Correct inflation pressure for low profile tires?
Jot down the factory recommended tire pressure posted inside the drivers door. Note the maximum tire pressure on the raised letters on the sidewall add the two pressures together and divide by two. Inflate to that pressure. At your convenience take your car to a progressive tire shop that supplies nitrogen to inflate car tires. Molecules are bigger so it won't leak off as fast. Hot and cold temperatures don't effect tire pressures as much as regular air. Nitrogen in an inert gas. The inside of your tires and wheels stay squeaky clean. Tire tread life lasts longer. If you positively know your wheel width or can find it out, call the manufacturer of your tires and ask them for their pressure recommendation for your car and wheel width. I guaranty it won't be the silly soft pressure posted on the drivers door post. Low profile tires are susceptible to bead breakage and wheel bending if you hit a hole and the tire pressures are too low.
Correct Tire Pressure for 18" Rims?
There is something wrong here. Your 18" tires can not have a Load Index of 85. A 225/50R18 tire in a Light Load range (very rare) has a Load Index of 83, in a Standard Load range the Load Index should be 88 and in the preferred Extra Load range (sometimes called Reinforced) the Load Index should be 92. With the original tires the recommended inflation pressure was probably 32 psi front, 30 psi rear at which inflation pressures the load carrying capacity of a tire sized P205/55R16 89H is 1,213 and 1,176 pounds respectively. When you change tire sizes you need to change the tire pressure to match those original load carrying requirements. On a tire sized P225/40R18 83W (Light Load) at those same inflation pressures your load carrying capacity is only 1,025 and 996 pounds respectively. It doesn't matter how much air you add since the Maximum Load of this size tire is insufficient. In a Standard Load (88W) or Extra Load (92W) range things improve slightly to 1,113 and 1,069 pounds at the factory 32/30 psi but it still isn't enough to match the factory spec. You need to increase the inflation pressure to 36 psi front, 34 psi rear ( 1,235 lbs/1,168 lbs) to match the original factory specs. As for why your tire is going flat, it needs to be checked for leaks. I'm not psychic.
How do I determine the correct tire pressure with plus size Wheels?
Yes doing a plus sizing like this usually results in a need to modify the inflation pressure. The reason for this is the lower profile tire does not contain as much air as the higher profile original tire and since it is the size of the air chamber that determines how much weight the tire can safely support you have to compensate by changing the inflation pressure. ***EDIT**** Your Lexus came originally with tires sized P205/65R15 92V inflated to 32 psi front and rear. At 32 psi the stock tires have a load carrying capacity of 1,334 pounds. This is the number you need to match. A tire sized 225/40R18 88W (or 88Y - makes no difference really) has a Load Index of "88" which you will notice is lower than the "92" of the stock tires. This means the 18's can only manage 1,113 pounds at 32 psi which is the equivilant of running the stock tires 15 psi under-inflated. That's bad. Unfortunately it doesn't get any better as the maximum load capacity of this size tire is only 1,235 pounds at 36 psi. What you need is to use a tire in this size with an Extra Load (XL) rating. The size will read like this: 225/40R18 XL 92W. It might say RF (for Reinforced) instead of XL. Either is fine so long as the Load Index is 92. Here you can achieve the correct load capacity but only by inflating them to 40 psi. The ride quality will likely be horrible, but you will look good. If you already have the tires and they don't have that 92 Load Index go back to where you bought them and tell the folks who sold them to you that they did a bad thing and are endangering your life by putting a tire with inadequate load carrying capacity on the car. I am quite serious about this. Chances are they picked the right size but some places just don't know or care about these things because they have not been slapped with the wrongful death suit that followed a catastrophic tire blowout yet.
Recomended tire pressure for Lexus IS 250?
I changed the original tires for the sport package: 225/40 R 18 front and 255/40 R 18 rear. What is the correct tire pressure? Thank you in advance for your help.
How do you know how much pressure should be in tires?
Many people will tell you to use the tyre pressure on the cars placard (usually in the glovebox or drivers door pillar…)THIS IS WRONG!!!It only applies if you have the original brand and type of tyre originally fitted to the vehicle!If (like most people) you have fitted a different brand or type of tyre to the vehicle, then you should follow the pressure recommendations on the tyre itselfThere will always be a maximum pressure rating on the tyre, you should (obviously) never go any higher than this pressure, you can go slightly lower to increase comfort, at the expense of higher fuel consumption and decreased road handlingMany 4wd owners fit ‘mudders’ or similar instead of the light truck tyres originally fitted to many 4x4’s, and I have seen many destroyed by drivers inflating them to the tyre placard pressuresFor those that dont know, the light truck tyres usually have a pressure around 50–70psi depending on brand, at/mt tyres usually are around 32psi, some mudders can be as low as 24psi.Obviously running a tyre rated at 24psi MAX at 70 psi will cause it to destroy itself in short order, with the accompanying risk of a crash with a major blowout..
What is the Ford Focus' tire pressure?
Recommended tire pressure for Ford Focus varies from 32 to 46 psi depending on year and trim. Find more info on Ford tire pressure below.Ford Tire Pressure
How do I find out psi on tires?
The recommended PSI for the make of tire can be found stamped on the sidewall of the tire. However, you should always fill your tires according to the recommended PSI for the vehicle, which can be found on a sticker usually on the inside of the door. This PSI number is calculated based on the vehicles weight and distribution. Tire PSIs are calculated based on what the rubber manufacture of the tire can handle.