Tire/Wheel Discussion

[hmp10]

Two options here: either Lucid went all out in pursuit of the best possible handling numbers and optimized for the biggest wheels at the expense of the others, or they took the middle ground and tried to make everything work well at the expense of a fraction of absolute performance on the biggest tire package. If I was a betting man, especially as this car wasn't built to concur the Nürburgring, my money would be on the latter.

View attachment 27177

Interesting. I suspect the former, as Eric Bach, the Chief Engineer of Lucid, has said that on his personal Gravity he's going to have two sets of wheels: the 22/23" for optimized handling, and the 20/21" for road tripping range. (Of course, all he probably has to do to switch the wheels is drive one set to work in the morning, give his key fob to the shop, and drive home on the other set.) That might suggest that the Gravity suspension calibration is optimized to the largest wheel set, although optimizing to the mid-size wheel set would seem to be the sweet spot for accommodating as many buyer choices as possible.

One of the reasons I want to use the Pirelli P Zeros when I switch the mid-size wheels to summer rubber is my assumption that, by staying with the same tire line that is on the larger wheel/tire package, I'll preserve more of its performance, at least in terms of tread pattern and compound, sidewall structure, etc.

But the variables propagate in so many directions once you start delving into this that it just leaves my head spinning. So I'm just going to stay with the mid-size wheels for several reasons, in this order:

- more choices of tires as new ones come to market
- probably better aerodynamics and thus more range than the largest wheels, once a more efficient tire is fitted
- looks (don't really want too much of a "gangsta-wheel-on-a-Camry" vibe from the hardware-exposed look on a Gravity)
- marginally better impact resistance to the potholes that are getting more common even in Florida
- marginally more compliant ride.

 

[SaratogaLefty]

I just put on a new set of 21" Pirelli PZero tires on my Dream Edition. Original were LM1 and the new ones are LM2. Initial observation is car is quieter with the LM2 tires on the freeway.

 

[Cosmo Cruz]

I personally got over the “they look better” thing a while ago —

 

[hmp10]

I'm still trying to track down efficiency data on the tires I'm considering for our Gravity when we pull off the Michelin Primacy tires. This data is very hard to find.

I did find out the Continental DWS06 Plus (the only all-season tire I think gets within spitting distance of max performance summer tires for sporty driving) have a 9.75 kg/to rolling resistance measure. But I can't find the rolling resistance for the Pirelli P Zero (non-EV tire) and the Michelin Primacy to which I'd like to compare it. (I still think the reason the large-size and mid-size wheel options on the Gravity have the same EPA rating, even though the mid-size wheel seems to be an aero design, has to do with lesser efficiency from the Michelins.)

Any idea what these numbers are?

 

[illopp00]

Tire Rolling Resistance Data Bank: Comprehensive Guide

Unlock your vehicle's potential with the right tire choice. Explore our comprehensive Tire Rolling Resistance Data for optimal performance

toptirereview.com

Getting into real weeds here

 

[hmp10]

Tire Rolling Resistance Data Bank: Comprehensive Guide

Unlock your vehicle's potential with the right tire choice. Explore our comprehensive Tire Rolling Resistance Data for optimal performance

toptirereview.com

Getting into real weeds here

I read tire reviews the way I approach Russian novels -- find them mesmerizing but really wish I could put them down because they just go on too long.

 

[Pragmatic]

Need to account for aero efficiency as well as rolling resistance.

 

[illopp00]

I am yet to be convinced the middle tire wheel package on the website has the correct range posted, not it's been officially EPA tested. I was thinking it's more like 407 miles based on the Air.

 

[Wulf0123]

I am yet to be convinced the middle tire wheel package on the website has the correct range posted, not it's been officially EPA tested. I was thinking it's more like 407 miles based on the Air.

I also don't trust the middle ones range numbers. I'm torn because I keep hearing that the Hankook have poor performance in rain, but I can't tell if that's compared to the larger ones or just other all weather. I keep leaning towards the 20s for the efficiency and ride, but also for handling some poor dirt roads. Feel like the Michelin would be a nice balance between handling and efficiency, but if they really get such poor mileage it definitely more forces me to stick with the 20s.

 

[hmp10]

I also don't trust the middle ones range numbers. I'm torn because I keep hearing that the Hankook have poor performance in rain, but I can't tell if that's compared to the larger ones or just other all weather. I keep leaning towards the 20s for the efficiency and ride, but also for handling some poor dirt roads. Feel like the Michelin would be a nice balance between handling and efficiency, but if they really get such poor mileage it definitely more forces me to stick with the 20s.

I agree the range numbers may be suspect. However, the comments about the Hankook's wet performance come from Tire Rack testing of an array of tires, including all-seasons and the Pirelli P Zero on the large Gravity wheels, and from a Motor Trend comparison of all-season tires.

