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Custom Aluminum Rotors - A possibility

Discussion in 'Roadster' started by wiztecy, Nov 11, 2014.

  1. wiztecy

    wiztecy Active Member

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  2. TOBASH

    TOBASH Member

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    #2 TOBASH, Nov 11, 2014
    Last edited: Nov 12, 2014
    Color me curious and interested.... Price?
     
  3. hcsharp

    hcsharp Active Member

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    Want. But the rotors aren't aluminum. Only the hats are. I would also worry about the hardware to attach the hats to the rotors. The Elise only needs 4 wheel lugs because it doesn't see the kind of torque that a Roadster does. The Roadster is much heavier and would probably need more of those small cap screws holding the two parts together.
     
  4. wiztecy

    wiztecy Active Member

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    Thanks Henry for the correction on that the hats are aluminum and the disc surface is cast/steel. I also was thinking the same and it caught my eye as well about the size of the hardware on how the hat's were attached to the rotor disc. We can talk to him about that and if we have an idea of what we want we sure can pass it along to him for feedback. I also have to ask for how deep/wide the grooved slots are. Might benefit to go deeper/wider. This helps the brake dust to escape and a place for the heat/off gassing to go. But they might also be just right where they are as is.

    So Dave got back to my email today and here's what he had to say:

    "Yes, I made those rotor sets. Happy to run a batch if you want to put together a group buy. To hit a 'good' price for the GB, we needed to hit 10(40 rotors) cars back then. I'm guessing we will be similar with the number but everything has gone up on cost by about 20% since then so take that into account when you send out feelers. Many of the folks who bought rotors also bought more aggressive brake pads at the same time, so we may want to bundle those as an option."

    Here's the cut & past of his pricing back in early '07:

    The pricing Dave put together is per set (four rotor-assemblies) and excludes shipping:
    ------------------------------------------------------------------------------------------------------------------------------

    Option 1 (Basic Setup): $998 per set of four. Total weight savings (all four corners): 5lbs. Cost per replacement rotor without new hats: $145. This option is $200 cheaper than replacing all four stock rotors, reduces unsprung/rotating weight by a significant 5lbs, and the replacement rotors are less than half the cost of OEM replacements.

    Option 2 (Lightest Setup): $1158 per set of four. Total weight savings (all four corners): 10lbs (attributable to using a rotor with slightly larger internal venting). Cost per replacement rotor without a new hats: $185. Replacing all four rotors costs about $50 less than stock, but cuts unsprung/rotating weight by twice as much (10lbs!), and the replacement rotors are still less than two-thirds the cost of OEM replacements.

    ------------------------------------------------------------------------------------------------------------------------------

    Today's prices :
    =========
    Option 1 -- Cost for all 4 rotors adjusted for 2014 prices(20% increase): (998+199.6): $1198
    Option 2 -- Cost for all 4 rotors adjusted for 2014 prices(20% increase): (1158+231.6): $1390
    (Need 10 people buying the full set to get the discount)


    Feel free to shoot ideas and interests here on this thread and we'll see where we go!

    We'll also have to change the title to something more accurate since the entire rotor is not aluminum, don't want to mislead people.
     
  5. TEG

    TEG TMC Moderator

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  6. wiztecy

    wiztecy Active Member

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    That was me :)

    I like the idea of a two piece rotor design. But EBC would be cheaper for sure and you'd get the slotted rotor design. Last word I received from EBC was that they wanted all the dimensions of the Roadster's front and rear rotor and lug spec. They didn't want to do an new design / machine work for us even though its close to the Elise. Anyone have an idea if the Lotus Europa or Evora has similar dimensions and wheel lug specs?

    So Dave just mentioned he'd like to see a set of rotors first to get the dimensions to ensure they're the same as the Elise. Does anyone have a extra front and rear we could send out? If not does anyone live close to or in Portland Oregon? That's where Dave's based.

    Thanks!
     
  7. wiztecy

    wiztecy Active Member

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    #7 wiztecy, Nov 12, 2014
    Last edited: Nov 12, 2014
    Henry, I missed this pic. It was on the Lotus link. It looks like the Hats are secured rather well. He has the orientation the allen head on the inside of the hat. They look like the right size and just would like to confirm he's using hardened bolts (have to inquire on the grade). If you look close it appears he also has safety wired the allen bolts together (by tying 2 together) so they can't back out :

    49065d1173469248-group-buy-two-piece-slotted-rotors-3301-rearunmounted1.jpg
    57407d1183881136-group-buy-two-piece-slotted-rotors-p7070111.gif
     
  8. TOBASH

    TOBASH Member

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    #8 TOBASH, Nov 12, 2014
    Last edited: Nov 12, 2014
    I love these. Also Aluminum dissipates heat better.

    Yes the rotor material must be steel, but I like these a lot.

    Is this a reputable place that can make new rotors to fit the Aluminum bits in a few years?

    EDIT - Answer was included above about rebuildability. Not about who this guy is or how long he will be around.

    Does he make cross drilled pieces?

    Best,

    T

    - - - Updated - - -

    No doubt he has wired these for safety. Surprised he is not using ARB's, but old school is good too, just might affect balance at high speed.
     
