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Lesson Learned: Keep your Brake Rotors Conditioned!

Discussion in 'Roadster: Performance' started by Doug_G, May 1, 2012.

  1. strider

    strider Active Member

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    Well, first off, these cars weigh more than a Roadster and so need larger brakes to slow them down. A 911 Turbo weighs 1,000lbs more than a Roadster. An Aston DB9 weighs 1,500lbs more than a Roadster. Even a 458 Italia weighs 600lbs more. There is also a factor of design/looks. People think large rotors look faster - more like a race car. Same reason Model S has 21" wheels. Not very practical but they look cool.

    Also, this discussion is mostly about street driving. If you track your car you will have no problem keeping your rotors clean (the subject of the thread). Also in a track situation, larger calipers/rotors help to dissipate heat since there is more surface area both in the pad and rotor so lower temperatures. This keeps the brakes cooler and allows repeated hard stops coming into multiple corners per lap. So if Tesla, like Lotus, offered a "track brake system upgrade" then I would expect larger calipers and rotors. But if this brake upgrade is to solve the subject of this thread, the size of the rotors and calipers are adequate to lock up the wheels and therefore are large enough. We just need a rotor/pad combo that will have good initial bite even when seldom used.
     
  2. Jaff

    Jaff Active Member

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    Sounds logical...thanks for the explanation!
     
  3. driver_EV

    driver_EV Member

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    Doug_G, what you say about hard braking makes perfect sense to me, and higher (maximum) braking forces at the calipers, that result from the conditions you describe (especially sticky tires) will heat up the rotors and pads dramatically. This is something that most of the Roadsters may never encounter in normal driving.

    The particular benefit I see is from very high temps. The pads and rotors will cook/burn off any oil residue that collects from the leaky ICE cars on the road. Leaving them very clean to provide the maximum braking response you describe.

    -good advice.


    This brings to mind the issue of flushing brake fluid that is presented in another thread. The key reason to flush brake fluid is to eliminate the moisture that contaminates the fluid over time due to atmospheric humidity levels. The issue is that with a significant amount of water in the brake lines, combined with the very high temps at the calipers while under racing conditions, or other extended use of friction brakes, the water can turn to steam, displace the hydraulic brake fluid, and cause loss of any brake operation. Unusual conditions, especially for an electric car, but for ICE performance cars this is a safety issue, and is why manufacturers have a brake fluid flush interval. So you may want to pay attention to fluid quality with the braking system.

    -Richard
     
  4. frequencydip

    frequencydip Sig 100 - #52

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    I'm willing to bet the brake upgrade would contain a improved brake booster.

    I would like to se an upgrade at least to the rear caliper to a two piston. A 4 piston upgrade to the front would also be nice. The discs on the car are sufficient but if they introduced lighter discs by using a floating disc that would be sweet. An all aluminum disc would also be nice but I hear aluminum squeals more than steel..
     
  5. DSA

    DSA R #212 Twilight Blue

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    Thanks for this detailed explanation - I was wondering how many hard stops would be about right for "one session" before things get too hot - it sounds like 10 hard stops should be about right. Rather than drive around non-stop for 10-15 minutes afterward, could you just stop and put on the parking brake for at least 30 minutes or so, especially if your hard braking session is close to home? That could let the brakes cool off without the pad in contact as well without having to drive non-stop for awhile.
     
  6. Doug_G

    Doug_G Lead Moderator

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    Do NOT turn on the parking brake after bedding in. That could warp your rotors. In fact it's best if you could avoid using the brakes altogether until they've cooled off.
     
  7. drees

    drees Active Member

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    Yep. Not sure what the Roadster's parking brake is like - but just stopping the car will lead to uneven cooling of the rotors with the pads sitting over one spot which can lead to uneven pad deposits on the rotor.

    If you do get uneven pad deposits on the rotor which will make the rotors feel warped, another bedding session may fix it, but worst case you'll need new rotors.

    Don't risk it!
     
  8. DSA

    DSA R #212 Twilight Blue

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    OK, good thing I asked. I did a session with ten hard stops to break in the brakes earlier today and drove around for a bit afterward to let the rotors cool. The brakes are now much less noisy than they used to be, but I think I need at least one more session to get them where they need to be.
     
