RealMarty

Yes, I'd put on the 245/45s.

You'll be going up a size from the standard 235/45s so your speedometer will read high by about 1% (no biggie -- no production car speedo is that accurate anyway -- you'll likely never notice it ).

The upside is you'll be putting as much tire on the std. rims as you can.

I'll be putting 245/45s on my GS430 when I burn through those ***** Bridgestones it will come with.

Kaban

Marty,

I think Lexus wised up and switched tires. Mine came with Dunlops D8 225/55 R/16's. It is still loud but I felt more confident riding on Dunlops than crapstones. At least I don't have to worry about my tires blowing apart like on Ford suv.

Juan C. Cos

The ideal setup on a tire upgrade is to retain the same tire CIRCUMFERENCE as stock. Going back to high school, this is calculated by 2¶r (¶=2.1416). R is calculated by 1/2 the wheel size x25.4mm + sidewall height (eg. 235x45%, already in mm). You need less than 2% difference. The ideal maximum tire would be 1.2 times the width of the wheel (8x1.2x25.4= 245 for the stock wheel).
Now on shorter sidewall tires: somebody already mentioned the benefits. The most negative aspect is RIDE HARSHNESS, and a close second (and also mentioned) possible wheel damage from potholes. Third would be cost of replacement (and usually more often). A lower profile tire transmits more of the road vibration due to stiffer sidewalls, and this can annoy you pretty quickly (as it's there ALL THE TIME), so before you plunk big bucks on such a setup, make sure you can live with them (17", 45s are the best compromise for me on a GS).
Want to mimick 18s? Raise the pressure to 44 on your 17s, and that's how it's going to feel (yikes!). I would never sacrifice the ride with 18s without changes in suspension (too soft to obtain any benefit in handling), and as mentioned before, 17 to 18 makes almost no difference.
Just one more point of view. And yes, I'm senile here at 39, so you don't have to listen to me.

Juan Carlos

RealMarty

Kaban,

Oops. I forgot to mention that I got the 17s on my GS 400. Those come with Bridgestone 235/45/17 RE 030s . They don't blow up. They just suck. You couldn't order the 17s on your 300 so you got the Dunlops.

lex430

My GS430 came w/ Michelin Pilot 225/55/16, the ride is very comfortable, and I think it's pretty quiet, however I don't really have much comparison w/ other tires.

So, going up to 18, w/ 245/40, is what I see most people on here are doing for their 18's, I was just wondering would 245/45 also fit? and would the difference be in just ride comfort/minor handling?

nanotech

iTrader: (2)

Why do people hardly ever mention michelin as a recommended tire on this site?

The very first thing a tire guy at Sears recommended to me was Michelin Pilot Sport XGT 24.

Would a larger sidewall, 245/50 mean a softer and quiter ride?

and what are the negatives of a larger sidewall?

Also, if the recommended size is 235/45, then why do you guys recommend 245/45?

Kaban

Marty,

Actually, I have gs 430 with the 16" rims. I guess they didn't all have Bridgestones only the 17 ones does.
Wow, Lex430 your car came with Michelin Pilots? my came with Dunlops D8 they are only R rated which has a top speed of 103 mph, but considering gs430 has a top speed of 150mph, I wonder why they only put R rated tires on mine.

lex430

I wanted to ask again, what are offsets on a rim? how important is that?

I am looking at a set of rims at 18x8.5 all around w/ 45 offset, what does the offset mean?

would I have any problem installing them on my GS430 currently running stock16's,

thanks,

zushwa

OK, there is plenty of confusion here so I'll add to it a bit. I'm in the same boat as some of you so I've done some research myself. These are just some observations so I might be completely full of $h!t!!

First, Pi= 3.14159265358979, but that's just from memory. I had some spare time in Trig class when I was a kid.

Second, that's too much math. If you keep the overall height the same as stock, the speedometer should be fine. If your car comes with 225-60R16, then 235-50R17 and 245-40R18 should all keep the same height. Of course this depends on the width of tire, then things get tricky. I found some really good articles about plus sizing. If I can find them I'll post them here. If there was a wheel forum then this would be much easier and probably correct, not laymen trying to hack their way through it.
Here's a pretty good article. Don't flip out because it's about American cars, the principles are the same.

http://www.gr8ride.com/articles/011680ah/011680ahb.pdf

Third, the 50# or 35# is the percentage of the overall height.

Fourth, the offset of the wheel can be explained better in the article than I can explain it. the 45 offset is fine for my LS but I don't know about the GS's.

I hope I didn't make things worse, I was just trying to help on a few little things I learned here and elsewhere trying to make the most of my Lexus. Sound familiar??

RealMarty

[QUOTE]Originally posted by nanotech
Why do people hardly ever mention michelin as a recommended tire on this site?

The very first thing a tire guy at Sears recommended to me was Michelin Pilot Sport XGT 24.

I always mention my XGT Z4s when I get the chance. I love them. I recommend them highly. But the reason the sales guy may have mentioned them first is:
a) because he carries them
b) he may be making a larger commission on them this month

Would a larger sidewall, 245/50 mean a softer and quiter ride? and what are the negatives of a larger sidewall?

In two tires of similar design on the same wheels on the same car with the appropriate tire pressure....yes the larger sidewall will ride softer, but not necessarily quieter. The noise is due primarily to the tread pattern. The downside to the extra height is that they are less responsive to turning inputs. They don't corner as well.

Also, if the recommended size is 235/45, then why do you guys recommend 245/45?

The extra width provides better grip due to the increased size of the contact patch. So why does Lexus use 235? Well, I could also ask why does Lexus supply those awful RE030s?
When Lexus puts things on the car it is always facing a compromise due to dollars, marketing pressures, production volume, etc., and because it doesn't know that I'M willing to pay a little more for a tire and may be willing to give up a fraction of an mpg for the extra grip.