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I am curious; the sticker says that the front tires need to be 35psi and rear 33psi (255s in the rear). The infotainment saus that my tire pressure is 45-46 psi. Which one is right?
 

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sticker is what it should be cold.. infotainment is what TPMS reports.. even if your tires are hot, 45-46 is too high.
 
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I am curious; the sticker says that the front tires need to be 35psi and rear 33psi (255s in the rear). The infotainment saus that my tire pressure is 45-46 psi. Which one is right?
It is likely that both are correct and that you need to correct your tire pressure.
The recommended pressure is best set in the morning just before sunrise. After sunrise is not terrible (maybe 1-2 PSI error), but don't adjust the tires to the pillar pressure after a substantial drive (4+ PSI error).

The pillar pressures are for "normal" driving. Higher pressures are recommended when carrying a full load of passengers and/or luggage. I believe there is a chart in the owners manual. If driving at sustained high speed such as on a track or the autobahn you should also increase tire pressure. I believe there is guidance in the owner's manual.

Now for my question: my door pillar on my Q4 (225 width all around) says 35 psi front and 37 psi rear. However, the weight of a Q4 is slightly biased towards the front. So why is the rear tire inflation pressure higher?

I'm also still not sure what PSI is right to set at sea level prior to my weekly drive over 9600 foot elevation Sonora Pass (+4 PSI due to the elevation change)

I can understand your 33psi rear since 37*225/255 = 33
 

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I should add: the low profile 19" tires on Giulia hold so little air that a bicycle floor pump is well suited for adjusting the pressure. Just don't overdo it, a good bicycle floor pump can put out 200PSI. IIRC about 10 strokes gained 4PSI in my 225 40R19s.
 

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“Now for my question: my door pillar on my Q4 (225 width all around) says 35 psi front and 37 psi rear. However, the weight of a Q4 is slightly biased towards the front. So why is the rear tire inflation pressure higher?“

Lockem, pillar pressures are actually for full load with passengers in the back....hence I keep the same pressures in all 4 (am mostly in car by myself)...wear is very even front and rear...
 

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Lockem, pillar pressures are actually for full load with passengers in the back....hence I keep the same pressures in all 4 (am mostly in car by myself)...wear is very even front and rear...
I don't think so, at least not in the USA. The recommended cold tire inflation pressure on the Giulia's tire placard is regardless of vehicle load condition. Some manufacturers do specify different cold tire inflation pressures depending on the vehicle load condition, and Alfa Romeo may specify it this way in certain markets, but FCA does not do this for the Giulia in the USA. As far as I know, there is just one recommended inflation pressure for all vehicle load conditions. Per the tire placard and the owner's manual:
Term: Definition
B-Pillar: The vehicle B-Pillar is the structural member of the body located behind the front door.

Cold Tire Inflation Pressure: Cold tire inflation pressure is defined as the tire pressure after the vehicle has not been driven for at least three hours, or driven less than 1 mile (1.6 km) after sitting for a minimum of three hours. Inflation pressure is measured in units of PSI (pounds per square inch) or kPa (kilopascals).

Maximum Inflation PressureThe maximum inflation pressure is the maximum permi: ssible cold tire inflation pressure for this tire. The maximum inflation pressure is molded into the sidewall.

Recommended Cold Tire Inflation Pressure: Vehicle manufacturer's recommended cold tire inflation pressure as shown on the tire placard.

Tire Placard: A label permanently attached to the vehicle describing the vehicle’s loading capacity, the original equipment tire sizes and the recommended cold tire inflation pressures.

Tire Loading And Tire Pressure
Note: The proper cold tire inflation pressure is listed on the driver’s side B-Pillar or the rear edge of the driver's side door.

Check the inflation pressure of each tire, including the spare tire (if equipped), at least monthly and inflate to the recommended pressure for your vehicle.

