JinDesu

iTrader: (2)

Trying to google tire sidewall information when I don't even know what to type in is difficult. What I'm trying to find out is how much is too much sidewall. Can anyone enlighten me? The stock sidewall on the 18" tire is 4". I've seen people use 245/40/18s and so on, which is a larger sidewall. Does the 0.3" additional sidewall really affect handling so much?

I would put this in the tire forum, but it seems to garner less replies than GD.

2tone

iTrader: (3)

i run 245/40, not sure but think it's a tad shorter than oem 225/45. oh well, i might be backwards. but yeah i'd like to know this too. i know it has to w/ the tire itself, b/c each manufacturer will have different sidewall stiffness/rigidity, regardless of the size of it.

NotAPreppie

225/45 is 1% taller than 245/40. 1% (or .3") is such a small change that it would be completely unnoticeable by a human without highly advanced measuring equipment and laboratory conditions. The make/model of tire you pick will make a more noticeable difference (different tires have different amounts of sidewall reinforcement). In this particular case, you would probably see an improvement in handling with the 245/40 because of the extra 20mm of tread on the ground.

Keep in mind also that tire section and sidewall height measurements from one manufacturer will not equal the same measurements from another. I saw a really interesting picture comparing two stacks of four tires with equal measurements but different manufacturers; one stack was several inches taller.

If you didn't try, how would you know?

JinDesu

iTrader: (2)

To the last point first, because I have a similar sort of thread which brought up the point. Unfortunately, with only 3 people posting in it, and one differing view from the other, it wasn't as conclusive for me.

I apologize for a mistake. I meant to say 245/45, not 245/40. 245/40 is 98mm sidewall, while 245/45 (which I want to get) is 110.25mm. The difference from 245/40 to stock is 0.1 inch, while the difference from 245/45 is 0.3 inch. However, my question still stands, and I appreciate your answer. I'm guessing if I select a tire with sturdy sidewalls, it would both improve ride comfort, protection of the rims, and still maintain very very similar handling. Do you agree?

NotAPreppie

Stiffer sidewalls generally lead to a stiffer ride. The tires are another suspension component and the stiffer you make them the more motion will be transmitted.

I can tell the difference between my winter tires (Nokian WR G2 in 225/50/17) versus my summers (OE Bridgestone Potenza RE040 in 225/45/18) though it's not enough that my wife notices. I can REALLY tell the difference with my race tires (Kumho Ecsta V710's in 245/35/18) but those have an incredibly reinforced sidewall and are a bit shorter.

That said, the rest are arguably true. All other things being equal (price, make/model, etc) I'd go with 245/40/18 for the extra width.

Georgia8er

A stiffer sidewall will result in less ride comfort, usually. Like NotAPreppie said there are a lot of other factors, especially between manufacturers, that could result in better or poorer in all of the categories you mention. If you want better handling, you're probably going to lose some ride comfort, especially when it comes to road noise.

I keep hearing about curb rash, but in all my years of driving I have only ran a rim against a curb once, and that was an emergency lane change. The tires with extra material to help with curbing aren't a bad idea, though.

rev29k

Like said, sidewall height is not as much as a factor as the stiffness of a sidewall. If you want a better handling, you will want stiffer sidewalls (one of the reasons race tires handle so well). If you want a smoother ride, you will want softer sidewalls. Another point to look at that thickness of sidewalls doesn't contribute much, look at a Formula 1 car's sidewall, it is a lot taller than what is on most sports cars, so sidewall height doesn't have much effect on handling characteristics, the stiffness has more of an effect.

JinDesu

iTrader: (2)

My situation is a little different. I'm aiming to use 17" wheels when I have the money to go aftermarket. I would be using 245/45/17s to get as close to my stock wheel diameter (26.3" vs 25.8"). By doing so, I'm introducing 0.3" more sidewall, which supposedly would reduce handling as it allows for greater sidewall flex. Now, if I were to choose a good tire (i.e. Potenza RE-11) with good sidewall rigidity, wouldn't that eliminate the handling issue? Also, with that additional 0.3" sidewall, I would protect my wheels a bit better.

rev29k

Yes, if you were to get a good tire with a stiff sidewall, you would be fine.

Just wondering though, why the RE-11? Are you going to auto-x/track your 8? If not, I wouldn't recommend the RE-11 as yes, it is an amazing tire (I am currently racing on RE-01R's), but they will last under 10k miles and thus aren't that great for just driving around on the street where you will never be able to experience their full potential. The only place you will be able to use all the grip they offer is at auto-x or at the track.

Georgia8er

You wouldn't be able to notice the handling difference from the overall diameter being .3" more, assuming everything else is the same. New/different tires will make the difference.

JinDesu

iTrader: (2)

That was like the first thing off my head with good sidewalls that I've read up on.

rev29k

If you want good grip in a tire that will last a little longer than 15k miles, look at the Bridgestone RE050A Pole Positions. Or even just the regular RE050A's would be fine for the street too. I have two seasons of auto-x and two track days on my previous set of Pole Positions and they still have a bit of tread left. Most tires are shot after just two track days.

JinDesu

iTrader: (2)

I was looking at the RE050A, but some reviewers said it has soft sidewalls. I'm looking more at the RE760 as it has a higher tread rating, and no one's complained about the sidewall.

My ultimate desire from my tires is a good combination of dry and wet traction. My stock 8090 Sports let me down in the rain, and are bumpy as heck. However, this is a little off topic =pp

CarAndDriver

Either of the two OEM stock tires are crap. Bridgestone worse than the Dunlops.

Have you checked out the User Surveys on Tirerack.com?