I currently have 245/45R-18 Dunlop Sport 5000 tires on a 05 LS430. To further soften the ride I am considering going with the Michelin Primacy MXM4 225/60R-18. This tire will be 2 inches taller. Would this be a mistake with the likelihood of contact with the shock and or wheel well. Sewell says maybe but I wondered what you guys had learned through experience.
Thanks!

 

bad bad bad.

1. Making the tire taller may increase the chance of bottoming out.

2. It will definitely screw up your speedometer reading.

3. You have to learn what the numbers are on tires. 245 is the width of the tire in millimeters. Length measuring from one end of the beaded lip to the other beaded lip.
45 is the ratio height of the sidewall. AND of course everyone knows 18 being the rim size.
The 18inch rims, if I recall are 18x8. meaning the width of the rim is 8inches
Having said that if you use a 225/60. 225 width (20 shorter from 245) and adding a taller sidewall means you are "stretching" the tire to fit the stock 8 inch rim.

For these reasons that is why factory rims and tires are the following.
17 inch Rims 17x7.5 with 225/55-17
18 inch Ricms 18x8 with 245/45-18

If you plan on using 60s, you're going to need a thinner rim.

In the end, you "may" get a softer ride, but you'll probably shorten the life of the tire.

 

^^^he explained it properly for you
Even the RX uses 235/55/18.

If you want to be a little safer, do what I did and go with 235/50/18.
It's the same oem size for the LS460.

 

Did the ride improve any when you did that change? Im curious becuase i have the same year and wheels the OP does and planning on doing the Michelins also. Do the 235/50's ride any better? Do they look out of place compared to the original size?

 

always check this site for these types of questions:

http://www.1010tires.com/tiresizecalculator.asp

Stock Tire - 245/45R18 >Search Tires Tire 1 - 225/60R18 >Search Tires
Section Width: 9.64 in 245 mm

Section Width: 8.85 in 225 mm
Rim Diameter: 18 in 457.2 mm

Rim Diameter: 18 in 457.2 mm
Rim Width Range: 7.5 - 9 in

Rim Width Range: 6 - 8 in
Overall Diameter: 26.68 in 677.67 mm

Overall Diameter: 28.62 in 726.94 mm
Sidewall Height: 4.34 in 110.23 mm

Sidewall Height: 5.31 in 134.87 mm
Radius: 13.34 in 338.83 mm

Radius: 14.31 in 363.47 mm
Circumference: 83.81 in 2128.7 mm

Circumference: 89.91 in 2283.7 mm
Revs per Mile: 779.6

Revs per Mile: 726.7
Actual Speed: 60 mph 100 km/h

Speedometer1: 55.9 mph 93.2 km/h
Speedometer Difference: - Speedometer Difference: 7.279% too slow
Diameter Difference: - Diameter Difference: 6.78%

 

with the extra 1/2" of sidewall, of course it's going to be smoother and quieter

these are bridgestone, so they're a little square on the outside. I think with different brands, it can give a different look.
I think dunlops are rounder at the edge.

I didn't wait for the suspension to lower a little more when I took the picture:



one more:

 

I had 235/50/18 Dunlop SPmaxx A1 tires(LS460 oem tire) on for a year. The ride and look was great but that was a terrible tire. I now have the Sp5000 which are terrible. I want to go to Michelin Primacy MXV4 but that is only available in a 245/45/18, the olny Mich in 235/50 is a MXMM or Pilot A/S which are not as smooth as the Primacy. I think I am going to order 245/45/18 Primacy, my friends love that tire and ride.