Tire And Loading Information Placard
This placard tells you important information about the:
1. Number of people that can be carried in the vehicle.
2. Total weight your vehicle can carry.
3. Tire size designed for your vehicle.
4. Cold tire inflation pressu res for thefront, rear, and spare tires.

Loading
The vehicle maximum load on the tire must not exceed the load carrying capacity of the tire on your vehicle.You will not exceed the tire's load carrying capacity if you adhere to the loading conditions, tire size, and cold tire inflation pressures specified on the Tire and Loading Information placard in “Vehicle Loading” in the “Starting And Operating” section of this manual.

Note: Under a maximum loaded vehicle condition, gross axle weight ratings (GAWRs) for the front and rear axles must not be exceeded. For further information on GAWRs, vehicle loading, and trailer towing, refer to “Vehicle Loading” in the “Starting And Operating”
section of this manual.

To determine the maximum loading conditions of your vehicle, locate the statement “The combined weight of occupants and cargo should never exceed XXX kg or XXX lbs” on the Tire and Loading Information placard. The combined weight of occupants, cargo/luggage and trailer tongue weight (if applicable) should never exceed the weight referenced here.

Steps For Determining Correct Load Limit—
(1) Locate the statement “The combined weight of occupants and cargo should never exceed XXX kg or XXX lbs.” on your vehicle's placard.
(2) Determine the combined weight of the driver and passengers that will be riding in your vehicle.
(3) Subtract the combined weight of the driver and passengers from XXX kg or XXX lbs.
(4) The resulting figure equals the available amount of cargo and luggage load capacity. For example, if “XXX” amount equals 1400 lbs. and there will be five 150 lb passengers in your vehicle, the amount of available cargo and luggage load capacity is 650 lbs. (1400-750 (5x150) = 650 lbs.)
(5) Determine the combined weight of luggage and cargo being loaded on the vehicle. That weight may not safely exceed the available cargo and luggage load capacity calculated in Step 4.
(6) If your vehicle will be towing a trailer, load from your trailer will be transferred to your vehicle. Consult this manual to determine how this reduces the available cargo and luggage load capacity of your vehicle.

Metric Example For Load Limit
For example, if “XXX” amount equals 635 kg and there will be five 68 kg passengers in your vehicle, the amount of available cargo and luggage load capacity is 295 kg (635-340 (5x68) = 295 kg) as shown in step 4.

Note:
If your vehicle will be towing a trailer, load from your trailer will be transferred to your vehicle. The following table shows examples on how to calculate total load, cargo/luggage, and towing capacities of your vehicle with varying seating configurations and number and
size of occupants. This table is for illustration purposes only and may not be accurate for the seating and load carry capacity of your vehicle.

For the following example, the combined weight of occupants and cargo should never exceed 865 lbs (392 kg).

Tires—General Information
Tire Pressure
Proper tire inflation pressure is essential to the safe and satisfactory operation of your vehicle. Four primary areas are affected by improper tire pressure:

  • Safety and Vehicle Stability
  • Economy
  • Tread Wear
  • Ride Comfort
  • Safety
Warning!

  • Improperly inflated tires are dangerous and can cause collisions.
  • Underinflation increases tire flexing and can result in overheating and tire failure.
  • Overinflation reduces a tire's ability to cushion shock. Objects on the road and chuckholes can cause damage that result in tire failure.
  • Overinflated or underinflated tires can affect vehicle handling and can fail suddenly, resulting in loss of vehicle control.
  • Unequal tire pressures can cause steering problems.You could lose control of your vehicle.
  • Unequal tire pressures from one side of the vehicle to the other can cause the vehicle to drift to the right or left.
  • Always drive with each tire inflated to the recommended cold tire inflation pressure.
Both under-inflation and over-inflation affect the stability of the vehicle and can produce a feeling of sluggish response or over responsiveness in the steering.

Note:


  • Unequal tire pressures from side to side may cause erratic and unpredictable steering response.
  • Unequal tire pressure from side to side may cause the vehicle to drift left or right.

