jlutherva

Aside from the DIC message, it this going to cause other track issues such as reduced performance, ABS issues, active handling issues in Comp Mode, etc?

I going to be running R6 Hoosiers 315/30-18 (F) 25.6" dia and 335/30-18 (R) also 25.6" dia. so the ratio of diameters is 1.00 as opposed to 0.959 for the OEM tires.

Jim

JDIllon

Just my .02 but I think you will have problems. I'm running 315-30/18s up front and 345-35/18s rear with no problems. And with the 710s I run 305s and 345s. Can't say for sure, I have never run that set up. But I think the rear is going to be to small for the cars systems. JD

jlutherva

Lat year I ran 295/30-18 (F), 345/35-19 (R), ratio = 0.944 at Road Atlanta and got the DIC Drag message but did not notice any performance changes.

I might have a pair of 318/30-18 R6's for sale at the NCM VIR event!

Jim

Bill Dearborn

Jim,
1 to 1 shouldn't do anything except to Traction Control. Active Handling is a yaw control feature of the ABS and is triggered by the results of a complex algorithm that uses steering sensor and yaw/lateral G sensor outputs to determine if the car is responding properly to the driver's steering inputs. Wheel speeds are not used in that computation but may be used in determining how long to apply a certain brake to correct a yaw error. However, just changing the rubber compound affects that calibration and the system would still know if a wheel is locking up (0 reading from sensor so should be able to compensate for differences within a certain range) so it would be hard to know which has the greater affect and how much that affect would be. You will not get a drag control message since the ratio of the rear to front tire diameter isn't greater than the stock ratio.

As long as the tires give you better turning response AH will not be triggered so you don't have to worry about that until you exceed the wider calibration settings used in Comp Mode and AH attempts to change the yaw of the car. I doubt you will notice much difference in how it responds when it does since it will automatically see the change in yaw is too much or too little and compensate. The system could be slightly more erratic (correction/overcorrection/undercorrection, etc) in its response due to the tire compound and size differences but I think the response will be more like a system that is slightly over damped (greater tire grip) Vs one that is underdamped and inherently unstable.

Last year I ran 305/35/18 R888s on the front and 335/30/18s on the rear of my car. That made the front tires slightly larger in diameter than the rear tires. TC was upset as the car speed got above 10 or 15 mph and I had to turn it off to just get off of pit lane. I usually turn everything off when I leave the garage so I really didn't try it in Comp Mode.

Go ahead with the tires and just remember to turn off TC at the minimum. With a 1 to 1 ration you might not feel a TC response until your speed is in the 70 to 80 mph range.

Not sure why you chose that size for the rear but most of the hot shoes I know run the Hoosier 315 front with the 345 rear on 18x11 and 18x13 rims. That keeps the nannies happy if you forget to turn them off but also provides more grip in the rear for coming off the corners harder.

Bill

jlutherva

Bill,
Thanks for detailed explanation. I'll sell the 335/30-18 R6 rear tires and replace them with 345/35-18. Paired up with the 315/30-18 fronts, that gives a F/R ratio of 0.955, very close to the OEM ratio of 0.958, then I don't have to worry about the Traction Control issues.

For future purchases, I think I'll do this math before I buy!


Jim

dfinke23

I am starting to hate several things about mine, and TC/TPMS/AH/BS is at the top of the list.

0Anthony @ LGMotorsports

We have done it before, but I have never left any of the driver's aids on to do it....I don't think the computer would be to happy if you did.

But as for running the same height tire on the car that is fine, might have to adjust ride height to keep chassis rake in place, depending on what you do with the tires.