gdavis

Today I noticed that my front tires/tyres looked low and I decided to check them at the filling station to make certain they were properly filled. So I went to the chart on the door frame at the driver's door and tried to understand the incredible chart that is there. WOW, what a chart!!!!!!!!!!!!!!

It's got info for maximum capcity and also for 4 passengers, and it's got pressures for all different tire/tyre shapes and sizes with lots of geometric symbols next to it. I am usually just fine with symbols, but I really am confused with this one. The main reason for confusion is that the front tires/tyres had only about 31 pounds (I don't know the metric for this one) and they seemed really rough riding. I have the 530 sports wheels with 18" run flat Dunlops (I think 245/40 R18). So it noticed that they show them up to around 36 psi for max load, so I compromised and put in 33psi. It seems to ride much better, I just don't want to wear the tread down in the wrong way.

Has anyone else gone through this and have a clear idea of the logic of this chart? (I assume that the chart goes on all country models since it shows metric and English measurements).

realtyman

The logic of the chart is pretty simple. Look at the chart to the left to determine the tire configuration of your car...

realtyman

...Then match the geometric symbol to the chart on the right and it will give you the recommended pressure.

I posted last week that my tires were at 25 front and 30 rear (yikes!).

I have since brought them up to 41 front and 45 rear ( a little over the recommended pressure). The Max. pressure on the sidewall is 51.

I tend to drive a little agressively and love the off/on ramps so a little more pressure is not a bad thing IMHO.

gdavis

from what I read on the chart, the 245/40 R18 ones are shown without and also with a circle symbol. Then when I refer to the chart I see 2 different sets of pressures- one without the circle and one with a circle. Which one is the correct one to use?

JDN

Refer to the picture below.
I also have the 18" wheels. The 275/35 on the rear has a square symbol. So, according to the chart, the right pressure for light load would be 35, max would be 42.
For the front 245/40 with the round symbol, the recommended pressure for the light load would be 32 psi and 38 psi for max load. I get the same pressure either way for the front.

Rudy

JDN's got it. You simply find your tire size and figure out what symbol (circle, square, triangle, etc.) corresponds to your size.

From there, the pressures are listed for your tire size and load capacity. If your tire doesn't have a symbol, use the tire pressures that are shown with no symbols.

mrbelk

The confusion is that there are two entries for 245/40/18 tires; one with a circle and one without. Is it possible that the one with the circle is for the runflat tire pressure? Do E60's come with 245/40/18's and non-runflats? Maybe on the 545 non-sport?

-MrB

kscarrol

545 non-sport has the 225/50 R17's front and rear, which is the one without a symbol and is 32-38 lbs front and 38-45 lbs rear.

JDN

The confusion is that there are two entries for 245/40/18 tires; one with a circle and one without. Is it possible that the one with the circle is for the runflat tire pressure? Do E60's come with 245/40/18's and non-runflats? Maybe on the 545 non-sport?

-MrB [/quote]
But you get the same tire pressure either way. I believe the chart wo the symbols are for a set up with the 245/40/18 on the front and rear. Can you order that way or is that a standard factory set up?

Rudy

JDN's got it again. Same pressures, no matter what you look at (circle or no symbol).

iDrive is easier to figure out than that chart, eh?