Will 315/30-18 cause AH/TC problems?

ajderzie · 08-28-2006, 03:13 PM

I'm looking to go to 275/40-17 F and 315/30-18 R. Will these work and not cause any active handling issues? The hight for the rears are 25.5" which is over an inch less than the stock 26.7" The fronts are the same diameter (25.7 vs. 25.6). The other option is to drop the fronts to 245/40-17 which has a diameter of 24.7.

Is the AC the same on the z06 vs. coupe? I have the coupe btw. Can the active handling be recalibrated for different sizes?

Thanks.

Too Tall Bob · 08-30-2006, 09:29 AM

Not sure about how those sizes will affect the AH, but I tried experimenting with 295/35x18's on all four corners of my Z06 track car and I forgot to turn off the AH before I went out, and I smoked the rear pads in 3 laps. It took me a lap or two to figure out why it was handling so strange....the AH was left on.

So, I guess that means that the AH was reading that the rear tires were spinning at the same speed as the fronts were and it was trying to slow them down by applying the rear brakes.

Not sure about re-calibrating as I don't use AH anyway.

ajderzie · 08-30-2006, 10:12 AM

Thanks for the reply. I'm leaning towards toyo ra1s. They would thus have to be 275/40-17 and 305/35-18. I think the overall diameters are closer to stock with this combo. Does this sound more reasonable for a roadcourse setup?

Too Tall Bob · 08-30-2006, 12:01 PM

Ironically, when I measured my Toyo RA1's 305x18's against the Kumho 710 315x18"s, they are identical in width.

Now, about my experience with the RA1's: I know that there will be some who just love the Toyo's and have used them for years, but for me, I will never use them again. I will always have Kumho 710's on my car from now on. I have worn out about 4 sets of RA1's in the last year or so, and they just don't give me the kind of confidence at the limit that the Kumho's do. The RA1's just seem to let loose suddenly without too much warning when right at the limit....high speed and low speed corners. I just know that I have NEVER spun or lost control of my car with the 710's. Even when just past the limit of traction, they seem to find a way to "save" me...very confidence-inspiring!! (I had a very high-speed spin going into turn one at Miller Motorsports Park last Saturday after a 148 mph straight when the back end just let loose and came around on me while using the RA1's. Even my street tires have never done that to me before!)

If you do choose to run the Toyo's, run as much Neg. camber as possible, and use 275's up front and the 305's in back to maintain a little understeer. I'd rather have it understeer than oversteer with those tires. Just my opinion.....

UstaB-GS549 · 08-30-2006, 07:01 PM

I normally run 275/40-17 fronts and 315/35-17 rears on the track. The Victoracer rears are 25.3" O.D. and the V710 rears are 25.4"

I can't see anything different about how ABS/TC/AHC feels or operates with this combination.

I currently have 315 Goodyears on the front 9.5" rims which are probably taller than the rears because the rear rims are 11" wide. Again everything worked fine driving to Blackhawk and running on the track.