Brakes feel underwhelming, anyone else?

[illopp00]

Michelin All Season 4 - 11/25 on square 22’s

Emergency braking felt fine.

I am in “creep” mode so the brakes always get some bite to them when I drive. In “hold” mode I can picture the rotors being less friendly once actual braking starts. My guess.

60-0 distance is super respectable on UHP All-seasons for a big car, I don't think anyone here is doubting actual braking power.

 

[037]

60-0 distance is super respectable on UHP All-seasons for a big car, I don't think anyone here is doubting actual braking power.

I am trying to set a baseline as small and middle wheel options have a very small contact patch’s area to the ground for efficiency reasons and that adds distance to braking.

Good to have to data to separate facts from feelings. Both are important.

 

[hwy17er]

Here's a fact: F=ma...it's a 3ton car!

 

[NoseyReporter]

So I never realized it but Marqie reached and offered to have one of the engineers talk to me about the brakes in the car. This was months ago and I just noticed it. I took Marqie up on the offer, so we'll see how the conversation goes.

Also, I personally feel 3.6 brought a change to how the high regen setting feels on the car. I wonder if this was an attempt to bring down the regen so that any physical brake application while regen would feel better "matched".

 

[037]

So I never realized it but Marqie reached and offered to have one of the engineers talk to me about the brakes in the car. This was months ago and I just noticed it. I took Marqie up on the offer, so we'll see how the conversation goes.

Also, I personally feel 3.6 brought a change to how the high regen setting feels on the car. I wonder if this was an attempt to bring down the regen so that any physical brake application while regen would feel better "matched".

I am happy to give you the answer before you go and talk to Marqie with the data I collected.

The 6/4 piston brakes in the Gravity are excellent, I did 3-5 back to back 70-0 with a 100-0 thrown in and they did not complain.

The main issue are the efficiency tires, the small Hankooks and middle Michelins are not a performance tire and thus provide a performance that should not be anywhere near an 828hp 6000lb missile that is our vehicle.

CarAndDriver has the large summer tire at 160-162ft braking distance from 70mph, that’s not terrible.

They have the Touring on the small tire at 170+ ft and that vehicle is over 500lb lighter.

I set out to correct the imbalance by going with a square 22x10 setup with Michelin All Season 4 in 265/285 size and stopped as short as 159ft from 70-0 and 295/285 setup that eeked out a best of 157.

Right now I am on a full summer setup with the large wheel and eagle F1 Assymetric 6 Goodyear tire in 275/40/22 and 295/35/23 and that stopped in a Porsche like 152ft from 70.

I am using Dragy Pro for performance measuring and data collection.

In summary: Tires are the issue not the brake system.

You can’t have efficiency and performance all at once, even though I think Gravity is the vehicle that comes close, for a 7 seater.

 

[NoseyReporter]

But I'm not talking about braking performance.

My GT is on the 22/23 setup with "performance" tires.

I've never once encountered abs on the car, meaning I never have reached the limit of friction between the tire and the road surface. My complaint is the feel and disconnect between result and input.

 

[037]

But I'm not talking about braking performance.

My GT is on the 22/23 setup with "performance" tires.

I've never once encountered abs on the car, meaning I never have reached the limit of friction between the tire and the road surface. My complaint is the feel and disconnect between result and input.

If you want to get a real feel for stopping 6000lb turn the regen brakes off.

 

[Eagleye]

... I wonder if this was an attempt to bring down the regen so that any physical brake application while regen would feel better "matched".

I agree with your complaints about the initial bite of the service brakes being poor. I bet a lot of the reason is that they attempted to tune the pedal feel to match the typical use case of a driver coming to a normal stop in traffic but misjudging the regen application and just needing to add a bit of friction braking to come to a full stop. If they pads were too grabby in that case it would be a jarring transition from regen to friction at the very end of the stop, so they optimized for a smooth, 7-seat-luxury-SUV calibration. It's an engineering tradeoff the makes sense, but still a bit of a shame.

 

[037]

Forgot to add the most obvious part:

Those those who use regen exclusively with the vehicle on the default HOLD setting, the physical brakes get barely any use and are thus not in an ideal spot to do any sort of braking.

Mine is set to CREEP and I use them for 6-0mph stops and they are always clean and ready to go.

 

[NoseyReporter]

I agree with your complaints about the initial bite of the service brakes being poor. I bet a lot of the reason is that they attempted to tune the pedal feel to match the typical use case of a driver coming to a normal stop in traffic but misjudging the regen application and just needing to add a bit of friction braking to come to a full stop. If they pads were too grabby in that case it would be a jarring transition from regen to friction at the very end of the stop, so they optimized for a smooth, 7-seat-luxury-SUV calibration. It's an engineering tradeoff the makes sense, but still a bit of a shame.

The system should be tunable though right?

I wonder if they can tune a initial higher pressure from the master cylinder depending on the level of regen being used. I don't know how the Gravity's brake system is setup but my guess its not fully mechanical.

 

[doubletwist]

The system should be tunable though right?