Fuel Economy
Underinflated tires will increase tire rolling resistance resulting in higher fuel consumption.

Tread Wear
Improper cold tire inflation pressures can cause abnormal wear patterns and reduced tread life, resulting in the need for earlier tire replacement.

Ride Comfort And Vehicle Stability
Proper tire inflation contributes to a comfortable ride. Over-inflation produces a jarring and uncomfortable ride.

Tire Inflation Pressures
The proper cold tire inflation pressure is listed on the driver's side B-Pillar or rear edge of the driver's side door. At least once a month:

  • Check and adjust tire pressure with a good quality pocket-type pressure gauge. Do not make a visual judgement when determining proper inflation. Tires may look properly inflated even when they are under-inflated.
  • Inspect tires for signs of tire wear or visible damage.
Caution!
After inspecting or adjusting the tire pressure, always reinstall the valve stem cap. This will prevent moisture and dirt from entering the valve stem, which could damage the valve stem.



Inflation pressures specified on the placard are always “cold tire inflation pressure”. Cold tire inflation pressure is defined as the tire pressure after the vehicle has not been driven for at least three hours, or driven less than 1 mile (1.6 km) after sitting for a minimum of three hours. The cold tire inflation pressure must not exceed the maximum inflation pressure molded into the tire sidewall.


Check tire pressures more often if subject to a wide range of outdoor temperatures, as tire pressures vary with temperature changes.

Tire pressures change by approximately 1 psi (7 kPa) per 12°F (7°C) of air temperature change. Keep this in mind when checking tire pressure inside a garage, especially in the Winter.

Example: If garage temperature = 68°F (20°C) and the outside temperature = 32°F (0°C) then the cold tire inflation pressure should be increased by 3 psi (21 kPa), which equals 1 psi (7 kPa) for every 12°F (7°C) for this outside temperature condition.

Tire pressure may increase from 2 to 6 psi (13 to 40 kPa) during operation. DO NOT reduce this normal pressure build up or your tire pressure will be too low.

Tire Pressures For High Speed Operation
The manufacturer advocates driving at safe speeds and within posted speed limits. Where speed limits or conditions are such that the vehicle can be driven at high speeds, maintaining correct tire inflation pressure is very important. Increased tire pressure and reduced vehicle loading may be required for high-speed vehicle operation. Refer to your authorized tire dealer or original equipment vehicle dealer for recommended safe operating speeds,
loading and cold tire inflation pressures.

Warning!
High speed driving with your vehicle under maximum load is dangerous. The added strain on your tires could cause them to fail. You could have a serious collision. Do not drive a vehicle loaded to the maximum capacity at continuous speeds above 75 mph (120 km/h).

Recommended Cold Tire Inflation Pressures
For vehicle speeds below 100 mph (160 km/h), recommended cold tire inflation pressures are listed on the Tire And Loading Information Placard located on driver’s side B-Pillar or the rear edge of the driver's side door.

When driving at speeds 100 mph (160 km/h) and above, increased tire pressures and reduced vehicle loading are required for high-speed vehicle operation.

For driving speeds above 100 mph (160 km/h) recommended cold tire inflation pressures are listed below under "High Speed Tire Inflation Pressure". Vehicle loading condition must
not exceed 688 lbs. (312 kg) (driver + three passengers + 88 lbs. (40kg) luggage).

Warning!
High speed driving with your vehicle under maximum load is dangerous. The added strain on your tires could cause them to fail. You could have a serious collision.

Here is what some US tire placards look like

2017 Alfa Romeo Giulia Base w/ 17" wheels



2017 Alfa Romeo Giulia Ti w/ 18" wheels
 

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Thats a nice wall of text and all...explain to me like I am a 2 year old why would pressures in the back be listed higher on a practcally balanced car if not for full load when balance is heavily spoiled towards rear..every car I ever owned had specified higher pressure in the back for fully loaded vehicle....for example Audis are very front heavy and driver only pressures are higher in front, when fully loaded they are higher in the back

I dont care which PC reason led FCA to specify these pressures without specifying at which load, this is physics 101....i can also confirm from my observation during 15k miles that tires wear and run equally profile width wise...when inflated as per B pillar car becomes harsh and bouncy beyond reason in the back...but yeah they are ready for another 3 passengers and luggage....or are you saying that when you pack family and luggage in the car you even further increase the pressure in the back? If affirmative, how much? And where is that specified in the manual?
 

