Help needed with tyre size.

[johnwhal]

Hi, just purchased a 2006 Mercedes CLK 220 CDI. I am looking to put new tyres all round on it and am slightly confused. It currently has 225/45/17's all round. I am led to believe that the rears should be 245/45/17's?. Also, which is confusing, when I look at the tyre spec on the diesel filler cap it shows 225/40/18 and 255/35/18 ????. Any advice would be greatly received.

 

[SpikyMikey]

The filler cap label normally lists more than one factory fit option for a particular model; wheel and tyre sizes and whether staggered or straight set up.

 

[DSM10000]

Hi, just purchased a 2006 Mercedes CLK 220 CDI. I am looking to put new tyres all round on it and am slightly confused. It currently has 225/45/17's all round. I am led to believe that the rears should be 245/45/17's?. Also, which is confusing, when I look at the tyre spec on the diesel filler cap it shows 225/40/18 and 255/35/18 ????. Any advice would be greatly received.

What range of tyre sizes are listed in the handbook?

 

[Bellow]

It currently has 225/45/17's all round. I am led to believe that the rears should be 245/45/17's?.

It is extremely unlikely that 245/45-17 can be used (at the rear) with 225/45-17 on the front. The tyres diameters have to be equal and adjustment for section width is adjusted by using a different aspect ratio. Here the aspect ratio is 45(%) for both widths.

Also, which is confusing, when I look at the tyre spec on the diesel filler cap it shows 225/40/18 and 255/35/18 ????. Any advice would be greatly received.

The above demonstrates my point.

 

[johnwhal]

What range of tyre sizes are listed in the handbook?

A Mixture of sizes.
Front Axle "Summer Tyres" 205/55/R16 91V
Light Alloy Wheel 7J x 16 HT ET 31
Rear Axle "Summer Tyres" 225/50/R16 93V
Light Alloy Wheel 8J x 16 HT ET 32
also
Front Axle "Summer Tyres" 225/45/R17 91W
Light Alloy Wheel 71/2J x 17 HT ET 36
Rear Axle "Summer Tyres" 245/40/R17 91w
Light Alloy Wheel 81/2J x 17 HT ET 30

It also list the last tyres as MOExtended - what does this mean?

 

[SpikyMikey]

MO and MOExtended (runflats usually) are tyres specifically developed for Mercedes. Audi do a similar thing (AO) as do BMW (* Marked).

 

[DSM10000]

A Mixture of sizes.
Front Axle "Summer Tyres" 205/55/R16 91V
Light Alloy Wheel 7J x 16 HT ET 31
Rear Axle "Summer Tyres" 225/50/R16 93V
Light Alloy Wheel 8J x 16 HT ET 32
also
Front Axle "Summer Tyres" 225/45/R17 91W
Light Alloy Wheel 71/2J x 17 HT ET 36
Rear Axle "Summer Tyres" 245/40/R17 91w
Light Alloy Wheel 81/2J x 17 HT ET 30

It also list the last tyres as MOExtended - what does this mean?

So your current set up is within the list of standard sizes

 

[SpikyMikey]

So your current set up is within the list of standard sizes

Not quite, as the OP has a square set up where the handbook states staggered.

 

[DSM10000]

Not quite, as the OP has a square set up where the handbook states staggered.

I think that either are acceptable.. If the rear wheels are wider than the front (ie 8.5 J rear and 8J front) then it may have been supplied with a staggered setup.

If using All season or winter tyres it would normally be the same width etc front and rear?

 

[WilliamMaldivess211]

MO and MOExtended (runflats usually) are tyres specifically developed for Mercedes. Audi do a similar thing (AO) as do BMW (* Marked).

It’s not that important though is it? Currently my Mercedes has AO tyres and our Audi has MO ones - that was all that was available

 

[rf065]

Hi, just purchased a 2006 Mercedes CLK 220 CDI. I am looking to put new tyres all round on it and am slightly confused. It currently has 225/45/17's all round. I am led to believe that the rears should be 245/45/17's?.

I had one of them from new, tyres were 225/45x17 front and 245/40x17 rear.

 

[SpikyMikey]

It’s not that important though is it? Currently my Mercedes has AO tyres and our Audi has MO ones - that was all that was available

There is a school of thought that it doesn't make any difference and it's just a marketing ploy.

 

[johnwhal]

Maybe the last owner decided to put 225/45/17's all round. (cheaper option ? ). Maybe when I change the front tyres ask them to see what size rim the rear ones are and then decide which way to go, just a thought.

 

[alabbasi]

Price and availability were probably the reason

 

[DSM10000]

I had a C320 petrol which had the same tyre sizes front and rear as standard.
As said , you cannot increase the width of the rear tyres and keep the aspect ratio the same. That would need to be reduced to keep the rolling radius the same.

 

[Bobby Dazzler]

Hi, just purchased a 2006 Mercedes CLK 220 CDI. I am looking to put new tyres all round on it and am slightly confused. It currently has 225/45/17's all round. I am led to believe that the rears should be 245/45/17's?. Also, which is confusing, when I look at the tyre spec on the diesel filler cap it shows 225/40/18 and 255/35/18 ????. Any advice would be greatly received.

If the car has staggered wheels - wider on the rear axle than on the front - and the front tyres are 225/45 17 on a 7.5j wheel then the rear will be 245/40 17 on an 8.5j wheel.

What follows is less likely to be the case. but if the wheels are the same size on the front and rear axles, then the tyres should be 225/45 17 on a 7.5j wheel at both the front and rear.

 

[colinallcars]

Maybe the last owner decided to put 225/45/17's all round. (cheaper option ? ). Maybe when I change the front tyres ask them to see what size rim the rear ones are and then decide which way to go, just a thought.

Take the wheels off, the sizes are stamped on the inside.