need new tires - should I get ps4s for my aero wheels or upgrade to 20"?

[al503]

Like F1, right? And Indy.

If I'm not mistaken, the 13" and 15" wheels, respectively are spec'd by the rules. F1 is looking at going from 13" to 18" within the next couple of years.

"A switch from 13-inch to 18-inch wheels is set be part of Formula 1's 2021 rules package that is currently being formulated by a team of engineers under Ross Brawn."

F1 pushing for bigger tyres to be introduced as part of 2021 rules

 

[Feathermerchan]

Probably to accommodate bigger brakes. Not for style points.

 

[mswlogo]

I think you'll regret OEM 20's. If you like OEM look go for 19". Not sure if they make that tire in 19" but there plenty of sticky/grippy/watt-eating tires to choose from.

I went from Aero/Primacy to OEM 19" with low-rolling-resistant/watt-sipping 19" tires. Zero difference in efficiency from Aero's.

BTW way OEM 19" are $330 each.

 

[la3541]

Thanks everyone for the great information! Sounds like the general consensus is to either put the PS4S on my Aero wheels or switch to forged 19".

 

[SammichLover]

The 18” PS4S tires alone should be enough to make you very happy. They’re great. Just don’t drive in the snow (or freezing conditions - ever) and expect about a 10% range hit.

This, except expect a lot less range hit than that. Maybe 5%. Assuming you don't go driving hog-wild with your newfound grip, which is a thing that might happen. YMMV

Cold PSI settings:

• below 38 PSI, straight out, your steering will be dead, probably not good for tires or wear either
• 38 PSI - 40 PSI, okay but a little low
• 40 PSI - 41 PSI perfect driving-around-town, amazing grip and handling, costing you a little range, but your tire wear should be very even
• 45 PSI pump it up to here for those long trips where you care more about range, it'll be smidgen off for handling and get a little greasy under HARD turning, plus higher risk of uneven wearing in the middle of the tire so make sure to bring the pressure back down when you get home

 

[AlanSubie4Life]

This, except expect a lot less range hit than that. Maybe 5%. Assuming you don't go driving hog-wild with your newfound grip, which is a thing that might happen. YMMV

I’m going to talk about Wh/mi in this case rather than %, now...

I think all else being equal, 25Wh/mi less with the MXM4 vs. (non-Tesla) PS4S is quite likely. (So PS4S at least 25Wh/mi worse.)

I understand you have not seen as much difference, but it is also warmer now than perhaps your prior comparisons - which affects efficiency of the battery a couple % perhaps, regardless of HVAC use - and also you may have been driving a little harder early on with your MXM4s.

It’s really hard to say without doing a side-by-side test on a set course.

I think it is good to assume 30Wh/mi (someone else confirmed close to this number above), and if you do better, great. It is better to get more range than you expect rather than less!

 

[SammichLover]

I think all else being equal, 25Wh/mi less with the MXM4 vs. (non-Tesla) PS4S is quite likely.

Actual says nope.

<edit> Unless you think I would have been getting sub-200Wh/mi cruising at 70mph across Kansas?

And BTW, if you think driving to Custer, SD in May represented warmer then usual.....you don't know the Rockies and/or the Gulf Coast.

 

[AlanSubie4Life]

Actual says nope.

It is true that the narrow non-Tesla PS4S tires may do better.

As far as South Dakota is concerned - it is really hard to compare data from a road trip to your day to day. If you are careful, you’ll generally get very good efficiency on a road trip.

I’m not saying you aren’t correct - I am just saying I would prefer to assume 30Wh/mi for now.

But I’d like to see data, and more user feedback. If you look at predicted ranges in the Teslike tables it looks like about 10Wh/mi or 20Wh/mi at 55mph depending on whether Aeros are installed or not - but doubt this data because, it is all curve fits from EPA coefficients as I understand it, curve fits are evil as compared to an actual physically accurate model, and I don’t believe the Aeros buy that much at 55mph.

Anyway, maybe the OP can chime in once he gets his PS4S and uses them for a while.

