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standard tires on 2.5

driver_EV

Member
Dec 7, 2011
209
43
Charleston, South Carolina
+size on all four now

Ok, with near 500 miles on the new tires, front and rear, this is what I found.

The (+size) A/S3 Mich on the rear work as well or better than the "A/S plus" did.
It is difficult to say exactly how different they are, without being able to switch back and forth, but the A/S3 also provide a smoother ride over bumps, are more quiet, and also allow(and need) air pressure adjustments to tune the handling of the car. The original Yoko tires were so stiff/rigid that slight tire pressure changes seem to not affect handling much at all.

The A/S3 tires may be a little better handling on the back of the Roadster than the A/S plus tires. I think they feel more solid.

The big difference with the car now is the addition of +size Ultra High Performance All Season tires to the front of the Roadster to go with the backs.

IMG_7131a.jpg


First the issues of concern:

1) clearance issue with front tires of 1/4 inch radius increase?
Driving around a bit demonstrated an unusual noise when turning the steering wheel fully to the right. Back in the driveway for visual inspection shows the liner in the wheel well was lifting away from its normal shape, so that the edge was able to rub the tire tread.

IMG_7143a.jpg

IMG_7147a.jpg


I just trimmed the edge section back to where it was more flush near the fasteners that keep it there.
The rubbing noise is gone, and there seems to be good clearance with the slightly larger front tires.

2) Tesla drive control error messages showing tire wear out of limits due to tires out of spec size?
This was a minor issue with the original Yoko tires on front and the larger size only on the rear of the car. I think the fault was "#1153 Wear Factor" indicating the Tesla drive system noticed the relative speed difference of the front vs. rear wheels was more than it wanted to see. This error message is gone now that the +size tires are on the front as well.

3) tire pressure "too high" warnings?
Due to running with higher tire pressures than TPMS expects with the new tires, especially when driving in summer temperatures. This issue remains, and is the only technical glitch remaining with the car running on these tires. The car benefits from dialing the pressure to mid-upper 40's, and the TPMS needs a recalibration, if that is possible to allow the normal warmed up temperature/pressure to be increase above the maximum of 51psi that is nominal for the original lower pressure rated tires.

This is more of an issue than before, because the tire overpressure warning message "noise" is more prevalent with the new front tires, because they need to run a bit higher than the rear to give the desired/exciting response and cornering forces without bringing back under-steer.

_____________________________________________

Now that these tires are getting some miles on them, it is more clear how they are working.

From memory now, the Roadster with original tires gave steering that was more tight, but was more of a harsh response over rough road surfaces, even small bumps can be startling. It was more stressful to drive over time, as the ride quality is more of a shake monster unless you have really good roads. Unless you do something about it otherwise, there was the under-steer, such that if you accelerate in a turn, you had better crank that steering wheel farther, or you will swing into the other lane, or off the side of the road. It was an unnecessary challenge in that way. And of course the original rear tires wear out way-fast, and do cost more to buy.


Driving on the all 4 +size tires does change the feel of the Roadster, and it allows for an analog adjustment of the car's handling. Change the rear tire pressure a little, you can get a big difference in under/over steer characteristics. Adjust the front tire pressure a little, and you get more of a slight change in handling and response while accelerating in/out of corners.

IMG_7229a.JPG


Add 2psi to rear tire pressure to give more under-steer, go for lower rear psi to get less under-steer and moves toward over-steer.

IMG_7227a.JPG


On front tires it is the reverse: more air in front tires gives less under-steer, and lower air pressure gives more under-steer.

Currently I am running 45-46psi in rear, and 47-48psi in front tires. I would like to spend some time at higher pressures, but will wait until the TPMS can hopefully be calibrated to operate correctly with the new tires that are rated for 51psi, instead of the stock Yoko 44psi spec. As it is, the car starts complaining about 51psi being "too-high" when they get warmed up, even though it is just fine for these tires, since their cold spec is 51!

Driving the car and accelerating out of a turn while making little or no steering correction is fun, and overall the car has a more solid civilized feel. It is remarkable, how different it drives from the roadster loaner I drove in ATL last summer on making a service center visit for the Model S. My ride quality is more smooth and comfortable, road bumps are not such a shock. It feels like a quality improvement.

These tires are all season, and have better wet road characteristics, I hit some wet pavement in turns with the old Yokos that lost traction unexpectedly, so these are an improvement in that way.

The slight increase in road clearance due to a "lift" of 1/4inch that has helped prevent some under-nose scrape, and rubs over steep driveways. I had two spots locally, that are no trouble to clear now.

IMG_7148c.JPG


These tires make me want to drive the Roadster even more.
 
