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What's the benefit of upsizing to 245? If the improvement is minimum I'd rather stick with factory spec 235 for the peace of mind. Also I believe 245 might be a little wide for 8 inch rim.
245/45R18 tires offer a little more road contact and a tiny increase in sidewall compared to OE 235 size. 245/45R18 tires are approved to be mounted on 7.5" - 9" wide wheels.
What's the benefit of upsizing to 245? If the improvement is minimum I'd rather stick with factory spec 235 for the peace of mind. Also I believe 245 might be a little wide for 8 inch rim.
Traction and appearance. More rubber on the road means stickier on turns. I also like the look of a wider tire.
Has anyone who contends with snow tried upsizing to 255/40 18 all-seasons? I know that a great deal depends on which tire and tread I choose. What I'd like to know is if one were to compare two tires that only differ in that one was a 235 and the other a 255, how much of a difference would it make in one's traction. I expect there to be some difference and I am prepared to drive more sensibly in snowy conditions, but will this thing turn into a sled with those extra two centimeters of width? FYI- I have a 2013 AWD non-F sport with the winter package. Thanks.
I lived in Boston for 8 years and it won't make that drastic of a difference, especially with AWD. That being said, I'd highly recommend getting a set of snow wheels/tires for the winter months. That may be the singularly best automotive purchase I've ever made.
I would argue 235 vs 245 is mostly just a personal preference.
The trade-off between these two are minor, and I guess, even under a strictly A/B testing, the difference would wane just after a few miles.
If we want to split hairs, here's the trade-offs that I can think of:
Traction: 245 has a small advantage.
Comfort: 245 should be a little better due to higher sidewall.
Fuel milage: 235 may be the winner because of marginally smaller contact area, some may argue 245 has better highway mileage because of practically higher gearing in the tallest gear.
Agility: maybe 235 because the sideway doesn't bulge as much as 245. Usually a wide tire/narrow rim combo would lead to imprecise handling, but the difference should be very minor here because both 235 and 245 accept 8 inch rim.
Odometer: 235 wins but again 245 would only be off by a little.
Acceleration: 235 wins because of shorter gearing and lower rotational mass.
Hydroplaning: 235 wins because of smaller contact patch.
Snow driving: 235 wins because narrower contact patch, it is easier to cut through snow.
Cost: 235 may be slightly cheaper due to smaller size. This may mostly depend on availability and brand.
At the end, the factory chose 235 for a reason, and I think it represents the optimal choice for typical consumers in terms of performance and cost. Plus maybe the suspension is tuned with 235 in mind. A small deviation is fine and it may be beneficial under certain circumstance. Just do not think it as an improvement on all fronts.
Last edited by terrryz; 03-27-19 at 04:27 PM.
Reason: grammar
I just put in a set of Falken Azenis and very happy with it. My car comes with 19 inch rim so I have 245 ( up from 235) , and 265 on rear. The difference in ride comfort is night and day compared to Bridgestone and Michellin that I had before. The ride is more quiet by 20% -30% going through bumps I don't feel like my car making a loud bang inside the cabin. Overall ,I am very happy. I am from Houston so the road here are either wet or dry condition.
Let us know how the Falkens wear... in the mid 2000's I went through 3 sets back to back, got about 18K per set. Got tired of buying tires almost every year, so switched to Goodyears. Paid about 30% more but easily got double the mileage. Never tried Falkens again.
But tech improves, so I'd be interested in how these new Falkens perform.
Comfort: 245 should be a little better due to higher sidewall.
The 245/45R18's have a slightly tallersidewall - which should aid comfort.
However the slightly wider tread width of 245 mm would also diminish ride comfort, as the wider the tread, the more comfort decreases!
You would have to test drive a 235/45R18 and 245/45R18 back to back yourself in order to determine if there is any gain in ride comfort and noise.
Imagine you have two 18" rims, but the first set is 8" wide, while the 2nd set is 9" wide, and you fit 235/45R18 to the 18"x 8", while 265/45R18 is fitted to the 18"x 9" wide rims?
In this case, don't forget the impact of the extra unsprung mass of the wider 18"x 9" rims & tires on the unsprung mass of the wheel-tires.
After impact with a bump, the heavier the unsprung mass, the greater the momentum is imparted onto the body of the motor vehicle - for diminished ride comfort.
Also, the heavier the unsprung mass of the wheels/tires, the more diminished the acceleration, braking, and more skittering over bumpy corners as the heavier wheel/tire combo is only able to track bumpy corners with a lower frequency of vertical oscillations.
Below, as rim diameter & width becomes larger, the unsprung mass of the wheel/tire combo & the friction increases, so maximum acceleration diminishes.
At high speeds, the extra frontal surface area of the wider wheel/tire combo will result in more wind resistance too.
Finally, don't forget the significance of the change in suspension geometry like the changes to positive scrub radius as you upsize from OEM 235/45R18 to 245/45R18.
With a zero scrub radius, the tire rotates about a central axis that is located at the center of the tread.
With a positive or negative scrub radius, the entire tread rotates about a central axis that is located offset from the center of the tread - making the steering heavier via more srubbing of the tread, and more tire wear etc.
I appreciate all of this input. There's a lot to consider. The bottom line, I suppose, is that changing from the OE size is a modification, and as with any mod, you're changing something about the way that the car was intended to operate. I'm okay with that up to a point. My only current mod is tinted windows and even for that, I had to give up one thing to gain another. At least with all of this information, whether or not I modify my tire size will be a fully conscious choice. Thanks to all for helpful info and advice.
03-26-19, 10:09 AM
