Tire/Wheel Discussion

[hmp10]

. . . or possibly the stock rims too. Maybe see if those are for sale?

Nope, nada.

 

[hmp10]

That biggest rim option is looking more interesting. I suspect that’s a very good tire [Pirelli PZ5] in terms of performance vs rolling efficiency.

There are some European reviews of the PZ5 on YouTube that have some interesting information. (The first is dubbed into English and compares the PZ5 directly to the PZ4; the second is in Polish but, fortunately, my partner is Polish and walked me through it. It does have a bit of information that is discernible to a non-Polish speaker. Basically, he thought the PZ5 was a significant step forward over the PZ4 in performance and efficiency.)

I'm pretty much on the verge of switching my Gravity Dream order back to the 22/23" wheels, but I'm going to hold off a few more days to see the test results "Tyre Reviews" is going to post.

 

[PetevB]

I'm pretty much on the verge of switching my Gravity Dream order back to the 22/23" wheels, but I'm going to hold off a few more days to see the test results "Tyre Reviews" is going to post.

No need to wait for the reports IMHO. They are going to be great.

Step back and you’ll see that performance tires have been progressing at a rate of .25% improvement in lap time per year over the last 20 years. EV tires have been progressing at an arguably faster rate as they’re a newer thing. The Pirelli PZero 4 was introduced in 2016, so nine years of development time, equivalent to 2.5 seconds on a two minute lap- an eternity. And while the PZ4s you’d get today on an OEM bespoke tire wouldn’t be the same as the ones from 2016, a PZ5 will benefit from all of that continuous development. Add the fact that it’s tuned specifically to this vehicle, accounting for whatever camber issues, etc that might be present? No brainer.

In a few years you might be able to improve on the OEM solution when tires have evolved even further. But right now? No chance you’re doing “better”. You can do “different”, ie priories different things, but if your priorities are close to those of the factory you’d be silly to do anything else. $.02

 

[hmp10]

In a few years you might be able to improve on the OEM solution when tires have evolved even further. But right now? No chance you’re doing “better”. You can do “different”, ie priories different things, but if your priorities are close to those of the factory you’d be silly to do anything else. $.02

I was hoping to do a little bit better on range with the mid-size aero wheels without giving up too much in acceleration, braking, and handling if I could find the right summer tire for those wheels.

I've been searching European tire retailers to see if a front/back PZ5 pairing would be available for the mid-size wheels, even if not specifically tuned for the Gravity, but no luck. The only summer tire that will fit both wheels is the Pirelli PZ4, with all the issues we've already discussed with different tuning for each axle as there are no front/back pairings with any one tuning spec.

So, if I have to pick one priority to go with, it is handling performance over range -- which pretty much means the PZ5 on the big wheels.

Lucid's choice to go with staggered diameters and widths means the choice of tires starts thin and narrows with each move up the wheel option so that at the 22/23" set there is only one tire on the market -- and even that tire is not currently available anywhere except through Lucid.

 

[037]

Spoke with the engineer and was strongly discouraged from messing with wheel sizing. Keep it 21/22 vs 22 all around.

 

[hmp10]

Spoke with the engineer and was strongly discouraged from messing with wheel sizing. Keep it 21/22 vs 22 all around.

I don't have any intention of messing with the wheel sizes.

However, in a recent video Kyle Conner said that a Lucid engineer told him the staggered diameters were used primarily for cosmetic reasons, not engineering reasons. I was just wishing Lucid had not gone down that path and had tuned the suspension for wheels that posed fewer problems with tire choices.

 

[037]

I don't have any intention of messing with the wheel sizes.

However, in a recent video Kyle Conner said that a Lucid engineer told him the staggered diameters were used primarily for cosmetic reasons, not engineering reasons. I was just wishing Lucid had not gone down that path and had tuned the suspension for wheels that posed fewer problems with tire choices.

Let’s just say I went to the top of the engineering pile with my question. It was a definite hell no.

 

[PetevB]

Spoke with the engineer and was strongly discouraged from messing with wheel sizing. Keep it 21/22 vs 22 all around.

I’d strongly recommend the same. The car was designed with stagger. Going back to the same diameter rims all around would increase rear slip angle, delaying rear response. Response will likely feel disjointed: turn, the front reacts, wait, the rear reacts, the rear overshoots, correction is required. If the car wasn’t designed with stagger this would have been addressed in other ways such as rear kinematic compliance, but given that it was and the rear OD is substantially larger than the front things are pretty locked in.

I do have a competition car with two sets of rims, one staggered 18s and 19s for street-able autocross rubber and a second set that’s not staggered for slicks. It’s impressive how much the staggered setup helps keep the rear “in phase” with the front.

 

[illopp00]

Spoke with the engineer and was strongly discouraged from messing with wheel sizing. Keep it 21/22 vs 22 all around.

Yeah they seem to have dialed that in from Sapphire and it's hard to argue with that.