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Thats a nice wall of text and all...explain to me like I am a 2 year old
The wall of text is a direct quotation from the owner's manual. So instead of me explaining it to you, how about you just read the owner's manual? If you can't be bothered, then I suspect that the rest of my post is going to fall on deaf ears also.

every car I ever owned had specified higher pressure in the back for fully loaded vehicle
We're not talking about every other car you've owned. We're talking about the Giulia and what FCA lists as the recommended tire pressure. You can deviate from the recommended pressure if you want. But your statement to Lockem, "pillar pressures are actually for full load with passengers in the back" is what I was addressing. Yes, the placard pressures are specified in a way that ensures adequate reserve load capacity at GVWR provided you adhere to the loading conditions, tire size, and cold tire inflation pressures specified on the tire placard. But that doesn't mean you should reduce the inflation pressure if you're not loaded to GVWR.

are you saying that when you pack family and luggage in the car you even further increase the pressure in the back?
No I am not saying that. I am saying that FCA doesn't recommend that you reduce the tire inflation pressure if you're lightly loaded. FCA wants you to use their recommended cold tire inflation pressure all the time for all allowable load conditions.
 

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^^ I mentioned the wall of text because you have exactly same manual as we all do, no need to post the whole thing while not answering the question...


FCA nowhere recommeds that you do not increase the pressure when fully loaded, you just made that up....,instead it simply omits recommendation which does not surprise me, whole manual is mostly a joke to start with

Beside that I have no clue why from your tone you seem to think somebody is picking up a fight with you....I simply asked you to put some light on your statement that rear tires should be inflated more with driver only even though front is slighty heavier already?

So you do not increase pressure when you put 3 people in the back and 100 pounds of luggage?
 

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^^ I mentioned the wall of text because you have exactly same manual as we all do, no need to post the whole thing while not answering the question...
So either your reading comprehension sucks or you haven't read it. Which is why I posted it to support my argument.

^FCA nowhere recommeds that you do not increase the pressure when fully loaded, you just made that up
RTFM.

....,instead it simply omits recommendation which does not surprise me, whole manual is mostly a joke to start with
RTFM.

So you do not increase pressure when you put 3 people in the back and 100 pounds of luggage?
I don't overload my vehicle and I follow the manufacturer's recommended cold tire inflation pressure per the manual. You do whatever you want as clearly you don't want to read, comprehend or follow the manufacturer's recommendations in the owner's manual.
 

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Mine were high 45+ upon delivery at the end of December in Chicago. When I questioned it at the service center they wanted to adjust to the 42 range since the cold would make it less. The car was drven but not very hot at the time. So the test of the winter was at that level. I just had them match the door settings. No worse for wear with 6500 miles in 5 months. No crowning.
 

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@fredomgli

I RTFM and it says what you claim (that pillar numbers are for all loads of car, say one or 5 people plus luggage) exactly nowhere

And yeah I will do what I want.....just as well as apparently you will continue to bounce around with tail of your car with overly inflated tires for the weight....

so we are all good....wasnt that easy?
 

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@fredomgli

I RTFM and it says what you claim (that pillar numbers are for all loads of car, say one or 5 people plus luggage) exactly nowhere
OMG. RTFM. I’ve quoted the exact language several times. They don’t describe weight limits in terms of 1 passenger or 5 passengers. They quote GAWR and GVWR and they discuss payload capacity. And they quote the recommended tire cold pressure! Period! Not for 1 person or 5 plus luggage. For all load conditions! I can’t believe I’m still arguing with you about this because it’s clear as day.
 

