ceoart

I checked with the Regional Rep for Lexus today and he confirmed that putting 18" or larger wheels on the GS will Effect the Speedometer! In fact it will read slower than you are really going! So some of you who said that they notice a 0-60 slow down this could very well be a reason.

lex430

how about milage reading? doesn't bigger wheel make less number of rotations, so let's say few years down the road, the car's milage may say 20k, but it should actually be 25k?

futuregs

also the less rotations the more gas you save. =]

NVRENUFHP

The wheel diameter is not relevent. The diameter of the tire is the relevent factor. If you go to a bigger wheel than OE, you need to mount a lower profile tire than OE so that the OE tire diameter is maintained. The bigger the wheel, the lower the tire profile needs to be. If the tire diameter stays consistent, tire circumference stays consistent and it is the tire circumference that will affect the speedo and odo (and the nav, as well?).

hellasboy

18" wheels will knock your speedometer off if you change the diameter of the wheel. If you keep the same diamter, the speedometer will stay the same.

If the 18" wheels weigh more than your stock wheels, then your speedometer will report lower #'s (let's say at the end of a 1/4 mile run) because your going slower (because of increased rotational mass)

NVRENUFHP

You are not really saying that wheel weight will affect speedometer readings are you? If so, you may wish to check into a basic physics class. Increased weight, on the wheels or anywhere else, may affect acceleration, top speed, or any number of other performance characteristics of a car, but it won't cause the speedo to be off.

Assume for the moment that your speedo is 100% accurate with OE wheels and tires. If you put on wheels that are bigger, smaller or the same size as OE but weigh 50 pounds (or a 100 or 200 pounds, for that matter) more than OE, AND have tires with a profile that maintain OE diameter, then your speedo will still be 100% accurate. It is tire diameter that is critical because the diameter determines circumference and circumference is what matters to the speedo.

KNKGS400

good reason to if you get a speeding ticket...

hellasboy

No, that's not what I meant. I really meant that your speed will be slower but it came out wrong. I meant to say that if someone who runs the 1/4 finishes at 97mph puts on larger wheels and they run the 1/4 again and get a 93 mph they might assume that there speedo is off when in actuality they are running slower because of the added weight of the larger wheel.

oh, also on my previous post, I said "diameter of the wheel" I meant the wheel/tire diameter ... you stated it better, the diameter of the tire.