Wheel size change / speedometer issue...

[octoberguy77]

I am thinking of putting a set of the 2006-2011 17" wheels on my 2005(came with 16" wheels) I am needing to know what to do to keep the speedometer accurate.....Would that be the gear that mounts to/inside the transmission?(I hope so because that would be an easy fix......OR?

[toytech]

The original equipment tires P225/60R16 (such as Eagle RSA's) measure approximately 26.6" in diameter and 7.2" in tread width. If you upsize one inch on rim diameter you can run with a P225/55R17 that measures approximately 26.8" diameter and 8" in tread width. This is called plus 1 tire fitting. I doubt that .2" difference will throw off the speedometer very much. If you are concerned with the effect on the speedometer, then you can buy a programmer and change the tire size in the PCM to recalibrate the speedometer reading. Ford doesn't use gears on the transmission output shaft to calibrate the speedometer anymore on the newer vehicles.

[octoberguy77]

Thank you very much on the info!! Its a great help! What is the name of the type of programmer??

[toytech]

Thank you very much on the info!! Its a great help! What is the name of the type of programmer??

I have been working mainly with diesel performance here recently, and I have just recently gotten back into gasoline performance, but several companies offer programmers that can correct the speedometer. Jet makes one that is for correcting the speedometer only and more that program other items as well. Hypertech also offers several scanners that can correct the speedometer. Superchips, Diablosport, and others are also on the market, and SCT makes an excellent programmer used by many custom tuners and dyno shops.

[1996vic]

I am looking to upgrade my 15 inch wheels to the 16 inch ones I see on 2000 or later models where is the best place to buy and what are the correct wheel dimensions.

[Sgt]

The difference between your stock wheels and the wheels you want to install is too small to throw off your speedometer. Lifted trucks usually don't get their speedometerrecalibrated until they hit about 33" inch tires. At that point re-gearing their differentials and calibrating their speedometer is a must. I have a 2009 charger that original had 16" wheels. I upgraded to 22" wheels and had my vehicle tested and speedometer was good. My point is, unless you're doing a serious change in weight, and size don't worry about your speedometer. Make sure your lug patterns match though.

[MFP71]

My car came with 16's stock, now has 17's, rode by the Your speed is: XX? box on the side of the road, at 40 mph on speedo, read 40 on radar...? I was kinda surprised to find it was still accurate!

[Pecos Slick]

There is not that much difference in the 16s and the 17s. Speedo should be fine.

[toytech]

It's not the wheel diameter that throws the speedo off, it's the outside tire diameter or height that causes the issue. You could switch from 15" to 24" wheels and as long as the tire height or diameter stays the same, it won't effect the speedometer calibration.

[Jake]

Try this:

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