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I should add: the low profile 19" tires on Giulia hold so little air that a bicycle floor pump is well suited for adjusting the pressure. Just don't overdo it, a good bicycle floor pump can put out 200PSI. IIRC about 10 strokes gained 4PSI in my 225 40R19s.
Thank you for this tip! I had no idea. So much easier than looking for a gas station!
 
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@fredomgli

I RTFM and it says what you claim (that pillar numbers are for all loads of car, say one or 5 people plus luggage) exactly nowhere
OMG. RTFM. I’ve quoted the exact language several times. They don’t describe weight limits in terms of 1 passenger or 5 passengers. They quote GAWR and GVWR and they discuss payload capacity. And they quote the recommended tire cold pressure! Period! Not for 1 person or 5 plus luggage. For all load conditions! I can’t believe I’m still arguing with you about this because it’s clear as day.
Then stop arguing......do you even understand the purpose of air in tires?

Follow your bible manual all you want, as an engineer I will never accept that tire should have same pressure whether there are 3more people and 100 pounds of luggage over them or there is no extra weight and behave same way...there is a reason why every other manufacturer specifies that, what is the reason FCA omitted it here is a mystery to me but it surely is not physics
 

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Then stop arguing......do you even understand the purpose of air in tires?

Follow your bible manual all you want, as an engineer I will never accept that tire should have same pressure whether there are 3more people and 100 pounds of luggage over them or there is no extra weight and behave same way...there is a reason why every other manufacturer specifies that, what is the reason FCA omitted it here is a mystery to me but it surely is not physics
As I've said, you're free to do whatever you want. Just know that you're not following the manufacturer's recommendations. Whether you agree or disagree with them is another matter altogether. But I won't let you spew misinformation unchallenged just because it doesn't agree with your opinion.
 

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Here is more-or-less the official guide to tire inflation pressures (on the Toyo tires website, the tire standards folks want $150 to get the officially official version):

https://toyo-arhxo0vh6d1oh9i0c.stac...ication_of_load_inflation_tables_20170203.pdf

There is a footnote stating that you should never use less pressure than the OEM spec, but that note contradicts the information written directly above it.

Anyway the original tires on my Q4 are Pirelli Cinturato P7 225 40R19 93V XL.
https://www.tirerack.com/tires/tires.jsp?tireMake=Pirelli&tireModel=Cinturato+P7+All+Season+Run+Flat

The 93 and XL are the only part of the tire specification that relate to tire pressure. XL means use the table for Reinforced (higher pressure) tires, starting on page 30 of the above PDF. The 93 corresponds to a number at the left of the table, labeling a row of load rating data for the tire. Find the OEM inflation pressure in the top row and come down that column to intersect the "93" row and read off the load rating that AR deemed necessary.

37PSI (rear) -> 1293 pounds
35PSI (front) -> 1235 pounds

Now compare with my potential upgrade tire a Michelin Pilot Sport A/S 3+ in 255 35ZR19 96Y XL
https://www.tirerack.com/tires/tire...odel=Pilot+Sport+A/S+3++(W-+or+Y-Speed+Rated)

Back to the XL chart to find the weight rating entry that exceeds the OEM tire weight ratings, then look up the inflation pressure

1301 pounds -> 33psi
1257 pounds -> 32psi

None of which answers my question: why does AR think the rear tires need 58 pounds each of extra load rating compared to the fronts even though in my Q4 the fronts should have 100-200 pounds/axle more loading?

Now there is more information to be extracted from the above:

1293*2 + 1235*2 = 5056 pounds, but the car only weighs about 3650 pounds. Add a driver and some "stuff" and you are still far short of that 5056 pound number. Although some of the excess seems likely to be to handle unbalanced loading, these numbers appear consistent with LowFlyer's hypothesis that the inflation pressure is for a fully loaded car. Since very few car drivers are going to plan ahead and adjust tire pressures to match load conditions, this seems LowFlyer's hypothesis seems even more likely.