I wonder if they can tune a initial higher pressure from the master cylinder depending on the level of regen being used. I don't know how the Gravity's brake system is setup but my guess its not fully mechanical.

I really hope they don't do that. At least on my air. I absolutely love the feel of the brakes, especially the initial bite. Other cars I've been in, such as my wife's Genesis gv60. I have brakes that bite way too hard when they finally kick in. I find it absolutely impossible to stop smoothly in her car.

If I want to stop quickly, I just pushed down a little harder, it's not THAT much extra effort. With the brakes as they are now *** I *** get to be in control of how hard the brakes are applied, and I really love that.

 

[NoseyReporter]

Well this is a Gravity sub forum.

 

[NoseyReporter]

I had a chance to talk with David Lickfold, a phone call that Marqie very kindly arranged for me. Honestly, I felt bad taking up his time. David's time I'm certain is valuable, so I'm very grateful that someone at Lucid, let alone David, is taking time out of his day to speak with me directly.

David asked me how the Gravity has been for me so far, and while I think this might have been an open ended leading question to my brake complaint, I instinctively complained about my second row seat squeak. Half way through complaining, I realized in my head I was wasting the David's time by talking about something that wasn't in his wheelhouse. I quickly pivoted to the brakes, as that was the real reason for the call.

What follows is just an interpretation of what I think David was trying to figure out.

I described to him my issue with the brake pedal. On high regen, when the Gravity is under full regen deceleration, if a car in front of me suddenly increases its rate of deceleration and I am required to apply a brake input. I feel the brake input required to increase the rate of deceleration requires too much pedal input. It throws alarm bells of in my head.

David started by asking me if I felt that the force required or the input distance was too much. I replied that I feel that travel distance of the pedal is too much. Essentially I think David was thinking about brake pressure vs brake pedal stroke. While I would prefer a stiffer pedal overall in the Gravity this is just a preference characteristic. I hate the feeling of an over-boosted brake pedal, its too soft and gives no feedback.

Then David ask if the Gravity was my daily driver, and if I drove any other cars in rotation with my Gravity. I suspect he was trying to determine if I was more accustomed to a different braking system feel because of constantly switching from one car to another. Fortunately the Gravity has been my only car I have been driving in the last 6 months. I used to commute almost exclusively by bike, as some of you may remember. However, I did tell David that I have had a lot of seat time in two cars: 2007 Cayman S and 2015 Subaru WRX. My Cayman was autox dedicated car, and the Subaru a dedicated track car. I mentioned to David that the Subaru was using a 6 pot Essex AP Racing BBK. He acknowledged I was an enthusiast, and hopefully this gave him some perspective from which I was assessing the Gravity's braking feel.

David then suggested we bring my Gravity into a service center for inspection. That he would have an engineer there to be with the technicians as they inspected the braking system. He made the point was that braking is subject, but before anything qualitative could be taken into consideration that they must quantitatively insure that the braking system of the car is performing to the specifications set forth by Lucid. Essentially, my complaint might easily be explained by a braking system that was not functioning as designed or out of spec. He didn't really elaborate what would happen if the system was determined to be in spec, but I assume my observations would just be taken into consideration for any future brake tweaks done via OTAs or model refreshes; assuming they fielded similar complaints.

I took the opportunity to take my complaint and ask David if they have ever felt this way about the Gravity's braking system. IE Has him or any engineer felt that under the same brake scenario felt that the brake pedal required too much pedal stroke. He said we are all different, and our perception of the brakes are all different because of our individual sensitivity and experiences, and that they also test several different iterations of the Gravity during development so its very hard to answer the question.

We concluded the call, and our next step is to bring my Gravity in for service and inspection.


When I sit back, and think about the problem, I don't dismiss the fact that the braking system might need a bleed or is function out of spec. However, I keep coming back to the challenge of the moment you apply brakes when the car is under regn. It must be a challenge to blend these two system. For one, there are two regen modes, standard and high. Both of which produce two different rates of deceleration or curves . Then I think of the brakes themselves, and how if you only stopped the car via the physical calipers it has its own stopping characteristics or curves. Forgive me if this is the incorrect way of thinking about this but I imagine when you first release the accelerator, the regen curve begins, and it follows a defined shape set by Lucid depending on whether you are in standard or high. However, along this curve, if you apply the physical brakes, then there must be a transition or inflection point in the curve and this point of change must be well blended. And realistically if you are in regen and apply the brakes, you would imagine the curve would steepen in slope because the driver is requesting additional deceleration than what regen is providing.

The challenge here is that the brake pad compound is fixed, so how do you blend the physical braking curve characteristic to two different regen curves?

I suspect if I drove around with the standard regen I might not have this complaint of the braking system. And perhaps the compound of the physical brakes are better "tuned" to the standard regen curve than the high regen curve. Thinking of my curve analogy, what I think I am feeling is a dip in the slope of the curve at the point where I apply the physical brakes, relative to brake stroke, in high regen mode. And to get the slope to steepen, I am required to input more pedal stroke that I'm accustomed to.

