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[Noize]

I've noticed a couple of people running this size setup. I want to run these on stock rims:

Front: 225/40/18 (slight upsize)
Rear: 245/35/18 (OEM size)

Here's the calculated difference from the tire size calculator:

Tire Size Comparison
Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
225/40-18 3.5in 12.5in 25.1in 78.8in 804 0.0%
245/35-18 3.4in 12.4in 24.8in 77.8in 815 -1.3%
I want to run something more hardcore than the RE760s, but don't want to pay T1R prices to do so.

Since this is a RWD car, I'm assuming I can get away with the very minor difference without tripping the ABS light or any trouble codes.

At current Tirerack pricing, these would be $648, which is pretty sweet for tires this nice. Thoughts?

Thanks in advance!

[larryn]

Those tires would work, as would slightly upsizing the rears to 255/35/18 as well, to match the front upsize.

[Noize]

Originally Posted by larryn

Those tires would work, as would slightly upsizing the rears to 255/35/18 as well, to match the front upsize.

Unfortunately, XS do not come in 255/35/18. I know that the combination of 225 in the front and 255 in the rear works, I just wanted to make sure it would be o.k. to do 225 in the front and stay 245 in the rear and not get a trouble code.

[Gary@TireRack]

I agree with Larryn. This would be fine since the 255/35/18 is not an option.

Gill

[Noize]

Thanks guys!

Gill, I'll call you to order soon.

[ZIPNBYE]

Out of curiosity, how will the car interpret the front's rolling slower than the rears (as they're up-sized a tick) in regards to the ABS system (furthermore, on a Canadian car, the ABS system is used for the TPMS without the use of those silly wheel sensors)?

[Noize]

Originally Posted by ZIPNBYE

Out of curiosity, how will the car interpret the front's rolling slower than the rears (as they're up-sized a tick) in regards to the ABS system (furthermore, on a Canadian car, the ABS system is used for the TPMS without the use of those silly wheel sensors)?

I agree, this was kind of the whole point of my post.

There is a guy with this same tire setup in the wheel/tire/what works thread, though, and I didn't see any reported problems.

IMO, there is probably an acceptable margin of error that the system can accept. I guess I'll find out soon enough. :biggrin:

[ZIPNBYE]

For World market cars (excepting the US who have the silly wheel sensors thanks to Ford Exploders), I think that this would trigger a tire pressure warning, as the car may think that both rears are low (rolling faster than the fronts).

[larryn]

Richard, I'd have to respectfully disagree. You lose well over an inch of circumference on your tires, as the tread wears down.

Also, the difference in diameter from the stock 215/40/18 to a 225/40/18 is less than a third of an inch (.315", to be exact). We all know that tire tread is about 1/2"+. So, that means there can be an inch+ tire variance in diameter.

215/40/18 = 24.77" diameter
225/40/18 = 25.09" diameter

[ZIPNBYE]

Diameter isn't the true test...it's revs/mile or /km. True on the loss of tread over the life and potential differing replacement schedules F to R, but you're not sure either...unless you've tested it.

Remember that the rest of the world doesn't use the TPMS sensors in the wheels, but the ABS to sense if one or more tires is rolling faster (under inflated) in comparison to the others. I don't know the threshold for a warning to come up, but it can't be too much for 35-series tires, given that they don't have much of a sidewall to begin with.

[mikeo]

The worst case is it might require a reset of the passive TPMS. Go ahead and go with that setup.