Ludicrous with 19s: dumb? or negligible difference?

[HankLloydRight]

19 > 21

Seriously? Do you understand how the scientific method works? Those results prove absolutely nothing.

First of all, you're cherry picking your results by leaving out the .90g and .91g results on the 21" rims.

That analysis is the epitome of "apples and oranges."

Let's see, we have three different organizations running these tests, likely under very different scenarios (weather, track, temperature, drivers, g sensors, etc):

• Car and Driver
• Motortrend
• Edmunds

These tests were all done on NINE different cars, each with different weights, suspensions, RWD/AWD, production improvements (early Sig cars to P85Ds), Performance or Performance+ enhancements, and different drivers:

• 2012 P85
• 2013 P85
• 2013 P85 Sig
• 2014 nonP 60
• 2014 P85+
• 2015 nonP 70D
• 2015 P85D (Car and Driver)
• 2015 P85D (Motortrend)
• 2015 P85D (Edmunds)

Not to mention, absolutely no controls over tire pressures or other variables between any of these tests.

Now if ONE organization used ONE car for exhaustive tests, on the same day, with the same driver, using the same make/model tire on 19" and 21" rims with conclusive results, then you might have a case. Otherwise, this is, at best, a pedestrian data analysis.

 

[AWDtsla]

You could put 17" wheels on the car with the same diameter tire, it won't make any difference for skidpad numbers. Hell you could run them underinflated and get better skidpad numbers.

 

[bhzmark]

Seriously? . . blah blah. Now if ONE organization used ONE car for exhaustive tests, on the same day, with the same driver, using the same make/model tire on 19" and 21" rims with conclusive results, then you might have a case. Otherwise, this is, at best, a pedestrian data analysis.

So where are the results from ONE organization with ONE Model S that shows that 21 is better than 19?

We only have the magazine results that we have. From that information there is no support for the claim that 21 is better than 19 on the Model S.

To the contrary the

SAME MAGAZINE reports the SAME .89g SKID PAD on both 19 and 21

2014 nonP 60 with 19" Eagle RS A2 = skidpad .89 http://media.caranddriver.com/files...eview-car-and-driver2014-tesla-model-s-60.pdf

2015 P85D with 21" skidpad .89g Car and Driver http://www.caranddriver.com/reviews/2015-tesla-model-s-p85d-10000-mile-update-review

 

[HankLloydRight]

So where are the results from ONE organization with ONE Model S that shows that 21 is better than 19?

We only have the magazine results that we have. From that information there is no support for the claim that 21 is better than 19 on the Model S.

And there is absolutely no "evidence" to support the claim that 19" rims are always better.

To the contrary the

SAME MAGAZINE reports the SAME .89g SKID PAD on both 19 and 21

2014 nonP 60 with 19" Eagle RS A2 = skidpad .89 http://media.caranddriver.com/files...eview-car-and-driver2014-tesla-model-s-60.pdf

2015 P85D with 21" skidpad .89g Car and Driver http://www.caranddriver.com/reviews/2015-tesla-model-s-p85d-10000-mile-update-review

On two VASTLY different cars (S60 RWD vs P85D AWD), on completely different tires (Eagle RS A2 vs Michelin Pilot Sport PS2), and the tests are over one year apart. So what's your point?

None of what you've posted is evidence or proves (or disproves) anything.

You're too busy trying to find (fit/shoehorn/cherry pick) the "evidence" to fit your pre-existing belief. That's called "religion". That's not how it works. In science, you do tests and record results from which you then draw conclusions based on the actual evidence to prove or disprove your hypothesis.

Sure, my hypothesis is that 19" rims are not always better than 21" rims (the inverse of your original statement).** But I don't have any evidence (yet) to support that, it's just my belief based on my experience of 30 years of driving high-performance cars, and I'm sure a lot of other people as well.

The absence of evidence doesn't prove the null hypothesis. That's like saying "Since you can't prove that god doesn't exist, he must exist". That's what you're trying to say, and the argument and logic just doesn't hold up.




