Upsizing to bigger tires - will speedometer and range auto adjust?

[charliemagpie]

I was going to say perhaps calibrate using GPS, but you said it so so much better.

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[GlockandRoll]

Why wouldn't it have a GPS spedo, not accurate enough for FSD I guess?

 

[Nidavellir]

Seems like this site and chart gives some good information


Comparison site

 

[GlockandRoll]

Use this tire size calculator...
https://tiresize.com/calculator/

 

[SolarWizard]

Its no big deal with a single speed motor.
Once you verify the correct speed with radar you’ll know what those specific tires and pressure read out as. Just mentally add that to your indicated speed.

The upside is a few thousand more miles on battery warranty

 

[Wmcgregs]

This is big for me, I want as big as I can go.

I am a little concerned about being off road with range because there definitely won’t be chargers when I get to rural GA mountains.

I know I’ll lose significant range with bigger AT tires, probably KO2’s. I’m assuming it comes with a 34-35”, I’d like 37’s.

so we’ll see how it does with range.

 

[Nidavellir]

It seems like the RC and MC CyberTrucks have 20” rims. If that’s the case these are the tires I want.

37” Tires

 

[cvalue13]

It seems like the RC and MC CyberTrucks have 20” rims. If that’s the case these are the tires I want.

37” Tires

it will have 20" rims, and I know you’re not alone in wanting 37s

the question is, in wanting 37s, how far are you willing to modify your CT suspension

 

[DumpsterFire]

On our Model 3's, driving a few blocks after I swtch from summer to winter tires, of exactly the same size wheels and tires, a dialog box pops up asking me to confirm the new tires. The system is incredible in its ability to sense a new set of tires, even when they are almost identical in size.

It's not only the tire size that the car takes into account, its also whether they are summer or winter tires! I think this is why the traction control is so precise and fast-acting when driving on icy roads, the system is just very sensitive, in a good way.

Come to think of it, I think it must be detecting the new tire pressure sensors!

On our Model 3's, driving a few blocks after I swtch from summer to winter tires, of exactly the same size wheels and tires, a dialog box pops up asking me to confirm the new tires. The system is incredible in its ability to sense a new set of tires, even when they are almost identical in size.

It's not only the tire size that the car takes into account, its also whether they are summer or winter tires! I think this is why the traction control is so precise and fast-acting when driving on icy roads, the system is just very sensitive, in a good way.

Come to think of it, I think it must be detecting the new tire pressure sensors!

I don’t think my model 3 has ever asked this when I’ve done my seasonal tire change over.
Then again it’s one of those “unique” summer of 2018 M3s that looks like it was assembled by a drunk 4 year old…. Haha.

I’ll have to investigate! Thanks for the info my man!

 

[Nidavellir]

cvalue13
the question is, in wanting 37s, how far are you willing to modify your CT suspension

Does it make a difference that the Cybertrucks suspension can move 14" that it will not be an issue?

 

[cvalue13]

Does it make a difference that the Cybertrucks suspension can move 14" that it will not be an issue?

In my book, the air suspension is more likely to make it a bigger and more expensive issue

but to level set, let’s clarify the difference between ground clearance, adjustable height, vs suspension travel.

• the air suspension’s adjustable height ranges more like ~5-6” between lowest to highest setting

• it’s the ground clearance that goes up to ~14”, only if/when the truck is in the highest air adjustment

• then there’s true suspension travel, how far the suspension can move due to going over bumps etc., which can be different when the truck is set at different air ride heights - while unclear, comments from last Q3 call suggested it’s possible that the CT is similar to the Raptor in having ~14” of suspension travel (which is surely only possible in higher or highest air ride settings)




Taking all those above variables, the last variable to add in: the CT will not allow the driver to just pick any air suspension height in all conditions and leave it there. Eg at highway speeds you’ll be unable to leave it in higher settings; in fact the higher settings will likely be speed limited to some ~low speed (eg 25-30). Conversely, at highway speeds it may for aero and safety reasons require the lowest setting.


