I decided on this size because I already had 2 brand new tires laying around that I had obtained in a parts trade. They're really nice tires (Potenzas). So I bought 2 more Potenzas of the same size and brand and had them installed. I wasn't worried about the tire width difference. I don't think anybody on this site would notice a width difference of 10 mm (1 cm). I do like the lower stance and I get better handling with the shorter 50 series sidewall. I also have effectively changed my final drive ratio so I get better acceleration. When you change axle ratio or tire size you're speedometer won't be off by the same mph throughout the entire range. It will be off by a percentage. So in my case if you take the needle off the speedometer and then put it back on so that it reads correct at 60, it won't read right above or below that speed. Besides my odometer would still be off by 8% too. My speedometer (and odometer) read 8% high because the circumference of my new tires is 8% greater than the old tires. I don't have a digital dash so I don't see how a chip is going to help me. My speedometer is cable driven right? So I have to slow the cable down 8%. I've only owned Mopars until now. I've owned cars built between '63 and '98. In those cars you change the speedometer pinion gear out to one with more or less teeth to correct for different final gear ratios or tire sizes. They're only about $5. I just assumed when I changed tire sizes that I'd just go down to the Ford dealer afterwards and order the correct speedometer pinion gear. Well they tell me they don't make gears with different teeth counts. I can have a speedometer shop install a reducer in my cable so that my speedometer and odometer read correctly but that's going to cost about $135. And then the speed sensor will still be reading 8% higher so the speed limiter will kick in at 101 mph instead of 110 mph. I was hoping that maybe the Ford dealership was giving me wrong information and somebody on here might be able to tell me who sells speedometer pinion gears or if you can even do that with a Ford. Are all Contours that come with the manual transmission built with the same final drive ratio and tire diameters? If they aren't then how does Ford get the speedometer and odometer to read correctly on their cars with cable-driven speedometers?
