Hi guys, I'm suffering from conflicting info.............
After 8wks of waiting I've finally received my WORK GS1 20 x 9.5 +22 & 20 x 10.5 +22. My looking to fit Falken 255/30/20 on the front and 285/30/20 on the rear. These sizes match the stock tyres in aspect ratio to within 0.2% as per the Miata tyre size calculator. Just about every tyre shop I call argues with me that I need a 35 series up front to keep the tyre walls close to the same, thus rolling diameter is similar front and back. According to the tyre calculator this puts the fronts out by 4.1% over stock. Will this mess with my VDC and should I be puttin' my foot down and sticking to those sizes I've researched OR just go with the flow and listen to the tyre guys, after all they are the proffesionals!!!?

 

bump, need an answer guys, I'm buying rubber in the week

 

I'd stick with the 255/30 and 285/30 combo. The 255/35 tire will be taller than your 285/30 rear tire which isn't a good recipe for the VDC.