I purchased some stock 18s and need tires, I saw the thread on GS430 tires, still had a question. is there room for 245 45 18s......they should give a better ride, overall diameter is 22 mm bigger so that means, 11 mm ~ 1 cm bigger from center of rim outwards....is there room, it is hard to tell since I have 17s and even the 18 with the 40s is bigger all around and wider so hard to simply look in the wheel well and guess....inputs are appreciated. I only ask this because I would like a little nicer ride, will it look too stupid

 

You should be fine.

my 2nd gen GS comes with 235/45/17 stock tires. I'm running 245s now with no problem. On 18s, i'm sure you would be fine, assuming lexus makes their wheel width the same as my OEM 17s.

 

If you do do it, please post picks and let us know how it rides.

What kind of tires are you considering?

 

are you wanting the 45's instead of the 40's for ride comfort?
there's not really that big of a difference.

I am running 245/40/18 on my 450h, and I am also running 245's but in a MICH PS2, which is like a 255 in any other tire.

The PS2's run one size larger than the number they say.

I have absolutly no problems with my current 245/40/18 and I love that the 245 look like the 255's of any other tire.

Let us know what you decide.

 

d'oh! i guess he was asking about sidewall height, rather than width.

 

my car came with 45 series tires. no rubbing or any issues and rides just fine.

 

Jace7 do you have a picture

 

Thanks, I appreciate it, I think I will look thru tirerack and find a suitable tire.

 

I wouldn't recommend changing tire sizes from stock. When you go with a 45 series tire instead of a 40, you will be changing sidewall height and that will change rolling diameter and speedometer accuracy. Although not likely, it is possible that you could have tire rubbing issues @ full lock. To make a long story short, if you have to increase sidewall height for comfort, stick with the 17s.

245/40/18 is the correct size for the 18" factory GS wheel if you want to maintain proper rollout. Going with a 245/45/18 will result in the following....

Approx 1" taller tire
Approx 1/2" increase in ride height.
Approx 3" increase in rollout
At 75mph your speedo will read 78mph assuming it's 100% accurate to begin with
It will also change your overall gear ratio will change performance and gas mileage.

Not a simple change by any means.

 

Robert, that is a similar reply I typed in last night right when CL forum was shut down for maintanance, so it never got posted.

Stock:
225/50-17: 225mm*0.50=112.50mm=4.43"

Replacement:
235/40-18: 235mm*0.40=94mm=3.7"
245/45-18: 245mm*0.45=110.25mm=4.34"

You need to maintain the overall ratio and the same outside diameter, so if you go up in 1" in rim radius, you will need to go down in 1" of tire profile height. Otherwise, you are asking for trouble

 

Great minds think alike.