Last edited:

Doug_G

Lead Moderator
Apr 2, 2010
17,881
3,351
Ottawa, Canada
Interesting - thanks for the information.

Unless you do something about it otherwise, there was the under-steer, such that if you accelerate in a turn, you had better crank that steering wheel farther, or you will swing into the other lane, or off the side of the road.

That sounds wrong to me. If you're understeering increasing steering lock makes it worse, not better. The appropriate response is to ease off the throttle.
 

driver_EV

Member
Dec 7, 2011
209
43
Charleston, South Carolina
That sounds wrong to me. If you're understeering increasing steering lock makes it worse, not better. The appropriate response is to ease off the throttle.

Not talking about "steering lock?".

Ease off the throttle is a good response, but not required if tires have not lost traction. In this circumstance, if you desire more acceleration, (and that would be why you decided to accelerate) additional induced under-steer would be corrected by adjusting the steering wheel further. But not everyone will think that is the appropriate response, but steering more works, unless you hit a slick spot in the pavement, or are going way to fast!

What you seem to be describing is when the front tires have lost traction and are sliding.
If that is the case, one should definitely should ease off the throttle.
I have experienced that, and it is a different thing (not merely under-steer).
 
Last edited:

Doug_G

Lead Moderator
Apr 2, 2010
17,881
3,351
Ottawa, Canada
What you seem to be describing is when the front tires have lost traction and are sliding.

That is the very definition of understeer - the car turning less than commanded due to the front wheels sliding. I'm not talking about complete loss of control here - just the tires sliding more than they ought.
 

driver_EV

Member
Dec 7, 2011
209
43
Charleston, South Carolina
That is the very definition of understeer - the car turning less than commanded due to the front wheels sliding. I'm not talking about complete loss of control here - just the tires sliding more than they ought.


Not wanting to argue the point, but you are not exactly correct there.

The car is turning less than commanded, but it is not due to the the front wheels sliding.
I am talking about normal driving here.
Perhaps you are thinking of some sort of drifting?


With all due respect, if the front end is "sliding", you have gone beyond the limits of available traction. This is not under-steer, and has nothing to do with the kind of driving I am talking about.

Under normal driving conditions, where you are not approaching the limits of traction, tires do not slide. They are rolling along on the pavement, and they do have traction that can be immediately demonstrated, by using your brakes for example. The Roadster normally does exhibit some under-steer under these conditions.

350px-TreadDeflected1.jpg


The technical term you are perhaps thinking of (is not slide) is instead "slip angle" and this happens pretty much all the time with all four tires while the car is turning at some significant speed, and while all tires have traction and the vehicle is fully capable of steering based on drivers input.

The behavior referred to as "slip angle" happens in both the front tires and the rear tires of a vehicle, when all four tires have very good traction i.e. when no tires are sliding. The concept is not obvious, so I understand the confusion. Again "under-steer" can and does happen under ideal road conditions, and even quite moderate speeds.

It is the relative differences in slip angle between the front tires and the rear tires that determines under-steer behavior I am addressing, and understanding how this works is how I have been able to deliberately accomplish this, and can readily control (now in fairly dramatic fashion) using only adjustments to tire pressure.

I point you and anyone else who does not understand what I am describing, or does not believe it, to fairly clear explanations on wikipedia.

Slip angle - Wikipedia, the free encyclopedia

The phenomena relates to the way tire tread deforms and allows a lateral vector to be introduced to the direction of wheel travel, -not a loss in friction with the pavement. (not sliding)

"A non-zero slip angle arises because of deformation in the tire carcass and tread." <snip> "This means that the tread element will be ‘deflected’ sideways."​

To cut to the chase on under-steer, here is a relevant clip of the related text, and the references that are provided on that page:

"The ratios between the slip angles of the front and rear axles (a function of the slip angles of the front and rear tires respectively) will determine the vehicle's behavior in a given turn. If the ratio of front to rear slip angles is greater than 1:1, the vehicle will tend to understeer, while a ratio of less than 1:1 will produce oversteer."

Pacejka, Hans B. Tire and Vehicle Dynamics (2nd ed.). Society of Automotive Engineers. p. 3. ISBN 0-7680-1702-5.
Cossalter, Vittore (2006). Motorcycle Dynamics (Second ed.). Lulu.com. pp. 47,111. ISBN 978-1-4303-0861-4.
+image borrowed from wikipedia
-enjoy.
 

Doug_G

Lead Moderator
Apr 2, 2010
17,881
3,351
Ottawa, Canada
Yes, it is called a "slip angle" because the tires are slipping. Tires do not reach maximum grip until they are slipping a little bit.

