Adjusting speedometer for different sized wheels

[tna9001]

Is there a way to adjust the speedometer calibration? I've got a M3P on the way and I'm going to replace the 20" wheels with 18's.

 

[mswlogo]

If you have new TPMS it will prompt for confirmation and it will also ask wheel size.
If you use original TPMS you can "Reset" TPMS and I assume it will prompt for tire size again.

Note that the diameter of all OEM tires are nearly identical so Speedo would be close enough.

But there could be several reasons why the car wants to know which wheel you have for traction control purposes, possibly minor speedo difference and tire pressure range.

 

[tna9001]

Awesome, thank you!

 

[Burrito]

if you size your wheel/tire combo correctly than you shouldnt need to adjust the speedo (much). for instance i went from 18s (stock) to aftermarket 20s and i think my speedo might be off like 1%, My 60mph on stock is now actually 60.9mph with the new wheels. tpms should reset after driving a bit

 

[Snow Drift]

The issue is tires, not just rim size. You can't use any 18" tires.

You need to keep the difference within 3% of stock tire size of 235/35-20.

Tire size calculator

Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
235/35-20 3.2in 13.2in 26.5in 83.2in 762 0.0%
235/50-18 4.6in 13.6in 27.3in 85.6in 740 2.9%
235/45-18 4.2in 13.2in 26.3in 82.7in 766 -0.6%
235/40-18 3.7in 12.7in 25.4in 79.8in 794 -4.1%

Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
235/35-20 3.2in 13.2in 26.5in 83.2in 762 0.0%
245/50-18 4.8in 13.8in 27.6in 86.9in 730 4.4%
245/45-18 4.3in 13.3in 26.7in 83.8in 756 0.8%
245/40-18 3.9in 12.9in 25.7in 80.8in 784 -2.9%

 

[RoBoRaT]

V9 2019.32.1 added Wheel Configuration.
under Service.

Assuming you are going from 20s to stock 18" or the same tire diameter.

 

[gcmak]

The issue is tires, not just rim size. You can't use any 18" tires.
You need to keep the difference within 3% of stock tire size of 235/35-20.

This is definitely key. Not to mention individual tire models will vary that diameter even more. For instance the tread width and overall tire diameter for a Hankook R-S4 tire will be greater in both dimensions than a Michelin PS4S.

Definitely wouldn't mind running 245 squared or wider for the track though.

 

[sdleo726]

Hi, I dropped down my M3P to 19x9.5” ET30 square and the overall diameter is 0.5% larger (26.6” vs 26.5” stock) with 275/35/19s.

Should I be resetting my TPMS and changing my wheel settings to the 19” option?

It seems like I should just keep the settings “as is?”

 

[Mahamilto]

That’s basically the same. I wouldn’t bother. 60mph reading ur going 60.2 about

 

[manofvoice]

Has anyone been successful at calibrating for anything with a 50R19?

 

[Airflow]

Hi, I dropped down my M3P to 19x9.5” ET30 square and the overall diameter is 0.5% larger (26.6” vs 26.5” stock) with 275/35/19s.

Should I be resetting my TPMS and changing my wheel settings to the 19” option?

It seems like I should just keep the settings “as is?”

Do you get any rubbing in the front with that sizing?

 

[Occhis]

Has anyone been successful at calibrating for anything with a 50R19?

Go to Tire Rack and you can get full specs on the tire you pick in every size available. Just match the diameter to OEM spec, right around 26.4” IIRC

 

[manofvoice]

Go to Tire Rack and you can get full specs on the tire you pick in every size available. Just match the diameter to OEM spec, right around 26.4” IIRC

Thanks. That was helpful. I got my wheels and tires.

 

[Level8Drummer]

So long story short, no Lol!

That is really a shame too. It shouldn't be a problem with a car as electronically advanced as a Tesla.

In theory the car should be able to self adjust since it sees your GPS speed on the interstate, and would see a consistent discrepancy from GPS speed to the wheel speed sensors indicated speed.

L8d