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standard tires on 2.5

smorgasbord

Active Member
Jun 3, 2011
3,194
5,059
SF Bay Area
... $200 less with almost the same specs.

Unfortunately, the UTQG (Uniform Tire Quality Grading) top rating for traction (AA), is still low enough threshold that there's a big difference in performance between the worst tire with that rating and the best tire with that rating, especially on the Roadster with its extremely high torque off the line, not to mention the demand that can be placed on the tires from twisty roads with the Roadster's great chassis, but high COG.
 

speedy99

Model 3 (2018, LR)
Aug 15, 2011
56
4
Santa Cruz, California
not to mention the demand that can be placed on the tires from twisty roads with the Roadster's great chassis, but high COG.

I always thought the Roadster had a pretty low center of gravity, given it's height to width ratio. Most of the heavy stuff is pretty low, except the PEM.

I've considered the performance limits much more related to the narrow tires (used to maximize range), and not the COG or suspension, which is why I am unwilling to sacrifice tire grip for longer life. (I have a roadster sport 2.5.)
 

smorgasbord

Active Member
Jun 3, 2011
3,194
5,059
SF Bay Area
I came up with two possibilities:
1) Roads have more grit/gravel on the shoulder side.
2) Right turns are sharper than left turns (at least in the US).

Getting my new AD08s put on as I type this. The service manager in Menlo just told me that the right side wears out due to the way the motor/transmission is laid out with more power going to the right tire.

As for the COG of the Roadster, while the Lotus Elise has a very low COG, the battery pack in the Roadster comes up to your shoulders, and that's just too much weight too high when pushing the limits on the track. In real world driving at safe speeds on real roads, the Roadster is just fine.
 

Doug_G

Lead Moderator
Apr 2, 2010
17,881
3,347
Ottawa, Canada
Getting my new AD08s put on as I type this. The service manager in Menlo just told me that the right side wears out due to the way the motor/transmission is laid out with more power going to the right tire.

AD08's fit the Roadster? I thought you still had to use AD07.

As for the COG of the Roadster, while the Lotus Elise has a very low COG, the battery pack in the Roadster comes up to your shoulders, and that's just too much weight too high when pushing the limits on the track. In real world driving at safe speeds on real roads, the Roadster is just fine.

By "too much weight too high when pushing the limits on the track" do you mean "don't use it on a track" or "it doesn't do that well on the track"?
 

smorgasbord

Active Member
Jun 3, 2011
3,194
5,059
SF Bay Area
AD08's fit the Roadster rear 225/45/17. Still have to use AD07s for the front, but I'm hoping that will change by the time I need new fronts.

My road/track thing is just my way of saying that if you're going fast enough for the weight distribution to really matter, for safety's sake you should be on a track. That's too fast to be going on roads with other traffic, pedestrians, bicyclists, etc.
 

smorgasbord

Active Member
Jun 3, 2011
3,194
5,059
SF Bay Area
Here are my stock AD07s after just under 5700 miles:
Left:
IMG_3634.JPG


and Right:
IMG_3633.JPG


The right one was at the wear bars, the left one wasn't - but pretty close.
 

hcsharp

Active Member
Jun 7, 2011
3,379
1,341
Vermont
Getting my new AD08s put on as I type this. The service manager in Menlo just told me that the right side wears out due to the way the motor/transmission is laid out with more power going to the right tire.
...

I doubt if that's correct because the right side tires have worn out faster on all cars I've ever owned. I always thought it was due to the way roads are crowned. Maybe those of you who have right-hand drive cars can confirm this?
 

qwk

P130DL
Dec 19, 2008
3,024
766
I doubt if that's correct because the right side tires have worn out faster on all cars I've ever owned. I always thought it was due to the way roads are crowned. Maybe those of you who have right-hand drive cars can confirm this?
It's because the roadster(and most cars) have an open differential. Cars with limited-slip wear both tires evenly.
 

W.Petefish

Active Member
Apr 29, 2011
1,060
11
In a locking differential there is a mechanism that essentially locks both sides of the axle together. In a limited slip there is a similar mechanism to this that makes one tire spin slightly slower than the other. The locking differential is useful for 1/4 mile applications and for off-road use. A limited slip differential is good when there is a chance that you might go off the road and into an area where you need something more than just one tire pushing.
 

TEG

Teslafanatic
Aug 20, 2006
21,790
8,781
It's because the roadster(and most cars) have an open differential. Cars with limited-slip wear both tires evenly.

Is that true?
I think many times uneven wear is due to alignment issues. Or different inflation of tires.
Sometimes people have uneven wear because their driving routine involves more turns in one direction than the other.
Or they are scraping the right side tires when parking at curbs.

With differentials, I thought open diff was similar to limited slip except in cases where you lose traction on one tire.
Say one of the rear tires ends up on a patch of oil or ice... With open diff it would start spinning (taking torque away from the wheel with traction), but limited slip would keep torque going to the "good tire". So a limited slip typically doesn't do much except in cases with very uneven left / right traction.
A 'locking' differential is mostly useful in extreme cases like off-road on sand, or in mud. Since it forces both the left and right to rotate at the same speed it would cause a lot of tire scrub going around corners. Not something you want in normal road driving.
I also heard another story that the right side can wear more because the driver sits on the left and so provides more weight and traction for the left tires, so the right driven wheel can slip more. Don't necessarily believe that, but read it. Looks like there are a lot of anecdotal, hypothetical reasons posted around to explain uneven tire wear. I think there can be various reasons from one car to another.
 
