Hey guys. I recently got a used set of aftermarket rims that came with new tires (Firestone Firehawk Indy 500), but the tires are 235/40/18 (Front) and 255/35/18 (Rears). Based on the online tire calculators available, the fronts are 1.5% larger than the rears. Will this cause any issues with the AWD system?

Thanks for your help.

 

That's a hard one to say for sure. The front tires are basically one size bigger than a stock F Sport front...and the rear is the same size as a stock F Sport rear.
As the primary drive wheels are the rear, they (in theory) will wear faster, therefore the size differential between the front and rear would be even greater.
Right now, brand new, the rear tires are rotating 13 times more per mile, which is about the the difference between a tire that is new, and the same size tire that is worn out, or almost worn out.

The easy fix would be to replace the front with two new Firehawk's that are 225/40/18, assuming that the rim is 18x8, or even 8.5.

 

I couldn't find anyone on CL discussing about this but on other forums people have said as long as you keep it within a 2% variance then it should be fine.

The 235/40/18 are on a 18x9 rim, so it's slightly stretched

 

For braking purposes shouldn't be more than 3% difference in tire sizes, so you're probably ok.

What's the rear rim size?

 

Rears are 18x9.5

Im just concerned about the AWD system with the slight tire variance between front and back

 

On a 2014 AWD IS350 F Sport I run 255/45/18's rear and 225/50/18's front. The tires are 3 inches larger/taller than OEM, and the variance is not an issue. If it is an issue, you should get a light on your dash telling you your tires are mismatched.

 

To be clear, probably something like "Check AWD system".

I would only advise going with a larger overall diameter if you need to do so for a specific reason.

 

Interesting... I’m curious why you would run such bigger tires? Im guessing it just takes away the gap. I actually used to do it back in the day on my integra. Fatter tires on stock blades and lowered. Looked good. Never thought about doing it on the IS tho. Do you have any pics? Intrigued how it looks...

 

Mostly due to potholes during winter. Easy to bottom out in PA. It also does fill out the wheel-well. Ride is smoother, mpg the same.

 

@ShrinkDoc Nice ride!

2014 Lexus IS 350 AWD. OEM Tire/Rims for me are front 225/40r18 8x18 ET45, rear 255/35r18 8.5x18 ET50.

I got 255/40r18 for the rear today (they were cheaper than the 35 aspect tires and bigger sidewall for DC potholes) and just got the "Check AWD System" light.
I'm assuming this is because of the increased difference between front and rear wheel diameters; (OEM: front diameter 25.1", and rear diameter 25", -0.4% difference) vs (with 255/40r18; front diameter 25.1", and rear diameter 26", +3.6% difference). (https://tiresize.com/comparison/)
To decrease the diameter difference between front/rear tires as much as possible I'm considering getting 225/45r18 for the front. This would make the diameter of both front and rear tires 26".

I'm wondering if I will get any rubbing at full lock, etc.? @ShrinkDoc I see you have 225/50r18 up front on your car, have you had any issues; rubbing, abnormal wear, etc.? Also any rubbing with the 45 aspect tires on the rear?