standard tires on 2.5

[Mitrovic]

Understeer
The subject is tricky to understand, and will require more time thinking before you can really "get it".

First you will have to forget about everything you state in that post.
These things do not relate in any way to what under-steer is, and are not what causes it.

Can you do that?



If so, then go ahead and forget about that stuff, and try this:

Read my shortcut explanation again (at least a few times) at the end of this page:
standard tires on 2.5

Spend a little time thinking about how the ideas I have presented relate to different degrees of change in the "orientation of the car" while taking turns with different cornering forces.

If you don't get an "aha!" from that, more explanation may help.

Try the parts of this article that talk about under steer:
Understeer and oversteer - Wikipedia, the free encyclopedia
-though that is way more detailed and tedious to read.

Keep in mind the behavior I am addressing does happen at normal driving speeds and conditions while cornering.

Richard

thank you for explaining. Why do you know this? And what makes you think that this is true?

( I do not want to say that it i snot true, but I heard other explanations from race drivers and race mechanics, so just wondering, thank you ).

B.t.w. I have eliminated a great deal of the understeer of my Roadster by changing the settings of the front suspension.

[driver_EV]

Richard

thank you for explaining. Why do you know this? And what makes you think that this is true?

( I do not want to say that it is not true, but I heard other explanations from race drivers and race mechanics, so just wondering, thank you ).

B.t.w. I have eliminated a great deal of the understeer of my Roadster by changing the settings of the front suspension.

Hi, Race drivers and race mechanics are focused on getting the maximum desirable driving characteristics, while pushing the cars to the absolute limits of performance (making it possible to win races). That is the context they are living in, and is where their advice comes from.

Have you ever asked the race drivers and mechanics if tire selection affects understeer? I am sure they would tell you "yes it does". Different tires can make understeer worse or better it just depends on how they are selected.

But adjusting the size of tires is not a technique(too crude/coarse) that race mechanics use to fine tune a car for maximum performance. They choose tires of an appropriate type for racing a specific car (maximum traction, best racing handling, racing specification, etc), and then fine tune the suspension for maximum racing performance, to the preference of the driver to get maximum speed, maximum braking, best cornering ability, and while handling in a way that the driver can have the best control, combining all of that, to win races.

My statements are not intended to apply to this context, and I have said a few times that I am not presenting information for race driving. So we are talking about different things. If you are wanting the tire specification I provided to apply to the race track and be competitive, I do not think so. (I understand the Roadster is a very safe car to crash in, but I still do not think it is a good idea) The tires I selected are not racing tires and I am not saying they will be correct for driving at the limits of speed and traction, ok?

About how/why I know this, and what makes me think it is true?
Well, I came to understand this years ago when I was working as a service tech for BMW. (I worked on BMWs built in the 1980's - year 2000, passenger cars, not race cars) The relationship between tires and understeer was told to me by a fellow tech, not sure where he got it.

Is it really true? how do I know it is really true? That is easy, I experience it every day I drive my car.
I have not adjusted suspension in any way at all. Only the rear tires were changed.

Is there a specific question about what I have done or said in prior posts? What exactly does not sound right to you?

Are you satisfied with your changes in the front suspension settings?

[augkuo]

I don't know why but always thought you weren't supposed to mix different kinds of tires for front and back. Does it make zero difference in terms of safety then? Seems like you found a good alternative but would be nice to have all 4 tires the same. AD07s and the AD048 I think are the only official options though. Thanks for looking into this.

That's mainly so that the tire stores can sell you more tires As long as the two pairs (front and back) are matched in size then that's ok - for AWD/4 wheel drive you would want all 4 tires to match so in that case you would replace them all with the same brand and size.

[S-2000 Roadster]

That's mainly so that the tire stores can sell you more tires As long as the two pairs (front and back) are matched in size then that's ok - for AWD/4 wheel drive you would want all 4 tires to match so in that case you would replace them all with the same brand and size.

There are plenty of good reasons besides just selling tires. ... but I see your smiley.

The Tesla Roadster has 16" wheels in front and 17" wheels in the rear, so you cannot literally match all 4 tires with the same size.

[hcsharp]

Richard

thank you for explaining. Why do you know this? And what makes you think that this is true?

( I do not want to say that it i snot true, but I heard other explanations from race drivers and race mechanics, so just wondering, thank you ).

B.t.w. I have eliminated a great deal of the understeer of my Roadster by changing the settings of the front suspension.