Last edited:

qwk

P130DL
Dec 19, 2008
3,024
766
Yes it is true. With an open diff the tire that usually gets traction is the right tire. There are probably many reasons for this such as a longer axle on the right side(usually).
 

TEG

Teslafanatic
Aug 20, 2006
21,790
8,781
...The 0-60 times would be a lot better if Tesla went with a limited slip.

I am not so sure about that. At the drag strip, wheel slip / spin wasn't really an issue. I think the smooth / even torque delivery avoids spikes that could break a tire free. Also, having ~900lbs of batteries basically over the rear wheels aids traction substantially. This assumes dry pavement though...
 

qwk

P130DL
Dec 19, 2008
3,024
766
I am not so sure about that. At the drag strip, wheel slip / spin wasn't really an issue. I think the smooth / even torque delivery avoids spikes that could break a tire free. Also, having ~900lbs of batteries basically over the rear wheels aids traction substantially. This assumes dry pavement though...
I'm pretty sure the firmware limits torque from a stop run. That's why it's difficult to spin the tires in a roadster. With a limited slip+some sticky tires and a track only firmware tweak, I bet you could get some much better 60' and 1/4 mile times. I wouldn't be surprised to shave a full 1 second in the quarter, putting the car in the 11's. The car would not get 200+ miles per charge though.
 

tomsax

Member
Jun 19, 2008
898
117
Sammamish, WA
I'm pretty sure the firmware limits torque from a stop run. That's why it's difficult to spin the tires in a roadster.

I think it's more accurate to say the Roadster limits how quickly torque ramps up, both for the driver's and the drivetrain's benefit. However, from the logs, it looks like it gets up to maximum torque very quickly. Below is a graph from my best 1/4-mile run.

100724_drag_race_graph.jpg


I was doing a two-footed launch. From the logs it looks like I had the brake on full and was pressing the accelerator down to the floor when the lights on the tree got low enough that I lifted off the brake. The torque graph is up around 280 fl-lbs at about the same time I turned the car loose, maybe even before the brakes were released.

It would be better to see data at a 0.1-second or better resolution. Maybe we'll get there someday with the Tesla Tattler or something similar.
 

WarpedOne

Supreme Premier
Aug 17, 2006
4,346
6,393
Slovenia, Europe
I doubt if that's correct because the right side tires have worn out faster on all cars I've ever owned.
That's because you drive left-hand-drive cars on right-hand-drive roads. Left turns offer better visibility than right turns with same radius so you engage them at higher average speeds.
I bet UK-specced roadsters with right-hand-drive driven on UK roads show more wear on left side tires.
 

qwk

P130DL
Dec 19, 2008
3,024
766
I think it's more accurate to say the Roadster limits how quickly torque ramps up, both for the driver's and the drivetrain's benefit. However, from the logs, it looks like it gets up to maximum torque very quickly.

The roadsters 60' time of 2.0s+ is an indication of either very poor traction, or launch torque limits. Since most roadsters have very little wheelspin at the track, it has to be the latter. I would bet that Tesla optimised the car for smooth takeoff rather that brute off the line torque to maximize smoothness, and minimize drivetrain breakage. After all, the roadster is not a track car.
 

tomsax

Member
Jun 19, 2008
898
117
Sammamish, WA
The roadsters 60' time of 2.0s+ is an indication of either very poor traction, or launch torque limits. Since most roadsters have very little wheelspin at the track, it has to be the latter. I would bet that Tesla optimised the car for smooth takeoff rather that brute off the line torque to maximize smoothness, and minimize drivetrain breakage. After all, the roadster is not a track car.

It takes far more torque than the Roadster has to get a 0-60 time below 2 seconds.

In what way do you think my graph of torque versus time and speed is wrong? Torque is close to maxed out before the car's speed even registered above 0.
 

qwk

P130DL
Dec 19, 2008
3,024
766
It takes far more torque than the Roadster has to get a 0-60 time below 2 seconds.

In what way do you think my graph of torque versus time and speed is wrong? Torque is close to maxed out before the car's speed even registered above 0.
I'm not saying your graph is wrong. It just baffling that an ICE with similar power and way less avg. tq/hp, can get much better 60' times. A high 12 second car trapping 100+ definately does get better 60' times than 2.0+. The rule of thumb is that you shave off about .2-.3 sec in the 1/4 mile for shaving off .1 sec in your 60' time.
 

Dave EV

Active Member
Jun 23, 2009
1,700
1,155
San Diego
I'm not saying your graph is wrong. It just baffling that an ICE with similar power and way less avg. tq/hp, can get much better 60' times. A high 12 second car trapping 100+ definately does get better 60' times than 2.0+. The rule of thumb is that you shave off about .2-.3 sec in the 1/4 mile for shaving off .1 sec in your 60' time.
One has to remember that while the Roadster applies 100% torque from a stop, it does not apply 100% power from a stop and has the disadvantage of only having a fixed gear.

Remembering that power is force (torque) applied over time, one realizes that one needs to apply maximum power (not torque) over that distance to get there fastest.

Then look at a torque/power curve for roadster, one quickly realizes that off the line while the Roadster produces a lot of torque, it doesn't produce more than 100 hp until you're going around 30 mph and that ideally you'd keep the motor spinning around 8,000 RPM to accelerate the fastest.

Don't forget that with a typical car one can also usually "launch" it (unless you've got a crappy slush-box) in the power band.

Put a 2-3 speed transmission in the Roadster and you'd easily produce better acceleration numbers. While an EV's torque curve is much better than an internal combustion engines, that doesn't mean that performance can't be improved by keeping the motor in it's sweet spot.
 

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