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.

 

[vfx]

... 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.

This is an import observation. Is it a bug?

 

[TEG]

...A couple minutes/miles into each drive and the problem disappears...

Could this be related to regen braking? When you do a full charge the pack isn't ready to accept more energy so the regen is disabled until you drive for a little while and "bleed off" some power until it is ready to start doing regen again.

 

[TEG]

...occasionally when I leave in the morning the car has not finished charging, and the issue does not exist...

Another sign it might be related to the pack not being fully charged on that drive...

 

[frequencydip]

This is an import observation. Is it a bug?

We'll if its a bug, its a bug that the car forgets the tire size when going into sleep mode.

This is the second set of tires I've put on the car, no problem previously with the AD07, problem with new 25 inch tire. I also have a second set of rims with Kumho ECSTA V710s and they have no problem as they are normal sized tires.

 

[btown]

I'm cross posting this from the Roadster 2.5 tire tread thread which I've been discussing this issue on as well since I think tire issues are pretty similar between the Roadster versions:

I put Michelin Pilot Super Sports on the rear a while back, so I figure it's time to give an update. Please see my previous posts in this thread regarding traction control so you'll understand what I have to say next. I'm still running the original Yokos on the front, so the rear tires are .1" larger than they should be. I ran the calculations to determine what amount of tread wear would be required to get to the point where the rear tire size was what the Roadster expected (again, read up on my previous posts regarding TC). According to my calculations, that point would be 20% tread wear. So I've been watching for the startup TC issue to go away, because it will be a decent indicator of 20% tread wear. So far I've put about 4500 miles on these tires and the startup TC issue is still present, but just marginally. So I am confident that I'm just starting to get closer to the 20% wear point. At this rate, I'm estimating these tires may last as long as 25,000 miles (5X the point where the TC issue totally disappears).

Overall I continue to be pleased with these tires. They are sticky enough to launch without TC in most reasonably flat dry pavement situations. I would NOT be willing to give that up! Where I notice the biggest difference is in cornering. The AD07s and AD08s rarely broke loose and even when they did, they didn't really squeal and tended to grab again fairly quickly. The Michelins will squeal on fairly aggressive cornering and definitely break out much sooner than the Yokos. Fortunately, after putting over 13K miles on the Roadster, my juvenile desires to push corners really hard have faded and I've settled down into a more reasonable driving manner. I still do full on launches regularly, but I just don't try to nail the corners... especially now that I'm not running the Yokos. I don't track the car, so I feel very comfortable with the new limits I have on cornering. It's a small sacrifice for not having to replace the rear tires every 6-7K miles and in the end, I may actually be safer than before. Now I know fairly well where the cornering limit is. With the Yokos, I tended to be way overconfident because it took so much to break them loose.

Then after posting this, I actually measured my tire tread and posted the following revised update:

Ok, I don't have a gauge yet but I did take a quick measurement of the tread depth which I think is about as accurate as I can get without having a gauge in hand at the moment. It turns out I'm at about the 50% point rather than the 20% wear point which I had hoped. I also checked my actual miles on these tires and it's 4,600 miles (I was only off by 100 miles).

So I would like to officially restate my estimate for the Michelin Pilot Super Sports to be around 9,200 miles. I'm sure I'll run them down until all wear bands are hit all the way across, so I'm now estimating I may be able to get somewhere around 10K miles. The warranty will help in that regard, so I'm still pleases with the tires overall.

Now.... Anyone have any theories on why I still have a slight startup (first few minutes of drive) TC issue??? The tires were supposed to be just .1" larger in diameter than the stock tires. With 1/4" of wear so far, the tires now have 1/2" trimmed off the original diameter. So these tires (in theory) are now 24.5" diameter vs the stock tires which start out at 24.9". Yet I still see a slight startup TC issue. Hmmmm.....

 

[wiztecy]

Thanks for the writeup! I've got 8,500 miles on my Rear AD07's and just getting ready to hit the wear band on the right rear tire. Contemplating about the AD08 vs. the Michelin Sports. Good to know about that stickiness on corners, makes sense since the wear is longer on the Sports. I think I'll be running the AD08's next, my commute is through twisty turns that go up and down a mountain where an accident can appear at any last second. One thing I know is that I feel the Tesla has the majority of its weigh in the back, once that back end breaks free its very difficult to return it. Similar issues with the Porsche 911 design, its like giant pendulum when the weight is focused in the back. I may move to the Sports after I wear the fronts out and do a full swap. I don't want my front to be sticky and my back to be less sticky. Would rather match the tires in terms of traction and have the front plow when I know I'm pushing it too hard.

Possibly someone can chime in on their experience when the backend has broken free.... if its recoverable and also how far it got away.

I also hope your TC blues go away!

 

[Doug_G]

I've spun my Roadster 2.0 a couple of times in autocross. Yeah, it can happen very quickly, and once it goes you're just along for the rides - get on the brakes!

Last year I was running Toyo T1Rs (not quite as sticky as AD07), TC off, and sway bars loose front, middle rear. Here's a newbie mistake caused by snap oversteer. I got distracted and momentarily lifted in a fast corner. Just for fun here's the video:

More recently I've been running A048's for autocross, and I've yet to spin it. Part of that might be that I'm more experienced, but the A048's are kick-ass. They just don't last very long.

For the street I run AD07 front and AD08 rear. The AD08 characteristics are very similar in to the AD07's so I don't think there is any greater risk of breaking the rear loose. Certainly if you've got the TC on then I wouldn't be concerned at all.

As it happens I've got Michelin Pilot Super Sports on my Infiniti. They're not quite as sticky as AD07 but pretty darn good, and are quite good in the rain. I haven't tried them on the Roadster but can give a general thumbs up based on their performance on my Infiniti. That said, I think AD07/AD08 is a great combination for the street, and I bet they'd work just as well on a 1.5.

 

[wiztecy]

Thanks Doug! Very helpful insight on the tires as well as the video. Great visualization seeing that backend break free, and like you said you're there just for the ride! Looks like lots of fun doing the autocross, a true way to test and see what your car can do!

 

[vfx]

Just put the MPSS on my rears (now 300 miles). Great price. So far it takes about 12 miles before the car learns them and the TC and regen return. Not happy about using the brakes to slow during a largely downhill 10 mile trip. I look forward to honing in on the "miles traveled" to wear point that everything is normal.

Can't Tesla widen the tire diameter tolerances on the car's software? Or add a learning feature like the 2.0'shave?

 

[Pantera Dude]

Here's a thought on the rear tire diameter issue. If the tire diameter is too large, how about just lowering the pressure? Seems like that would reduce the effective diameter? And since the problem seems not to extist during acceleration, perhaps that is due to the car squating which should again reduce the rear tire diameter?