 

[SammichLover]

As far as South Dakota is concerned - it is really hard to compare data from a road trip to your day to day. If you are careful, you’ll generally get very good efficiency on a road trip.

I'm comparing straight across both (and not Kansas). Both day to day and I made two trips to Fort Stockton area very close to each other, one on MXM4 and one an PS4S. Variable differences were small, couldn't tell the efficiency difference. That's at higher speeds, mostly, too because large portions are on 75mph and up speed limit road.

Couldn't say what the exact difference is but I'd be surprised if it is above 5%.

 

[AlanSubie4Life]

That's at higher speeds, mostly, too because large portions are on 75mph and up speed limit road.

Couldn't say what the exact difference is but I'd be surprised if it is above 5%.

It is better to do this efficiency comparison (measuring Wh/mi difference) on surface streets at speeds below 40mph. It is very easy to have a mild 5mph tail wind (or headwind) on the freeway and that makes at least +/-6% difference at near 70mph. Negligible effect on surface streets as long as the winds are mild.

At a true steady 75mph on open roads, the efficiency difference will also be a smaller % due to the considerably higher overall Wh/mi. In the OP’s LA area, even with max freeway traffic speed generally at 75-80mph, aero losses are often less due to other traffic, and relatively rarity of actually hitting those 75-80mph speeds.

Anyway the PS4S are great (don’t track them!) and I recommend the OP get the 18”s - he said he was willing to take a hit on efficiency. Just wanted him to be prepared.

 

[SammichLover]

It is better to do this efficiency comparison (measuring Wh/mi difference) on surface streets at speeds below 40mph.

Imma going to have to call Goal post move!!!!

Plus efficiency is so good at that speed it doesn't matter in any practical sense.

It is very easy to have a mild 5mph tail wind (or headwind) on the freeway and that makes at least +/-6% difference at near 70mph.

Good thing I'm not an idiot and can read weather report as well as make a note every time I get out of the car. Discerning exactly what is going on can be challenging in West Texas because of wind. That's why sometimes you need to toss out certain legs entirely when you're trying to compare. There's a reason they have thousands upon thousands of turbines out there.

And if it was just one thing, maybe. But it isn't. Every way I've looked at this, it comes up negligible. I have to stretch to call it 5%. You still haven't answered, you really think the MXM4 would get 200Wh/mi or lower in that particular Kansas leg?

Anyway the PS4S are great (don’t track them!) and I recommend the OP get the 18”s - he said he was willing to take a hit on efficiency. Just wanted him to be prepared.

Just wanting to make sure bystanders are not misinformed leading them give the option a pass for dubious reasons.

 

[AlanSubie4Life]

Imma going to have to call Goal post move!!!!

How is this a goal post move? The actual answer is the same in either case. I just was saying it is easier to measure the answer correctly at low speed. You can still apply the same answer, in Wh/mi, at high speed. It is always the same (assuming same pressure/temp/surface etc.).

If I ever get MXM4s (and I think I probably will within a few weeks) I will then have data. And I will be able to swap back and forth.

Good thing I'm not an idiot and can read weather report as well as make a note every time I get out of the car.

No you are not and I am not suggesting that. It is just that 1) 5mph makes a big difference and most people feel that as relatively calm and 2) for a 100-mile trip it is hard to keep track of exact winds every step of the way.

 

[SammichLover]

What are you going to compare the MXM4s to?

Also, you don’t need exact 2mph type of granularity for wind speed when you’ve got enough data. Specifics disappear into the average.

The odds become very low, there just isn’t any support in the data for your supposing about what these tires mean for efficiency.

 

[AlanSubie4Life]

What are you going to compare the MXM4s to?

If I do it, the comparison will be:
Tesla stock PS4S 20” compared to
235 width MXM4s on some aftermarket 18” wheels. Not exactly the comparison we have been discussing here as the PS4S in question are somewhat different - 18” PS4S are narrower, but also somewhat stickier (more gravel spray) than the stock 20” PS4S - so I suspect nearly a wash between those two PS4S.