  9. adiggs

    adiggs Active Member

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    I'm in the Portland, OR area with a 2.5 Sport. I'm kind of overwhelmed for the next month or so as I finish a class, but around the middle of December or later, I would be happy to meet up with this fellow and show him a Roadster. I'm assuming all the measurements and testing he needs to do is non-destructive :)
     
  10. wiztecy

    wiztecy Active Member

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    #10 wiztecy, Nov 12, 2014
    Last edited: Nov 12, 2014
    Thanks adiggs! No rush so that works. Rather take our time on these and do it right. Also good to have a connection with a custom fabricator too! I'll forward you his contact info and address in a PM. Yes, non-destructive testing will be conducted.


    Well as for his reputation, he made these for the Elise back in 2007 and its 2014 and he's still in business so that should say something. Will search more on his name to see if there's any negative reviews but so far his reputation has been pretty good on the Lotus Forum. I think the rotor disc must be from some other manufacturer and he's sourcing the part and making the hats fit. As for the safety wire throwing the wheel / rotor off balance, any weight imperfection close to the rotation of the wheel has very little effect to the overall balance of the entire wheel. We could ask about fitting some other disc of choice, can ask why he chose this one.

    As for the cross-drilled rotors, we can ask. But I personally hate them. I've always read that they cause the rotor to crack right from the drilled area. And from my experience they just clog up with brake dust so any thing good they did do such as offgassing/dissipating heat now has been taken away. I've always found slotted to be the best choice for rotors. Retains strength, gets rid of heat, gas, and whisks away brake dust.

    Do a search on google for "drilled rotor cracking" and view all the pics. Here's one I pulled that looks as close to our rotor on the Roadster. Notice it has slots as well. No cracking around the slots, only on the drilled sections:
    CrackedRotor1.jpg
     
  11. TOBASH

    TOBASH Member

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    #11 TOBASH, Nov 12, 2014
    Last edited: Nov 12, 2014
    Agree with everything you said, but note I mentioned balance at "high" speed. The higher the speed the closer the weight needs to be perfect, and weight imbalances closer to the center manifest.

    Once upon a time, in another life almost, I needed to balance my rotors on my '79 T/A LTD. 10'th Anniversary Ed. because I had issues at 115 and not lower. I couldn't get the shimmy to go away after checking tires, rims, brakes, bushings, tie rods, rear axles, bearings, etc... Finally I had a friend at a speed shoppe get me new rotors. First set of rotors were NOT warped, but turned out there were just a couple of ounces of steel stuck in a vent. Problem disappeared with new rotors. Damned Ol' Injun!

    It is obvious you know your stuff, but little imperfections become evident the closer to 3 digits we get.
     
  12. hcsharp

    hcsharp Active Member

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    There's not enough weight in those wires to cause any balance problems. They are also balanced before shipping and I wouldn't be surprised if he assembles them with wire before balancing. He has a great reputation with the Lotus community and has sold A LOT of these rotors to people who drive very fast.

    My fear has more to do with the number of screws, not whether they will back out. The Roadster has a lot more torque applied to the rotors when the brakes are applied because it's heavier than a lotus. He's using grade 8 (hardened) cap screws but they can still shear. I've read the Lotus thread about these rotors and the guy knows his stuff. If he thinks it's safe then I would trust him but I'd like to get his opinion. I also want his opinion on whether they rust as easily as the stock rotors.

    He was selling them for $1207 for a set of 4 back in 2008 before getting too busy and turned it over to a retail aftermarket supplier (I know the feeling!). Assuming 20% increase that's only $1,450 per set which is very reasonable and less than Tesla charges for rotors that aren't as good. Nobody bought the heavier ones. I want some if he thinks they're safe on a Roadster.
     
  13. wiztecy

    wiztecy Active Member

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    Dave came back and it was around $1400 he's estimating for all 4 rotors:

    "Once you get an idea of the interest I can get together price estimates. $1400 a set would be a guess-timate if they are similar in size to the Elise, lower weight and better braking with correct vaning for the air flow and slotted to clean the pads."

    Very good point Henry about shearing off the bolts. I'll add you to an email I have with Dave so you can ask some technical questions on the rotors.

    Dave does fabrication for other cars as well. Here's what he said when I asked him about where he sources the rotor discs:

    "Most of our car parts are prototyped in house and we do final assembly/QC for CNC'd parts. The rotors are made to my specification and cast/machined in the US."
     
  14. wiztecy

    wiztecy Active Member

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    #14 wiztecy, Nov 19, 2014
    Last edited: Nov 19, 2014
    UPDATE:
    =====

    Henry and myself have been communicating with Dave regards to the rotors. We're modifying the design of the rotors a bit. For one we need to be confident that mounting of the hat to rotor disc will hold up to the Roadsters increased weight and torque of that of the Elise. For that Dave will be adding two more mounting points, so instead of 8 hardened bolts he's going to use 10. That's the same amount of bolts that he uses for the Acura NSX rotors (which he also makes).