Maybe all the above is already enough to point towards why the CT’s suspension may be particularly challenging for upscaling the rubber. If nothing else, the lowest suspension setting (eg in aero mode at hey speeds) is likely unavoidable at times, and becomes the limiting factor for basic wheelwell clearances.

And even at higher air suspension settings, having such drastic travel (eg ~14”) means the tires articulate up into the wheel well.

all of this is why the Ford Raptor 37” tire package, even absent the complications of adjustable ride height, required significant suspension and a fascia changes to the truck. It’s not simply a Raptor option that adds only larger rubber.

None of which is to say it’ll be impossible to fort 37s on the CT and not have mechanical, ride quality, or safety issues. While seemingly unlikely, it’s possible Tesla has designed the suspension to already handle an up-size.

But if they haven’t designed it in, then folks trying to fit 37s will be embarking on an experiment, and the most familiar/experienced will be doing so prepared to make material suspension modifications.

 

[JBee]

37" would only add 1" to one side of the wheel that comes into contact with the wheel arch, so I think there should be enough clearance all around.

The more limiting factor might be the upper steering knuckle. This is the limiting factor on MY, and on the CT it also looks close. (The one that bent up)

The suspension travel is also not necessarily the range of height adjustment that is possible. That is likely to bbequite a bit less than total wheel travel the suspension can do. I'm not sure which one EM meant when he said 14".

But being independent suspension all round, the suspension limits should at least not change camber as much as a live axle, which is both good and bad. With a live axle both wheels stay perpendicular to the axle, whereas independent suspension stays more perpendicular with the bottom of the vehicle, whilst the wheels are fully articulated.

 

[SolarWizard]

cvalue13
the question is, in wanting 37s, how far are you willing to modify your CT suspension

Does it make a difference that the Cybertrucks suspension can move 14" that it will not be an issue?

With 4WS adding 37s is not just going to be adding a little height to the suspension. Also are you cool with ~ 230 miles of range?

Also ridge grapplers are junk tires generally but especially for this application

 

[HaulingAss]

I don’t think my model 3 has ever asked this when I’ve done my seasonal tire change over.
Then again it’s one of those “unique” summer of 2018 M3s that looks like it was assembled by a drunk 4 year old…. Haha.

I’ll have to investigate! Thanks for the info my man!

That's odd, we have three Model 3's from March 2018-September 2018, and they are all very well put together. Super reliable too, never had a problem.

When you do seasonal tire changes are you changing just the tires or the wheels too?

 

[ÆCIII]

I imagine it will be similar to the current tire size selection available in the cars

Those different wheel size configurations don't change the outer tire diameter or circumference. The various wheel and tire sizes are all designed to have the same outer diameter so that the revolutions to speedometer conversion will always be consistent.

The purpose of the wheel configuration menu in the Tesla U/I is to allow the car to more accurately predict range based on different wheel types mounted on the car. Even though the outer diameter of the tires are the same, other factors such as aerodynamic drag and wheel weight will make the range slightly different. The wheel configuration in the U/I is designed to help calculate a more accurate estimate of remaining range.

However I do think it would be a cool feature if Tesla could somehow use GPS over a certain distance in combination with the number of wheel revolutions it takes to go said distance for a speed calibration function that would work with varying sizes of wheels and tires. Only problem with that is some would abuse such flexibility so Tesla would have to specify tire size limitations. Some would put tires on so large that unexpected torque loads could risk harming the drive unit, or there would be no doubt be some people going the other extreme and putting tiny wheels and tires to make the vehicle very low, which also risks damage to the battery and decreases driver visibility.

So if such a feature were ever activated there would have to be reasonable tire size limitations but some would most likely still abuse them anyway. But if Tesla took this a step further and made the final drive unit gear ration slightly variable adjusted with software, then the drive units would have no problem and speed calibration could be compensated for in that way. But that adds cost and complexity for all VINs to allow for use cases that really aren't in high demand by everybody.

- ÆCIII

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