Premature tire wear from regen braking system

[mal_tsla]

Only the tires are touching the road. If you're slowing down or speeding up by a specific rate (g-force) the friction at the tires is the same.

Basic physics, right? The only things in this thread merit further consideration are:

1. Overinflated tires will wear more in the center. Reduce pressure to get even wear across the tire = longer tire life.

2. If regen is predominantly on two out of 4 wheels, that could make those two tires wear faster. But my thoughts on this are that the weight of the car shifts forward when decelerating, enough to call into question just how rear-biased regen braking could be.

 

[TomB985]

How is the ride and handling at 35 PSI?

Much better the recommended 45. The pressure seemed high to me when I got the car, so I pulled up TRA load inflation tables and saw that this size only needed 29 PSI to adequately support the car. Lexis uses the same size in their GS-series, and the recommended inflation is 33 psi. The GS weighs within a couple hundred pounds of the Model 3; it is not a light car.

I was impressed immediately with the ride quality difference, and handling did not seem to be negatively affected. It's also easy to live with because the car permits the driver to adjust the warning threshold for the TPM S system. I believe Tesla recommends 45 psi for increased efficiency, but I did not notice any difference when lowering pressures. I'm sure it is a little more efficient at the higher pressure, but not enough to justify the increased wear and harsher ride in my opinion.

 

[Kevy Baby]

I believe the OP's initial assertion is broadly correct. Standard brakes exert a force to slow the car down by creating friction between the rotor and the brake pads. As a result, the brake pads slowly wear down and need to be replaced periodically. Regenerative braking shifts that force to the resistance between the tire and the road. This shift WILL increase the rate at which the tires wear. This is similar too, but in reverse, of the increased wear that tires mounted on the drive wheels (mostly the front wheels these days) of ICE cars compared to the wear of the non-drive wheels (typically rear wheels).

I am a believer in never down-voting without an explanation.

You've got some facts wrong here. While break pads to create friction on the rotor (or drum), the part that causes the vehicle to slow down is the connection between the tire and the road. If you were suddenly airborne, you could jam your foot on the break pedal and bring the tire rotation to a dead stop but it will have zero impact on the vehicle's momentum. Or if you're on the ground and jam on your brakes (without anti-lock), you can bring the tires to a dead stop rotationally, but your vehicle will continue its forward momentum (and this causes very little wear on your brakes and really bad wear on your tires).

Friction brakes and regenerative braking essentially do the same thing: increase the rolling resistance of the tires. Then the friction interplay between the tire and the road is what causes your vehicle to slow. If you match the rolling resistance force generated by friction brakes to the rolling resistance force generated by regen, the tire wear will be exactly the same. With the same 60-0 braking times using 100% regenerative vs 100% friction brakes will give exactly the same time wear.

Personally, I believe the biggest cause of premature wear by the OP is the tire pressure. There may be wear also caused by acceleration (because even the single motor takes off damned quick) and by harder than normal braking. But the harder braking cannot be attributed specifically to the regen - it is a matter of learning how to drive again. I know for me, with over 1 million ICE miles under my belt, when I got the Tesla, I had to learn how to drive again.

 

[Kevy Baby]

Much better the recommended 45. The pressure seemed high to me when I got the car, so I pulled up TRA load inflation tables and saw that this size only needed 29 PSI to adequately support the car. Lexis uses the same size in their GS-series, and the recommended inflation is 33 psi. The GS weighs within a couple hundred pounds of the Model 3; it is not a light car.

I was impressed immediately with the ride quality difference, and handling did not seem to be negatively affected. It's also easy to live with because the car permits the driver to adjust the warning threshold for the TPM S system. I believe Tesla recommends 45 psi for increased efficiency, but I did not notice any difference when lowering pressures. I'm sure it is a little more efficient at the higher pressure, but not enough to justify the increased wear and harsher ride in my opinion.

Does anyone know why Tesla recommends such a high tire pressure? Sure, it helps improve the mileage, but this can't be the reason?!?

 

[TomB985]

Does anyone know why Tesla recommends such a high tire pressure? Sure, it helps improve the mileage, but this can't be the reason?!?

Elon Musk on Twitter

 

[Kevy Baby]

Elon Musk on Twitter

Thanks!

Now I am off to lower my tire pressure (last I checked, they were at 42-43 PSI)

 

[TomB985]

Thanks!

Now I am off to lower my tire pressure (last I checked, they were at 42-43 PSI)

Good deal. Let us know what you think!

 

[Msjulie]

I've been at 35 PSI since 3,000 miles, and my tread looks fantastic.

I've run 45 cold since forever, maybe it's the roads but wear is even and all that... ~27k with more to go..

 

[boriszima]

Good thread to read. I noticed, which makes sense, my tires start to worn out faster in our lovely Los Angeles stop and go traffic commute compared to my previous drive without traffic. Having a heavy car does not help nor a fast car either. I was down to 4/5 in rear and 6/7 in front in my Model 3 AWD at 18,500 miles or so. Will it make it to 25K? Maybe. I keep my tires at recommended 42/43 but was lazy to rotate until then.

there might be a factor as mentioned if regen is biased towards one of axles compared to braking on all 2 that tires wore out quicker but uneven across front to back.

 

[abasile]

Does anyone know why Tesla recommends such a high tire pressure? Sure, it helps improve the mileage, but this can't be the reason?!?