I also eliminated most of the understeer by adjusting the front suspension, and prefer that to driver_EV's solution in which he essentially reduced the rear tire grip by using different tires. He likes how it feels so it's OK for him. YMMV

[driver_EV]

I also eliminated most of the understeer by adjusting the front suspension, and prefer that to driver_EV's solution in which he essentially reduced the rear tire grip by using different tires. He likes how it feels so it's OK for him. YMMV

Your Mileage Would Be The Same, actually, anyone with an unmodified Roadster Sport with factory specified "performance " settings would get the very same results I do. It is a perfectly simple and "easy to duplicate" way to tune the car. All user preference adjustments are available to further increase or decrease the steering response of the car as desired. Tire pressures, suspension adjustments all still work to make it more perfect for you. With a different setup, or tires that are different from what I selected, in that case then, YMMV.

I plan to dial up rear tire pressures slightly (trying up to 45lbs for now) and evaluate higher speed steering response. Higher tire pressures will damp down the steering response a bit to help prevent over-steer.

The original Yoko tires were down past the wear bumps, so their grip was becoming very questionable.

The new tires are designed as all-weather performance, year-round traction, including light snow. The original tires are limited to warmer season driving.

I do not experience any "grip" issues. The traction control light comes on sometimes, it did before the tire change, -not a problem. The tire change is not about grip.

The real difference is understeer is gone, and the car to me is easier and more fun to drive. Its not "OK" for me, -it is SUPER for me.

Roadster driver ggr from San Diego CA has tried the same tires and reports to be happy with the results.

[driver_EV]

Update:

GGR and others who try out these tires:
Increasing rear tire pressure definitely seems to be a further improvement.
Tire pressures are set prior to driving, before tire temperatures increase.

Front tires: 30lbs
Rear tires: 45lbs

<inserted update>
as of September 2012:
Front tires: 30-35lbs (psi)
Rear tires: 48lbs (psi)
<inserted update>

Small adjustments above 40lbs(psi) to the rear of the car are quite noticeable due to the majority of vehicle weight back there.
Next I am trying out a boost of front tires to 35lbs, still keeping 45lbs for rear tires.
Getting this narrowed down to what seems ideal.


-another update for March 9th:

Increase of front tire pressure does not change handling to a noticeable degree. Dropped front pressure back to 32lbs, keeping slightly above the 30lb spec due to the tread wear looking like the edges may be thinner than the middle part of the tread. This may be the way the tires were when new, I did not check them closely though when the car was new. This may make little or no difference at all, and does not seem to be a particular benefit from perspective of steering response.

Now for the rear tires we get great benefit from adjusting the tire pressure with these new tires.
Setting the rears at 40lbs on these new tires demonstrates very clearly the difference in steering response, even to the point that it feels like it may become over-steer at high speeds and cornering force. (very exciting really) Setting rear tire pressure to 45lbs tames this down quite a lot. My personal preference is somewhere between these two settings. It is really nice that the car can be tuned with rear tire pressure now.

Refined as of April 3rd:
My preference currently, and may be final settings for these tires on the car: (Overall steering feels very responsive, neutral and predictable)

Front tires: 30lbs
Rear tires: 43lbs - 45lbs

For a bit more response at low speeds (<40mph) try rear pressure at ~43lbs.

I like running the rear tires at 45lbs. Slightly higher tire pressure is good for higher driving speeds and longer range drives.

*** Late April updated again:
Hard cornering with power applied can start a wee bit of over-steer, but higher rear tire pressure moderates that and two actions are 100% effective at controlling this: Ease slightly off the accelerator or straighten the steering wheel just a bit.

Car is very exciting to drive. It has quick steering response, under-steer is no more!
Fun fun fun.
(I am so happy this car exists, and that I am alive now and able to own it!)

It is hard to believe I have put almost 5000 miles on these tires in less than 3 months! I still am very happy with my selection of these rear tires.
The tire tread on these is still standing tall. The original tires would be getting worn at this point, as I had to replace the originals before they hit 8000 miles, but these Michelin tires are doing great.

MichelinPilot Sport A/S Plus

They work great for sporty daily driving.


I had an interesting experience while driving on a 1200+ mile trip across the Southeast US.
Since I wanted to get the best range, I dialed up the rear tire pressure to 46lbs(psi) -rather like turning the volume on my "stereo" up to 11 right?
I then set off on the first part of my journey, from the Atlantic coast to stop in Augusta Georgia.

