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Discussion Starter #1
I'm on my 3rd set of Michelin MXM4 tires. I think this is the stock tire. I've been adding about 40 pounds but the sticker in the door jam indicates 32 pounds.


What's the correct pressure?
 

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Not necessarily. The door jamb is for the OE tires and a "typically" loaded vehicle.

Higher pressure means:

1. Center of the tire may wear more than the outsides. (Bad if that happens, since it impacts tire life.)
2. Lower rolling resistance (sidewall flex) in normal driving = slightly better fuel economy.
3. Possible harsher ride.
4. Lower tire heating during highway driving (less flex = less heat generated)

Lower pressure means:

1. Outsides may wear more than the center. (Bad if that happens, since it impacts tire life.)
2. Higher rolling resistance (sidewall flex) in normal driving = slightly worse fuel economy.
3. Possible softer ride.
4. Higher tire heating during highway driving (more flex = more heat generated)

The "sweet spot" printed on the door jamb assumes many things; the actual load range of the tires (yours may differ from factory delivery), the load in the vehicle and how it's distributed, your normal highway speed and thus level of heat generated, etc. Those assumptions may or may not be true for you.

The sidewall on the tire has printed the maximum load per-tire at the stated maximum rated inflation pressure. That's an absolute limit that should never be exceeded. The closer to that load limit you get with less inflation the higher the risk of a heat-related failure, which can be catastrophic (that's to be avoided!) I am not aware of any tire manufacturer that publishes an easily-accessible load-derating curve for their tires, and IMHO that sucks -- and you can bet there is one since HEAT is the primary issue as load rises.

In general you probably want to consider the door sticker the LOWER limit and the sidewall pressure the UPPER limit -- and an absolute. Where you run between those two points depends on many things; if you get abnormal wear patterns (center or edges wearing more than the other) you're definitely running too low or high tire pressure, but if not then the trade-offs are more complex.

I typically (for everyday driving) run my rear tires ~2psi below my fronts on most FWD vehicles as I usually have little or nothing in the trunk and nobody in the rear seats. If I'm going to be traveling somewhere with a full set of suitcases and such in the back, then I run equal pressure. I favor the higher end of the pressure scale as well but I've not run into the center of the tires wearing before the sides; if I did I would cut it back since giving up tire life for a tiny increase in MPG, never mind the likely impact on traction, is not worth it.
 

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Not necessarily. The door jamb is for the OE tires and a "typically" loaded vehicle.

Higher pressure means:

1. Center of the tire may wear more than the outsides. (Bad if that happens, since it impacts tire life.)
2. Lower rolling resistance (sidewall flex) in normal driving = slightly better fuel economy.
3. Possible harsher ride.
4. Lower tire heating during highway driving (less flex = less heat generated)

Lower pressure means:

1. Outsides may wear more than the center. (Bad if that happens, since it impacts tire life.)
2. Higher rolling resistance (sidewall flex) in normal driving = slightly worse fuel economy.
3. Possible softer ride.
4. Higher tire heating during highway driving (more flex = more heat generated)

The "sweet spot" printed on the door jamb assumes many things; the actual load range of the tires (yours may differ from factory delivery), the load in the vehicle and how it's distributed, your normal highway speed and thus level of heat generated, etc. Those assumptions may or may not be true for you.

The sidewall on the tire has printed the maximum load per-tire at the stated maximum rated inflation pressure. That's an absolute limit that should never be exceeded. The closer to that load limit you get with less inflation the higher the risk of a heat-related failure, which can be catastrophic (that's to be avoided!) I am not aware of any tire manufacturer that publishes an easily-accessible load-derating curve for their tires, and IMHO that sucks -- and you can bet there is one since HEAT is the primary issue as load rises.

In general you probably want to consider the door sticker the LOWER limit and the sidewall pressure the UPPER limit -- and an absolute. Where you run between those two points depends on many things; if you get abnormal wear patterns (center or edges wearing more than the other) you're definitely running too low or high tire pressure, but if not then the trade-offs are more complex.

I typically (for everyday driving) run my rear tires ~2psi below my fronts on most FWD vehicles as I usually have little or nothing in the trunk and nobody in the rear seats. If I'm going to be traveling somewhere with a full set of suitcases and such in the back, then I run equal pressure. I favor the higher end of the pressure scale as well but I've not run into the center of the tires wearing before the sides; if I did I would cut it back since giving up tire life for a tiny increase in MPG, never mind the likely impact on traction, is not worth it.
Ok, I stand corrected. yeah what Ticker says is absolutely correct.

Seriously though for mere mortals who won't "baby" their cars like many of us, wouldn't the door jam be the "most" reasonable, safest pressure to follow?

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FWIW, i would also think lower pressure would make wheels more exposed to pothole damage, which is one of the reasons I am running my winters about 1-2 psi higher. Of course this can also affect snow traction since the contact patch may not be optimal for the best snow traction.

