Ownership How to Fix Your Speedometer for Different Size Tires

21:15  26 may  2017
21:15  26 may  2017 Source:   Road & Track

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How to Fix Your Speedometer for Different Size Tires . Have you changed your tire size or final-drive gear? You just made your speedo and odometer inaccurate. Here's how to fix them both. Most Popular. Bring a Trailer. By Chris Perkins. May 3, 2017.

How do you know if your car is reading the accurate speed? And if it isn’t accurate, how do you go about fixing a problem? If you are curious, his speedometer is off due to Fenske adjusting the final drive ratio, and different wheel and tire combos can similarly throw off the speedo .

How to Fix Your Speedometer for Different Size Tires© Bring a Trailer How to Fix Your Speedometer for Different Size Tires

If you've ever modified a car with smaller or larger tires or, perhaps, a different final-drive gear, you've immediately screwed up your speedometer. This is, of course, annoying, but for modern cars with a digital speed sensor, there's a relatively easy way to fix it. Our pal Jason Fenske at Engineering Explained shows you how in this new video, using his own Honda S2000 as an example.

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This particular fix should work for any car with an electronic speedometer-so, not your '67 Camaro with a gauge driven by a cable coming off the transmission. You'll need to buy a speedometer recalibration device to perform this fix–Fenske uses one called Yellow Box, but you can find other options to suit your application.

The Dodge Demon's massive drag tires are just barely street legal

  The Dodge Demon's massive drag tires are just barely street legal We wouldn't recommend wet weather driving.That wheel and tire combo, meant to fill out the Demon's new wide wheel arches, is frankly impressive. Lightweight 18- by 11-inch wheels are wrapped in special Demon branded Nitto NT05R tires measuring an astounding 315/40R18 at all four corners. Not only does that trump the old Camaro Z/28's 305 section tires, it makes the Demon the first production car to come equipped from the factory with drag radials, claims Dodge. Presumably, the goal with the Demon is to provide enough power and grip to rotate the Earth underneath the car rather than propelling the car itself down a dragstrip.

Have you changed your tire size or final-drive gear? You just made your speedo and odometer inaccurate. Here's how to fix them both. If you've ever modified a car with smaller or larger tires or, perhaps, a different final-drive gear, you've immediately screwed up your speedometer .

Have you changed your tire size or final-drive gear? You just made your speedo and odometer inaccurate. Here's how to fix them both. If you've ever modified a car with smaller or larger tires or, perhaps, a different final-drive gear, you've immediately screwed up your speedometer .

Fixing your inaccurate speedometer will also require some real-world testing to determine the percentage of error introduced by your new tires or gearing. For that, you'll need a GPS-connected device to verify speed–a phone app, a portable navigation system, or something like a VBox should do the trick.

Once you've got a percentage to work with, plug the calibration device into the speed sensor–in Fenske's case, attached to the transmission–and follow the instructions to program in the correct amount of compensation. As an added benefit, this fix will also make your odometer accurate, since it uses the same sensor that feeds the speedometer.

You'll need to be a little handy to make this work, but the end result is worth it-and it's way easier than the old days, where you'd have to fiddle with speedometer gears and hope you did the math correctly. After all, you don't want to get pulled over for speeding when your car tells you you're doing the speed limit.

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Demon's Tires Are Too Wide For Assembly Line .
Dodge's Brampton, Ontario plant was designed to accommodate cars with 275mm wide tires. The Demon has 315s.Originally, Dodge's Brampton, Ontario plant, where the Challenger is built, was only designed to accommodate tires no larger than 275mm wide. Until the Demon and the Widebody came into being, 275mm tires were the widest fit to a Challenger, but the new models use 315mm and 305mm width tires, respectively.

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