Good question.
Had a peek in WIS to see if there was any mention of different tyre pressures for 16,17 or 18 inch wheels. Couldn't find anything. Every document related to tyres just refers to the info on the fuel filler flap. My guess is there isn't any difference in the advised pressure for different sized wheels. But if you find the car handles better with a slightly higher tyre pressure, then I would set it to that value. As long as you use your common sense and don't double or triple it there should be no problem I guess.

 

My 2008 SLK 280 came with 17 inch OEM tires.

The door card indicates that the front size is 225/45/R17 and the cold tire pressure should be 32 PSI.

The rear size is 245/40/R17 and the cold tire pressure should be 35 PSI.

The tire size and pressure on this model seems to be on the door frame rather than the fuel filler cap.

 

So i guess that if now i'm using 17 inch tyres i should use this information and not the one that's in my fuel filler cap....

 

There should be a maximum cold inflation pressure on the side wall of the tires. Do not go above that as it can adversely affect handling and the life of the tire.
I usually inflate mine one or two psi less than that. Also try to keep the pressures the same in the fronts and the same in the rears.
Try not to let the difference be more than 2 psi. Depending on the tire and the car they are on, you could easily tell a difference in handling.
If you have wider tires in the rear, they may have a higher max cold pressure than the fronts. Check the side wall to see. If the max is higher then adjust accordingly.

 

My SLK 300 also has cold 32 front and 35 rear.

 

I would say that the tire pressures on my vehicle ID's are the minimum for 17 inch tires.

I've got mine set at the 32/35 PSI levels and it seems to work well. I've got Michelin Pilot Sport A/S 3 tires on my vehicle and I replaced the Struts with Bilstein B4's and the Shocks with Bilstein B6's. The ride and handling seems very good.

Note that the information on my Fuel Filler Door indicates that warm pressure can be up to 4 PSI higher.

If it helps, the cold bar is listed as 2,2 on the front and 2,4 on the rear, with +0,3 bar for warm tires.

I am attaching pictures of the cards and maybe that will assist you as well.

 

Tyre pressure may vary with different makes of tyre and even different grades of tyre within that make.


I'm with dedgar, personal choice, but no more than a 2psi spread if you use different pressure front and back.


The reason for there not being an exact same set cold pressure is for the type of use and handling/grip/wear expectations that you desire for the car.


Better grip = faster wear.


The best way to sort it for yourself is to set it at the top and see how it feels.
Then set it to the bottom and see the difference.
The answer likely is somewhere in between.


Variations in weather, driving style, journey length will feel different for the same pressure.
That's why only you can find the ideal pressure for your set up.


Typically I use between 32 and 35 on mine.

 

Hi All!

Just check my tire pression just in the morning before leaving home

Guess What? My tire pression was 0.2 PSI lower that the recomendation on the fuel filler cap!

Looks like in this car if you check pression with the tires cold or warm makes a lot of diference!

Now the car feels much better! I guess everytime i have to check tire pressure i have to do with the tires cold!

 

And not all gauges read correctly ! !
especially those cheap forecourt tyre inflaters that get thrown around .

Get a digital gauge
And tyre's loose pressure per month so check regular . :nerd:

 

Looking at the Michelin Digital Tire Inflator

Michelin High Power Wheel Tyre Inflator Pump Electric Air Compressor 12V 12265 | eBay