jsdriver

Hi,

My new C300 sedan has 18" wheels with Pirelli P7 run-flat tires: 225/45 in the front and 245/40 in the back. The filler cap calls for 38 psi front and rear. Does that sound right?

MBOCD

Sounds about right. On my C300 Coupe it says 45 at the back and 39 at the front. Attached image of sticker.

http://prntscr.com/ow2ta7

Pope_RW

I have the same, one set of tire pressures on the driver door and a different set on the fuel filler door.

jsdriver

It never occurred to me to check the door panel because the instructions say to use the filler cap instead. My door panel specs 41/48. That makes more sense given the relative tire sizes. It also explains why I thought the car was delivered with the pressures set way too high. It will be interesting to see how upping the rear pressure affects handling.

Pope_RW

My driver door is 39psi front for 225/45r18 and 45psi for 245/40r18 rear

Simon Guertin

I believe these are the maximum, not the recommended pressures

dtd

Recently when I had the B service at the dealer, the SA brought them down to 36 psi on all 4 tires. I had 39psi front and 41psi rear just like yours.

jsdriver

I've had dealers misset tire pressures in the past. Every other car I've ever owned put the recommended pressure on the door sticker. I'd love an explanation of why Mercedes thinks two different stickers with conflicting numbers on them is helpful. FWIW tirepressure.com calls for 38 front/45 rear for this tire/wheel/car combination. No idea where they get their data.

GreekUPS

I run 36 all around on my 18” AMG Wheels.

jsdriver

What sizes are the front and rear tires?

GreekUPS

225/45 18” front
245/40 18” rear
Fuel door states 36 psi all around.

jsdriver

This just gets weirder by the reply. My fuel door states 38 psi all around for the same size tires. My driver's door also states different numbers from what others have reported.

jsdriver

As an experiment I added 5 psi to my rear tires. Am now running 38 front/43 rear. The car is transformed. Steering is less twitchy. Acceleration and cornering are better. Suspension is smoother. Even the stiff-as-a-board run-flat tires are quieter over bumps. Cheapest upgrade ever.

GreekUPS

Good to hear you like the upgrade. I would check on the rear tires every once in a while. Another member posted a while back that the center of his rear tires were wearing with the higher psi.

Post #6
https://mbworld.org/forums/c-class-w...19-wheels.html