I used to run 235/255 front to rear. There were no fitment issues, and frankly, I like my rubber sticking out well past my outer rim. Curbing wheels is stupid and unnecessary. LOL. But it was a bit edgy and sometimes squirrely. Next set I went bigger. 245/265. And I did this on Ventus V12 evos. Comfy to be sure, but not track worthy, almost scary in some rain or on twisty downhills. But yeah, a mild upsize is feasible.

However, you need to be extra mindful of soft sidewalls. You'll definitely increase tire roll regardless of the tire selection. You could be inducing an additional .5" to 1" of slop side to side, in addition to increasing peak lateral loads on the bead. not ideal. Think of it like a ski boat doubling back and suddenly snapping the rope on an innertuber. A small amount of tire stretch is recommended for performance applications because the tire roll/the load transfer is shorter in distance and time.

So, stay away from the Hankooks and earlier Continentals. They both have gooey comfort-built sidewalls and behave poorly when not under minimal stretch.

Oh, and there's another one for you. You're going to lose some comfort due to the stiffer sidewalls you'll need. Keep that in mind.

 

Thanks for the reply. I really appreciate the detailed response.

Given what you said, would you recommend me getting the extra load (XL) version of the Michelin Pilot Sport 4S if I went with 235/255 in order to reduce tire roll? Also, overall, do you thing it was worth the comfort reduction and tire roll to get that bit of extra grip?

 

On the XL, I don't think that will help the sidewall roll as much as it will increase ride harshness. I could be wrong. Also you'll be taking a substantial weight penalty and if the whole tire is more rigid, you'll effectively be reducing your contact patch over the regular version. Personally, I think the regular 4S Michelins(an excellent tire, btw)will bridge the gap best. Budget version would be a Firestone FireHawk Indy 500. Also, 10mm probably isn't enough to even notice outside of a road course. You should be fine.

Sorry to be vague on the 'feel' questions, but it's all totally up to preference. Do you have any experience going back and forth on the same chassis with different sidewall stiffness or ratio? If not, this is as good a time as any to experiment - see where your personal preferences lie.

My car is on 255 and 275 at 35 sidewall ratio. Wheels are 9.5" front and 10" rear. Most older people who ride with me say it's too harsh. But most of my buddie's cars are much harder than mine. I'm on the middle setting for compression on my BC 2ways with their standard rate springs. I'm mentioning all this not to give you a baseline, but to convey all the factors that go into ride quality.

My experience is likely to be so very different from yours based on measurable data AND individual perception that it's effectively useless until we take a ride in one another's cars.

In short, I can only tell you what will happen/what should result from your proposed changes; not how you'll feel about it. My personal opinion is to go as hard as seems logical/affordable, then dial it back or up once you have a feel for things.

 

Thanks for all the information Odelagt! I ended up going with the 235/40/19XL and 255/40/19XL. I couldn't find the a non-XL version anywhere so they either don't make them regular weight load for those sizes or they just don't have any stock. I couldn't really afford to wait since I'm on a spare right now (one tire was losing air right before I stored it at the beginning of winter) and really need new tires. They should be arriving this week so I'll try to update on my overall impression after a few test drives!

 

Oh, bummer. Well, the 4S is an excellent tire, I'm sure other than your wallet you'll be happy.