    The second requirement we were looking for were corrosion resistant rotors. We looked at using different alloys/materials but they were not cost effective, wore too quickly as apposed to the steel, or not within reach of the suppliers we have access to. Henry had an idea of targeting what Chevy did with the Volt, they use a Ferritic Nitro-Carburizing (FNC) process which basically injects and atomizes Nitrogen into a very hot (750F+ degree oven) that gives the steel a durable hardened surface, basically a coating. With this process the hardened surface is really good at repelling corrosion such as rust, but also as an extra benefit the rotor surface becomes amazingly hard so they don't wear down as fast. I did some research and calling today and found a company in San Jose who does this FNC (steel heat treatment) process. I talked to the contact, indicated our requirements and expectations and he confirmed he can do this job for us. Treating all the rotor discs with the FNC treatment. He also indicated he can add another process if we like to help prevent corrosion which is an additional oxide process they'd put the discs through. Its black oxide, you'd see this with gun barrels and steel machine parts that are prone to corrosion. I do believe this will wear off eventually, so the disc braking surface will be prone to this. The venting of the rotors of course will benefit from it. I have to ask more to see really what happens here as well as cost.

    I passed this idea as well as the FNC contact I had made to Dave where he agreed this sounds like the route to go in terms of making the rotor corrosion resistant. It should be the cheapest way to go as well vs. using another alloy and the most durable one as well.

    The next step is to have Dave measure the front/back rotors to get the exact specifications. He wants to guarantee the disk has the same geometry as the Elise rotor. Adiggs has graciously volunteered to help us here since he lives in the area. So sometime in the middle of December, if this still works, he'll drive over to Dave's shop. They'll have to jack up the Roadster and remove the front and rear wheels so Dave can get accurate measurements.

    Since we're adding the FNC process and possible black oxide process the cost will go up some. But I truly believe the final outcome of the rotor be quite a bit better. I don't see this process being too extreme in cost, but I've never done it so I really don't know. But we'll try to do it as economical as possible. Such as to piggy back on another FNC job since the rotors don't take up all that much room in an oven.

    So to make this worthwhile as well as cost effective to get a group rate we need a target of 10 sets of rotors. So a set would include both front and rear cast steel discs that have gone through the full FNC heat treatment process bolted to their aluminum hats which are nickle plated. We can discuss the black oxide coating and I can further inquire regards to the price increase.

    I know I'm interested in purchasing a set, Henry is interested in a set. I don't know if TOBASH is interested in a set. So if you have interest in the group buy let us know so we can keep moving forward. Thanks!

    Also floating around changing the title to this thread to, "Custom Brake Rotor Upgrade - Group Buy". Better suggestions for a title are welcome.
     
  15. hcsharp

    hcsharp Active Member

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    I'm in! It's looking like the price will be less than what Tesla charges for replacement rotors. But these will be much better. They'll be lighter by 10 lbs which is most important in rotating unsprung weight, much more corrosion resistant, and GM's research reported slightly better braking power. Thanks to wiztecy for getting this going.
     
  16. adiggs

    adiggs Active Member

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    This question is probably a bit off topic, but related - the change in rotors would go well with the Carbotech brakes/brake pads, would it not? I ask as I've never been one to tweak my car, but for some reason, I'm thinking it worthwhile / fun for the Roadster. And the way I read things, that's one of the bigger upgrades for little money that makes a difference in how the car drives.

    I'm at least considering getting in on this (probably with performance driving school next summer too ...).
     
  17. wiztecy

    wiztecy Active Member

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    #17 wiztecy, Nov 20, 2014
    Last edited: Nov 20, 2014

    Yes. Actually Dave recommended changing out the pads to a high performance pad which they did on the Elise forum, but we already found we like the CarboTechs so they'll work very well with these rotors. I agree that this is one of those upgrades that will make a huge difference in the way the brakes feel and perform. Also in going this route we can always have new rotor/discs made up without being dependent on Tesla. And braking is one of those components on the car that is never bad investing in, the better and quicker you can stop the better off you, others, and the Roadster is in the long run.
     
  18. dsm363

    dsm363 Roadster + Sig Model S

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    #18 dsm363, Nov 20, 2014
    Last edited: Nov 21, 2014
    Would you recommend messing with this while car is still under warranty? I'm interested as well.
     
  19. hcsharp

    hcsharp Active Member

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    I'd be shocked and amazed if it had any affect on your warranty. We've all replaced our pads already and they didn't complain about that (except they won't install them for us). You can always put your old rotors back on. The new rotors will be better quality, and race-track tested on a car that's heavier than the Roadster. Seems like everybody wins.

    - - - Updated - - -

    Can't find it now but when GM researched the FNC treatment they found shorter stopping distances in wet weather, and after the rotors would normally have formed a thin layer of rust. This is because they are more corrosion resistant so they don't get as much rust build-up which is important for any EV. They should work great with the Carbotech pads.
     
  20. MLAUTO

    MLAUTO Member

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    The Elise rotors are not the same castings as the Tesla. The Tesla hubs are larger so the center portion of the rotor is also larger. Shouldn't be a problem if the aluminum hats are made to fit. The biggest problem I see is that the rear rotors on the Tesla are about an inch bigger in diameter than the front, while the Lotus uses the same front and back.
     

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