Tire size and handling

I know choosing different tire widths can change a way a car handles but by how much?

Im buying wheels that are 18x9 and I have 3 different tire setups I'm contemplating.  Car is a 2013 e550 coupe RWD.

245/40 front 275/35 rear

265/35 front and rear

265/35 front 275/35 rear

Thanks for any input.

Wider generally means more grip but by increasing grip you could expose new handling problems...I would go with the 265/35 front and rear setup for low cost/ease of rotation, staggered setups are a pain.

What are the wheels? If the wheels are sized for the first setup, adding more front tire is likely to change the feel more than actual performance, and not in the positive direction.

GameboyRMH said:

staggered setups are a pain.

this

In reply to GameboyRMH :

Thanks. I'm leaning towards that too for the ease of rotatio 

In reply to ProDarwin :

Yes they are, but my car and may Mercedes comes that way. Pretty much any v8 comes that way lol. I'm also leaning towards the square setup 

dps214 said:

What are the wheels? If the wheels are sized for the first setup, adding more front tire is likely to change the feel more than actual performance, and not in the positive direction.

Wheels are 18x9 so all 3 setups should be able to fit. So you're leaning on the first setup?

If the car comes with a staggered setup that's wider on the rear and you switch to a square setup, that will shift the handling balance toward oversteer, whether that's a good thing or not depends on how the car handles currently.

MercedesE550 said:

dps214 said:

What are the wheels? If the wheels are sized for the first setup, adding more front tire is likely to change the feel more than actual performance, and not in the positive direction.

Wheels are 18x9 so all 3 setups should be able to fit. So you're leaning on the first setup?

No if the wheels are all the same size I'd go with 265s all around. Actually I'd probably want 255s if that's an option. I was saying if the front wheels were narrower than you probably wouldn't see much of a benefit from stuffing more tire on them. If the wheels are the same size I don't see any reason to run staggered tires, it just makes things look weird and hinders tire rotation. It's just a matter of which size to use then.

Good reasons to run a staggered setup are to squeeze the last morsel of performance out of the car as you reach the packaging limits of wheel size, or to get an extra spare for OLOA

Looks, handling performance or cruising comfort?   Square setup, after that I would say 265 will still be a bit wide for a 9” rim for performance, turn in may be squishy instead of crisp.   If you don’t care about that still no wider than 275 or they will look ballooned it looks are a concern.  I currently have 255 F 285 R on 9.5” rims, next round will be 265 or 275 square.  255s look too stretched for my liking but correct and I want to be able to rotate them, 285s look too ballooned and I have adjustable sway bars front and rear to adjust for what this change may do to my handling.

So what are your expectations of these tires?

FWIW, I think staggered tire sizes on square wheels is just a dumb thing to do.  Especially if it's more than, say, a 10mm stagger to fit the maximum possible tire under the car or something. 

I don't think 265/35R18 on an 18x9 would be squeezed, here are 245/40R18s on 18x8s, on paper this is an ideal fit, although a slight stretch is good for performance:

Handling means different things to different people. Street handling, track handling, etc?  For a street sports car I'll almost always tend towards lighter unsprung weight, even at the expense of grip. For true performance driving or competition, different math. 

Aspect ratio and the specific tire in question all impact how well the tires fit on the wheels. 

Out of the sets I have for the E38, the 235/50 on 18x8 winter setup looks a little bulgy, but some of that may be the sidewall shape of those tires.  They'd probably fit better on 8.5s, although the tread might look a little narrow at that point.  The summer setup is 255/45 on 18x9 (pretty much a perfect fit, any narrower a tire would be stretched) and 275/40 on 18x9.5 (good fit, maybe a hair on the chunky side, but not bulgy).  The stock rear setup was 255/45 on 18x9.5, which definitely looked stretched.  Those perceptions match with the relative wheel and tire widths as expected.  For the 235/50 on 18x8, there are 29.375mm of tire per inch of wheel.  For the 255/45 on 18x9 it's 28.33mm per inch, and for the 275/40 on 18x9.5 it's 28.95mm per inch. 

ShinnyGroove (Forum Supporter) said:

Handling means different things to different people. Street handling, track handling, etc?  For a street sports car I'll almost always tend towards lighter unsprung weight, even at the expense of grip. For true performance driving or competition, different math. 