** This is not the same as saying the 21" rims are always better than 19" rims.

 

[jerry33]

Sure, my hypothesis is that 19" rims are not always better than 21" rims (the inverse of your original statement).** But I don't have any evidence (yet) to support that, it's just my belief based on my experience of 30 years of driving high-performance cars, and I'm sure a lot of other people as well.

You have a good point. Starting with first you have to define "better". No question that a shorter sidewall gives a crisper handing feeling in almost all cases. As that's many folks' definition of better it's certainly correct to say that 21" wheels are better than 19" in that context.

For almost any other context, and there is a problem reducing the rather large number of variables down to just the wheel diameter to get real data. Tires in one size may have very different characteristics than the same make and model tire in some other size for a variety of reasons. Add to that there is a financial incentive to larger wheels and tires (from the tire manufacture, wheel manufacture, tire store, etc. point of view) so there won't be much of a push to show smaller wheel diameter is better.

My opinion is that the small gain in crisp steering feeling is not worth the cost and reduction in other areas. It would be easier to see if you could obtain the radar graphs from the tire manufacturers.

 

[HankLloydRight]

My opinion is that the small gain in crisp steering feeling is not worth the cost and reduction in other areas.

Now that's a valid point! Yes, as I've posted above, there are plenty of trade-offs with the 21" rims. And completely subjective ones, too. In my case, I would have never *bought* the 21" rims, but they came with the Inventory car I bought, and at time, Tesla was unwilling to swap out for 19" rims. So I got the 21" rims by default. But now that I have them? I love them. They're a fantastic addition to the car in terms of looks AND handling. But I'm willing to accept the trade-offs (more susceptible to damage, more expensive tires, heavier, etc) for the benefits in other areas. I also minimized the 21" tire cost issue by un-staggering my 9" rear wheels and can now buy the same size tires all around AND rotate my wheels, so that eliminates one of the downsides of the + setup. I also bought 19" TSTs with all-season tires for winter use, so my 21" rims get used 7 out of 12 months.

But I realize that not everyone is willing to accept those trade-offs. That doesn't mean any of these blanket statements/beliefs are true:

19s are superior in all respects. Search the forum.

By "all respects" I mean everything. the 19s handle better with equivalent tires. Search the forum and read the evidence.

No they won't. Demonstrably false. Search the forum, read the magazine stats and reports from intelligent people who have driven both.

 

[bhzmark]

And there is absolutely no "evidence" to support the claim that 19" rims are always better.

On two VASTLY different cars (S60 RWD vs P85D AWD), on completely different tires (Eagle RS A2 vs Michelin Pilot Sport PS2), and the tests are over one year apart. So what's your point?

None of what you've posted is evidence or proves (or disproves) anything.

You're too busy trying to find (fit/shoehorn/cherry pick) the "evidence" to fit your pre-existing belief. That's called "religion". That's not how it works. In science, you do tests and record results from which you then draw conclusions based on the actual evidence to prove or disprove your hypothesis.

Sure, my hypothesis is that 19" rims are not always better than 21" rims (the inverse of your original statement).** But I don't have any evidence (yet) to support that, it's just my belief based on my experience of 30 years of driving high-performance cars, and I'm sure a lot of other people as well.

The absence of evidence doesn't prove the null hypothesis. That's like saying "Since you can't prove that god doesn't exist, he must exist". That's what you're trying to say, and the argument and logic just doesn't hold up.

** This is not the same as saying the 21" rims are always better than 19" rims.

I provided lots of evidence informing my belief that 21" wheels show no improvement over 19" on handling. And therefore I conclude that since 19" are cheaper, lighter, and more durable for tires and wheels, and with cyclones they look virtually the same, and they provide no handling benefit --> 21" have costs over 19" and no benefits. --> 19" are better than 21". qed.