After charging a few hours, I set off on the next leg of my journey toward Atlanta. Shortly after getting on the Interstate, I heard a "gong" sound.
I was puzzled, and looking around, then heard it again. Finally I saw a message on the info display indicating a problem with tire pressure, so I took an exit and pulled over to investigate, then seeing a message that said the RH rear tire pressure was too high! I found this perfectly amazing, not because it happened, nor because the tire monitoring system on the roadster worked perfectly (I could not be happier about that), but instead, what impressed me was that the warning was exactly correct for the not spec tires!

I am running rear tires that are non-spec for the roadster, and the pressure limits are very different from the Tesla spec tires. I must conclude the tires manufactured today have a RFID chip or metal strip device (inside the tire?!) that the car tire pressure monitor can "read" that indicates what the manufacturer tire pressure limits are for the mounted tires and then the car TPMS issues alarms based on that! The max pressure rating for the new tires is 51psi. Overpressure warning indicated 52psi! Perfect! Has anyone heard of this feature?

So why did I exceed the max pressure, and what did I do? The pressure increased because tire temperature increases when driven, and increasing the temperature of the air in the tires causes tire pressure to increase in proportion to temp. Also the ambient temperature increased in the middle of the day from the early morning start time. Another factor would be elevation was probably 350 feet above my starting near sea-level elevation.

What did I do? well it took a minute or two to get pulled over, get my tire pressure gauge out and verify pressures. It did match the TPMS indication of the car! I then just let a slight amount of air out of the tires, so the pressure was then 50psi. and continued on my journey with no other issues. After the trip was done I checked the pressures with tires cooled completely and they were back to my roadster preference of 45psi.

I will ask the Tesla service folks about the tire pressure monitoring system to confirm it really is this smart!

----

-Update Sept, 2012:
- at the annual service a couple of months ago I did ask about TPMS operation. Rangers indicate it is a proportional monitoring, in that if some pressure indication gets much higher than the other tires (above some percentage) it will issue an alarm.

So, based on that, I now have a reason to increase the front tire pressures as well as the rear, and I have done so.

Increased front psi does not seem to affect steering response at all, but should allow higher rear tire pressures without causing the TPMS alarm. 51psi is the max pressure for the Mich tires, that is measured cold (prior to driving). I now run at around 48psi in the rear, and around 35psi for the front -(original Yoko's still in fine condition at about 18,000 miles, and plenty of tread depth).

[-another update Oct, 2012: Based on my experience with this, the TPMS pressure alarm level for tire pressure "too high" is fixed, and not proportional, at least for the rear tires. It always goes off at 51psi. This needs to be adjustable or possibly disabled. I will go back to Rangers on this request.]


So for a further update, here is a picture of the drivers side Michelin (LH rear tire) after 10,000 miles of daily roadster sport driving:



I think the ~48psi or so for these tires on the Roadster is most appropriate. Lots of torque/load back there in perf. mode would likely be better handled with higher air pressure. The reduction in tendency to over-steer is a diminishing difference at this point, and I think the tires are nicely in the sweet zone for my daily zipping and zooming around the countryside.

In addition, I have had other (Roadster folks) drive my car with these tires, and they all agree that this is a winner. These tires cost less than the originals, weight is less, are quiet, they give a smoother ride, are lasting a lot longer, and they prove to be a drive-ability hop-up.

Changing the rear tires to this specification (and changing nothing else) provides very delightful, increased sporty steering response, in addition to the other benefits, to this awesome daily driver.

-enjoy.

[driver_EV]

Above post is updated with a report on 10,000 miles on these tires.

[j-g]

Anyone look at or install Bridgestone Potenza RE 970 AS Pole position tires on the rear? According to specs, they are identical size to the AD07's with 835 revs/mile and come with a tread life warranty. Test results on Tire Rak look good too. I would like to know if these tires create regen or TC issues with Roadster 1.5 (2008)

[Jackyche]

That's an good find and I'm interested in the results as well. Its the first one I've come across that has the same rev/mile as the AD07's. However, and perhaps someone can shed light on this, the diameter is 25" versus 24.9" on the AD07. How can they have different diameter and same rev/mile?

Someone on another thread had a theory that the 0.1" difference may be the cause of the TC on the regen.

Anyone look at or install Bridgestone Potenza RE 970 AS Pole position tires on the rear? According to specs, they are identical size to the AD07's with 835 revs/mile and come with a tread life warranty. Test results on Tire Rak look good too. I would like to know if these tires create regen or TC issues with Roadster 1.5 (2008)