dgghostkilla

Edited with new info
new Tires came psi Maxed Out at 50.
What psi do i need to have them at?
my stock 17 inch rims with the continental tires was 30 psi in the front and 35 psi in the back.
This new wheels/tires are 18 inch with 4 225/40R18XL 92W BW YOK YK580
The tires say max 50 psi but i don't know that is what i need for normal driving
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sdchrisc

i always go 5 psi below max so i would say 45

Sportstick

Great looking wheels. Per MBUSA, label on fuel filler flap for normal usage (you and a guest/light load/normal driving). Label on driver's door opening b-pillar for max load.

sdchrisc

the label is for stock wheels and tires.. youll def be under inflated.. just sayin...

Sportstick

The tire pressure doesn't know or care if the wheel is stock or aftermarket. His tire size is not extraordinary in any way. The label still applies. Overinflation burns out the center of the tire contact patch faster and from prior postings, we know the OP wants and needs these tires to have a good long tread life.

sdchrisc

not all tires have the same max psi load as the stock ones.. do some research before trying to help

Sportstick

30 years in the auto business includes quite a bit of research, thanks. The max pressure of 50 psi on his sidewall is NOT an indicator in anyway of recommended pressure for daily use and is not relevant to his question. Given the similar size, the pressure recommended by Mercedes still governs for optimal chassis performance. Vary at your own risk.

dgghostkilla

so the sticker on the side of the door that has the psi! I had assumed that the stickers on the door and the gas tank door did not apply to the new wheels/tires because of different size.

I am confused as hell.
Tires came psi Maxed Out. What psi do i need to have them at?
my stock 17 inch rims Were with the continental tires was 30 psi in the front and 35 psi in the back.
This new wheels/tires are 18 inch with 4 225/40R18XL 92W BW YOK YK580
The new tires say max 50 psi but i don't know that is what i need for normal driving

Sportstick

OP: With your recent edit and now that we see your labels, we know you have changed from 17" to 18", so I would ask someone with 18" to inform you of their label values. I also had, but still have 17", or I would offer my information. 50 psi is not the answer, and there is no formula to subtract from max to get the right reading. The 18" label on someone else's car will be helpful, and will likely show 1 or 2 psi higher than yours.

danlnyc

Keep it at 38-40 PSI for everyday use.

mhad2480

Good looking set up. Turn around was pretty quick from when they sent you the wrong wheels.

dgghostkilla

Yep. They say 3 weeks but it was about a week and half.

DonjuanOriginal

Wheels Look Good. I like the colour match.

RLE

18" pressure is 33/38. I prefer 33/35 for less thumping on tar strips. Certainly not 40.

When I changed from 17" to 18" (B4 delivery), I purchased the correct 18" label for the gas door. The B-post label cannot be changed, BTW.

dgghostkilla

so I'm getting many different numbers. i don't have a stagger setup so all tires are the same size. so should i do 35 all around, or 38 all around ?

mhad2480

Sorry, but look at the post count and spend a little time here getting to "know" the people on the forum before you try you put people down. Sportstick has close to 3k posts here and is one of the more helpful/informed members from what I have seen.

The numbers you are getting from people with the / in the middle is a high low range, not front to back. I would suggest starting with the higher number and letting a little air out if you feel the ride is too harsh for your liking.

RLE

You still need higher pressure in the rear. My C300 Lux came with 225/45-17 front and rear and the B-post label calls for 28F/33R.

And, your new wheels/tires came with 50psi so that you could lower them to whatever you want without needing an air source. Should be obvious.

No one would ever run them at max pressure.

dgghostkilla

thanks guys.
so i left it at 38 in the back and 35 in the front.

Sportstick

Keep in mind that the pressure will vary about 1psi for every 10 degree Fahrenheit change in outside temperatures. We recently went from 40s to almost 80, so my tire pressure increased about 3 psi. So, with the changes the country is currently experiencing while we transition from Winter to Summer (what happened to Spring?!?!?), it's good to have a handy gauge and check periodically due to climate, on cold tires first thing before the morning drive, as well as for normal monthly tire maintenance.

dgghostkilla

I was thinking what if i go get the air replaced with nitrogen aint it like 20 bucks or less to get it done and then i would not have to worry about the temp whats your take on this?

mhad2480

Don't worry, there should be another cold front headed your way pretty soon. Enjoy the 80's while you can.

Sportstick

Thank you for your kind support.

Sportstick

Air is just under 80% nitrogen. The problem becomes how to truly replace the air with higher concentrations of nitrogen. Simply deflating the tire and re-inflating will still result in a blend, although perhaps at a higher concentration. The real value of nitrogen is that it is a larger molecule than oxygen, so it does not "leak" through porous wheel metals as easily, maintaining pressures longer.

Bottom line, I think for daily use on passenger cars, nitrogen sellers may have an overinflated opinion (sorry) of the value. A handy gauge and a simple one-time $40 compressor (on Amazon) for home use, or a nearby gas station really does the job.

Some homework reading:

http://www.getnitrogen.org/sub.php?v...eratureeffects

coolvi

2009 C300 4Matic Sport 17". Driver's door pillar says 28/33, fuel door suggests 30/35. I did go with 33/38 when I moved to C63 18" rims, which caused terrible wear pattern on the rears (due to over inflation). Unless you normally have rear passengers, make your own rules based on the average load conditions. I'm running at 31/34 at the moment being the only person in the car over 90% of the times.

joejitsu

What would be a better pressure for 19s? As your wheels size goes up should your psi stay about the same as stock?