From Tire Rack:

And in their objective measures, the Hankooks were dead last:

From Motor Trend:

 

[PetevB]

I also don't trust the middle ones range numbers. I'm torn because I keep hearing that the Hankook have poor performance in rain,

Unfortunately good rain performance and low rolling resistance are diametrically opposed. To get good rain performance you want large, deep voids between tread blocks along with soft rubber. But these things both cause tread block squirm, which requires energy. People often complain about how quickly EV tires wear out, generally failing to realize that they usually start new with much less rubber before the wear bars than their non EV counterparts because that’s a simple way to increase EPA range.

As for getting both good wet performance and range there are options. The first one I’d look at would be to get fresh rubber before the rainy season. Realize that the tire that ranks worst for rain performance will, when new, crush the tire that ranks best if it’s even half worn. In some places like California the rainy season is easy to time. Similarly two sets of rubber, one for summer and one for winter, will destroy the best all season rubber run year round. The performance advantage is so great that it’s law in Germany, and there is zero doubt in my mind that I’d have been in a massive multi-car wreck on the autobahn if it hadn’t been (sudden slushy snow around a bend at speed, three cars wide, we all moved over one lane in unison due to hydroplaning).

In California back in the day on my BMW 1M my routine used to be a fresh set of extreme performance summers from ~May through November on one set of rims followed by a fresh, full depth set of “rain tires” for the winter. There’s little chance that those with a Gravity, myself included, will burn through rubber as quickly as a tail-out autocrossed 1M, but one set of full tread depth either all season or winter rubber on at the beginning of the season (and in a perfect world a second set of dedicated summer rubber put on the moment the season ends) is still an option to evaluate for maximum performance. It’s hard to overstate how much worse worn performance rubber is- harder rubber, less of it so less compliant, a fraction of the void space, etc. Even road noise. If you’re driving in the rain anywhere near the wear bars you’re basically screwed regardless of how good the tire is.

Back to the first part of your statement I fully agree the middle tire option range numbers are suspect and likely to be much better than what’s reported currently.

 

[PetevB]

Interesting. I suspect the former, as Eric Bach, the Chief Engineer of Lucid, has said that on his personal Gravity he's going to have two sets of wheels: the 22/23" for optimized handling, and the 20/21" for road tripping range.

Circling back I realize you’re correct: the Gravity essentially must be tuned to work best from a performance perspective on the largest wheels. Because what I said about tuning the suspension to the tires can’t be true for the Gravity, at least in one important way:

Back to the physics: the tire works best when the face is held flat to the road, but the car rolls over in corners and the tire deflects, so to hold the outside tire flat in a corner you need camber. Of course static camber works against the inside tire as it’s in the wrong direction, and it also hurts braking performance in a straight line. To avoid this you engineer in dynamic camber or “camber gain”. As the car rolls the suspension compresses, and as it does so the kinematics adds camber. Something between .6 and .9 degrees of camber per inch of suspension compression is typical, and this lets the wheels be quite flat to the road both in a straight line and leaned over in a corner.

But the Gravity has height adjustable suspension to the tune of over 4 inches. If it had even a half degree of camber gain per inch then at its lowest setting it would have two degrees more camber than at the highest. Straight line braking performance would be hugely compromised, the tire would wear the inside edge, etc. So the Gravity must have little to no camber gain. This simplifies things greatly: anything that reduces deflection in a corner is best. Active suspension with variable spring rates to limit body roll in a corner would go a long way, but even then the tire itself will deflect. And thus the tires that deflect least will have the most performance potential. So it makes complete sense that the Chief Engineer would have those two sets of rims, as tire selection aside the biggest rims should have a significant performance advantage as those tires will deflect least.

 

[Elfin]

Circling back I realize you’re correct: the Gravity essentially must be tuned to work best from a performance perspective on the largest wheels. Because what I said about tuning the suspension to the tires can’t be true for the Gravity, at least in one important way:

Back to the physics: the tire works best when the face is held flat to the road, but the car rolls over in corners and the tire deflects, so to hold the outside tire flat in a corner you need camber. Of course static camber works against the inside tire as it’s in the wrong direction, and it also hurts braking performance in a straight line. To avoid this you engineer in dynamic camber or “camber gain”. As the car rolls the suspension compresses, and as it does so the kinematics adds camber. Something between .6 and .9 degrees of camber per inch of suspension compression is typical, and this lets the wheels be quite flat to the road both in a straight line and leaned over in a corner.

But the Gravity has height adjustable suspension to the tune of over 4 inches. If it had even a half degree of camber gain per inch then at its lowest setting it would have two degrees more camber than at the highest. Straight line braking performance would be hugely compromised, the tire would wear the inside edge, etc. So the Gravity must have little to no camber gain. This simplifies things greatly: anything that reduces deflection in a corner is best. Active suspension with variable spring rates to limit body roll in a corner would go a long way, but even then the tire itself will deflect. And thus the tires that deflect least will have the most performance potential. So it makes complete sense that the Chief Engineer would have those two sets of rims, as tire selection aside the biggest rims should have a significant performance advantage as those tires will deflect least.

