Contour Enthusiasts Group Archives Forums Modifications Wheels & Tires How do I correct speedometer reading???

Sorry guys. I've never owned a Ford product before. I've got a '97 Contour. It had 205 60 15's originally. I recently installed 195 50 15's. I knew my speedometer would read high before I changed tire size but I thought it would be a simple fix by changing the speedometer pinion gear to one with more teeth. My speedometer now reads 8% high so I figured I could by a gear with 8% more teeth than the stock gear. But the local Ford dealership is telling me they don't sell gears with more or less teeth on them. So if you change your final drive ratio or tire size, how do you get your speedometer to read correctly? P.S. I've got the 2.0 with 5 speed.

You have to buy a chip.

Why the tire size change? To give it a lower stance but have a narrower tire??

Like Keyser said, you can get a chip, or maybe open up your instrument cluster, remove speedo needle, and have someone pace you at a set speed, set the cruise control and place the needle back on, that should get it pretty close.

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?

They change the speedo gear. In earlier Mustangs with cable drive the gear is located under the drivers seat basically under the car. There is a small bolt to remove and viola. I guess you would have to change the gear on the differential on a 95 tour. A chip is easier.

Your odometer and speedo are not cable driven on a 97 as far as I know. Zetec and duratecs do have different final ratios. Which are swappable if that could help you any.

I had just assumed that I had a speedometer cable since I had an analog speedometer dial. Also I have a Ford Service Manual on CD ROM which refers to a speedometer cable. But I looked under the car today and I DO NOT have a cable. Just a connector on top of the speed sensor with 3 wires coming out of it. So I guess I have 2 choices - change the speedometer gear or buy a chip? And that's if I can find a gear. How do you remove the gear? I saw a roll pin on the speedometer gear housing. It looks like you have to pull it out with vice grips? How much benefit is there to buying a chip? Does anyone have any documented performance gains? How much does gas mileage suffer? Thanks for all your help guys.

No idea about the speedo gear, but the chip helps out a bunch on an ATX and a little on MTX, gets rid of the speed limiter and adds just a little more power. I'd say gas mileage stays the same, maybe evens gets a little better as long as you're not flooring it because you wanna test the chip all the time.