.