WiffleballTony

Hi All,
I understand this has probably been discussed at length many times. However, after my extensive searchings of the interwebs I was unable to locate the answer to my question(s). So please be gentle.

I'm a novice, so bear with me. I purchased a 2012 GT and have consequently added some power mods to it. However at this point the car is overwhelming the stock wheels and tires the car came with 18x8 (235/50ZR18). As such I am looking to regain traction. I also wanted to change the wheels so I could fit bigger brakes and probably save some unsprung weight. I am leaning towards the Enkei PF01s. My initial idea was to go 255/45-18s up front and 285/40-18s in the back.

I plan on taking this car to the track in a few years (I do not currently), I also plan on doing some suspension upgrades in the future as well. So the question(s) are:
1) Understeer will be added by the increase of rear grip from the back tires. How bad will it be? Since I am also adding grip up front, wouldn't the overrall grip be better than what I have currently and thus be a net improvement in handling?
2) Am I future proofing myself by going big in the back if I plan on adding really big power adders ie twin turbos etc? Being able to put down the power better out of the turns?

Thanks for your time!

Fox Fader

Dang, no replies. I'm interested in some answers from the fiduciaries here.

danzcool

With the right suspension that will be way better than stock. I'm running 285/40 in the rear and 255/45 in the front, with the continental extreme contact DW, koni sport dampers, steeda sport springs, steeda hd strut mounts, and adjustable sways, I've had it fine tuned to be pretty neutral in the corners (at 500 HP). at the power level I've got now, I've just got to be gentle in the corners (with power oversteer on demand, lol).

So, by adding some wider rubber up front you've increased grip, by getting better damping all around you reduce the need for understeer, by increasing the negative camber (with caster camber plates or the steeda HD strut mounts) you basically can dial in as much grip as you need. With an adjustable sway bar you can dial in the lateral weight transfer and keep the car flatter.

Norm Peterson

It is entirely possible (and quite likely in this instance) to get an increase in lateral grip AND have the amount of understeer increase. In simple terms, you're still adding more grip at the rear than you are at the front; in slightly more advanced thinking, your rear slip angles will be reduced by more than the front slip angles, and this difference in slip angles will be with you at all cornering g's (not just the max-lateral-g point where one end or the other gives up and starts drifting wide).



With more tire back there you will have a little extra cushion against a careless right foot . . . unless you also re-balance your suspension for more neutral behavior generally.

"Careless right foot" here means you can expect it to be "trickier" to hold the car on the limit with the throttle without going beyond. You may find it easier to drive if, say, you intentionally use 4th instead of 3rd on corner exit, 5th instead of 4th, etc.

If you really get carried away with making big power it may not matter how much tire you put back there or what the suspension tuning is; you'd just be able to overpower it anyway without even trying.


Norm

WiffleballTony

Thanks for the replies guys, I appreciate the time to explain the answers to me. Cheers!