Going to 17" from 16" tires - - how do I recalibrate speedo?

[Greg K]

I have a 2001 Aurora with the V6 3.5 engine. I am going to put on the 17 in chrome rim with the larger tires. It currently has the 16in tires. How will this affect my speedometer and how can I correct it?

[RCA1186]

You can't correct it short of having the PCM tuned. Northstar performance may be able to do it, but I'm not sure of that. Outside of that you would have to get a tire size that when mounted to the 17" rim produces the same overall diameter as the 16" rim and tire. i/e thinner (shorter) sidewall.



tiresize.com/speedometer-calibration/

[Greg K]

That's what I thought, but nice to have some confirmation!
I will just have to mentally keep in mind my speed is slightly different than what it will be showing.
Or use my smart phone speedo app.
Much appreciated, Greg

[tigger]

Yeah, I wouldn't sweat it. If you use the stock tire size for the 17" wheel (235/55R17), you'll only be about 1mph off @60mph...

[Greg K]

I've now installed the 235-55-17 tires and I find -- using the GPS Speedometer app -- that I just add 10 per cent to whatever my speed shows and it's pretty accurate.

[AmunRoo]

You probably don't need to adjust the speedometer. As long as the outer diameter is roughly the same, you're not really changing anything. I'm running 255-35-20 in my speedometer is dead on.

When I ran 265 40 20 I was off by I think 1.5 mph

[Paulaurora]

Never had an issue with spedo . If you put 20s than maybe but up to 18th never an issue. Buick Regal had 18 options and most came with 17th with same trans just 3.8L engine not 3.5. Never was an issue with spedo form 16th to 18th on regal . So most likely wont be an issue on Aurora