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Put me out of my misery - winter tyres Technical Question ?

travelininstyle

Active Member
Joined
Aug 15, 2008
Messages
298
Location
LANCASHIRE
Car
C-Class Sports Coupe AMG 220 Cdi
Hello Guys - I have a 09 Plate CK 220Cdi.Normal Summer tyre orientation is 225/45 R17 & 245/40 R17 - So back in Summer,I decided to buy a set of winter tyres.I decided to do as much homework as possible and went first on Fulda's technical site,that allows you to put year,age and model type,to guide you to the correct tyres for your car.Secondly and most importantly,I checked in the rear of the Car Handbook and for Winter tyres,it clearly states (and concurs with Fulda) that 225/45 R17 91H are suitable for both axles !! - and I think I recall,I ran this past the forum.Anyway,this morning,I had the tyres fitted.The tyre guy said that they were a tight fit ? - anyway,I set off and immediately a message came up 'Reset run flat setting.....
After that,a red light came on saying 'check tyre pressures and settings' - I immediately went back to the tyre depot - I know that the guy had correctly inflated the tyres,but he was struggling to re-set the error message.I am hoping that once the 'Re-set run flat' error is done that everything will be fine,but I am still a little concerned if the size correlation has something to do with this.I am booked in at MB Dealership for a service on Wednesday,so any help that the forum can provide,I will be greatly appreciative of before hand.Incidentally,the tyres were re-fitted on to the exosting alloys and not steel rims,just to clarify,as I know this has some baring.
 
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So, you've put 225/45/17 tyres on the same alloys that had 245/40/17's? I could be wrong but isn't that you're problem?
 
So, you've put 225/45/17 tyres on the same alloys that had 245/40/17's? I could be wrong but isn't that you're problem?

As I said,I was guided by the handbook and Fulda Tyres site - I do not profess to know if its right,or wrong - what you are saying then,is that the alloys are wrong ?
 
You've obviously got wider rear wheels haven't you. That had originally has 245 tyres and now you've fitted 225. I bet it's a bit of a stretch?

As I say, I could be wrong. Somone better informed will be along soon I'm sure.
 
I think (not definitive) that you should replace like for like. Certainly on my SL, all four wheels the same size, my winter tyres, as per hand book, are all the same as summer tyres with the exception of the allowance for a one letter reduction in speed rating.
It is illogical to my mind to be changing tyre size.

Mic
 
Your tyres all being the same size should not be a problem, since staggered is an option not standard on all models. I suggest that those without a staggered set up will have 225s all round. But...maybe the car needs to be told this by someone with STAR.

BTW 225s are fine on 8.5" wheels, so don't worry that they have been stretched.
 
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If you've got run flat sensors, it just needs resetting in the settings.

I had two new tyres put on the front and the car kept pinging this 'check tyre pressures' and it stopped once I could be ****d to read the manual and reset the sensor.
 
Your tyres all being the same size should not be a problem, since staggered is an option not standard on all models. I suggest that those without a staggered set up will have 225s all round. But...maybe the car needs to be told this by someone with STAR.

BTW 225s are fine on 8.5" wheels, so don't worry that they have been stretched.
Thank you -I feel slightly more relieved,but I will ring MB on Monday to confirm.:rock:
 
As Sweetpea says, you will get those warnings if you didn't reset the Run Flat Monitor.

The monitor just measures the rotations of the wheels, it doesn't measure pressure.
So if you change tyres or simply fill up the air it will go off.


245 tyres will probably be a 7.5 or 8" wide rim, which will take a 225 tyre no problem, and always best to use 4 the same with winters, so you have done the right thing.
 
:bannana:
As Sweetpea says, you will get those warnings if you didn't reset the Run Flat Monitor.

The monitor just measures the rotations of the wheels, it doesn't measure pressure.
So if you change tyres or simply fill up the air it will go off.


245 tyres will probably be a 7.5 or 8" wide rim, which will take a 225 tyre no problem, and always best to use 4 the same with winters, so you have done the right thing.
:bannana:Thank you I will raise a glass to you tonight !!!!!
 
Agreed... in fact we get lots of cars in where people have used the same size tyres all around... I guess the tyre fitter just looks at one of the front tyres and then changes all the same size.

Due to the difference rolling radius, The run flat monitor just needs resetting and can be done with the steering wheel controls... its all in your manual.
 
Usually MERCEDES recommend the same size of winter tyre all round e.g. 225/45/R17 but perhaps neglect to mention its best [ but not necessary ] to reduce the back wheel rim width to the same as the front if you have staggered wheels. This not a problem when folks have a complete set the winter rims+tyres to change to.
 
I ran 225/45 winter tyres on the 8.5j rear wheels for 10 months without problems so don't worry about suitability.

Just watch the rims as they'll now be slightly more vulnerable to kerb rash.
 
I ran 225/45 winter tyres on the 8.5j rear wheels for 10 months without problems so don't worry about suitability.

Just watch the rims as they'll now be slightly more vulnerable to kerb rash.
Thanks MR D - like your new Avatar - trust you and Mrs Dazzler are all ready for Christmas.
 
Thanks MR D - like your new Avatar - trust you and Mrs Dazzler are all ready for Christmas.

No problem.

Almost. Presents pretty much done, and mostly wrapped. The half-decorated dining room shatters the illusion though - we have lots of family coming over for Christmas too!! :eek:
 
I have exactly the same set up 7.5 rims front & 8.5 rear on17's winter tyres are 225x45x17 all round and no problems :thumb:
 

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