Assuming all the above is true, and not just me pulling stuff outta my ass. I guess this scenario makes sense, because how can you get two different physical pad curve characteristics from the same exact pad compound when applying the same pedal stroke? Maybe this solution is the best, and I'm being particular sensitive.

 

[Saksak]

[…] However, I keep coming back to the challenge of the moment you apply brakes when the car is under regn. It must be a challenge to blend these two system. For one, there are two regen modes, standard and high.

The challenge here is that the brake pad compound is fixed, so how do you blend the physical braking curve characteristic to two different regen curves?

Lucid doesn’t do brake blending, which is indeed challenging.

The way I look at it, taking your foot off the accelerator provides deceleration due to regen. When you step on the brakes, you add physical braking to that deceleration - there is no blending.

Have you tried driving without regen to get a feel for the brakes?

 

[doubletwist]

Lucid doesn’t do brake blending, which is indeed challenging.

The way I look at it, taking your foot off the accelerator provides deceleration due to regen. When you step on the brakes, you add physical braking to that deceleration - there is no blending.

Have you tried driving without regen to get a feel for the brakes?

With the Lucid I like to think of it as YOU (as the driver) are in charge of the 'blending'. Once you are completely off the accelerator, all of you braking is regen, then you control with the brake pedal how much physical braking gets added to that.

 

[The_Don]

I am happy to give you the answer before you go and talk to Marqie with the data I collected.

The 6/4 piston brakes in the Gravity are excellent, I did 3-5 back to back 70-0 with a 100-0 thrown in and they did not complain.

The main issue are the efficiency tires, the small Hankooks and middle Michelins are not a performance tire and thus provide a performance that should not be anywhere near an 828hp 6000lb missile that is our vehicle.

CarAndDriver has the large summer tire at 160-162ft braking distance from 70mph, that’s not terrible.

They have the Touring on the small tire at 170+ ft and that vehicle is over 500lb lighter.

I set out to correct the imbalance by going with a square 22x10 setup with Michelin All Season 4 in 265/285 size and stopped as short as 159ft from 70-0 and 295/285 setup that eeked out a best of 157.

Right now I am on a full summer setup with the large wheel and eagle F1 Assymetric 6 Goodyear tire in 275/40/22 and 295/35/23 and that stopped in a Porsche like 152ft from 70.

I am using Dragy Pro for performance measuring and data collection.

In summary: Tires are the issue not the brake system.

You can’t have efficiency and performance all at once, even though I think Gravity is the vehicle that comes close, for a 7 seater.

This is great info, thank you. I'm a performance car enthusiast and while I appreciate the speed of the my Air (I know we're talking about Gravity), I really don't like the relative braking performance. Good to know a stickier summer set is a real needle mover.

Any idea of range impact?

 

[037]

This is great info, thank you. I'm a performance car enthusiast and while I appreciate the speed of the my Air (I know we're talking about Gravity), I really don't like the relative braking performance. Good to know a stickier summer set is a real needle mover.

Any idea of range impact?

I’m not the best person to talk to about range, after I made sure I got the most efficient vehicle in the size and power than I wanted I proceeded to drive it as I want so getting to a 2.4 dynamic is a struggle.

If I ever end up tailgating someone more efficient for any significant distance I will come back and post my comparison.

The last time I did this with my winter all season set over 50 miles I was in the same range bracket as the large wheel setup. My all seasons are a much lighter set of 22x10 wheels at 31# each. Large wheel is 38/40#

 

[037]

Lucid doesn’t do brake blending, which is indeed challenging.

The way I look at it, taking your foot off the accelerator provides deceleration due to regen. When you step on the brakes, you add physical braking to that deceleration - there is no blending.

Have you tried driving without regen to get a feel for the brakes?

I tried 70-0 with no regen, the amount of force required was kind of startling…was done back to back with regular regen and high regen, results were within 10ft but the feel was all over the place.

 

[The_Don]

I’m not the best person to talk to about range, after I made sure I got the most efficient vehicle in the size and power than I wanted I proceeded to drive it as I want so getting to a 2.4 dynamic is a struggle.

If I ever end up tailgating someone more efficient for any significant distance I will come back and post my comparison.

The last time I did this with my winter all season set over 50 miles I was in the same range bracket as the large wheel setup. My all seasons are a much lighter set of 22x10 wheels at 31# each. Large wheel is 38/40#

Ha, I'm sitting at 2.9 on the more efficient Air so sounds like we're not all that different!

 

[Saksak]

I tried 70-0 with no regen, the amount of force required was kind of startling…was done back to back with regular regen and high regen, results were within 10ft but the feel was all over the place.

I’m thinking the amount of brake pressure to reach a given deceleration rate varies with the amount of regen, making the brakes feel different at the different regen settings. I agree - it takes a surprising amount of force on the brake pedal to slow down with no regen, but the Gravity is a heavy vehicle.

I’m reading that the brakes are fly-by-wire with a hydraulic backup. I doubt the brake springs plus hydraulic back-pressure is tunable.