David Lickfold Does a Deep Dive on Gravity Driving Dynamics

@hmp10 mobile, so can’t watch the video, but I will ask you the important question: which tires should I get? ;)

I'm trying to find a source for Chinese tires. Where's the thrill in trying to keep the Gravity under control all the time? 😏
 

@hmp10 I offer you the budget tire in that test against the Pirellis:)
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. . . the important question: which tires should I get?

For all the sophisticated suspension engineering in the world, the most important thing of all in driving a car is what is going on at the point the tire patch contacts the pavement. I think it's the most under-rated and under-examined element of vehicle dynamics by a car owner. There is no easier way to undercut all the work of a suspension team than to make a careless tire choice.
 
For all the sophisticated suspension engineering in the world, the most important thing of all in driving a car is what is going on at the point the tire patch contacts the pavement. I think it's the most under-rated and under-examined element of vehicle dynamics by a car owner. There is no easier way to undercut all the work of a suspension team than to make a careless tire choice.
I don't disagree. But it's also a bit of black magic to figure out which tire is ideal for a certain vehicle and certain driving patterns. Consumer Reports is so influential with tire choices because they boil it down it a handful of digestible ratings, and you just pick the highest rated tire that does well on the metric you think you care about the most. It's difficult enough to develop the expertise to do better than that, and it's not really feasible for most people to test fit a set of tires to a see how you like them. Particularly if you're thinking about specific weather conditions. For me personally, I'd generally just trust the engineering team that made the OEM tire choice, or else I'll buy a 3PMSF tire recommended by Consumer Reports. If I was racing, then I wouldn't leave it at that.
 
Throwing my hat in..
I think the 20"/21" tire choice is pretty good. For good rain and snow (all season) performance the EVO is a good tire choice. I think the others are maybe constrained with tire sizes and testing. I trust Lucid to give us the best tire choices.
(hmp10's point) - Owning other high performance cars and matting the pedal at 45 mph with 80 degree weather in 3rd gear and the rear tires light up is not a good stock tire choice - this was GM. Lucid I think is way better solution overall.
 
I don't disagree. But it's also a bit of black magic to figure out which tire is ideal for a certain vehicle and certain driving patterns.

It certainly is. That's probably why the Tire/Wheel Discussion thread has gone to 9 pages on this forum. And there were some very knowledgeable / very interested "tire people" on it (@PetevB, @Elfin, @037, @illopp00, et al.) who had a lot to contribute. As many years as I've spent as a layman reading about tires, I probably learned more about the subject in the tire discussions on this forum -- especially from the engineers -- than in any one other place.


Consumer Reports is so influential with tire choices because they boil it down it a handful of digestible ratings, and you just pick the highest rated tire that does well on the metric you think you care about the most.

At least people who check out CR reviews are giving it something of a go when they choose tires. But so many people choose tires with no consideration beyond the best price they can find or what some guy at a tire store is trying to push that day without really understanding what that may entail. To the extent they think about handling and braking at all, they probably assume it's the car that will take care of that more than the tires.

But just consider that tire review that @illopp00 posted above. As with most tire comparison tests, this test was conducted using the same car for all the different tires. And when you look at just one key metric -- wet braking -- you see the braking distances cover a range from 22.48 meters for the best tire to 31.42 meters for the worst (and cheapest) tire. That's a 40% increase in wet stopping distance in the same car, all attributable solely to the tire.


I trust Lucid to give us the best tire choices.

I agree, especially as all three tire choices are stamped "LM1", which means Lucid worked with each tire manufacturer to tune the tires to Lucid's key criteria for each tire. However, it's also important to understand what Lucid's criteria were for each tire. For instance, I'm pretty sure Lucid leaned heavily toward optimizing the Hankooks for range, as it wanted to maximize the range it could advertise for the Gravity. But to do that, it seems Lucid was willing to compromise wet performance significantly -- a widespread criticism of the Hankooks -- and that's something buyers to whom that matters need to know.
 
Some decades ago one of the car mags was answering the "what tire size?" question. This was when wheel size choice was just starting.
They took a BMW sedan to the track and tested a Michelin in 15", 16", and 17" sizes (decreasing sidewall profile). At the time 15" wheels were standard on the BMW sedan.
After the day of testing the drivers were asked which size was better.
They all liked the 15"

The German engineer: "Ya, we tuned the suspension for the 15" .

Just did A/S to summer swap. I have a completely different car now. The Lucid air suspension was clearly tuned for 21" wheels.
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I agree, especially as all three tire choices are stamped "LM1", which means Lucid worked with each tire manufacturer to tune the tires to Lucid's key criteria for each tire. However, it's also important to understand what Lucid's criteria were for each tire. For instance, I'm pretty sure Lucid leaned heavily toward optimizing the Hankooks for range, as it wanted to maximize the range it could advertise for the Gravity. But to do that, it seems Lucid was willing to compromise wet performance significantly -- a widespread criticism of the Hankooks -- and that's something buyers to whom that matters need to know.
Do you suppose the primary reason there is a 21/22 option is just so there is a stock all-season performance option?

I switched after reading about the Hankooks on the wheel/tire thread; it seems almost dangerous to put wheels with poor stopping characteristics on such a heavy and powerful vehicle. I guess the "best" option would have been to stick with the 20/21s and get aftermarket tires, but I'd prefer not to have that extra step.
 
..I guess the "best" option would have been to stick with the 20/21s and get aftermarket tires...
If you can. Tire choices are very limited by size and load capacity specs, especially for the first few years.
 
Do you suppose the primary reason there is a 21/22 option is just so there is a stock all-season performance option?