  9. goyogi

    goyogi Member

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  10. Doug_G

    Doug_G Lead Moderator

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    My Ranger did brake service today, as part of the annual. I was rather surprised by just how tiny the front pads are. The ones in my S2000 are twice the size! The S2000 only has one piston but has a heck of a lot more stopping power (the first time I tried a harder stop with them I unintentionally locked the wheels, because I pressed the brakes like I do in the Roadster).

    I'm now thinking that the problem with the Roadster brakes, aside from crappy pad material, might just be insufficient margin. They're fine when they are sparkling clean, but a little bit of crud, glazing and corrosion renders them inadequate.
     
  11. wiztecy

    wiztecy Active Member

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    They're the same pads, rotor size, and calipers as the lotus elise which the roadster is pushing over 1000 more lbs. They're just underspec'd for the Telsa Roadster and like Doug said once you start getting dust and crud in them you loose their braking ability.
     
  12. hcsharp

    hcsharp Active Member

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  13. strider

    strider Active Member

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    Well, to be fair, it's 800lbs. Also, within reason, the only reason to have larger rotors and calipers is to better dissipate heat in a repeated use scenario. With today's modern brakes you don't need massive brake components to out-brake the tires.

    That being said I think we're all still trying to figure out whether the problem is the size of the brakes or the interaction of the compound and rotor when daily driven with light use. It's definitely not the brake lines, calipers, or master cylinder. When I have a "moment" I have a rock-hard pedal, the car just doesn't slow down like I expect it to. I posted in the brake pad thread that I switched to the CarboTech's today so we'll see how they do.

    I know Tesla is planning a "brake upgrade" at some point but Idk what it's going to consist of.
     
  14. wiztecy

    wiztecy Active Member

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    #54 wiztecy, Sep 16, 2012
    Last edited: Sep 17, 2012
    My dodge truck had braking issues similar to the Roadster... brakes feel fine but when you really need them they just were not there. Dodge then made the rotors larger on the next generation dodges, 2nd gen to 3rd gen and added 1" to the rotor. Same calipers but a larger caliper mounting assembly to house the larger brake pads. They ran these dangerous brakes from 1994-2002 on all dodge 2500 trucks including the diesels which I have. I did the upgrade myself, put new rotors all the way around and new brakes as well. Night and day difference. The issue there was that the rotor was too small to handle the 7500lbs or mass going down the road. I can stomp on it now and braking really means I'm stopping now. This lack of braking was a pure DANGER and a threat to others on the road. How is a truck going to stop with a load in it when it can't even stop with no load? I'm a firm believer that larger pads and braking surface means you'll also stop faster. Its like Fred Flintstone stopping his wooden rock ride in a size 8 pair of shoes vs a size 10. I'd sure he'll do better off in a size 10 :)

    I also feel 800lbs is allot over spec of a car of such a small size and weight ratio for braking. We don't even know what margin Lotus had when it designed the braking system. I don't know when you had your rotors resurfaced if you had warping on your rotors too but that just seemed odd to me. Mine were warped on the backs, where the majority of the weight is. Now given that the brakes never worked in the first place, I never had the physics of braking work with the car. Front diving down, suspension locking over the wheels, and squealing tires. Makes sense to me why the back warped... they were dragging like an ebrake trying to slow the majority of the mass down. And that was really it, with the stock OE pads it did feel I was stopping with just the eBrake. I'm sure if I removed 800lbs back there I wouldn't of had as bad of braking nor the warped rotors. I'm curious if we read the braking threads in the Lotus Elise forums if they had braking issues, if not, weight is a factor.

    Update: So I did a quick google search and people in the Elise forums complained about not being able to stop when the brakes are wet, which makes sense, but also the huge accumulation of dust from the OE pads. I do feel too much dust can play a factor in poor braking, its like micro marbles working against you. Driving for a week with the CarboTech pads I get 1/10 the amount of dust the OE pads were giving me.