 

[Elfin]

I’d strongly recommend the same. The car was designed with stagger. Going back to the same diameter rims all around would increase rear slip angle, delaying rear response. Response will likely feel disjointed: turn, the front reacts, wait, the rear reacts, the rear overshoots, correction is required. If the car wasn’t designed with stagger this would have been addressed in other ways such as rear kinematic compliance, but given that it was and the rear OD is substantially larger than the front things are pretty locked in.

I do have a competition car with two sets of rims, one staggered 18s and 19s for street-able autocross rubber and a second set that’s not staggered for slicks. It’s impressive how much the staggered setup helps keep the rear “in phase” with the front.

I feel like you're talking about a level of driving that's not applicable to 99% of drivers.
I do reasonably well at autocross and I don't notice these things. I would note that many people run square setups on cars that come stock with staggered wheels because most cars understeer from the factory. It being a bad idea to run different outer diameters than the factory tires make sense though.

I'm very annoyed with Lucid for designing an AWD car with staggered wheels. I'm very skeptical that there is any meaningful performance advantage and it's a huge loss in practicality.

 

[WeighingGravity]

So, bottom line it for a practicality-minded driver who has never taken a car on a track or pushed a car to probably even 90% of its limits. I'm interested in having a little bit of fun on back roads but need to balance that with range efficiency, ride comfort, and all-season performance. (I really, really don't want to have to change rims in the winter, and I live in the mid-Atlantic so I get temps between 15-100F, a couple meaningful snowfalls each year, and plenty of rain) I don't want to spend $1200/tire on replacements, and I really don't want to have to replace a bent rim.

Middle size wheel with spec'ed all seasons?

 

[PetevB]

I feel like you're talking about a level of driving that's not applicable to 99% of drivers.
I do reasonably well at autocross and I don't notice these things.

I feel confident you'd notice if you ran the test. You'd at least be able to tell that one option "feels better" than the other, though you might not be able to verbalize why. So much of this does come down to feel. Pro tire testers spend virtually all of their time optimizing for feel. Get that right and time against the clock is a byproduct.

I would note that many people run square setups on cars that come stock with staggered wheels because most cars understeer from the factory. It being a bad idea to run different outer diameters than the factory tires make sense though.

Most classes don't allow adjustable swaybars if the cars didn't come with them stock, so you're left with limited tools the adjust handling balance, often leading to all kinds of weird alignments, tire pressures, etc. When suspension is adjustable, however, things get simpler for most racers: as much rubber as will fit. Neither of these are very applicable to street cars.

I'm very annoyed with Lucid for designing an AWD car with staggered wheels. I'm very skeptical that there is any meaningful performance advantage and it's a huge loss in practicality.

As an engineer the optimum is staggered from a performance perspective. The math is pretty simple: you want to maximize drive out of corners for the best lap time, weight transfers rearward on acceleration, you want all the rubber loaded evenly for maximum grip so that outside rear tire needs a bigger contact patch. The tire height difference is a smaller factor, but larger OD does help traction as well (minimally). I agree it does compromise other things though- you can't rotate your tires, spares become a bigger issue, etc. So it becomes a question of performance vs practicality, and we all have our own ideal point on that continuum.

 

[PetevB]

So, bottom line it for a practicality-minded driver who has never taken a car on a track or pushed a car to probably even 90% of its limits. I'm interested in having a little bit of fun on back roads but need to balance that with range efficiency, ride comfort, and all-season performance. (I really, really don't want to have to change rims in the winter, and I live in the mid-Atlantic so I get temps between 15-100F, a couple meaningful snowfalls each year, and plenty of rain) I don't want to spend $1200/tire on replacements, and I really don't want to have to replace a bent rim.

Middle size wheel with spec'ed all seasons?

That's my bet for your use case. As I've said I expect the mid size wheels will eventually be revealed to have ~430-435 miles of range on the 5 seater, so slightly less range and somewhat more grip and performance than base. The big option is a no-go for winter, so that's out, the smaller wheels would likely work fine but too but wouldn't for example brake as well in the wet and might not have as responsive a feel.

All reading tea leaves pending real info.

 

[hmp10]

As an engineer the optimum is staggered from a performance perspective. The math is pretty simple: you want to maximize drive out of corners for the best lap time, weight transfers rearward on acceleration, you want all the rubber loaded evenly for maximum grip so that outside rear tire needs a bigger contact patch. The tire height difference is a smaller factor, but larger OD does help traction as well (minimally). I agree it does compromise other things though- you can't rotate your tires, spares become a bigger issue, etc. So it becomes a question of performance vs practicality, and we all have our own ideal point on that continuum.

I have a confession. I'm nowhere good enough a driver to do the things with a car -- much less an SUV -- that might tease out this tier of handling differences being discussed on this thread.

It's more psychological with me. I just enjoy a car (or any technology I own) more for knowing it is the best that can be had for the criteria I worry about. The many powerful cars I've owned have sometimes tempted me to do more with them than I should given the limits of my capabilities, and it's reassuring to know there's as much capability as possible on tap with the car to save me from myself.

Also, for some reason, reading about tires has always fascinated me. I can't come close to guessing the number of hours I've spent reading car magazine tire reviews, usually turning to any article on tires before checking out anything else in the issue. And in later years, the technical articles on the Tire Rack website and the numerous tire reviews on YouTube by them and others has stepped in as car magazines have moved to the sidelines.

