Hello fellas.
I am planning to purchase a new set of wheels - considering going for 18 inches to replace the standard 17. 225/40/18 is the recommended tire size for the car with a tire of this size (or 255/35/18 but thats overkill), but I was thinking about, would it be a good idea to get 225/45/18 for a little bit of extra rubber. The advantages in my mind is a slightly more gentle ride, slightly less noise and a bit more filler in the wheel arch as there is quite a bit of an air gap in there. Or am I a complete idiot and am ruining the cars looks and/or steering/suspension function by doing this?

 

If had an F Sport package IS the front rims are 18x8 +45 with a 225/40/18, and the rear is 18x8.5 +50 255/35/18.
The tire size is matched to the height and width of the tire.
Depending on what rim size you finally decide on, that will dictate the tire size.

You can use a 225/45/18 without issue on a stock IS.

 

Thanks for the answer. Are their any advantage of using a wider tire for the rear wheels or should I do fine with 225 all around?
Also, do you mean that I can't or shouldn't have a specific tire size depending on what size of rim I pick? The websites where I've looked around for wheels, where you can type in your reg plate, tells me if I don't remember incorrectly, that 18x7.5 to 18x8.5 would work.
Also with 114/3 bolts, correct nav or wider together with a nav ring, and an ET rating that matches the originals +- 10/15.
Have I understood this right?

 

I may not have understood all that, but can provide some info that will help clarify the info you're finding.

The staggered setup was a factory option when you purchased an F Sport package. The package was partially aesthetic and partially performance.
Many owners have gone from staggered (wider rear wheels) to square (same size wheels all around).
Through trial and error regarding fitment, it's possible to fit anywhere from 18x8 to 18x9.5 on the front. For the rear you can fit anywhere from 18x8.5 to 18x10.
The offset will determine final fitment/clearance. At that point you will choose the tire size appropriate to the rim and vehicle.

 

Makes sense. I should try my best to match the rims with the originals for best fit. The shop I'll buy from provides fitting guarantee too.
However about the tyres. Do you think its a good plan for the extra profile with the tyres or is it just a gimmick of mine?

 

You don't necessarily have to use the specs that your original wheels have.
If you have the big brakes up front, like on an IS 200t, 300, or 350, then chances are an aftermarket rim with the same specs won't fit.
Keep in mind Lexus made the spoke pattern so it would fit around the big brakes....the wheel size and offset is almost secondary.
You have to make sure whatever wheel you choose clears the brakes.
Usually folks will order with lower offsets to avoid any clearance issues.
Depending on how wide you want the wheels to be the offset would change slightly.

You should check out the wheel thread to get some ideas: https://www.clublexus.com/forums/is-...exclusive.html