    Here's an interesting clip from the Lotus forum:
    ----------
    With the right pads, I'm not sure they can be classified as weak. However, they were designed for the 1500 lb. Elise S1 and not changed for the S2 or Exige, save for the small 4-piston Cup front brakes. Every part on these cars were designed with weight savings in mind, along with reasonable cost considerations. Lotus certainly got what they paid for when they sought out a brake system solution. That said, there are very good upgrades out there for cars that ended up heavier than the S1 and/or have engine modifications.
    ----------

    I'm happy to hear you have the CarboTech's on!
     
  15. Doug_G

    Doug_G Lead Moderator

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    Yes, 800 lbs. I disagree about "the only reason". IMHO the pads are so small that when they are a little bit degraded you don't have enough stopping power. If the pads were larger - and I'm not even talking about making the rotors larger - then there would be more surface area and if it weren't at 100% then it would still be sufficient.

    My S2000 has an almost identical weight to the Roadster, but the pads are much larger. And let me tell you, it stops better!
     
  16. strider

    strider Active Member

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    Good point, I should have restricted my statement to larger rotors.
     
  17. VolkerP

    VolkerP EU Model S P-37

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    GeorgeB mentions brake maintenance (on Model S) to avoid having to swap the rotors:

    So either Model S brake maintenance has different approach than Roadsters, or the Roadster owners receive superfluous replacement parts - who pays for these?
     
  18. NomoC8

    NomoC8 Member

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    Okay, I haven't even taken delivery of my roadster, but I had to register and reply. There are a lot of misconceptions and false statements.


    First, the subject of the thread is "conditioning" the brakes. By conditioning, it means removing the rust from the rotors. This rust will increase braking distance. The rotors rust because of infrequent use. The rotors get little use because of regen. braking and low mileage. The rust prevents the pads from creating friction.


    Second, Ederhard's comment was to do it on a wet road to reduce tire wear.


    Third, the physics of braking has been touched upon, but there are some clarifications needed. Pads clamping down on rotors takes kinetic energy and converts it to heat, thereby slowing the car down. Regen. braking takes some of the kinetic energy and converts it to electricity, also slowing the car. This leaves less of the kinetic energy that needs to be converted to heat. Therefore, there is less use of the pads and rotors.


    The issue of pad size increases the surface area so more friction can be created, decreasing stopping distance. The size of the rotor, venting, cross drilling, and slotting allow the heat to get dissipated more quickly and eliminate the gas that forms between the pad and rotor. The enemy of braking is loss of friction. The gas and heat reduce the ability of the pad to create friction. So does water on the rotors and anything else which reduces the friction (ie rust).


    The vast majority of braking is created by the front brakes. The rears are mostly along for the ride.


    Fourth, the S2000 weighs ~800 pounds more than the roadster.


    Lastly, what most people refer to as warped rotors is usually due to uneven pad deposition. Never stop or use the e-brake with hot brake components.
     
  19. bonnie

    bonnie Oil is for sissies.

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    Sorry, I'm missing your point here. Did you mean to correct any advice in the thread?
     
  20. Doug_G

    Doug_G Lead Moderator

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    I take issue with that statement.

    Right... that was exactly the point I made at the start of the thread.

    I'm not sure it will actually have that effect. You won't get as much braking force and will probably have to repeat the process more times to achieve the same result, so it might be a wash.

    Besides, any Roadster owner will tell you, the rears wear out 3X as fast as the front. So a tiny bit of extra wear on the fronts is no biggie!

    Okay... all true but I don't see where the "misconceptions and false statements" fit in here.

    That is a false statement. According to the manufacturer's specifications, my S2000 AP1 weighs 2,756 lbs. My Roadster weighs 2,937 lbs. It weighs ~ 200 lbs LESS than the Roadster.

    True. Did that even come up in this thread??? :confused:

    - - - Updated - - -

    I will make one follow-up comment. As I mentioned elsewhere I switched to Carbotech AX6 pads (as recommended by other forum members). They have much better stopping power than the stock pads, especially after they are warmed up slightly (i.e. the second time you use them).

    The other great thing about these pads is they scrub the rotors nicely. It seems that regular street use is sufficient to keep them reasonably clean, without resorting to periodic scrubbing sessions.
     

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