Tire pressure change with new wheels/tires?

[FistToFast]

Hi,

I changed to 17x8 wheels with 215/40 tires.

Should this effect the tire pressure I need?

Thanks guys

 

[kivnul]

Most likely, no. Monitor your tire wear and adjust as needed.

 

[Zormecteon]

Think about it this way.... If the car weighs 3000 lbs (I know, I know it's less but this is a theoretical post) and the weight is evenly distributed front/back, then that's 1500 each end, or 750 lbs each tire. .. lets assume 40 psi all around, then each tire puts 18.75 square inches of contact onto the ground. It doesn't matter what the tire size is, tall narrow, or fat wide, it has the same size contact patch. The shape of the patch varies but they have to have the same area as long as the pressure is the same.

I don't have the exact figures as far as weight and distribution front/rear but the principle holds. A wider tire will have a wider contact patch, but it will be shorter because at the same pressure it supports the same weight but will contact an identical area.

If you want to put more rubber on the ground, lower the pressure in the tires.But this will increase both drag and rolling resistance.

 

[SirThomas88]

Think about it this way.... If the car weighs 3000 lbs (I know, I know it's less but this is a theoretical post) and the weight is evenly distributed front/back, then that's 1500 each end, or 750 lbs each tire. .. lets assume 40 psi all around, then each tire puts 18.75 square inches of contact onto the ground. It doesn't matter what the tire size is, tall narrow, or fat wide, it has the same size contact patch. The shape of the patch varies but they have to have the same area as long as the pressure is the same.

I don't have the exact figures as far as weight and distribution front/rear but the principle holds. A wider tire will have a wider contact patch, but it will be shorter because at the same pressure it supports the same weight but will contact an identical area.

If you want to put more rubber on the ground, lower the pressure in the tires.But this will increase both drag and rolling resistance.

I may just be intoxicated or dumb (or both), but I read that 5-6 times and I still have no idea what you're talking about.

 

[Zormecteon]

I may just be intoxicated or dumb (or both), but I read that 5-6 times and I still have no idea what you're talking about.

The point is that no matter what size or shape the tire, they will put the exact same amount of rubber on the road, assuming that they are filled to the same air pressure. The shape on the contact WILL vary.

 

[felopr]

stick to the pressure on the door imo