DEREKC

Yes, fitment question again - on a LS430 UL.

Here is what I learned. Please correct me if I am wrong.

Am I right to say that whether the tires will rub (or fit) depends on three critical dimensions - 1.) height (or called diameter), 2.) the width and 3.) the offset of the rims (to shift the wheel in or out) REGARDLESS of the size of the rims, the bolt pattern, the center bore, clearance of brake calipers?

Rim size alone is not enough to determine the fitment. Rim Size plays a role in calculating the height of the tire thou.

It all comes down to whether the tires would touch the well or fender under the extreme steering/suspension condition, right?

Am I right that the following is the formula to calculate the height of a tire?

Height of size wall x 2 + tire_size = width x profile_ratio% x 2 + tire_size x 25.4 mm/in

For the stock wheels on my 2004 LS430 UL, they are 225/55R17, so the height is:

225x.55% x 2 + 17 x 25.4 = 247.5 + 431.80 = 679.30 mm.

Am I right to say I should stay within 3% of the tire height (diameter) of stock tires when changing the size of the tires so as not to overtorque or undertorque the powertrain and affect the accuracy of the speedometer?

Am I right to say the width of the tire should not be more than 3 inches the width of the rim?

I am being offered, at a good price, a set of 19 x 8.5 rims with a choice of offset of 20, 32, or 38. (bolt pattern of course 5x114.3 and unknown center bore, and unknown clearance for brake calipers.)

If I buy these rims, what offset should I choose? If even 38 is not enough, can I should spacer?

And for the tires, I hope to get 245 width for the front and 265 for the rear (245mm = 9.64in, 265mm = 10.43in, both are within 3 inch +/- the rim width of 8.5in.)

To stay within 3% of the stock 679.3mm tire height, it should be between 658.92mm and 699.68mm,

Then, I need for the front,
245x40/19 which has a height of 245x40%x2 + 19x25.4 = 678.60mm

And for the rear:
265x35/19 which has a height of 265 x 35 % x 2 + 19x25.4 = 668.10mm
Or
265x40/19 which has a height of 265 x 40 % x 2 + 19x25.4 = 694.60mm

If I have to choose between the car tilting forward or backward a bit, I would say forward (Can the air suspension be reprogrammed to compensate?). That means I should use, for the rear, 265x40/19 tire size which is 16mm taller than the front tires of 245x40/19 or the stock tires. That also make less gap beteen fender and tire.

I think I am ok with the height then, the questions now I have are:
1.) whether the width of 245mm for the front and 265mm for the rear will rub assuming the right offset is used.
2.) what offset should be used for the front and rear? I have a choice of 20, 32, and 38 (in mm I assume). I read something that 43 is needed for 20" wheel. It depends on other dims too, right?
3.) Can I or should I use spacers to compensate the offset if none of the 20, 32, or 38 is right?

If you have changed your wheels+tires on your LS430 successfully or unsuccessfully (rubbing), could you please let us know the dimensions you use - tire size and rim width, offset.

Here is the stock 17" wheel + tire dimension:

Front/Rear TireSize RimSize RimWidth Offset Rubbing?
_________________________________________________
Front 225/55/17 17" unknown unknown No
Rear 225/55/17 17" unknown unknown No

Your expertise to shed some light on these issues is highly appreciated.

DEREKC

Me again. One more concern.
The LS430 is using indirect system to monitor the tire pressure and warn the driver. It uses the abs to count the rotations of each wheel. The under-inflated one turns more per mile then the rest three.

In my staggered setup, the radius of the rear tires is bigger than the front, would that create a false alarm in the tire pressure monitoring??