Pilot Sport 5

[Tatsu333]

Originally Posted by gen3v8

Doing the math the 18" tire is smaller but this calculator says otherwise. The difference is very little as you say.

https://www.willtheyfit.com/index.ph...h=8&offset2=48

I think you're missing part of the math...

The overall diameter is 2x sidewall height + wheel diameter, so while a 235/40 has a shorter sidewall than a 225/45, you need to add in another inch for the increased wheel diameter.

235/40R-18:

(235 * 0.4 * 2) + (18 * 25.4 mm per inch)

(188 mm total sidewall height) + (457.2 mm wheel diameter) = 645.2 mm overall diameter


225/45R-17:

(225 * 0.45 * 2) + (17 * 25.4 mm per inch)

(202.5 mm total sidewall height) + (431.8 mm wheel diameter) = 634.3 mm overall diameter


645.2 / 634.3 = 1.017, therefore the 18" combo is theoretically 1.7% taller.


Michelin's specs for another model of tire (Pilot Sport All Season 4) say 815 revs per mile for the 235/40R-18's and 833 revs per mile for the 225/45R-17's, which suggests a difference of slightly more than that - about 2.2%.

[gen3v8]

Originally Posted by Tatsu333

I think you're missing part of the math...

The overall diameter is 2x sidewall height + wheel diameter, so while a 235/40 has a shorter sidewall than a 225/45, you need to add in another inch for the increased wheel diameter.

235/40R-18:

(235 * 0.4 * 2) + (18 * 25.4 mm per inch)

(188 mm total sidewall height) + (457.2 mm wheel diameter) = 645.2 mm overall diameter


225/45R-17:

(225 * 0.45 * 2) + (17 * 25.4 mm per inch)

(202.5 mm total sidewall height) + (431.8 mm wheel diameter) = 634.3 mm overall diameter


645.2 / 634.3 = 1.017, therefore the 18" combo is theoretically 1.7% taller.


Michelin's specs for another model of tire (Pilot Sport All Season 4) say 815 revs per mile for the 235/40R-18's and 833 revs per mile for the 225/45R-17's, which suggests a difference of slightly more than that - about 2.2%.

Originally Posted by gen3v8

It certainly is not the diameter because the 235/40/18s are bigger. Even more so against worn 225/45/17s.

yep.oops

[CrowsFeast]

I see OP's comment about the claimed weights for each wheel (sometimes claimed weights don't match up with actual weights), but has anyone double checked the tire weight?

Also, it's not just about unsprung weight but also moment of inertia (related but not necessarily directly to wheel and tire weights). A significant reduction of tire weight will have a bigger difference to acceleration than weight close to the hub (axis of rotation). The new wheels, though the outer band is 1/2" further from the axis of rotation, may have a lighter outer band but more weight closer to the hub (leading to the proposed increase of ~2.5 lbs). This would also reduce the moment of inertia, leading to higher acceleration.

It may be that none of this has happened and there isn't actually any difference at all. I'm just thinking these are some possibilities.

[alphasaur]

Can't even find these tires in the us lol

[Tatsu333]

Different model of Michelin (Pilot Sport All Season 4) because TireRack doesn't list the Pilot Sport 5, but in that model, a 235/40R-18 is 24 pounds vs. a 225/45R-17 at 23 pounds, so heavier tires in addition to heavier wheels likely for the OP.

[ROFL it's Waffle]

Originally Posted by Sam86

I recently went from a 225/45/17 set of Pilot Sport 4 tyres on 17x7.5 wheels to 235/40/18 Pilot Sport 5 tyres on a 18x8 set of wheels. (For some reason the PS5 tyres were several $100 cheaper than the standard PS4 tyres of the same size?)

(blah blah blah....)

But yea, PS5 tyres on 18x8, significantly faster feeling of acceleration off the line, something I fully wasn’t expecting and am very pleased about. I don’t think it’s placebo at all. Even 3rd gear at 3K rpm it felt like sudden acceleration where as on the PS4’s, anything under 4-5K in 3rd was slow.

Interesting article on this topic .
https://www.tire-reviews.com/Article...ot-Sport-5.htm