Reducing brake drag?

[gearchruncher]

Has anyone figured out any options to reduce brake drag?

I have an M3P that I track a fair amount. I'm on my 3rd set of brake pads at under 18K miles.
The car also uses about 330-350wh/mi at 65 MPH on flat ground. I've driven identical routes with other M3P's and the car uses a lot more energy. I do have 265 tires on the car, but that's not enough to increase drag by 40-50%.

I recently was thinking about brake drag, and apparently Tesla does use a special caliper boot to retract the pads more than other cars to minimize drag. @MountainPass says that these tend to wear out when used in anger:

We also learned that the low-drag seals that help make the Model 3 so efficient lose their effectiveness after a few track days, as they are cooked and no longer seem to have the same kind of effectiveness as when they were new.

So I went out to my car, took a wheel off and spun the rotor. Didn't seem like much drag to me, but it's hard to tell with the AWD system. Then I knocked back the pads just a touch with a screwdriver until I could just barely see an air gap between the rotor and pad- and WOW, the rotor was way easier to turn. There was also no brake noise present that is otherwise present on all 4 corners of the car.

So I'd like to try to reduce brake drag on my car, and see if this is the source of high energy use. Tesla doesn't sell replacement brake hardware, so I can't try replacing the boots. Other car manufacturers that have focused on low drag have used springs which separate the pads some, and there are even aftermarket ones for some cars like the Insight.

Anyone ever tried anything or have any good ideas on how to push the pads out just a very small amount when not braking?

 

[The Other Dan]

You could try and talk to an engineer at Girodisc. Maybe bounce some ideas off them?

 

[mpgxsvcd]

Do you have significant suspension mods? Maybe the angle is causing issues or something?

That Wh/mi sounds EXTREMELY high. I average 269 Wh/mi even with weekly trips to the Dragstrip. Something really must be dragging there.

 

[The Other Dan]

Do you have significant suspension mods? Maybe the angle is causing issues or something?

That Wh/mi sounds EXTREMELY high. I average 269 Wh/mi even with weekly trips to the Dragstrip. Something really must be dragging there.

View attachment 906452

Damn! I wish I could get anywhere close to that. M3P with 265 PS4S and I'm averaging 315wh/mi.

 

[gearchruncher]

My 10,000 mile AVERAGE is 495 wh/mi on 265 PS4S....

I do have suspension mods, but I also run zero toe, which should be quite efficient, unless there is something about my exact ride height or something that causes massive aerodynamic issues.

 

[mpgxsvcd]

My 10,000 mile AVERAGE is 495 wh/mi on 265 PS4S....

I do have suspension mods, but I also run zero toe, which should be quite efficient, unless there is something about my exact ride height or something that causes massive aerodynamic issues.

Honestly, I think the key here is the 235/45/18 tire dimension. There is a specific reason why they chose that size for the most efficient wheel setup.

Certainly, the Aero wheel covers give the best efficiency. However, I believe that almost any 18x8.5” wheel with a 235/45/18 tire will give exceptional efficiency with the stock suspension. I saw a 10% improvement in efficiency by simply going to the 18” wheel setup even with what is said to be a high rolling resistance tire.

I think that going with a wider tire does affect efficiency with this particular car especially if you also have suspension mods and a high rolling resistance tire.

 

[mpgxsvcd]

Damn! I wish I could get anywhere close to that. M3P with 265 PS4S and I'm averaging 315wh/mi.

What wheel diameter is that with?

Here is my most recent average efficiency. No track time during the winter so it improved slightly. However, preconditioning the battery while moving really hurts my average efficiency for the month. I did a bunch of preconditioning testing in January that made my average for that month look much worse than it actually is.

 

[gearchruncher]

Can we not make this an overall efficiency thread? There are plenty of those. Yes, there are differences based on wheel setup. However, I am hitting >350wh/mi on flat ground at 65MPH. I have 19" wheels, and I've compared with people with 20" wheels and I use way more energy. It's not the wheel diameter.

I'm interested if anyone has played with brake drag and seen any improvements.

 

[mpgxsvcd]

Can we not make this an overall efficiency thread? There are plenty of those. Yes, there are differences based on wheel setup. However, I am hitting >350wh/mi on flat ground at 65MPH. I have 19" wheels, and I've compared with people with 20" wheels and I use way more energy. It's not the wheel diameter.

I'm interested if anyone has played with brake drag and seen any improvements.

Do you have another set of wheels and tires you can try? The only way to really tell what is causing the issue is to isolate it. If you can switch to wheels and tires that should be efficient you could determine if the wheels and tires are causing an issue or if it is something else.

