Tire sizes - Rolling Diameters

[Captain Ahab]

Attached is a list of M3 OEM tire sizes - rolling diameters and theoretical top speeds (20 inch assumed for theoretical top speed, 18 inch as baseline for ratio of rolling diameter) - also a couple of tire options I wanted to see the numbers crunched on.

As you can see, approved OEM tire sizes do have varying rolling diameters - and thus effective gear ratio.

It is my findings that changing tire configuration changes speedometer calibration. - This concept is essential to testing any theory our vehicles are programmed to follow a specific accleration: acquire data a the track or GPS. You will see for yourself that "best effort" is always given: that is to say I believe that - under identical conditions - motor output is limited to the same (current limit?), no matter the wheel/tire configuration. This SUGGESTS there is no connection that the SOFTWARE tire size setting will affect actual measured performance (provided the same wheels and tires are used in the testing). You could validate software behavior by doing dyno testing under identical physical conditions - just software tire/wherl tire selection.

 

[jackmott]

Acceleration can be limited by g force, which can be measured directly, it does not need to use wheel speed or gps.

 

[Captain Ahab]

Test for yourself. In my testing, there is zero evidence to suggest that there is a "target" accleration rate.

My testing suggests that there is a level of effort target that operates the drivetrain within thermal and electrical current limitations (safety margin programmed).

As far as an accleration being a theroetical target for performance, I disagree.

Yes, accleration can be measured by a device. You can also calculate accleration from a velocity vs time plot. Accleration is the mathematical derivative (slope) of the velocity plot vs time. This is where the Draggy fails, it uses an acclerometer to plot accleration; mechanical movements add to the noise of the accleration plot. The actual accleration I have observed is pretty much a straight line along the x-axis, at a specific y-value. You will observe on your Dragy a linear velocity plot, but the Dragy measured accleration plot will vary up and down along the actual accleration line.

When using my GPS Draggy VELOCITY data (accleration plot is not true on the software), I assure you that the slope of the velocity curve does NOT vary with SOFTWARE wheel and tire selection. The slope of the velocity curve changes with the physical hardware changes (like temperature, mass, and state of charge).

 

[Captain Ahab]

Test for yourself. In my testing, there is zero evidence to suggest that there is a "target" accleration rate.

My testing suggests that there is a level of effort target that operates the drivetrain within thermal and electrical current limitations (safety margin programmed).

As far as an accleration being a theroetical target for performance, I disagree.

Yes, accleration can be measured by a device. You can also calculate accleration from a velocity vs time plot. Accleration is the mathematical derivative (slope) of the velocity plot vs time. This is where the Draggy fails, it uses an acclerometer to plot accleration; mechanical movements add to the noise of the accleration plot. The actual accleration I have observed is pretty much a straight line along the x-axis, at a specific y-value. You will observe on your Dragy a linear velocity plot, but the Dragy measured accleration plot will vary up and down along the actual accleration line.

When using my GPS Draggy VELOCITY data (accleration plot is not true on the software), I assure you that the slope of the velocity curve does NOT vary with SOFTWARE wheel and tire selection. The slope of the velocity curve changes with the physical hardware changes (like temperature, mass, and state of charge).

Borrow my non-OEM lower profile tires and see for yourself.

 

[gearchruncher]

Attached is a list of M3 OEM tire sizes

When did Tesla ever put a 265 or 275 on the Model 3 OEM (rows 9 and 11)?

 

[tm1v2]

When did Tesla ever put a 265 or 275 on the Model 3 OEM (rows 9 and 11)?

Or a 245 width tire? It's nice to include other sizes but that list seems to go way beyond OE Model 3 sizing. (Yes Tesla has shipped 245 width on 8.5" wide wheels on other cars, but I haven't come across Model 3 OE tires in that width.)

In fact...has Tesla ever shipped a Model 3 with anything besides 235 width tires all around? (Regardless of wheel size or tire category.)

 

[gearchruncher]

In fact...has Tesla ever shipped a Model 3 with anything besides 235 width tires all around?