Note that the tables give some probably usable values for single occupant driving. Assuming 600 pounds total less than the max we get ~4PSI less than the full load inflation pressure, although that should probably be a larger reduction in the rears and a smaller reduction in the fronts.

Pickup truck and heavier truck operators are mostly already familiar with the need to change tire pressure with vehicle loading. My pickup even has unloaded and fully loaded tire pressures on the sticker.

Disclaimer: I am not recommending that anyone use my text above to decide to use lower than the OEM specified minimum inflation pressures. Try any of this at your own risk and only if you understand the risk and responsibility AND DO NOT BLAME ME FOR THE RESULTS--I AM NOT MAKING ANY RECOMMENDATION. Besides the potential for under-inflated tires to overheat and fail, a lower inflation pressure increases the risk of impacts damaging the tire or wheel. Tires with stiff sidewalls may have more problems with reduced inflation pressures (this is a big issue with MT and HT tires which often have very stiff sidewalls but may also be an issue with RFTs).
 

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lockem, the answer is because Alfa have built in a safety margin to account for customer use and misuse/ abuse, tire wear, tire damage (which is cumulative and often difficult for a layperson to observe and properly identify), ride and handling targets, fuel economy, etc.

You really have to take those tire charts about industry standards for load range and inflation pressure with a giant grain of salt. Tires are possibly the most complex component on the vehicle and load range and inflation pressure hardly tell the whole story. Plus, the tires are vehicle agnostic. The tires have no idea if they’re going on a Giulia or a Volkswagen Passat. Which is why proper tire selection and recommended cold tire inflation pressure is determined by the vehicle manufacturers whose job it is to safely and properly integrate the equipment (in this case tires) into the vehicle they assemble.
 

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Thank you for this tip! I had no idea. So much easier than looking for a gas station!
I've been using bicycle pump for even a higher profile tire for years. Pumping it up from zero pressure would give you a workout, but just adding a few psi pressure is really easy with the bicycle pump. As you said it beats going to the gas station.
 

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Wow, my head is spinning! :D

First of all I recommend an inexpensive compact 12 volt inflator (see below). Mine fits neatly in a space in the trunk along with my high quality air gauge and one new digital gauge. So far it works great. The inflator and my two gauges are within 1 psi of each other. Good accuracy!

Secondly, ignore the infotainment tire psi readings on the screen except when indicating that you are losing air. It is not that accurate and varies some from day to day, left tire to right tire and also how the tires heat up after driving. They are not meant to be an exact reading, only a fairly close estimate. I use the on screen reading only to warn me if there is a leak. For example, if one of my front tires which normally reads on the screen at about 31-32 when cold or up to 34-35 psi when driving, (I fill them when needed to exactly 32psi as specified for the fronts and 35 psi for the rears), reads down below 30psi like at 25-29 pounds then I suspect there is a slight leak. If it reads down to 20-24psi then I would know I had a more serious leak. Usually it's only me in the car and sometimes my wife and a few groceries in the trunk (clarification: wife's in the passenger seat and the groceries are in the trunk ;) ). Not enough extra weight to worry about. I check my info screen tire psi readings whenever I leave the garage in case they are down a noticeable amount. My run flat Bridgestones have never been down more than a PSI or two. I check them with my hand gauge several times a month.

Thirdly, IMO there is a reason why Afla Recommends 32psi in the front and 35psi in the rear even though the front and rear tires are the same size. It's top secret and I don't want to argue right now. Besides my Italian is not very good. :D

AHAHOO 12V Portable Air Compressor Car Tire Inflator Pump - Preset Pressure Auto Shut Off - Digital 150 Psi Tire Gauge ----- Lots of these available online under different brand names for about $45 from Amazon.
1.95 pounds --- 8 x 6.3 x 3.2 inches. Cheap but so far so good.
 

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