235/40/R18 vs 225/40/R18?

[Mech_Mike412]

This year I'm running Alzor 349 wheels that will soon be powder coated. I'm gonna be running Pirelli P Zero All Season Plus for my next set of tires too. Since the offset is approximately 10mm less than OEM, meaning the wheel will set closer to being flush with the edge of the fender, I was concerned about potential rubbing. My car is stock ride height with a future potential 1" drop.

Currently I have Nitto Motivo 235/40 on the S Line 18x8 OE wheels. The tires have been great to me but I'm looking for something with a stiffer sidewall with a quicker turn in.

Now, are there any benefits to running the 225s? I know I can get the 225s tires a few bucks cheaper than the 235s. Other than cost, would it be a good idea to run a narrower tire for this setup? Or is it nothing to worry about?

Thanks Gents!

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[medrads2020]

You're not going to notice much of a difference between the two sizes with Quattro and Stage 1. The biggest difference would be which brand tire you end up buying. The only benefits of running 225/40/18 tires for you would be subjective unless you plan on autocross or road racing.

235/40/18 are only 1.9mm taller than the factory 235/45/17. You should be fine running these on stock suspension. I can't say with certainty on aftermarket suspension, because if you drop enough you will eventually rub. 225/40/18 are 6.1 mm shorter than the factory tires and will fit fine, although they may look stretched. Some people like this look.

[StatusQuo]

Yeah the biggest difference you will get will be on tire compound and design. I'd get 225 for a sightly stiffer sidewall.

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[Mech_Mike412]

Okay. Maybe I'll just stick with the 235s gir now. I'm only gonna drop it around an inch or so, nothing crazy.

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[medrads2020]

I'm planning on getting 18x8.5 +35mm offset wheels this summer. I'm going with 235/40/18s. I'll eventually drop it 1.2 inches, and my calculations say it won't rub. You should be fine with a similar setup.

[Mech_Mike412]

I'm planning on getting 18x8.5 +35mm offset wheels this summer. I'm going with 235/40/18s. I'll eventually drop it 1.2 inches, and my calculations say it won't rub. You should be fine with a similar setup.

But you're running a wider wheel than stock. Stock for the S-Line cars is 18x8, so your overall tire height will be less than stock

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[medrads2020]

But you're running a wider wheel than stock. Stock for the S-Line cars is 18x8, so your overall tire height will be less than stock

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The width and offset of the wheel only influence how closely the tire approaches the fender. An 8.5 inch wide wheel with a +35mm offset will be much closer to the fender than factory. Width and offset have negligible impact on tire height.

[Mech_Mike412]

The width and offset of the wheel only influence how closely the tire approaches the fender. An 8.5 inch wide wheel with a +35mm offset will be much closer to the fender than factory. Width and offset have negligible impact on tire height.

Do you have the factory sport suspension? I'm not saying I don't believe you but what I see here is if I go from the factory offset to a 35 offset on 235s w/ sport suspension, I'm concerned about the tire clipping the wheel arch and rubbing the fender liner. This is the rear of the car, not the front. The front doesn't concern me.

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[medrads2020]

Do you have the factory sport suspension? I'm not saying I don't believe you but what I see here is if I go from the factory offset to a 35 offset on 235s w/ sport suspension, I'm concerned about the tire clipping the wheel arch and rubbing the fender liner. This is the rear of the car, not the front. The front doesn't concern me.

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The front tires are the ones that should concern you because you can turn them. The rear tires stay straight and if they don't rub just sitting there, it's unlikely that they'll rub when driving, especially with a conservative drop.

If you're going with 18x8 +35mm offset wheels and 235/40/18 tires, they won't rub.

The size of the tire is reported as "width/aspect ratio/rim diameter." Tire height is calculated by multiplying the width of the tire by its aspect ratio and adding the wheel diameter. To calculate the overall height of a 235/40/18, you would perform the following equation: 2(235mm X 0.40) + 18inches = tire height. Convert the mm to inches and add to 18. You'll get 25.4 inches.

Doing the same for the 235/45/17 factory tires, you'll get 25.33 inches. The difference of 0.07 inches is pretty small compared to the gap you'll have between the top of the tire and the fender.

[Mech_Mike412]

The front tires are the ones that should concern you because you can turn them. The rear tires stay straight and if they don't rub just sitting there, it's unlikely that they'll rub even with your car lowered.

If you're going with 18x8 +35mm offset wheels and 235/40/18 tires, they won't rub.

Tire height is calculated by multiplying the width of the tire by its aspect ratio and adding the wheel diameter. The size of the tire is reported as "width/aspect ratio/rim diameter." To calculate the overall height of a 235/40/18, you would perform the following equation: 2(235mm X 0.40) + 18inches = tire height. Convert the mm to inches and add to 18. You'll get 25.4 inches.

Doing the same for the 235/45/17 factory tires, you'll get 25.33 inches. The difference of 0.07 inches is pretty small compared to the gap you'll have between the top of the tire and the fender.

Okay. I understand what each measurement is, maybe not the equation though haha. The reason I was referring to running a narrower tire is so that the sidewall protrudes less giving more clearance for the wheel arch when the suspension is compressed. But if you say it's nothing to worry about, I won't worry about it haha

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[Mech_Mike412]

Update: went with the 235s and the fitment was perfect20180412_093714.jpeg

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