Indeed, it's good for optimal range ("mileage"), but I've also found that raising the tire pressure reduces shoulder wear for those of us who frequently drive curvy roads.

 

[Holo]

I am a believer in never down-voting without an explanation.

You've got some facts wrong here. While break pads to create friction on the rotor (or drum), the part that causes the vehicle to slow down is the connection between the tire and the road. If you were suddenly airborne, you could jam your foot on the break pedal and bring the tire rotation to a dead stop but it will have zero impact on the vehicle's momentum. Or if you're on the ground and jam on your brakes (without anti-lock), you can bring the tires to a dead stop rotationally, but your vehicle will continue its forward momentum (and this causes very little wear on your brakes and really bad wear on your tires).

Friction brakes and regenerative braking essentially do the same thing: increase the rolling resistance of the tires. Then the friction interplay between the tire and the road is what causes your vehicle to slow. If you match the rolling resistance force generated by friction brakes to the rolling resistance force generated by regen, the tire wear will be exactly the same. With the same 60-0 braking times using 100% regenerative vs 100% friction brakes will give exactly the same time wear.

Personally, I believe the biggest cause of premature wear by the OP is the tire pressure. There may be wear also caused by acceleration (because even the single motor takes off damned quick) and by harder than normal braking. But the harder braking cannot be attributed specifically to the regen - it is a matter of learning how to drive again. I know for me, with over 1 million ICE miles under my belt, when I got the Tesla, I had to learn how to drive again.

Great explanation Kevy Baby. I stand corrected, thank you!

 

[jerry33]

Personally, I believe the biggest cause of premature wear by the OP is the tire pressure. There may be wear also caused by acceleration (because even the single motor takes off damned quick) and by harder than normal braking.

Bad alignment is also a big factor.

 

[jerry33]

Does anyone know why Tesla recommends such a high tire pressure? Sure, it helps improve the mileage, but this can't be the reason?!?

In general, higher tire pressure:
Keeps the tire cooler so the lifetime is longer (and safer at high speeds and/or high loads).
Reduces the chances of pothole damage.
Makes the car feel snappier.
Reduces rolling resistance.
Reduces stopping distance in most cases.
Reduces hydroplaning.
Reduces uneven wear.

In general, lower tire pressure:
Reduces tread damage on gravel roads and washboard surfaces.
Reduces vehicle damage from vibration on gravel roads and washboard surfaces.
Improves flotation off-road
Improves traction in many off-road conditions.

 

[Zhelko Dimic]

With tire pressure consistently between 40-42 PSI cold, the center treads were down to 2/32" and still with beefy tread depths on the outer edges. The wear on all four tires look identical.

The tires were rotated in X pattern at 8000 miles.

Center worn means you need more pressure for equal wear.

 

[jerry33]

Center worn means you need more pressure for equal wear.

You mean less pressure, however, that's not common with modern tires because most have a very large crown radius. Apparently the ones on the Model 3 have a small crown radius.

 

[Needsdecaf]

In general, higher tire pressure:
Keeps the tire cooler so the lifetime is longer (and safer at high speeds and/or high loads).
Reduces the chances of pothole damage.
Makes the car feel snappier.
Reduces rolling resistance.
Reduces stopping distance in most cases.
Reduces hydroplaning.
Reduces uneven wear.

In general, lower tire pressure:
Reduces tread damage on gravel roads and washboard surfaces.
Reduces vehicle damage from vibration on gravel roads and washboard surfaces.
Improves flotation off-road
Improves traction in many off-road conditions.

Correct until you over-inflate. Then you end up reducing the contact patch because the center of the tire is pushed out further. Which leads to premature center wear, worse handling, worse braking and a weird feel as the contact patch is not as intended.

 

[Needsdecaf]

There's a big difference when all the regen braking comes from the rear tires, though. Very different than proportional 4-wheel braking.

Not sure what you mean by proportional 4 wheel braking. If anything, having the car brake from the rear will extend tire life as during friction braking, somewhere around 75% of the braking force (and therefore wear) comes from the front due to weight transfer.

 

[jerry33]

Correct until you over-inflate. Then you end up reducing the contact patch because the center of the tire is pushed out further. Which leads to premature center wear, worse handling, worse braking and a weird feel as the contact patch is not as intended.

That was certainly true with bias-ply tires. With radial tires, it depends. If the tire's crown radius is large (e.g. almost flat), as many of them are, the steel belt will not expand and so the tread stays flat. If the crown's radius is small then that will happen. Unfortunately there is a lot of stuff left over from the days of bias-ply tires. If you check the tire's wear occasionally, you can adjust the pressure to suit.

 

[TomB985]

Not sure what you mean by proportional 4 wheel braking. If anything, having the car brake from the rear will extend tire life as during friction braking, somewhere around 75% of the braking force (and therefore wear) comes from the front due to weight transfer.

It doesn't work that way, though. Tires wear EXTREMELY fast when they skid, and there's a lot more traction available to the front end when slowing. Full regen at lower speeds can put the rear tires on the hairy edge of breaking free, which increases wear substantially.

The tires don't care much about weight when just rolling down the road. Sliding accelerates wear exponentially.

 

[jerry33]

Full regen at lower speeds can put the rear tires on the hairy edge of breaking free, which increases wear substantially.

It hasn't worked that way in 130K miles on my S, tires wear about the same front and rear. Braking with regen doesn't wear the tires out more, high speed or slow speed. Standard regen is really fairly gentle--about the same as you would normally brake.