I'm looking into replacing the rubber on my IS F. I know a common upgrade is to run 245's in the front and 275 in the rear. I was wondering if anyone has tried to run 285's.

 

Some are running 285s in the rear with no problems.

 

Yep, 285's no problems. Keep in mind different tire manufactures are slightly different in size.

 

With FIGS setup you can go even wider in the rear. There are some 285s that will fit in the front as well.

 

Going wider tires with 35/30 series tires F/R would result in a smaller overall diameter tire from my calculations. IIRC to match OEM diameter we'll need 255 fronts and 295 rears.

That's what's holding me back about widening in my upcoming tire change. Don't want to mess with the speedo/odo by changing tire diameters.

Lobuxracer, any thoughts on that?

 

If my memory is correct, when I was looking for tires set up for my car, I saw someone was running 305 for the rear and 285 for the front as well, but he might need fender rolling.

Yes, I believe it will be offset by 2% of actual speed. If you still have your car under warranty then this might be an issue, but if not then from my experience with the set 245 & 275 I'm running right now is fine and it improved a lot on traction.

 

Only the rears count for the speedo/odo functions. I proved this with the car on jackstands when I was bedding the rear brakes (it's really hard to get them hot while driving, even on the track). Yes, the 295 is the ideal width, but without the right wheels, you'll be hard pressed to get them on the car without cutting or rolling the fenders.

I'm a huge fan of maintaining the OEM diameter for a bunch of reasons, not the least of which is the VDIM will still work correctly. It's hard to say if it will or won't with different sizes, but normally in the industry if you are +/- 2% you're considered OK.

For the front, a 255/35/19 and a 295/30/19 will be the same rolling diameter as the OEM 225/40/19.

For the rear, the only exact equivalent is 295/30/19. Everything else is a little one way or the other.

275/35/19 is 2% smaller, so it's considered acceptable, but not ideal.

 

Let's keep this in perspective. If you drive 100,000 miles on the car with those tires it will ONLY result in an additional 2,000 miles on the odo, not a big deal in my opinion. Certainly will not affect resell value, significant gas mileage, or significant speedo error (in stead of 100 mph you will read 98mph).

 

Me, here:

https://www.clublexus.com/forums/is-...-position.html

The 245/285 combo is .2" shorter in OD than the stock sizes, 25.8" vs 26.0". That's a difference of less than 1%, 3/4% to be exact. As with the 225/255 stockers combo, the 245/285 combo has the same ODs front to rear.

Lou

 

^ yup, I'm running his set up and I freaked love it

 

I'm running 305s, speedo is a little bit off and they rubbed before any fender mods. I still get a slight rub but I have Figs Arms in the garage and toe links on order. If I had to pick I would run 295/30-19 on the right wheel.