Yes that would be my next comment, what's the use case? The tires in question also make a difference as sizes are guidelines, not hard numbers. For normal street tires 265s on a 9" wheel are fine though 255s might still be better. For something like 200tw tires that tend to run wide it's starting to get a bit pinched. As much as I still think it's dumb, for something like autocross where all that really matters is the time on the clock, there is justification to just stuffing as much tire on the wheel as possible. It'll be a tiny bit faster at the expense of feel and uneven tire wear. But for normal street driving where all that matters is your enjoyment, the upside of stopwatch performance goes away and you're just left with the downsides. In that situation you're better off just sizing the tire to the wheel and being done with it.

Basically it will be a street only setup. Something aggressive for spirited driving. But since you guys are saying 265 should be max on a 9" wheels, then 275 is out of the picture. So that removes option 1 and 3. So 265 squared it is. The tires I'll be getting are general Gmax RS, A good all around tire.

dps214 said:

ShinnyGroove (Forum Supporter) said:

Handling means different things to different people. Street handling, track handling, etc?  For a street sports car I'll almost always tend towards lighter unsprung weight, even at the expense of grip. For true performance driving or competition, different math. 

Yes that would be my next comment, what's the use case? The tires in question also make a difference as sizes are guidelines, not hard numbers. For normal street tires 265s on a 9" wheel are fine though 255s might still be better. For something like 200tw tires that tend to run wide it's starting to get a bit pinched. As much as I still think it's dumb, for something like autocross where all that really matters is the time on the clock, there is justification to just stuffing as much tire on the wheel as possible. It'll be a tiny bit faster at the expense of feel and uneven tire wear. But for normal street driving where all that matters is your enjoyment, the upside of stopwatch performance goes away and you're just left with the downsides. In that situation you're better off just sizing the tire to the wheel and being done with it.

"In that situation you're better off just sizing the tire to the wheel and being done with it."

well that's the thing, in a 9" wheel you can safely go from 235 to 275 according to tirerack.

GameboyRMH said:

I don't think 265/35R18 on an 18x9 would be squeezed, here are 245/40R18s on 18x8s, on paper this is an ideal fit, although a slight stretch is good for performance:

What is amusing is that looks more stretched than the 235/40s I used to have on my car's stock 18x8 wheels.

For summer tires I did a -1 to 235/45s on 17x8s and couldn't be happier with the results.  Better everything: looks, turn-in, ride quality.

MercedesE550 said:

well that's the thing, in a 9" wheel you can safely go from 235 to 275 according to tirerack.

 

And I've seen 285s mounted on 17x7 wheels and I used to have 295/50s mounted on 6" wheels.

There's "safely", there's "possible", and there's "best performance".

"Best performance" is also a bit vague.  Are you concerned about handling or maximum lateral grip?  The two are not always the same and are sometimes at odds with each other.

I've been really happy with the Firestone Indy 500 for a performance daily.  Great wet and dry behavior.  Apparently the are a rebranded swanky Continental.

For a spirited daily, in a less powerful car,  I'd consider going with 245 square. That's the "right" size for 9" wheels and may or may not be a bit cheaper. Narrower means less sidewall flex, and may feel slightly more nimble. Because your car is fairly powerful/torquey the right answer may be a bit wider.

84FSP said:

I've been really happy with the Firestone Indy 500 for a performance daily.  Great wet and dry behavior.  Apparently the are a rebranded swanky Continental.

I like them too, they have a nice feel. I I would say the wet performance is better than expected. They're an older Bridgestone (parent company) design.

For a daily, I would make sure the tire includes some rim protection, or aim for a bit on the wider side.  Signed, someone who parallel parks frequently.

Snrub said:

For a spirited daily, in a less powerful car,  I'd consider going with 245 square. That's the "right" size for 9" wheels and may or may not be a bit cheaper. Narrower means less sidewall flex, and may feel slightly more nimble. Because your car is fairly powerful/torquey the right answer may be a bit wider.

Kind of. For performance tires that tend to run wide and have lots of grip, sure. But for normal summer tires that are more true to size, at least 255s are fine. And like you said for that car I'd definitely be erring on the side of too much tire, just not going crazy with it. I'd take whichever of the 255/265 options is a better match to the stock diameter...or if one is way cheap I'd go with that.