Downgrading from 19" to 18"

[Gazwould]

They are just a rough guide and will carry misinformation as tyre width and aspect ratio stated on the sidewall will wildly differ from manufacturer to manufacturer and even within a manufacturer .

This gives some unexpected results .


The number 1 rule is just keep with what sizes Mercedes is quoting for your car .

 

[ALFAitalia]

It's the rolling radius that matters.

The smaller diameter tyre may have a sidewall height that gives a compatible rolling radius but there are so many different aspect ratios (sidewall height expressed as a percentage of tyre width) available that you have to ensure you pick the correct value.

That's why there are wheel and tyre calculators avaliable to help make the correct choice.

Roiling radius is just half rolling diameter....so it does not matter which you use.

 

[DSM10000]

Roiling radius is just half rolling diameter....so it does not matter which you use.

My point is that if you want to maintain the same with an 18 inch wheel as you had with a 19 inch then the tyre aspect ratio for the smaller wheel needs to change.

 

[ALFAitalia]

Absolutely ......

 

[OneForTheRoad]

Yawn

 

[ALFAitalia]

Might be me.... but that all sounds suspiciously AI!
Especially as most was just duplicating what's already been said. I won't clicking on that link!

 

[SpikyMikey]

Downgrading from 19" to 18" wheels can have some benefits, like improved ride comfort, as the thicker tire sidewalls on 18" wheels tend to absorb road imperfections better. You might also notice reduced road noise and potentially lower replacement costs for tires. On the downside, you could lose a bit of the sharper handling feel and aesthetic appeal that the larger alloys offer, especially on an AMG Line model.

When swapping wheels, ensure the new set has the correct offset (ET), bolt pattern, and load rating for your car. It’s also worth checking your car’s manual or a tire size calculator to find the appropriate tire size to maintain the correct rolling radius and avoid speedometer inaccuracies.

If you’re looking to sell or exchange your current alloys, local online marketplaces can be a good option. For instance, I’ve had success with jiji.ng when looking for car parts and wheels—it might help you find buyers or a replacement set. Good luck with your decision! Let us know how it works out.

Is there a bot in the house ?

 

[Gazwould]

Much of Jiji's benefits mentioned AI or not comes from lighter unsprung mass but fails to get a mention , this includes ride quality , partly because the smaller lighter wheels exert less bump force and so the damping becomes more accurate .