Tire Pressure
- Thread starter Ndx
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You can run whatever PSI(or do you guys up north use something else) you'd like up to the max on the sidewall.
34-35 seems to be the standard of tire places and dealerships.
I like running 40 for the however many more mpgs it may get me theoretically. It also means I don't have to refill them as often.
34-35 seems to be the standard of tire places and dealerships.
I like running 40 for the however many more mpgs it may get me theoretically. It also means I don't have to refill them as often.
You can use this manual to determine the base pressure,
http://www.tiresafety.com/images/Tire Replacement Manual.pdf
However, each tyre has different construction, so you can adjust slightly higher or lower to match your driving style.
What I find so far, most modern car does not like pressure less than 32 psi if you expect good handling.
http://www.tiresafety.com/images/Tire Replacement Manual.pdf
However, each tyre has different construction, so you can adjust slightly higher or lower to match your driving style.
What I find so far, most modern car does not like pressure less than 32 psi if you expect good handling.
Higher pressure will also help protect rims from damage.
Those Generals need high pressures to handle well. The ride is great at lower PSI, but handling suffers. At >45 PSI they handle really well. They're rated to 51 PSI, IIRC.
Only downside is wear.
Only downside is wear.
Higher pressure helps gas mileage immensely.
Originally Posted By: Ndx
So I Have mazda 3 Gt sedan.
Stock tires are 205 50 17
i upgraded to 225 40 18 ( what tire pressure should i have )
but my concern is tire pressure ... i have 34/34 psi front and rear
tires are GT Exclaim UHP
Thank You Guys
On every vehicle sold in the US, there is a sticker – commonly called the vehicle placard - that lists the original tire size and the proper pressure for that size. The placard is usually located on a doorpost or in the glove box – but sometimes it is located in the trunk or on the fuel filler door.
According to Tire Guides, your placard ought to say the original tires were P205/50R17 88V inflated to 32 psi front and rear.
In order to carry the same load, a 225/40R18 91W needs - well.... it turns out these are interchangeable from a load carrying capacity point of view, so the placard pressure would apply.
Personally, I like a car that handles crisply. So I use 3 to 5 psi above the placard pressure. I also get better fuel economy, better wet traction, better snow traction, better tire durability, better tire wear, but I do have a degradation in ride harshness (but I am willing to put up with it.)
Since these tires are already geared for handling, the increased pressure might ride too harsh for you, but I should mention that the increased pressure is also more likely to prevent a rim being damaged.
So I Have mazda 3 Gt sedan.
Stock tires are 205 50 17
i upgraded to 225 40 18 ( what tire pressure should i have )
but my concern is tire pressure ... i have 34/34 psi front and rear
tires are GT Exclaim UHP
Thank You Guys
On every vehicle sold in the US, there is a sticker – commonly called the vehicle placard - that lists the original tire size and the proper pressure for that size. The placard is usually located on a doorpost or in the glove box – but sometimes it is located in the trunk or on the fuel filler door.
According to Tire Guides, your placard ought to say the original tires were P205/50R17 88V inflated to 32 psi front and rear.
In order to carry the same load, a 225/40R18 91W needs - well.... it turns out these are interchangeable from a load carrying capacity point of view, so the placard pressure would apply.
Personally, I like a car that handles crisply. So I use 3 to 5 psi above the placard pressure. I also get better fuel economy, better wet traction, better snow traction, better tire durability, better tire wear, but I do have a degradation in ride harshness (but I am willing to put up with it.)
Since these tires are already geared for handling, the increased pressure might ride too harsh for you, but I should mention that the increased pressure is also more likely to prevent a rim being damaged.
Last edited:
Does higher PSI negatively affect the life of suspension components?
Originally Posted By: Quattro Pete
Does higher PSI negatively affect the life of suspension components?
Obviously more pressure affects the transmission of road irregularities, and therefore shortens component life, but a little more pressure would hardly be noticeable. A lot more might.
Does higher PSI negatively affect the life of suspension components?
Obviously more pressure affects the transmission of road irregularities, and therefore shortens component life, but a little more pressure would hardly be noticeable. A lot more might.
My BMW has 225/40 18 on the front and tyre pressure in owners manual is 38 psi. Try that maybe as 34 is way to low.
Originally Posted By: CapriRacer
According to Tire Guides, your placard ought to say the original tires were P205/50R17 88V inflated to 32 psi front and rear.