I have always noticed that when I wash my car and don’t dry the discs they get some corrosion on them. Typically I never use my friction brakes so the corrosion doesn’t go away immediately.

Maybe try washing the discs and letting them sit while they dry. If the corrosion wears off with driving it might be an indication that your brakes are in fact the issue?

 

[The Other Dan]

My 10,000 mile AVERAGE is 495 wh/mi on 265 PS4S....

I do have suspension mods, but I also run zero toe, which should be quite efficient, unless there is something about my exact ride height or something that causes massive aerodynamic issues.

Has it been this way since you went on coilovers, or is this a relatively new development? Wondering if the cars rake/aero has been negatively impacted. I generally hear that the typical person who has lowered their car, sees increased efficiency. I know your setup isn't typical.
I would think you'd see more variability if it was rotor friction. Either an increase or decrease after an autox since you've been working them hard.

 

[android04]

Has anyone figured out any options to reduce brake drag?

I have an M3P that I track a fair amount. I'm on my 3rd set of brake pads at under 18K miles.
The car also uses about 330-350wh/mi at 65 MPH on flat ground. I've driven identical routes with other M3P's and the car uses a lot more energy. I do have 265 tires on the car, but that's not enough to increase drag by 40-50%.

I recently was thinking about brake drag, and apparently Tesla does use a special caliper boot to retract the pads more than other cars to minimize drag. @MountainPass says that these tend to wear out when used in anger:

So I went out to my car, took a wheel off and spun the rotor. Didn't seem like much drag to me, but it's hard to tell with the AWD system. Then I knocked back the pads just a touch with a screwdriver until I could just barely see an air gap between the rotor and pad- and WOW, the rotor was way easier to turn. There was also no brake noise present that is otherwise present on all 4 corners of the car.

So I'd like to try to reduce brake drag on my car, and see if this is the source of high energy use. Tesla doesn't sell replacement brake hardware, so I can't try replacing the boots. Other car manufacturers that have focused on low drag have used springs which separate the pads some, and there are even aftermarket ones for some cars like the Insight.

Anyone ever tried anything or have any good ideas on how to push the pads out just a very small amount when not braking?

First of all you can try cleaning and lubricating the guide clips that the brake pads insert into (and that they slide along).

As for drag reducing springs clips, I've tried finding some that were specific for Model 3 years ago and couldn't find any. You would probably have to buy a whole bunch of different size and shape ones to find some that fit. Years ago I even went as far as trying to look up dimensions for a line of spring clips to try start with ones of the correct size, but the manufacturer didn't have specs that I could find on that.

As for the caliper boots, maybe you can buy a whole set of calipers for cheap online because Tesla won't sell just the boots. However, if temperature and hard use damages their properties it will happen again if you keep tracking the car.

 

[The Other Dan]

Were you able to dig into this at all?

 

[gearchruncher]

I have some springs and various things on order to try some stuff out. Gonna see what I can do this weekend.

 

[stevehifi]

FWIW - I've run 265 200TW tire on the street with BBK (that has anti-knock back springs which would contribute to even more drag) and get about 350wh/mi.

When I run the stock wheels on the street with 235 I'm seeing about 300 wh/m.

 

[chobra]

Has anyone figured out any options to reduce brake drag?

I have an M3P that I track a fair amount. I'm on my 3rd set of brake pads at under 18K miles.
The car also uses about 330-350wh/mi at 65 MPH on flat ground. I've driven identical routes with other M3P's and the car uses a lot more energy. I do have 265 tires on the car, but that's not enough to increase drag by 40-50%.

I recently was thinking about brake drag, and apparently Tesla does use a special caliper boot to retract the pads more than other cars to minimize drag. @MountainPass says that these tend to wear out when used in anger:

So I went out to my car, took a wheel off and spun the rotor. Didn't seem like much drag to me, but it's hard to tell with the AWD system. Then I knocked back the pads just a touch with a screwdriver until I could just barely see an air gap between the rotor and pad- and WOW, the rotor was way easier to turn. There was also no brake noise present that is otherwise present on all 4 corners of the car.

So I'd like to try to reduce brake drag on my car, and see if this is the source of high energy use. Tesla doesn't sell replacement brake hardware, so I can't try replacing the boots. Other car manufacturers that have focused on low drag have used springs which separate the pads some, and there are even aftermarket ones for some cars like the Insight.

Anyone ever tried anything or have any good ideas on how to push the pads out just a very small amount when not braking?

Maybe its one or both of these things happening?

Model 3 Owner's Manual | Tesla

Understand your vehicle's braking system and stopping features.

www.tesla.com