I need to replace my fronts to Potenza RE960AS, my fronts has 0% left. But my rear tires still has around 45% left, so I won't be changing them yet.

Don't ask me how that is happening, I don't know why.

Anyway, I heard mixing brands is bad for the VDC, but how bad? Can I get away with mixing the RE960 with my stocks PS on the rear?

 

No, you'll be fine, as long as you get the right sizes. I've run many different "mixed" setups front/rear, and no issues with VDC or anything at all.

 

Normally I'd agree, but I found that to not be true, with the case of the Pilot Sports and RE960AS....

In my case, I had new RE960AS on my rears, and Pilot Sport A/S on the front, which still had 8/32" tread left.

My VDC kept flipping out whenever I took mild sweepers. I had to bite the bullet and get new RE960AS for the fronts as well...

I'm not sure why the VDC was flipping out, as I replaced the tires with the same size...

I did notice that the RE960 are ever so slightly taller, as I think according to tire-rack specs, the 275/40-18 I'm running are 1/10" bigger than the Pilot Sports in the same size.

They feel like they have the same amount of grip, as I can still toss the car around pretty good... I would think it can't be grip differences, because the VDC was flipping out when I wasn't even going that fast, like 40mph on a sweeping turn that I normally take at 70+.

 

I even had problems with my VDC when i only changed the rear tires. The car felt better traction in the rear and the VDC kicked on everytime i went around a aharp turn.

 

This is definetly a car specific problem. The VDC system can't tell you have different tires, it only senses slip and adjusts accordingly, so each specific pairing of tires may cause slipping or not, depending on brand, wear, camber settings etc. My suggestion would be to try and get the same brand tire, but be ready to change out all 4 if the VDC starts giving you trouble