im trying to cure a bit of understeer(stock tire sizes on stock wheels), and im probably gonna be needing some tires by december/january.
was thinking that maybe going to 225's up front maybe be benificial, but im worried if it'll cause excessive oversteer.
does anyone have experience with running these or similar tire sizes?

thanks,
vance.

 

Going from 215 fronts to 225 fronts will not cause your car to go from "a bit of understeer" to "excessive oversteer".

That said, when are you getting "a bit of understeer"? Any under or oversteer in any production s2000 with reasonable alignment settings is going to be 90% due to driver inputs. Well-balanced and responsive cars are supposed to tend toward oversteer on the brakes or lifting off the throttle and tend toward understeer under power (up to the point where power-on oversteer due to impending wheelspin is a factor, which in a stock S2k shouldn't even happen in anything but 1st gear).

Also, 225/45-17 fronts on 17x7s will be taller and will bulge out more than 245/40-17 rears on 17x8.5s, giving a big fronts/little rears look that may or may not bother you. Most who run 225 fronts run 255 rears.

 

In my experience, the best staggered setup for stock rims is either 235/40F 255/40R or 245/40F 275/40R.

Your other option is to invest in a non-staggered setup (I'd suggest Tire Rack C3s or 949 6ULRs) and a front swaybar. Your total cost will likely be $1500-2000 more than wider tires alone, but worthwhile for serious competitive driving.

 

im getting understeer mid corner and even exit (unless I stomp gas)
im not an awesome driver or anything but it just seems like my fronts tend to give way before the rears.
ill be getting an alignment too, but after the tires get on

and 245/275 might be a bit tooooo big for me

 

Reread (or read for the first time!) my post above. Here is the pertinent part:
Well-balanced and responsive cars are supposed to tend toward oversteer on the brakes or lifting off the throttle and tend toward understeer under power (up to the point where power-on oversteer due to impending wheelspin is a factor, which in a stock S2k shouldn't even happen in anything but 1st gear).

Once more: getting on the gas induces understeer. This is NORMAL. You need to modify your line so that your turn radius opens up as you are adding speed after apex, also taking into account that the act of accelerating reduces front end grip.

What alignment specs? If a stock car, for reduced understeer you could have them maximize front camber (should get you in the -1 to -1.5 degree range), with -1.5 to -2deg rear camber, zero front toe, 0.2deg total rear toe in.

Alignment settings and driving technique will have a more profound effect on under/oversteer than 215 vs. 225 fronts will.

 

If I may politely disagree, I switched from a 225/245 setup to a 215/245 setup, and found that the car displayed much more persistent understeer despite a more aggressive alignment and a modification of driving habits. IMHO anything less than 225 width in front is too narrow for the S2000.

I'd also disagree that wash-out understeer under power is a trait of a well-balanced car. In an ideally balanced setup, you should be able to exit every corner in a slight four-wheel drift at neutral steer (0* of steering input).

 

I have 225 up front, 255 in the rear Dunlop Star Specs. LOVE them.

 

Will furthr address flick's comments later, short version:
I've driven on 205/225, 205/245, and 225/245 16s and handling balance isn't affected with modest stagger changes, in my experience at the track.
Regarding understeer on the throttle, this will not happen to any seriously troublesome degree if driving technique is remotely near correct. That was my point. If you're lollygagging in a corner and decide to get on the gas, this flat WILL induce understeer unless you're in the powerband in first or otherwise have enough torque to break the tires loose.

On the gas unloads the front tires, taking away front grip. Proper line and technique take this into account.

 

If you are cornering with zero steering input, you're most likely not fully utilizing grip available at the front and overworking the rears. Been there with the z,and while it was great fun,after I adjusted sway bars to use the outside front more and relieve the outside rear a bit went nearly a second faster at nhis.

 

I didn't say cornering with zero input, i said exiting on neutral steer. You should be winding off steering lock as soon as you pass the apex.