The track pack comes with 245/35ZR20's... So yes, and that config is supported in the car wheel configurator. They're not wheels on the car from the factory, but they are a Tesla option that your service center will install.

 

[Captain Ahab]

My source on tire wheel combinations. - Is the source correct? I am not 100% certain.

As I stated, I calculated some non OE options.

Any questions?

 

[gearchruncher]

None of those 265/275 rears are correct. All Model 3's have always come with square setups. The only non-235 size ever is the after-sale track pack.

This is a much better guide (each wheel lists what tires have come on it):

The Tesla Model 3 Wheel Guide

Tesla Model 3 Factory Wheel Specs and Options. Factory Spec Wheel Upgrade Options. 18" Model 3 Aero Wheel Specs: 18X8.5" Offset: +40 PCD: 5X114.3 Center Bore: 64.1mm Weight: 21.6 lbs (Without Aero Cover). 19" Model 3 Sport Wheel Specs: 19X8.5" Offset: +40 PCD: 5X114.3 Center Bore: 64.1mm. 20"...

tsportline.com

 

[Gimmethecash]

Attached is a list of M3 OEM tire sizes - rolling diameters and theoretical top speeds (20 inch assumed for theoretical top speed, 18 inch as baseline for ratio of rolling diameter) - also a couple of tire options I wanted to see the numbers crunched on.

As you can see, approved OEM tire sizes do have varying rolling diameters - and thus effective gear ratio.

It is my findings that changing tire configuration changes speedometer calibration. - This concept is essential to testing any theory our vehicles are programmed to follow a specific accleration: acquire data a the track or GPS. You will see for yourself that "best effort" is always given: that is to say I believe that - under identical conditions - motor output is limited to the same (current limit?), no matter the wheel/tire configuration. This SUGGESTS there is no connection that the SOFTWARE tire size setting will affect actual measured performance (provided the same wheels and tires are used in the testing). You could validate software behavior by doing dyno testing under identical physical conditions - just software tire/wherl tire selection.

The 275/30/20 height on that attachment is showing the diameter (27.6”) of a 275/35/20. A 275/30/20 is 26.5” tall.

 

[Captain Ahab]

Thanks for the input!

Sorry guys, that's all you get for free.

 

[Captain Ahab]

For what it's worth:

My aim in all of this was to anticipate, and then real-world investigate, the outcome of utilizing tires with different rolling diameters.

In part, I wanted to determine if there was some sort of software/hardware configuration that may yield different performance.

Thus far, my findings are that - at this time - it is different physical configurations, and physical operation conditions, that are the sole means able to influence real-world performance.

Yes, there are a number of selectable traction and drivetrain management strategies available in track mode that could possibly offer different real-world performance. However, testing traction and drivetrain options in track mode was not within the scope of my testing.

The only Tesla software settings I have tested performance on is for tire and wheel configuration.

My hardware changes tested have been inclusive of different rotating mass and different tire rolling diameters.

I would love to see a set of back-to-back dyno plots and 1/4 mile runs with different tire diameters.

I may eventually acquire this data and share it. However, my personal life is... difficult, and has been in the way of acquiring meaningful data.

If I had it, I would share it.

Anyone in Ganisville, Florida with an M3P want to do dyno and strip testing with different wheel and tire configurations?

I can crew: jack the car up and down, swap wheels with mounted tires, and torque to 129 ft.lbs.

I currently have one OEM wheel/tire configuration and one set of non-OEM rolling diameter tires (unmounted).

Anyone want to do some testing?

 

[Lindenwood]

Just to confirm, @Captain Ahab , you are trying to assess how rolling diameter affects linear forward acceleration?

I have been curious about this, since the power produced by the motors drops off at relatively modest speeds. 0-60 may be slightly increased by taller tires, but I am curious if longer straight-line acceleration times (like 1/4 mile) would end up a wash since the slightly reduced gear ratio also means more power is available for later into the race.”?

 

[Captain Ahab]

Lindenwood,

Yes, I am interested in the potential of our hardware under different effective gear ratios. Specifically, linear forward acceleration (as you wrote).