Tire/Wheel Discussion

[PetevB]

Tire Rack says that their search filters only generate sets of staggered tires that are compatible. (They will, however, sell a set their filter doesn't produce that includes two different tires if the buyer signs a liability waiver.)

lol. They’ve sold me a few sets of 235/40/18 and 305/30/19s for a ‘69 911 and I’ve never heard of this waiver. It’s a more recent addition, obviously.

Frankly I don’t believe the Tire Rack has the info to accurately judge compatible sets for specific cars. It’s great that they (or the manufactures?) are flagging potential incompatibility, because there are numerous other areas we didn’t even get to. Examples: Porsche GT car tires often have a fraction of the tread void area of more general tires of the same type. If mounted only on one axle this can lead to sudden snap spins due to uneven hydroplaning when it rains. Or sidewall stiffness which impacts total spring rate and hence cornering balance. Or stacked rubber compounds that are designed to optimize grip as the tire wears. Or different amounts of silicas that impact wet vs dry grip, potentially changing balance from understeer in the dry to oversteer in the wet or vice-versa. The list goes on. And on, and on.

You begin to understand why, as long as the tire design is relatively new, I recommend going with OEM tires as long as the design performance objectives are aligned with yours. Optimizing this stuff is a full time job, and doing it correctly requires data civilians don’t have access to. Black Magic. So while I’ve personally done some of this with varying degrees of success I typically recommend against it, knowing that those who know will ignore me. I’d feel much better if there were generic, not manufacture tuned tires available in these sizes that could predictably perform relative to one another. In the absence of that it seems largely a crap shoot without more info or more options.

 

[hmp10]

I’d feel much better if there were generic, not manufacture tuned tires available in these sizes that could predictably perform relative to one another. In the absence of that it seems largely a crap shoot without more info or more options.

I do get the point of the possible advantage of the largest wheels for mounting Pirellis. My two problems with those wheels are that they are not an aero design for range purposes, and there are no all-season tires available for them. So if I wanted to use all-seasons for cold weather road trips, I would have to buy an extra set of wheels as well as tires.

I have come close to just throwing in the towel and getting Continental DWS06 Plus tires for the mid-size wheels to run year-round. I absolutely loved the Continental DW tires on our first Tesla, and the DWS's are one of the very few ultra-high-performance rated all-seasons, and they get rave reviews as well. The problem is that even the best all-seasons will not match the straight-line traction and braking of the P Zeros, which kind of defeats the purpose of getting a Dream Edition if the traction control system is going to erase the power add. (I never drive sustained speeds above 80-85 mph, but I do love jack-rabbiting away from stops with clear road ahead.)

Tire Rack does stock non-manufacturer-tuned PZ4s in the two sizes for the mid-size wheels. But they do not show them as a suitable pairing, probably because the load and speed rating for the 265 is too low (SL / 104W).

They also show tuned tires that carry a "Sport" designation as well as the manufacturer tuning designation, perhaps indicating they at least share the same outer tread block for sport tuning vs. luxury tuning?

Interestingly, neither the Pirelli nor the Tire Rack website shows LM-tuned P Zeros in the 22/23" sizes for the largest Lucid wheels. So either the Gravities delivered in December with those wheels were shod with non-manufacturer-tuned tires, or those tires are not yet listed in the Pirelli or the Tire Rack catalogs.

 

[PetevB]

I have come close to just throwing in the towel and getting Continental DWS06 Plus tires for the mid-size wheels to run year-round. I absolutely loved the Continental DW tires on our first Tesla, and the DWS's are one of the very few ultra-high-performance rated all-seasons, and they get rave reviews as well.

Best of luck… No chance you’d get the range of OEM Michelins in my mind, but ditto with the Pirellis.
OEM Michelin specs below. Note the 1/32 deeper tread depth on the rear. The Lamborghini tires are likely closest given this, not sure if those are front or rear fitment.

 

[hmp10]

Best of luck… No chance you’d get the range of OEM Michelins in my mind, but ditto with the Pirellis.

The P Zero PZ4 is part of Pirelli's Electric tire line:

And it might actually be pretty good on range. Note its range test results in a 100-mile test (on a Tesla Model 3) against the class leader, the Hankook iON evo AS that comes on the smallest Gravity wheels. And it ran right in the pack with EV tires from Goodyear, Yokohama, and Bridgestone.

Also, Continental claims the DWS06 Plus is EV-tuned, whatever that means. Another Continental in the above test, also "EV-tuned", fared well in the range test, too. I don't know if that's any indication of the DWS range, of course. I did find that the DWS has a rolling resistance of 9.75 kg/to, but I don't know if there's any way to convert that to watt hours/mile.

 

[hmp10]

@PetevB, I just noticed the tread widths on the Michelin Primacy specs you posted: 8" front and 8.9" rear.

That's almost an inch narrower on the front than the Pirellis (8.9"). In fact, the Michelin tread width on the rears is the same as the Pirelli tread width on the fronts.

Could that be correct, or is it an error?