Both Rivian and Tesla have camber gain on their air suspensions (and it causes tire wear problems!). If Lucid was truly "compromise nothing" they would put active toe and camber adjustment on the vehicle.

https://www.caranddriver.com/news/a46132454/lamborghini-active-wheel-carrier-revealed/

Interestingly the Gravity does have the ability to adjust rear toe because each rear wheel has its own steering rack.
Anyway, I hope the suspension is not tuned for the fastest lap times because that usually leads to lots of inside tire wear when driven below 10/10ths...

 

[WeighingGravity]

Big thanks to hmp and petevb, you guys are really generous to share your knowledge with the forum.

 

[hmp10]

Big thanks to hmp and petevb, you guys are really generous to share your knowledge with the forum.

Thanks, but I have no more than a layman's understanding of what questions to pose when it comes to tires. People such as @PetevB (an engineer) and @Elfin (engineer or suspension guru?) are the ones with the answers.

 

[hmp10]

. . . what I said about tuning the suspension to the tires can’t be true for the Gravity, at least in one important way . . . .

How do you think swapping the Michelin Primacy all-seasons for Pirelli P Zero summer tires -- something I'm hoping will improve range a bit -- will affect handling on the mid-size wheels?

 

[PetevB]

Both Rivian and Tesla have camber gain on their air suspensions (and it causes tire wear problems!). If Lucid was truly "compromise nothing" they would put active toe and camber adjustment on the vehicle.

https://www.caranddriver.com/news/a46132454/lamborghini-active-wheel-carrier-revealed/

Interestingly the Gravity does have the ability to adjust rear toe because each rear wheel has its own steering rack.
Anyway, I hope the suspension is not tuned for the fastest lap times because that usually leads to lots of inside tire wear when driven below 10/10ths...

One can certainly still have camber gain and the associated issues, but it can’t practically get enough for the largest wheel size to not be substantially better.

If it were me I’d probably let camber go positive at the highest ride height, maybe half a degree, then I’d limit camber to perhaps 1.2 degrees negative at the lowest ride height to avoid burning out the inside edge in highway cruising. So I’d probably get a max of .4 degrees per inch of camber gain. Using something like 3 degrees per G of body roll (I’m assuming very flat, more like a track car, due to the spring rate adjustable air suspension) the outside wheel would compress around an inch and a half, so I’d dynamically add ~.6 degrees to the static camber, which at low ride height is about a degree to begin with. So perhaps up to 1.2 + .6 = 1.8 degrees of camber, but the car’s rolled over 3 degrees so you’re 1.2 degrees the wrong direction before you consider tire deflection. 0.9 degrees per inch of camber gain, more typical for a sports car, would put the tire nearly flat to the road in the same corner, but then you’re looking at positive one degree of camber at the top down to negative 3.8 degrees at min ride height- forget it.

My (current) conclusion is that the Gravity will disproportionally benefit from bigger rims vs most cars, as minimizing any extra camber loss due to tire flex will be particularly important.

 

[PetevB]

How do you think swapping the Michelin Primacy all-seasons for Pirelli P Zero summer tires -- something I'm hoping will improve range a bit -- will affect handling on the mid-size wheels?

Short answer is I don't know. Can you link the two tires you're looking at? I did mount PZero Electrics on my Model 3 before I got rid of it so I have experience on those, but I doubt they are the same generation you're looking at. In general summer tires beat all seasons everywhere except when it gets cold, maybe 50 degrees being a crossover depending, but you're not looking for an "in general" answer.

 

[hmp10]

Can you link the two tires you're looking at? I did mount PZero Electrics on my Model 3 before I got rid of it so I have experience on those, but I doubt they are the same generation you're looking at.

I've been driving the Pirelli P Zero Elect LM1 tires on our Air since late 2021 and have found them excellent in wet and dry handling and tread wear.

Here are the tires that will come on the Gravity with mid-size wheels:

Here are the Pirellis I'm looking at for the Gravity. Although they don't identify them as part of Pirelli's "Elect" line of EV tires, the Tire Rack testers say some of Pirellis are stamped with the "Elect" logo even though the tires aren't listed as such, so it's not clear what is actually available currently. (Note that they're not an exact "set", as the front and rears have different load ratings, and the rears have the acoustic foam.

Here are a new series of P Zeros that show in the Pirelli website but apparently aren't yet in production. They are definitely EV tires, and they have the "Seal Inside" coating that seals punctures and allows the tires to stay in service. I find that appealing, except that this sealing compound adds 3-4 pounds to the weight of the tire, depending on size -- and puts that weight on the outside diameter where you least want it.

 

[Elfin]

Here's a good thread on how Rivian toe and camber change with ride height.

https://www.reddit.com/r/Rivian/comments/12i03ck/alignment_changes_due_to_ride_height_changes_some

The author's conclusion is that you should get the car aligned at the ride height you want to drive at most of the time and not lower the car for range on road trips.