285/30/19 is it an overkill?

[Terrykal]

Hi,
I recently purchased for my daily car (even though due to the situation I am working from home more than a year now) a 13 plate c218 CLS 350 AMG Sport.
Car is looking great and drives great too, better than my ex c219 500 (which I still believe is a better looking car) and my s211.
Till now I am still cleaning it (interior first since previous owner was a golf player pensioner with a pet).
This comes from factory with 19" AMG alloys, fronts 8.5jx19 et34.5 and rears 9.5x19" et48.

First weird thing is that instead of having 245/35/19 in the front (to much the 245/40/18 or 245/45/17) Mercedes decided to use 255/35/19 which give a total larger diameter on the total wheel. I guess they did it for cost purposes and maybe for a more comfort ride.

Second weird thing is the wide rear tyres. I can understand you want to have wide tyres on a AMG engine but why to put 9.5j and 285 wide tyres on a 350 engine? I can understand that the engine's torque output is quite high but then if it wasn't an AMG edition then it would have 245/40/18 at all corners, correct?

Question is if you would think that would be a good idea to have 8.5jx19" at all corners meaning to have front alloys at the rear axle too. So one can have 255/35/19 tyres at the back too.
That would save some weight on the rear axle so power output would be a bit quicker, rear suspension would have an easier job to do and also car would be a bit more comfortable for passengers.
What do you think?

 

[Phillip Butler]

It may be just aethetics. I've a CLS350D shooting brake and have just changed the winter wheels and tyres back to the original summer set.
The 285/30/19 rears weigh a ton.

 

[Blobcat]

That’s the same size as the rears of my 911...
Expensive fashion in many cases. I’d go smaller with your car as I prefer comfort

 

[dry run]

I guess to call it an AMG line, they just carry over some of the parts from the AMG - front spoiler, side skirts, AMG floor mats, wheels & tires, etc.

Properly mapped, the 350d engine can give you more torque than an Aventador!

 

[LostKiwi]

We have 285/35x19 on the rear of the SL500....

 

[bembo449]

id keep it staggered , the torque of your engine will put down its power better with more tyre , its not like you can see it from the driving seat anyway and the weight difference is hardly relevant , no point saving weight if your spinning all the power away through lack of traction

 

[LostKiwi]

id keep it staggered , the torque of your engine will put down its power better with more tyre , its not like you can see it from the driving seat anyway and the weight difference is hardly relevant , no point saving weight if your spinning all the power away through lack of traction

Tyre width does not affect grip (for a given tyre pressure). It merely changes the footprint.

 

[oigle]

Tyre width does not affect grip (for a given tyre pressure). It merely changes the footprint.

AND it makes for higher level of aquaplaning in the wet....

 

[LostKiwi]

AND it makes for higher level of aquaplaning in the wet....

More road noise and less economy too....

 

[Terrykal]

Thank you all for your contribution and your thoughts.
The best "trick" that Mercedes did in the past was to use different offsets when producing the c219 cls500. Fronts were et28 and rears et18. All came with same width so you had same tyres at all corners.
This was you had a staggered look (with rears giving a more aggressive footprint) and at the same time you didn't have the sacrifice in road noise, economy, extra weight on the rear axle etc.
I will try to weight and compare a front one with a rear one. Of course with the current combination of alloy+tyre and see the differences.
I had read online that when saving 10kg on the accelerating axle is like saving 100kg of chassis' weight. If I can recall correctly.
To be honest, for my personal taste, the look of these 19" AMG alloys are just fabulous

 

[Terrykal]

Here is the difference between front and rear wheel (alloys and tyres) , as a graph.
With the rear's et48 , even though they are 9.5j, rear tyres edges seem to be at the same line with the front ones..

 

[bembo449]

More road noise and less economy too....

so why aren't you two running bike tyres on the back of your cars ? you would save weight and fuel at the same time

 

[bembo449]

More road noise and less economy too....

absolute rubbish ! I'm about to fit 22s on my 300c , any money you like on it , I wont see any difference in fuel economy

 

[LostKiwi]

absolute rubbish ! I'm about to fit 22s on my 300c , any money you like on it , I wont see any difference in fuel economy

It's the width that screws economy as it increases aerodynamic drag and cornering effort.

 

[LostKiwi]

so why aren't you two running bike tyres on the back of your cars ? you would save weight and fuel at the same time

Because it would look pooh on a 230.
I'd happily go back to narrower tyres on 16s on the E class but can't see the point in spending the money.

 

[Terrykal]

Personally, whenever I changed my tyres to a wider set of tyres I have been always seen a decrease on mpg (so increase in fuel consumption) on the motorway.
Most recent examples that I have were with 2lt engines, a petrol bimmer from 205 to 225 and a diesel bimmer from 205 to 255. Same conditions of driving and same motorways.

 

[LostKiwi]

Personally, whenever I changed my tyres to a wider set of tyres I have been always seen a decrease on mpg (so increase in fuel consumption) on the motorway.
Most recent examples that I have were with 2lt engines, a petrol bimmer from 205 to 225 and a diesel bimmer from 205 to 255. Same conditions of driving and same motorways.

My E class increased consumption nearly 10% going from 205s on 16s to 245s on 17s. As noted same French motorways, same driving.

 

[oigle]

Yep I agree. In my early days as a Mazda dealer, we sold an RX2 to a guy that hooned somewhat. Knew the topspeed of the vehicle after multiple speed runs. Decided to lair it up with a set of "fatties" Same rolling circumference. Car was 10kph slower. He was P1SSED.

 

[oigle]

so why aren't you two running bike tyres on the back of your cars ? you would save weight and fuel at the same time

I took the 255/55/17's off my ML and put on 235/65/17's. Same rolling circumference. Better ride, better steering (no tramlining), better economy, safer on wet roads. It's not a sports car so ultimate grip on corners not an issue. 75000km average tyre life. Would never revert.

 

[Terrykal]

Just a quick update in regards to the weight differences.
I was surprised to see that front ones are just 0.5kg lighter than the rear ones. I am talking for the total actual weight of the alloy with the tyre on so the total wheel weight.
both axles have Falken fk510
front wheel 8.5*19 + 255/35 falken weights about 23.5kg (tyre tread about 5.5)
rear wheel 9.5*19 + 285/30 falken weights about 24kg (tyre tread about 3.5)
this practically means that swapping to 8.5*19 at the rear axle will save you 1kg for the same AMG alloys. Keep in mind that different manufacturer tyre will have a different weight so for example a continental tyre might be heavier than the tested. Definitely the ride will be smoother and all the advantages that have been discussed above will be gained.