Wandl

My LS460 takes 235/50/18s as stock replacements.

Would the vehicle be able to take a 235/45/18 or 235/55/18 as an equal replacement, or no?

In addition, since this vehicle has TPMS, would regular "mom and pop" stores be able to install tires with the TPMS in mind or would a chain (i.e. Goodyear, Firestone, Lexus dealer) be the best option here?

t2d2

iTrader: (8)

There are several tire size calculators available that'll tell you the percentage difference of any tire configurations. This is my favorite for its simplicity, but there are others with lots of added features (and clutter):

http://www.miata.net/garage/tirecalc.html

From what I found in reading up on it a couple weeks ago, it's best to stay within ~0.2" of stock diameter, which is the overall tire height. Your proposed sizes will be outside that range. If you change the sidewall ratio without changing the width, you're changing the height.

Wandl

gotcha thanks - great tool! HElps me a lot

mkeeney

While the tire size calculator uses the proper formula for determining the tire size, it doesn't reflect reality. Tires that are a stated size must be within a specified range. They are not exact measurements at all. The only reliable information is the diameter and section width of the actual tire published by the manufacturer.

As a real world example, when I worked for a major tire manufacturer, we produced a 305/35-24 and a 315/35-24. The thing nobody knew was that they were exactly the same tire. They were made with the same mold except one sidewall read 305 and one read 315, and we charged about $200 more for the 315's. The range for 305 and 315 overlap, as most sizes do.

Since the sizes you listed are very close to each other, you're probably fine. The best thing to do is to check the manufacturer's web site for the specs on each one and compare the actual dimensions.

t2d2

iTrader: (8)

^^^ Very true. I've got two sets of identically spec'd tires with about a half inch discrepancy in outer diameter. That definitely complicates staying within a certain percent of stock.