But I'll wait for ticker to correct me.

Seriously though should have waited for ticker to comment on this thread first since his explanation is always the most thorough.

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The in-snow traction compromise from higher pressure may well be true as well -- but the impact in that regard should be quite small. Not zero though!

What you really want to know in terms of where the *minimum* safe pressure is you don't have -- the load derating curve for the tire with pressure (down from the maximum on the sidewall) AND the weight each wheel carries. Without that it's a guess. The manufacturer doesn't want to be sued so I would treat the door jamb numbers as *minimums*; they likely have the derating curve for the OE tires (but you don't) and thus you're likely safe running there -- but perhaps not below that point. Anywhere between door jamb and tire sidewall pressures are going to be safe, but "safe" and "best option" are two different things.

If the ride quality is unacceptable at a higher (but at or under sidewall rating) pressure then obviously you don't want to run there either. However, assuming tire wear is even and ride quality acceptable higher pressure will result in slightly better fuel economy and less tire heating -- and both are good things.

The specific tires matter quite a bit when it comes to this as well, especially as regards ride quality change with inflation pressure.
 

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Discussion Starter #7
Every little imperfection in the road feels like a hammer blow to the car. I'm dropping the pressure.
 

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It's so bad that I'm thinking about new wheels that would allow for a higher profile tire.
One of the reasons I bought a "Sport" (as opposed to Touring) is that I did NOT want the low-profile tires and wheels.

I had low-profile tires and wheels on a Volvo 850T a number of years ago. Never again will I own them on a daily-driver. Yes, they're more-precise in their handling and road feel. The harshness is IMHO simply not worth it, never mind the radically-increased risk of not only tire but *wheel* damage from potholes and similar. Oh, and the added expense too; the tires, despite having LESS material in them always appear to cost more -- usually by a lot too.
 

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Every little imperfection in the road feels like a hammer blow to the car. I'm dropping the pressure.
Actually I find dropping the pressure is worse for ride quality. Increasing pressure adds a bit more cushion. IMO

Your wheels are also exposed to more abuse.

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Oh, and the added expense too; the tires, despite having LESS material in them always appear to cost more -- usually by a lot too.
This is true. The factory rim size is 19" and we don't have other trim choices in our place. The cost of a single tire is equivalent for a set of tires for our CR-V 98.

I was told that 18" and 20" tires are much cheaper and way easier to look for in stores. They said that 19" tires are somewhat rare. At least, here in our region this is true.

Going back to tire pressure, the door sticker indicates two pressure settings. One is for a fully loaded car and the other is when driving alone.

I decided to be in-between, the fully loaded pressure setting is too harsh for me while the other setting is too soft when a friend is with me from time to time. Since I lose tire pressure for a about 1 psi in a month or so (I believe this is normal, please correct me on this), I won't be below the recommended pressure by the time I check my tires and use my tire inflator.

If I may add, having a tire inflator saved me a lot of trouble back then. I got a punctured tire and I observed the harshness of the ride. I checked my tires and found out one of them is deflated. I used my tire inflator until I reached a vulcanizing shop.

One more thing, the gasoline station is quite far from us. If I were to drive there and have my tires filled up, my tires are already warm. I've read that the pressures indicated on the door sticker are cold tire pressures.
 

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The two main items that change tire pressure are temperature and time.
Tires generally lose 1psi per month
Temperature changes are mirrored by tire pressure in a 10*F-1psi ratio; temperature gets 20* warmer and tires go up 2psi. If the temperature goes down 40* tires should drop 4psi.


On my car the door jam recommends 32psi cold.I check my tires when hot and have them set at 34F and 32R.
Them fancy tires TickerGuy runs only cost $52 a pop when you have an '03 6i with base 16" rims
 

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Yeah, and the 17" rim version isn't much more. There's plenty to like in a tire that does ok even on snow, is reasonably quiet, has great dry traction and runs 50k miles for about $75..... It doesn't matter much if you only put 10k miles on the car in a year, as they'll deteriorate before they wear out. When you do 30-40k miles in a year..... :)
 

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Discussion Starter #15
Actually I find dropping the pressure is worse for ride quality. Increasing pressure adds a bit more cushion. IMO

Your wheels are also exposed to more abuse.

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I drive around very carefully. I'm not about slamming those Michelins into pot holes and dragging them over railroad tracks. They're the sweetest tires...


Dropped the pressure down to 31 back and 32 front. Did some highway and city driving last night and the ride was much more comfortable. Big difference.
 

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Discussion Starter #16
Yeah, and the 17" rim version isn't much more. There's plenty to like in a tire that does ok even on snow, is reasonably quiet, has great dry traction and runs 50k miles for about $75..... It doesn't matter much if you only put 10k miles on the car in a year, as they'll deteriorate before they wear out. When you do 30-40k miles in a year..... :)

What tire are we talking about?
 
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