And I have to say . . . this thread has been a hoot.

 

[Elfin]

As an engineer the optimum is staggered from a performance perspective. The math is pretty simple: you want to maximize drive out of corners for the best lap time, weight transfers rearward on acceleration, you want all the rubber loaded evenly for maximum grip so that outside rear tire needs a bigger contact patch. The tire height difference is a smaller factor, but larger OD does help traction as well (minimally). I agree it does compromise other things though- you can't rotate your tires, spares become a bigger issue, etc. So it becomes a question of performance vs practicality, and we all have our own ideal point on that continuum.

What's the advantage of narrower front tires though? Certainly all wheel drive changes the optimal tire widths?

 

[Elfin]

I still want this tire setup. I assume these are not Hankook Ions...

 

[PetevB]

What's the advantage of narrower front tires though?

Let's ask why "more" isn't simply better? Why not mount 355s all the way around? Because bigger rubber has downsides: it hydroplanes more easily, it's heavier, impacting unsprung weight and hence ride and suspension performance, it takes more width within the vehicle impacting trunk space and especially turning radius, it has more rolling resistance impacting range, etc. So you need to stop somewhere, ideally at an optimum that takes all these factors into account. And the back optimizes slightly larger due to both the weight transfer and the fact that they don't need to turn (as much): you don't feel the gyroscopic effect through the steering wheel on the rear, etc.

Certainly all wheel drive changes the optimal tire widths?

Absolutely. If the Gravity as RWD it'd have absolutely massive rear wheels in a vain attempt to get all the power down. So both all wheel drive and the weight distribution help prevent it from looking like a clown car and bring the optimum much closer together.

 

[PetevB]

I have a confession. I'm nowhere good enough a driver to do the things with a car -- much less an SUV -- that might tease out this tier of handling differences being discussed on this thread.

It's more psychological with me. I just enjoy a car (or any technology I own) more for knowing it is the best that can be had for the criteria I worry about. The many powerful cars I've owned have sometimes tempted me to do more with them than I should given the limits of my capabilities, and it's reassuring to know there's as much capability as possible on tap with the car to save me from myself.

Also, for some reason, reading about tires has always fascinated me. I can't come close to guessing the number of hours I've spent reading car magazine tire reviews, usually turning to any article on tires before checking out anything else in the issue. And in later years, the technical articles on the Tire Rack website and the numerous tire reviews on YouTube by them and others has stepped in as car magazines have moved to the sidelines.

And I have to say . . . this thread has been a hoot.

I get that. I think for most even a 15 mile difference will be pretty academic with a range this long. But I will say that even well below the tires limits I think most can get a glimpse of and appreciate what "right" feels like in car handling. This is part of the reason I've been encouraging you to at least try the biggest wheels, even if you decide to sell them later to get something that's tuned more for your preferences.

Personally I'm not sweating the decision because A) this will be my wife's car which I'll drive on the weekends. B) this means there will basically always be kids in the car, kids toys, sometimes a 75 pound German Shepard, which in turn means that C) if I got to the limit of the stickiest tires I'd run the risk of putting one or more of the above through a closed side window through a corner. Thus because I do occasionally like getting to the limit I almost see less sticky tires as an advantage. But I'm also very interested in feel, so given the opportunity I'd like to try before buying if possible.

 

[Elfin]

Let's ask why "more" isn't simply better? Why not mount 355s all the way around? Because bigger rubber has downsides: it hydroplanes more easily, it's heavier, impacting unsprung weight and hence ride and suspension performance, it takes more width within the vehicle impacting trunk space and especially turning radius, it has more rolling resistance impacting range, etc. So you need to stop somewhere, ideally at an optimum that takes all these factors into account. And the back optimizes slightly larger due to both the weight transfer and the fact that they don't need to turn (as much): you don't feel the gyroscopic effect through the steering wheel on the rear, etc.

Absolutely. If the Gravity as RWD it'd have absolutely massive rear wheels in a vain attempt to get all the power down. So both all wheel drive and the weight distribution help prevent it from looking like a clown car and bring the optimum much closer together.

I'd rather have the extra 20mm of width and 0.6" of diameter in the front and live with all the downsides.
0-60 in 3.5s would be no problem with RWD. I would be curious the relationship between tire width and traction.
What are your thoughts on the Dream Edition having equal power front and rear? That seems like a much bigger compromise than any of this tire stuff.

 

[hmp10]

This is part of the reason I've been encouraging you to at least try the biggest wheels, even if you decide to sell them later to get something that's tuned more for your preferences.

Not to worry. I actually chose the biggest wheels in my original Gravity order, understanding that they would offer the best dynamic performance. It was only when I switched to the Dream Edition and saw a further range drop that I began trying to figure out if I could keep most of the handling advantages while dropping one wheel size . . . if I could find the right tires. My exploration of this question played out on this thread.

I'm now back to the starting point: the biggest wheels for driving around Florida and a second set for cooler-weather road tripping. Once I found out about the Pirelli PZ5s going on the Gravity the deal was done.