You provided no evidence supporting your belief that 21" wheels are superior on any handling dimension. Certainly no handling benefit that exceeds the cost and burdens of the 21 wheels and tires. (Perhaps it came to you in a dream and that is acceptable to you in lieu of evidence and test results.)

Or if you just like the way it looks, then that is fine. Can't really argue about matters of taste.

But don't pretend the car handles any better with 21s. There is simply no reason to believe that it does and the mag tests give good reason to believe that it doesn't.

 

[jerry33]

That doesn't mean any of these blanket statements/beliefs are true:

Blanket statements about tires are almost never true in every case. There are just way too many variables. There is also a big placebo effect. If the driver thinks a particular tire is good then he or she will unconsciously drive to maximize the benefits of that tire--and vice versa. When testing new tires, tire manufacturers go to great lengths to eliminate the placebo effect.

The book we can write about what we don't know about tires is far larger than the book we can write about known tire knowledge.

 

[HankLloydRight]

I provided lots of evidence informing my belief that 21" wheels show no improvement over 19" on handling. And therefore I conclude that since 19" are cheaper, lighter, and more durable for tires and wheels, and with cyclones they look virtually the same, and they provide no handling benefit --> 21" have costs over 19" and no benefits. --> 19" are better than 21". qed.

You can conclude anything you want to, but you still haven't provided any proof to support your belief. You're still just saying "I really,really,really,really,really,really,really believe this is true, therefore it has to be". You continue to ignore the evidence that they do provide handling benefits (your excluded the .91g skidpad results from your 'conclusions'). That's fine. I don't really care what you believe. But you've never provided anything other than your beliefs to support your points.

You provided no evidence supporting your belief that 21" wheels are superior on any handling dimension.

Neither did you!! Don't you get it? Just because you say they don't handle better, doesn't make it a fact. I've already proven why the results from the magazines you posted are completely irrelevant to your argument.

Certainly no handling benefit that exceeds the cost and burdens of the 21 wheels and tires. (Perhaps it came to you in a dream and that is acceptable to you in lieu of evidence and test results.)

Wha??? You're somehow equating handling benefits with other costs, like one cancels out the other. They are completely independent dimensions.
And again, you provided no evidence nor applicable test results.

But don't pretend the car handles any better with 21s.

I don't have to pretend. I know they do.

There is simply no reason to believe that it does and the mag tests give good reason to believe that it doesn't.

Sure, there are lots of reasons. The magazine tests prove nothing since they are unrelated test under different conditions. And I'm repeating myself here, but just because those test don't prove one thing or disprove another, doesn't make your argument more valid (see my previous post).

I'm sorry, but I'm done with this silly argument. My final statement on the matter is this: You can not make blanket "this is always true" statements on something as highly subjective as "handling". You can talk about tradeoffs and real differences, but still, nothing you've presented proves your case. Just saying it does, doesn't.

 

[brianman]

The 19" tires make the car feel very cushy -- not in a good way. The 21" convey much more road feel. Plan on replacing them every 10k miles or fewer.

Not sure if I'm disagreeing or not, but I will call this out...

My 2014 P85D with 19 MXM4s is a much harsher ride than my P85 Sig with 21" Continental summers. The latter feels positively luxurious, while the former is not at all "cushy".

YMMV.

 

[bhzmark]

animated gifs are a poor substitute for any test data showing 21" are better.

I'll rely on Car and Driver test results.

2014 nonP 60 with 19" Eagle RS A2 = skidpad .89 http://media.caranddriver.com/files...eview-car-and-driver2014-tesla-model-s-60.pdf

2015 P85D with 21" skidpad .89g Car and Driver http://www.caranddriver.com/reviews/2015-tesla-model-s-p85d-10000-mile-update-review


Hint: even if a 21" 35 aspect ratio tire summer tire would be stickier than the otherwise same but 19" 45 aspect ratio summer tire on some other cars, it won't on a Model S -- unless you do some more hacking. Those who actually read the Car and Driver articles (or was it Road and Track) may figure this out.