Just because you have some slip angle does not mean you are understeering; that is a normal situation as you approach the limit of grip. Understeer means that the front wheels are slipping more than the rear, causing the car to turn less than intended. Oversteer means the rear wheels are sliding more than the front, causing the car to turn more than intended. In the extreme this can lead to a spin, but that is a nearly total loss of grip.
 

driver_EV

Member
Dec 7, 2011
209
43
Charleston, South Carolina
Yes, it is called a "slip angle" because the tires are slipping. Tires do not reach maximum grip until they are slipping a little bit.
No, -Not if by "slipping" -you mean "sliding", "skidding" or otherwise losing "grip".


Just because you have some slip angle does not mean you are understeering;
I never said that it does.


that is a normal situation as you approach the limit of grip.
Discussions of "limit of grip" are not part of the points I am presenting, and it is also not related to the steering behavior I have addressed.
(I don't do that, so it is irrelevant here).



"slip angle" is a technical term with a specific definition that does not include slipping, sliding, or losing grip.

-there is lots of confusion on Internet discussions. Generally they are related to "pushing the limits", racing, etc.
DriftingStreet.com presents information that conflicts with itself, and illustrates how sliding and skidding gets mixed in with "slip angle":
Oversteer Understeer - Slip Angle



If you do decide to take the time to read and understand the relevant material in my previous post, you would be able to submit a specific challenge to it, -if you still disagree, or have a question.


Otherwise I doubt you will reach "maximum grip" on the subject, and my hope for that happening soon is now "slipping and sliding away".
-with apologies to Simon and Garfunkel. :)
 

Doug_G

Lead Moderator
Apr 2, 2010
17,881
3,351
Ottawa, Canada
No, -Not if by "slipping" -you mean "sliding", "skidding" or otherwise losing "grip".

I think what we have here is a problem in communications. Inherently, when there is a slip angle, the pavement is not moving in line with the rubber. There is some "slippage" involved. It's not that the tires are skidding or lost grip, it's just that there is some lateral movement across the tire. This is not a loss of grip; in fact some "slipping" is required to reach maximum grip.
 

jerry33

(S85-3/2/13 traded in) X LR: F2611##-3/27/20
Mar 8, 2012
19,727
22,802
Texas
I think what we have here is a problem in communications. Inherently, when there is a slip angle, the pavement is not moving in line with the rubber. There is some "slippage" involved. It's not that the tires are skidding or lost grip, it's just that there is some lateral movement across the tire. This is not a loss of grip; in fact some "slipping" is required to reach maximum grip.

If the tires actually slipped, the slip angle would be zero. Slip angle is the deviation between the way the wheels are pointed and the way the contact patch of the tire is pointed. It's basically caused by flexing in the sidewall. Tire deviation angle would be a more correct term.

Understeer happens when the slip angle of the front tires is greater than the slip angle of the rear tires. If the slip angle of both tires are equal, then you have neutral steering, and oversteer is when the slip angle of the rear tires is greater than the slip angle of the front.

Slip angle is affected by tire construction (stiffer is lower), tread depth (lower is lower), and air pressure (higher is lower).
 

driver_EV

Member
Dec 7, 2011
209
43
Charleston, South Carolina
Slip angle is the deviation between the way the wheels are pointed and the way the contact patch of the tire is pointed. It's basically caused by flexing in the sidewall. Tire deviation angle would be a more correct term.

"deviation angle would be a more correct term." +1

The tire tread elements are sort of "walking" at an angle from the wheel alignment as the tire rolls, because the flexing of the tire structure allows for that deviation due to the cornering force. On the tires I have changed to, this is more pronounced, and tunable.
 

Bob L

Junior Member
May 30, 2011
6
0
Colorado Front Range
Getting towards the end of life for my second set of rear tires on my 2.5 (~14,000 miles). Thing I really noticed on both sets is the increase in road noise as the tires wore down to the tread bar. Also, both sets wore significantly more towards the center as if 40 psi was too much pressure. Wonder what difference it will make if I drop the pressure to 38 psi. Front tires still have lots of rubber on them. Guess I am just not having as much fun as I should be :)
 

Doug_G

Lead Moderator
Apr 2, 2010
17,881
3,351
Ottawa, Canada
Pretty normal for the fronts to last 3X as long as the rears. Also they definitely do get noisier when they're getting worn.

Keep a close eye on them if you're approaching the wear bar. They seem to somehow end up bald before you know it!
 

hcsharp

Active Member
Jun 7, 2011
3,385
1,345
Vermont

That's funny it shows the price as $192 when I go there. But I'm much more worried about the "closeout" aspect of this deal. Where else can you get these?
 

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