In order to carry the same load, a 225/40R18 91W needs - well.... it turns out these are interchangeable from a load carrying capacity point of view, so the placard pressure would apply.
Just when I thought I'd learned something, Capri restores my ignorance . I thought the 88 and 91 were capacity "related" and that 91's would handle more load than 88's at the same pressure ... or rated pressure?...
Capri, how about another of your great explanations here.
George
According to Tire Guides, your placard ought to say the original tires were P205/50R17 88V inflated to 32 psi front and rear.
In order to carry the same load, a 225/40R18 91W needs - well.... it turns out these are interchangeable from a load carrying capacity point of view, so the placard pressure would apply.
Just when I thought I'd learned something, Capri restores my ignorance . I thought the 88 and 91 were capacity "related" and that 91's would handle more load than 88's at the same pressure ... or rated pressure?...
Capri, how about another of your great explanations here.
George
Originally Posted By: George Bynum
Just when I thought I'd learned something, Capri restores my ignorance . I thought the 88 and 91 were capacity "related" and that 91's would handle more load than 88's at the same pressure ... or rated pressure?...
Capri, how about another of your great explanations here.
George
[Booming voice] "Pay no attention to the man behind the curtain........"
OK, here's how it goes:
There are different tire standardizing organizations throughout the world. These organizations set what the tire sizing means. that would include the physical dimensions and the load / inflation pressure relationship.
However, if you boil them down, there's just 3 standards. US, European and Japanese.
According to Tire Guides, the original tire size had a "P" in front of the size - meaning the tire was designed to the US tire standard - 88 Load Index. However, this is for the Standard Load (SL) version. The Extra Load (XL) version is 90 Load Index.
SL tires and XL tires have the same load / inflation pressure relationship - except that the XL version can use more pressure and therefore more load. (Side note: In theory, the tire standardizing organizations could create an XXL version and use even more pressure and load.)
Here is what the Load Indices (How's that for remembering my Latin!) would be for the other standards:
European: SL = 89 XL = 93
Japanese: SL = 89 XL = not in the standard.
I went and looked up on General Tire's web site what the Load Index was for the new tire size - and it was 91.
There's a bit of confusion about the tire size on the web site. There are 2 different 225/40R18's listed and it looks like I made a mistake and chose the wrong one. Here's what the tire standards say about a 225/40R18:
US: SL = 88 XL = not in the standard
European: SL = 88 XL = 92
Japanese: SL = 88 XL = not in the standard.
My mistake not withstanding, the tire is an XL just as indicated on the web site - so the load / inflation pressure relationship is the same as a SL 88 Load Index - the same as the original tire.
Ta - Da!!!
Just when I thought I'd learned something, Capri restores my ignorance . I thought the 88 and 91 were capacity "related" and that 91's would handle more load than 88's at the same pressure ... or rated pressure?...
Capri, how about another of your great explanations here.
George
[Booming voice] "Pay no attention to the man behind the curtain........"
OK, here's how it goes:
There are different tire standardizing organizations throughout the world. These organizations set what the tire sizing means. that would include the physical dimensions and the load / inflation pressure relationship.
However, if you boil them down, there's just 3 standards. US, European and Japanese.
According to Tire Guides, the original tire size had a "P" in front of the size - meaning the tire was designed to the US tire standard - 88 Load Index. However, this is for the Standard Load (SL) version. The Extra Load (XL) version is 90 Load Index.
SL tires and XL tires have the same load / inflation pressure relationship - except that the XL version can use more pressure and therefore more load. (Side note: In theory, the tire standardizing organizations could create an XXL version and use even more pressure and load.)
Here is what the Load Indices (How's that for remembering my Latin!) would be for the other standards:
European: SL = 89 XL = 93
Japanese: SL = 89 XL = not in the standard.
I went and looked up on General Tire's web site what the Load Index was for the new tire size - and it was 91.
There's a bit of confusion about the tire size on the web site. There are 2 different 225/40R18's listed and it looks like I made a mistake and chose the wrong one. Here's what the tire standards say about a 225/40R18:
US: SL = 88 XL = not in the standard
European: SL = 88 XL = 92
Japanese: SL = 88 XL = not in the standard.
My mistake not withstanding, the tire is an XL just as indicated on the web site - so the load / inflation pressure relationship is the same as a SL 88 Load Index - the same as the original tire.
Ta - Da!!!
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