titus820

Quick question: I live in an area where snow can become a problem for the winter seasons. I want to buy snow tires to put on the oem 18'' wheels, I understand that the snow tires are narrower. I want to get the bridgestone blizzak ws80 which is 225 all around. Do they fit on the oem wheels? Do they have side effects?

Thanks in advance!

cmes2001

Hi!

225/40 only fit the front 18X8 wheels. The rears are 18X9 and 9 inches is too much for 225 tyres.

You would better use 235/40 on all four wheels.

Cheers!

Vladds

I t6hink this is a great question and was planning to ask this to Mercedes.
This is because in the Owner's manual they specifically call for 225/40/18 for both front and rear for winter.


This raises two questions:
1. What rims do they have in mind for the rear
2. How do they plan to compensate for the different wheel diameter and error in speedometer.


I may call Mercedes of North America today, then I will post the answer.

roadkillrob

Technically the rim width lookup tables show 7.5-9" rim width for 225/40/18, so technically it will fit on stock wheels. Diameter is 4mm small, so should not be an issue, but like cmes2001 said, why not go 235/40, it will fit better on the rears, be the same diameter and then no worries.

Even better, why not get cheap wheels, the cost of switching over and the amount of damage likely to incur at each switch over to your wheels is not worth the savings, the wheels pay for themselves after a few seasons of change over and then you can just switch them out yourself, or pay a lot less to have them swapped on rims. They you can go 8" wheels all the way round!

Vladds

To me the radius is 4 mm larger and that is definitely an issue.
Also, with this being an issue and Mercedes being the Engineering heaven that they are, they probably have a "secondary protocol" that we don't know about, to account for this error.
I want to get this info from them, there is probably a winter wheels mode that changes the readings everywhere.
As far as the rest, maybe they will suggest to buy a second set of front wheels, let's see.

I agree about not wanting to stretch the tires to the max and not wanting to repeatedly take the tires off, vs having two sets of wheels.

I disagree about using 235 series tires.
The importance of using narrow winter tires is not well understood. One size down changes the pressure on the contact patch quite enough to make the difference between ok behavior to great behavior in snow. I am willing to bet that Mercedes posted 225 and not 235 based on calculations and they are usually right.

nobbyv

No, it's not. The radius is 1.25mm more when using a 225/40 versus a 255/35. In other words, negligible.
https://tiresize.com/comparison/

I just got my Nokian R2s in 225/40 all around. That's what both TireRack and MB recommend. They'll be going on the stock wheels permanently, as I run a different set of wheels/tires in the summer.

Vladds

225/40/18 has a radius of 225x40/100+ 457.2/2= 90+228.6=318.6mm radius
235/40/18 has a radius of 235x40/100+ 228.6= 94+ 228.6= 322.6 mm. The increase per radius is 322.6-218.6= 4 mm

The difference of diameters is 645.2-637.2= 8 mm
Edit:
I just called them. They refer to the dealer as to which tire works with which rim. Maybe I got the wrong rep and have to try again.
As far as menus for different diameter, there are none.
So what remains is I will check whether the wis wiring diagram show that there is such thing as a distance pickup on the transmission, or the distance is via formula and averaging data from all 4 wheel speed sensors. I expect the latter.
If this is the case then the formula may offset the difference in the diameter of the fronts, to an extent,

nobbyv

You're right; I didn't realize you were referring to the fronts. I was referring to the rears.

AMGangster

I work for Tire Rack and can confirm 225/40R18 works perfectly fine. I have ran that size on my car for several years. However, 235/40R18 fits the rear wheels better. I chose the WS80 last year in this size.

Alex.currie44

Owners manual says 235/40 R18 on 8 X 18 ET 45 wheels on BA.
I just ordered Replika R170 8.5 X 18 ET 43 wheels with Nexen Winguard Sport tires 235/40 R18 V 92 and they will be just fine. They will be 8 mm closer to the fender but clearance will be ok.
With TPM sensors $1765 CDN including tax and shipping from 1010Tire.com
Yes not an expensive tire but of the 121 days between Dec 1 and April 15 I am only around 46 days so buying expensive tires name brand is a lousy investment. When they are 6 years old they might have 12000 km on them

Alex.currie44

Page 346 of the 2013 manual says
BA 235/40 R18 95 V XL
M+Si15
8.0 J x 18 H2

If you go the same tire on both axles (BA) then you can rotate them front to back season to season which you cannot do with the staggered set up.

Vladds

I cant see in the diagrams any speed sensor, other than the wheel "Rpm sensors".
So it's some kind of formula that accounts for differences in wheel rpm while turning and probably diameter differences due to tire pressure changes., in order to determine from the 4 signals vehicle speed and distance travelled.

Jasonoff

How are they in the dry? I'm considering the 255 for the rear (although a lower load index but I never have passengers in the car).

I'm just concerned about burning them up too quick.

Alex.currie44

In Canada the TPMS is not standard. You have to order it.
That said they do have a passive system that starts with manually setting tire pressures. When you start out you reset the monitoring system. From that point forward it compares wheel speeds off the ABS sensors in the wheels. When one tire losses air its diameter shrinks and the wheel has to go faster to keep up with the other three and the sensor sees that and alarms.

Alex.currie44

I have tried to make the point. When it comes to winter tires go the same on all four corners and all these issues go away. Performance is compromised anyway so keeping the stagger in not really all the critical and you can move fronts to back every season to even out wear and get the most out of them.

Jasonoff

What issues? How does swapping front to back benefit you? It doesn't matter if they wear at different rates.

Alex.currie44

Your fronts are important as they give you steering input and they typically wear faster because of cornering. If you run the same tires on the front season to season they wear out faster than the rears and then you are into replacing fronts only if you want to be economical while the rears deteriorate. By moving them front to back season about they wear more evenly that is all. If it wasn't important to have 4 winter tires they wouldn't recommend them on both axles. Years ago a service manager showed me a rim and fender damaged when a client said two were enough which is true if all you do is drive in one straight line. The guy lost control first storm and hit a curb and bounced into a wall in an uncontrollable slide in wet snow. He was the one who suggested year about rotation.
Back in the day when tires were not directional we cross rotated them.
Your choice by all means. I have just found that whether it was either of my W124, my W211s, my W212, R170, R172 this was good practise.

thesaintusa

For the winter I run a square set up so I can move the rear tires to the front and the front to the rears every other season.

Even out the rate that they wear.

But I find that the rears wear more than the fronts.

FWIW I need a new set of 'summer tires' as I was only able to get 10,000 km out of the stock OEM Contis Wore them down to the wear bars (front and rear). But my winter tires that are now on for the 3rd winter look almost new.

Clearly my driving habits in the winter (not wanting to wear down the winter tires) has an impact on the longevity of the tread

Alex.currie44

Exactly my man! Totally with the concept!

zcct04

Menu for different tire diameters? Don't waste your time. The 225/40 tire is 1.2% bigger diameter than stock at the front and 0.4% smaller than stock at the rear. That's not enough to make any difference at all. The difference between a new tire and a worn out one is at least double that amount. There's no need for any kind of adjustment.