1.5 Roadster Tire Thread

[frequencydip]

If it is the oversize, why would regen get better after a couple miles of driving?

The computer learns the rotational difference between front and back and learns it after a few minutes... I have not tried but a oversized tire in the front would likely also solve the problem. So far everyone with this issue has a 25 inch tire in the rear and either stock or same size as stock in the front.

[smorgasbord]

The computer learns the rotational difference between front and back and learns it after a few minutes...

And then forgets it for the next drive?

[jerry33]

How could a tire with the same diameter have a different RPM assuming the tire is not slipping...

Different hysteresis, different crown radius, different belt construction, etc. A tire is not just round and black, it's a very complicated piece of technology. That's why most tire manufacturers list the RPM as one of the specs of the tire.

[btown]

The tires I have are .1 inch larger and that translates to about 3/32 of tread depth or 33% has to wear off before its the same size as a new AD07, so in about 4,000 miles the problem should go away....

It's interesting how such minor differences make such a difference. I'd always heard the traction control allowed about a 2% slip before kicking in. Heres the rotations per mile for the three different rear tires I've used so far:

AD07: 835
AD08: 836
MPSS: 833

That's about a .24% difference between the MPSS and the stock tires. I wonder if TC kicks in at .2% instead of at 2%?? Regardless, I find this to be only a minor inconvenience since it goes away rather quickly during each drive.

My math puts me wearing down to the match point at 2400 miles if the tires really go 15K (which is what the warranty is when running different tires in the front vs back). It's also possible the issue will go away earlier, as I would presume there is at least some fudge factor involved in the default ratio they use. I'll make sure I note how many miles I'm at when the issue clears.

[smorgasbord]

Let's consider a rear stock AD08. It's diameter according to Yokomaha, at the 225/45R17 size is 24.8", with a tread depth of 9/32". The standard for tire life is remaining tread depth of 2/32". That means the tire diameter will change from 24.8" to 24.36". And that means the revs per mile changes from 836 to 857 or so.

Thus, I find it really hard to believe that the traction differences being reported are mostly due to differences in "new" tire diameters. And remember, we can go through 3 or 4 rears before we replace the fronts.

[jerry33]

Thus, I find it really hard to believe that the traction differences being reported are mostly due to differences in "new" tire diameters. And remember, we can go through 3 or 4 rears before we replace the fronts.

New tires also have mold release on them, which makes them slipperier for the first 300 miles or so.

[frequencydip]

Let's consider a rear stock AD08. It's diameter according to Yokomaha, at the 225/45R17 size is 24.8", with a tread depth of 9/32". The standard for tire life is remaining tread depth of 2/32". That means the tire diameter will change from 24.8" to 24.36". And that means the revs per mile changes from 836 to 857 or so.

Thus, I find it really hard to believe that the traction differences being reported are mostly due to differences in "new" tire diameters. And remember, we can go through 3 or 4 rears before we replace the fronts.

The issue is the tire is over sized not just sized differently, the larger 25" tire is revolving at 833 rotations per mile in btowns example its just outside of the range that tesla designed the computer to handle. It makes perfect sense if the rear tire is revolving to slow compared to the front when regen is on that computer thinks the rear tire is slipping on something like ice, its spinning to slow and it reduces regen to compensate. There are no issues under acceleration only regen.

Yes the new tire mold issue can cause lower traction but thats only the tire needs to break in before it reaches its maximum potential the tire still has tons of grip when brand new.

[btown]

I've had the tires and characterized the behavior enough to say I am absolutely sure it's not mold release or tire temperature. It is too consistent on hot or cold days (we're seeing pretty wild swings in temperatures this year). A couple minutes/miles into each drive and the problem disappears. I'm confident it's the tire diamater.

[jerry33]

I've had the tires and characterized the behavior enough to say I am absolutely sure it's not mold release or tire temperature. It is too consistent on hot or cold days (we're seeing pretty wild swings in temperatures this year). A couple minutes/miles into each drive and the problem disappears. I'm confident it's the tire diamater.

The one other suggestion I have is that those tires have a nylon cap ply which can take a set overnight--especially if the temperature varies considerably from day to night. This will work itself out after a few miles. It's minor enough that you won't feel it, but the traction control might.

[frequencydip]

The one other suggestion I have is that those tires have a nylon cap ply which can take a set overnight--especially if the temperature varies considerably from day to night. This will work itself out after a few miles. It's minor enough that you won't feel it, but the traction control might.

The only issue is the diameter, no one with normal diamater tires has ever reported the issue. Also occasionally when I leave in the morning the car has not finished charging, and the issue does not exist because the car never went to sleep after completing a charge. It only forgets about the new tire size when it enters sleep mode.