 

[SammichLover]

If I do it, the comparison will be:
Tesla stock PS4S 20” compared to
235 width MXM4s on some aftermarket 18” wheels. Not exactly the comparison we have been discussing here as the PS4S in question are somewhat different - 18” PS4S are narrower, but also somewhat stickier (more gravel spray) than the stock 20” PS4S - so I suspect nearly a wash between those two PS4S.

LOL

That's got roughly zippo to do with the discussion here.

All your pokes at my data pale in comparison to the leaps you're proposing. Really that assumption at the end is circular to your other assumptions leading to your guess about 18" PS4S vs MXM4.

 

[AlanSubie4Life]

LOL

That's got roughly zippo to do with the discussion here.

Ok...

You’re right, there are no similarities.

I’m sure braking distance is not correlated at all with stickiness and rolling resistance. Haha.

As I have always said, my numbers are an estimate and are intended to capture what I think is about the worst you are likely to observe. If it’s “only” 20Wh/mi, I would not be particularly surprised.

 

[SammichLover]

You’re right, there are no similarities.

Well the word PS4S is there, I guess?

I went back and added detail to explain. You're just lining up a circular confirmation.

 

[AlanSubie4Life]

Well the word PS4S is there, I guess?

Right. And while they have significant differences which I have already mentioned, I don’t expect them to be THAT different - I’d say rolling resistance is likely to be roughly proportional to their stopping power. So sure, if the PS4S you have don’t stop as well as the Tesla 20” (I don’t have the data), they probably roll a little easier.

The MXM4 to PS4S (admittedly, PS4S 265/35R18, non-Tesla width, 9.6” not my 8.8”, but with standard (???) PS4S compound) are 125feet and 105ft respectively. That suggests a significant difference in stickiness and that will impact rolling resistance. If anything, Daniel’s experience with them is that they have higher rolling resistance than the stock 20” - but yes, his tired are quite wide.

That’s the source of my educated guess (estimate)! And I do think it represents a high end guess, as I said above.

If I had actual data on efficiency, I thought was good, I would quote it. But I do not.

 

[SammichLover]

Right. And while they have significant differences which I have already mentioned, I don’t expect them to be THAT different - I’d say rolling resistance is likely to be roughly proportional to their stopping power. So sure, if the PS4S you have don’t stop as well as the Tesla 20” (I don’t have the data), they probably roll a little easier.

The MXM4 to PS4S (admittedly, PS4S 265/35R18, non-Tesla width, 9.6” not my 8.8”, but with standard (???) PS4S compound) are 125feet and 105ft respectively. That suggests a significant difference in stickiness and that will impact rolling resistance. If anything, Daniel’s experience with them is that they have higher rolling resistance than the stock 20” - but yes, his tired are quite wide.

That’s the source of my educated guess (estimate)! And I do think it represents a high end guess, as I said above.

If I had actual data on efficiency, I thought was good, I would quote it. But I do not.

Bottom line you're proposing using circular logic, using your assumptions to confirm your assumptions.

 

[AlanSubie4Life]

Bottom line you're proposing using circular logic, using your assumptions to confirm your assumptions.

You can review my original “claims” which were clearly “ballpark”. I also stated the potential issues with my estimates. I don’t really see a problem with that post. Are the numbers high side? Perhaps. I have no way to know for sure. I think that was pretty clear.

need new tires - should I get ps4s for my aero wheels or upgrade to 20"?

This is accurate. I put PS4Ss on my car about 2000 miles ago replacing the stock MXM4s on my 18" wheels with Aeros and it's been less efficient by 25 Wh/mi.

Or.... we can go with data. I am assuming the above PS4S were 235/45R18 from context. Note the above is likely (assumed from context) in spite of warming temps in San Diego (which would typically result in general improvement in efficiencies), but comes with the usual caveats that it is not an instrumented side-by-side test (which you do not have data for, either). We can’t go with “it is just what someone said on the internets” to discount it, because that applies to all of us!

If you have additional data showing the exact results you have experienced, it would be great to see them. Sounds like 5%. 5% of what, how many miles, what you are comparing to, your test course with screen shots before/after, conditions, etc. If you want to be precise (which as I said, is not that important to me, but seems important to you).