 

[PetevB]

@PetevB, I just noticed the tread widths on the Michelin Primacy specs you posted: 8" front and 8.9" rear.

That's almost an inch narrower on the front than the Pirellis (8.9"). In fact, the Michelin tread width on the rears is the same as the Pirelli tread width on the fronts.

Could that be correct, or is it an error?

Did you also notice that of the 285 Pirelli PZ4 options the only one marked Electric has an even narrower footprint? And that it's over half an inch narrower than the next narrowest option? No it's not an error- less rubber on the road reduces rolling resistance, so tires with efficiency as a goal will tend to be narrower. This is also why I'm confident saying that you won't get the range of the OEM Michelins.

It's easy to read a tire test and imagine at all tires of that brand name will perform similarly. Instead PZero PZ4 is really a marketing name for a tire platform which can come in a wide range of different constructions, compounds, tread patterns, etc. Just because some tires built on that platform can have low rolling resistance does not mean they all will. Lamborghini specified a wide footprint, deep tread blocks and quite likely the softest rubber and a grip optimized construction, all of which will hurt rolling resistance. Which is fine for Lamborghini, which doesn't care a whit about rolling resistance. An EV manufacture optimizing for range on the other hand would not make those choices, they'd spec a narrow tire with less tread depth and likely a different compound and construction. The PZ4 has a version like this and it's marked Electric. So they all say "Starbucks" but one's actually Pikes Place and another is Cafe Verona. They are not entirely dissimilar, but they are far from the same thing, and tasting notes from one (ie range tests) don't apply unless you're looking at the same flavor. You're looking at different flavors and assuming they will taste the same. Bad assumption.

 

[Elfin]

My conspiracy theory is that OEM tires are just a way for tire companies to make extra money and for car manufacturers to lower costs. They sell the tires to automakers at a discount and then charge a premium to the consumer for tires that are only marginally different.
I put "generic" Michelin PS4S tires on my Model 3 and ran better lap times than my friend with Tesla specific PS4S. We've also driven side by side on a road trip and I got better efficiency even though I'm running 265/40R18 and he's running 235/35R20. Obviously not a scientific test but my point is that all this stuff is within the margin of error.

 

[hmp10]

This is also why I'm confident saying that you won't get the range of the OEM Michelins.

This is what is so frustrating about the information Lucid puts on its website. The Dream Edition order configurator says a Gravity with the Pirellis on the largest wheels will have the same range as the Michelins on the mid-size wheels -- 370 miles. You know that almost certainly can't be right, but you have no idea which figure is wrong or by how much.

It would be easy to assume they just didn't bother to test the range on anything but one of the Dream wheel/tire options, but yet they show a 410-mile range for the Hankooks on the smallest wheels. And they also show an array of ranges for the Grand Touring, with variances based on wheels, tires, and even seating capacity. So either they were just guessing on most of these, or they didn't do any actual testing of either the largest Dream wheels or the mid-size Dream wheels. (This raises another issue. The range for each wheel size on the Grand Touring changes with the choice of 5- or 7-passenger seating, as does the cargo capacity. But on the Dream Edition, the cargo capacity changes with seating choice, but the range doesn't. Why would going to 7 seats lose significant range on each of the Grand Touring wheel options but not on any of the Dream Edition's? Or is this all just sloppy website programming?)

This makes it devilishly difficult to figure out what tires on what wheel dimensions of what design might yield the the balance one wants between performance and range. In the old ICE days, range was far less a concern as gas costs didn't usually loom large in the equation for expensive cars. But with EVs, range can become a huge issue, especially as vehicles start dropping quickly below the 400-mile mark on cars in which you know you'll fall well short of EPA ratings in real-world road tripping. And when the manufacturer gives what is very likely bum information, you're really left behind the 8 ball.

 

[PetevB]

My conspiracy theory is that OEM tires are just a way for tire companies to make extra money and for car manufacturers to lower costs. They sell the tires to automakers at a discount and then charge a premium to the consumer for tires that are only marginally different.
I put "generic" Michelin PS4S tires on my Model 3 and ran better lap times than my friend with Tesla specific PS4S. We've also driven side by side on a road trip and I got better efficiency even though I'm running 265/40R18 and he's running 235/35R20. Obviously not a scientific test but my point is that all this stuff is within the margin of error.

lol. Yea, with some manufactures and some tires you’re likely right. No one with an off the rack BMW 325i’s going to tell the difference. But in other cases my experience says you’re very wrong. I’ve driven plenty of Porsche on N spec and non-N spec rubber, the difference between these is generally as obvious as a different alignment or a change in ride height. Which given that my GT3 PSC2s both had much less void area and nearly an inch more rubber on the road that the off the rack model shouldn’t come as a surprise. My editor would insist all cars had N spec rubber before we ran road tests back when I wrote about cars for a living…

More perspective here:

Not all Michelin Cup 2 Tires Are Created The Same - MotoIQ

They may look the same, smell the same, and be the exact same size; but not all Cup 2 tires are created equal, and for good reason. Michelin produces off-the-shelf…

motoiq.com