TOPENDMS

Whats an IS500?

beezmarkee

Lexus 3IS V8 5.0, swapped from RC F.

cdqnguyen

I have a set of 18x9 +30 rims that I'm thinking about putting on my is250 AWD. Will be dropped on RSR Downs. What size tires do you guys recommend?

VisualEcho

On a 9 a 255 will be a slight stretch, a 265 will be square, and a 275 will bulge (depending on the make/model of tire). So if fitment is an issue I'd choose the 255.

Blaque Diamond Wheels

You can run a 245 or 255

Sasnuke

I would go with the 255. It's a slight stretch, but the offset is a little low for the rear, so the 255 will help with any rubbing issues.
275 would be a rub concern...the 265 would be a question mark.

cdqnguyen

Thanks guys. I was thinking about going with 245 all the way around but if I go with the 255 I only need to buy 2 tires since I recently purchased new rears!

VisualEcho

A lot of guys like a shorter sidewall, so going with a bit wider tire, and changing the aspect ratio usually gives them that.

I think it's easier for you as well, going squared, it's super hard to match the sidewalls on staggered.

cdqnguyen

I wasn't sure about going 255 all the way around because I was afraid it would rub but hopefully it works. Yeah, initially I was trying to do the oem sizes but don't want stretched tires.

Dzjnmstrd

Hello Fellow IS Owners!

I drive a 2015 is350 F-Sport and wanted help with some wheel fitment issues.I have been using the website willtheyfit.com to find exact measurements compared to the stock wheels. I am having trouble visualizing the size comparison in the front. I know the front wheels (stock) are 18 x 8 et45 and have a inset of 146.6 mm. The potential new wheel size is 18 x 9.5 et 38 and will have a inset of 158.7 mm. Will the difference of 12.1 mm (.5 in) run a risk of hitting the knuckle? Thank you in advance for input!

***EDIT***
The car is on coil overs, if needed can purchase a front camber adjustment A-arm, and roll the front fenders. Main objective: Fit the front wheel without more than -2 degrees of camber.

VisualEcho

You don't need to compare to stock, you need to compare with the maximum that will fit.

I think you'll find that 9.5 in the front is a very tall order, so yeah, that 12mm is going to probably cause you issues.

My fronts are 19 x 8.5 +35 with a 235/40 or 245/40 and work fine, but I don't think a 9.5 would have worked. We will see what @Sasnuke says, he's the guru here.

Dzjnmstrd

I agree with your response. I will wait for the gurus response. Appreciate it!

Sasnuke

LOL! Thanks VE! I was just crunching the numbers on this one.
VE is right, the 9.5 is a little much for the front. The issue is if the offset is too high to keep it from sticking out the fender, then it will hit the knuckle. If the offset is too low, then it clears the knuckle, but sticks out past the fender.
Even if you get the rim to miss the knuckle, the tire is gonna hit it for sure.
You'd want to aim for a 9 inch on the front as the max.

VisualEcho

There is a way you can make a larger tire fit easier by making the wheel itself larger (perfect size/offset), as it crowns the tire.

I discussed this very thing with a chap here once, and we came up with the following:

Front: 19 x 9 +35 with 245/40
Rear 19 x 10.5 +45 with 285/30/19

It would take a slight increase in negative camber, front and rear to make it work, but we think it would work.

But I think those are about the limits. Does that seem about right @Sasnuke ?

Dzjnmstrd

I really appreciate the quick response! The information given has really made me reconsider. Good thing I didn't purchase the wheels yet! I will look more towards running the specs you provided