Originally Posted by VVG
By going to a 255/35 tire, you are increasing the front tire diameter by 7mm compared to stock. By going to a 285/30 tire, you are decreasing the rear tire diameter by 14mm compared to stock. That is a 21mm F/R diameter differential change and will affect how your DSC functions to a small degree.
I am staying with the stock 245/35 front size and going to a 285/30 rear. This will give identical F/R tire diameters. I am running 12.5mm spacers on the front and this should offset any increase in understeer caused by increasing the rear tire width while keeping the front the same.
This is on ZCP wheels.
This is true, but you really need to look at the specs for the actual tire you are going to be using. Some tires have pretty large section widths and others aren't that bad relative to the increase in tread width, which can affect whether you're going to rub or not. I'm currently running 255/35 front and 285/35 and I have a bit less than 1" difference in tire diameter between front and rear (RE-11). I think there may be theoretical reasons why the DSC might have it's function affected, but I put 4 and 1/4 track days on this set up (sequential) and I found no effect whatsoever on MDM activation or intervention compared to stock sizes, so I would expect DSC to be similarly affected. Perhaps there might be a few percent difference in activation, but it's not detectable by me.