I think that's a real possibility, especially as there is no range advantage with the mid-size wheels over the 22/23" wheels. Of course, that'a assuming the order configurator has the range figure right for the Michelins, something which several of us suspect might not be the case.
 
I am now leaning toward the 21"/22" tires. Good compromise and I need to deal with lots of rain. The Michelin's seem like a better option all around. I can sacrifice a little range for safer driving in rain as hydroplaning is no joke.
 
I am now leaning toward the 21"/22" tires. Good compromise and I need to deal with lots of rain. The Michelin's seem like a better option all around. I can sacrifice a little range for safer driving in rain as hydroplaning is no joke.

We do, too, in south Florida (at least once our current drought is over). That's why we're opting for the mid-size wheels on our Gravity road tripper after I saw the wet performance test results for the Hankooks, although I would have liked to get the range the Hankooks deliver.


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We do, too, in south Florida (at least once our current drought is over). That's why we're opting for the mid-size wheels on our Gravity road tripper after I saw the wet performance test results for the Hankooks, although I would have liked to get the range the Hankooks deliver.


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I would give you a heads up to wait for full test reviews as the Michelin Primacy is LM spec and is not the same well reviewed tire you see on TireRack, for example, the traction rating goes from A to B which means whatever they did impacted the standard rain test enough to drop a grade. Not sure it’s worth an upcharge unless you are going the 22/23 route.
 
I would give you a heads up to wait for full test reviews as the Michelin Primacy is LM spec and is not the same well reviewed tire you see on TireRack, for example, the traction rating goes from A to B which means whatever they did impacted the standard rain test enough to drop a grade. Not sure it’s worth an upcharge unless you are going the 22/23 route.

As we're getting Gravity Dreams, there is no upcharge for wheel selection. We're getting one with the 22/23" wheels for performance in local driving (year-round in south Florida) and one with the 21/22" wheels for cold-weather roadtripping.

This is not as excessive as it may sound. We were ready to replace two of our cars, anyway (Model S Plaid and Honda Odyssey), and given the road test reviews of the Gravity and its apparent chameleon-like ability to cover both the sports sedan and people/cargo hauler bases, we just decided to make them both Gravities. It means we can deal with different weather conditions without wheel swaps, only have to get used to the elaborate driver controls and UI's of a single model, and only have to deal with one company for repair and maintenance.
 
I would give you a heads up to wait for full test reviews as the Michelin Primacy is LM spec and is not the same well reviewed tire you see on TireRack, for example, the traction rating goes from A to B which means whatever they did impacted the standard rain test enough to drop a grade. Not sure it’s worth an upcharge unless you are going the 22/23 route.

I'm not sure this matters much, if at all. From the Tire Rack explanation of UTQG ratings:

"The Traction grade, or traction rating, as they are commonly called, is based on the coefficient of friction of a locked (skidding) tire in a straight line on a wet surface. It doesn't evaluate any dry performance, cornering of any sort, or hydroplaning resistance.

The test tires are simply pulled on a 'skid trailer' at 40mph over wet asphalt and concrete test surfaces. The brakes are momentarily locked, and sensors measure the coefficient of friction as the tire skids.

A tire that is on the verge of lockup but still rotating will generate a different coefficient of friction than the same tire if it is skidding. Since the vast majority of vehicles on the road today have anti-lock brakes, tire manufacturers design their products to work more effectively with these systems, as opposed to at full lockup. Because of this, the Traction rating isn't as real-world applicable today as it was when the test was designed." [my emphasis]
 
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I'm not sure this matters much, if at all. From the Tire Rack explanation of UTQG ratings:

"The Traction grade, or traction rating, as they are commonly called, is based on the coefficient of friction of a locked (skidding) tire in a straight line on a wet surface. It doesn't evaluate any dry performance, cornering of any sort, or hydroplaning resistance.

The test tires are simply pulled on a 'skid trailer' at 40mph over wet asphalt and concrete test surfaces. The brakes are momentarily locked, and sensors measure the coefficient of friction as the tire skids.

A tire that is on the verge of lockup but still rotating will generate a different coefficient of friction than the same tire if it is skidding. Since the vast majority of vehicles on the road today have anti-lock brakes, tire manufacturers design their products to work more effectively with these systems, as opposed to at full lockup. Because of this, the Traction rating isn't as real-world applicable today as it was when the test was designed." [my emphasis]
not going to argue real world as it doesn't exist yet, I am just noting that there is in fact a scientific difference and you should keep an eye on it. There is 0 chance TireRack will test Lucid specific tires vs those that are non brand specific so it's all going to be subjective. Unless a car magazine decides to get us some data to tell us if it's good enough.
 
not going to argue real world as it doesn't exist yet, I am just noting that there is in fact a scientific difference and you should keep an eye on it. There is 0 chance TireRack will test Lucid specific tires vs those that are non brand specific so it's all going to be subjective. Unless a car magazine decides to get us some data to tell us if it's good enough.

I'm aware of that. However, for people who don't design and conduct tire tests, there is little else objective we can turn to in making tire decisions other than whatever test results we can find.

While the long tire discussions we have had on this forum have brought me around to the view that there's no gain in second guessing the decisions Lucid made, it is still important to understand what criteria were in Lucid's sights when they made those decisions. For example, I'm convinced Lucid, in its zeal to advertise impressive range for the Gravity, made some decisions in choosing and then tuning the Hankooks that don't make it the right tire for our Gravity in dealing with south Florida's often torrential downpours. Fortunately, Lucid made a different decision in choosing a different all-season tire for another wheel set, and what test data there is that I can access tells me it's the better choice for our needs.
 
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