CLS 20 inch tyres. confusion over sizes.

[Sunnyd]

Hi.
Can anyone point me in a right direction.been all over internet and online shop selling tyres giving different size compare to charts.
I've looked online and so far best tyre size for my alloys:

20x8.5J ET35 255/35/20 (245/30/20 in online shop)

20X10J ET35 275/35/20 or 275/40/20 or 275/30/20

I'm really stuck. can someone point in a right direction please

 

[renault12ts]

First of all, you can't have the same profile ratio front and rear if the rears are wider than the front.

So, if you want 255/35 on the front you need 285/30 on the rear.

Or 255/30 all round.

What does your handbook say?

 

[Sunnyd]

First of all, you can't have the same profile ratio front and rear if the rears are wider than the front.

So, if you want 255/35 on the front you need 285/30 on the rear.

Or 255/30 all round.

What does your handbook say?

It isnt sayiong anything, as 20in wheels is not an option on cls.
How did you worked out sizes?
And what is profile ratio? Sorry Im new to all this.
in this topic 20" on a CLS (219) - MBClub UK - Bringing together Mercedes Enthusiasts

person got
Front - 20x8.5 ET35 with 255x35x20 tyre
Rear - 20x10 ET32 with 275x35x20 tyre

another person
front 245/30 zr 20 8.5j
rear 275/30 zr20 10.5j

so you see,why I am confused

 

[renault12ts]

It isnt sayiong anything, as 20in wheels is not an option on cls.
How did you worked out sizes?
And what is profile ratio? Sorry Im new to all this.
in this topic 20" on a CLS (219) - MBClub UK - Bringing together Mercedes Enthusiasts

person got
Front - 20x8.5 ET35 with 255x35x20 tyre
Rear - 20x10 ET32 with 275x35x20 tyre

another person
front 245/30 zr 20 8.5j
rear 275/30 zr20 10.5j

so you see,why I am confused

The profile ratio is the height of the tyre walls.

It's a ratio of the tyre's width. So a 255/35 tyre has a tyre wall 35% of 255mm which is 89.25mm. So if you have wider tyres on the back you need a lower profile ratio so the tyre walls are the same (or very nearly).

Anybody suggesting the same profile ratios front and rear also doesn't know anything.

 

[exvolvoman]

It's also to do with the circumference of the tyre...

 

[renault12ts]

It's also to do with the circumference of the tyre...

I suspect if the diameters are the same the circumference will be the same...

 

[b1g1an]

Circumference of the original fitment is what you should go by and then juggle the width/aspect to get as close as poss whilst keeping within the spec recommended for the particular wheel.

This will do the maths for you... Tire Size Calculator - Tire & Wheel Plus Sizing

 

[Sunnyd]

The profile ratio is the height of the tyre walls.

It's a ratio of the tyre's width. So a 255/35 tyre has a tyre wall 35% of 255mm which is 89.25mm. So if you have wider tyres on the back you need a lower profile ratio so the tyre walls are the same (or very nearly).

Anybody suggesting the same profile ratios front and rear also doesn't know anything.

ok thanks.

When Ive got the car this tyres was on:

Front 245/35/20
Rear 270/30/20

Had spacers (2 or 2.5cm) fitted too.However all 4 tyres was heavily worn on inner edges, hence I thought sizing is wrong. when took for tracking camber is out -1.4'' on all 4 of them, however reading online it is seems to be normal for cls.

So, big question, what is the ideal sizes..please?

 

[Abb]

I had 20" wheels on my CLS, the rears were 295/25/30 on a 10.5j wheel and the fronts were 255/30/20 on a 9j. These are definitely the correct size tyres for the size wheels. Whilst I appreciate yours are slightly narrower, the profile will be similar if not the same. Certainly wont be the same profile front and rear.