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  1. #1
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    Well, I really screwed up. So now what?

    I thought I thought of everything. Alas, I did not.

    Almost done building my bike. Installed the shifters, disc calipers, etc. Rotors not included with the new Dura-Ace shifter/brake sets. Fine.

    I'm looking at the rotors and it seems that Shimano has completely abandoned 6-bolt for all of their 140mm rotors. All of them are centerlock. And there's no such thing as an adapter that fits centerlock rotors to 6-bolt hubs. This issue had completely skipped my mind when I ordered my wheels. Last time I built a bike with disc brakes, 6-bolt was still ubiquitous. Only Shimano Saint used centerlock.

    So now what?

    Use another brand of rotor? Go with 160mm Shimano rotors (which I'm not keen on doing)? Replace the hubs on my wheels with centerlock hubs?

  2. #2
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    Use another brand of rotor. They all have to meet industry standard specs, so any 140mm rotor should work. Sell your rotors on eBay.

  3. #3
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    Quote Originally Posted by Waspinator View Post
    Go with 160mm Shimano rotors (which I'm not keen on doing)?
    Is that even possible with your build? If so, what is the problem? You will get better braking and less chance of overheating. Weight difference will be negligible if that is your concern.

    Quote Originally Posted by Waspinator View Post
    Replace the hubs on my wheels with centerlock hubs?
    If you haven't built up your wheels yet and you can return the 6-bolt hubs, this is what I would do. Otherwise, do what Peter P. suggested.
    “Statistics are like bikinis. What they reveal is suggestive, but what they conceal is vital.” -- Aaron Levenstein

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  4. #4
    'brifter' is a lame word.
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    Quote Originally Posted by Peter P. View Post
    Use another brand of rotor. They all have to meet industry standard specs, so any 140mm rotor should work. Sell your rotors on eBay.
    Where did you come up w/ this? ALL brake system manufacturers recommend using only their rotors. If you ever have the chance to speak to their people they'll give you some pretty good reasons.
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  5. #5
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    Quote Originally Posted by cxwrench View Post
    Where did you come up w/ this? ALL brake system manufacturers recommend using only their rotors. If you ever have the chance to speak to their people they'll give you some pretty good reasons.
    No maintenance manual I know of explicitly says you must match the rotor and caliper brand. If the info is only coming from the manufacturers, then it's for marketing and sales reasons.

    I wouldn't be surprised if the same marketing applies to carbon rims and rim brake pads. Yet you'll find many people experimenting with aftermarket pads. Hmmm...

  6. #6
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    Quote Originally Posted by Peter P. View Post
    No maintenance manual I know of explicitly says you must match the rotor and caliper brand. If the info is only coming from the manufacturers, then it's for marketing and sales reasons.

    I wouldn't be surprised if the same marketing applies to carbon rims and rim brake pads. Yet you'll find many people experimenting with aftermarket pads. Hmmm...
    And lots of people end up voiding their warranty. Shimano engineers their systems to manage the heat in a particular way. SRAM engineers their systems to work differently. If you use a Shimano Ice Tech rotor w/ an Avid/SRAM brake system you can end up w/ the aluminum core melting from between the stainless steel friction surface. Ask me how I know. I'm sure people mix and match all the time, I won't ever recommend it. It's too easy to do things the right way and minimize the potential for problems. If you want to ignore the recommendations of the manufacturers and their offices full of people that know way more about brake systems than you do, fine. But don't recommend it here.
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  7. #7
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    Quote Originally Posted by cxwrench View Post
    And lots of people end up voiding their warranty. Shimano engineers their systems to manage the heat in a particular way. SRAM engineers their systems to work differently. If you use a Shimano Ice Tech rotor w/ an Avid/SRAM brake system you can end up w/ the aluminum core melting from between the stainless steel friction surface. Ask me how I know.
    Interesting. I not sure how much difference there is between brake disc alloys, but this certainly would be a legitimate concern not to mix parts. I am no engineer, but my guess would be that since SRAM systems use DOT5 fluid, they are designed to run much hotter than a Shimano system which uses mineral oil. One might come to the next conclusion that "hey, if SRAM systems can run hotter, a SRAM disc would certainly work in a Shimano system. But wait! It could very well be that SRAM system runs hotter due to more heating building up in that SRAM disc due to the alloys being different. So.....now we are heating up a Shimano system past the boiling point of mineral oil....and then......well, you can see this might not end well. I had not thought of the scenario CXWrench mentioned with the aluminum core melting, but as you can probably guess, that would not end well either.

    OP, Let me be clear that I am only speculating what might happen and have no first hand experience. CXWrench is an experienced mechanic who works for racers and has most likely seen some catastrophic results due to some hacks. I would take his advice and not mix brands when it comes to brake systems.
    “Statistics are like bikinis. What they reveal is suggestive, but what they conceal is vital.” -- Aaron Levenstein

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  8. #8
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    Of course, you know my answer.
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  9. #9
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    Quote Originally Posted by Lombard View Post
    I am no engineer, but my guess would be that since SRAM systems use DOT5 fluid, they are designed to run much hotter than a Shimano system which uses mineral oil.
    Actually Shimano's mineral oil boils at 536F. DOT 5.1 boils at 518F.

  10. #10
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    Quote Originally Posted by Lombard View Post
    CXWrench is an experienced mechanic who works for racers and has most likely seen some catastrophic results due to some hacks.
    On another hand, CXWrench sees systems used at levels of force and duration which most riders simply wouldn't achieve.

  11. #11
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    Quote Originally Posted by Maelochs View Post
    On another hand, CXWrench sees systems used at levels of force and duration which most riders simply wouldn't achieve.
    Possibly for some items on the bike. However, when it comes to braking down a long steep mountain, gravity doesn't care whether you are a racer or not.

    Quote Originally Posted by Fajita Dave View Post
    Actually Shimano's mineral oil boils at 536F. DOT 5.1 boils at 518F.
    I stand corrected. So then I guess the only advantage to DOT fluids are that they are hygroscopic?


    Last edited by Lombard; 10-09-2017 at 04:51 PM.
    “Statistics are like bikinis. What they reveal is suggestive, but what they conceal is vital.” -- Aaron Levenstein

    "Beware of geeks bearing formulas."
    -- Warren Buffett

    "Education is what you get when you read the fine print. Experience is what you get when you don't. -- Pete Seeger



  12. #12
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    Quote Originally Posted by Lombard View Post
    Possibly for some items on the bike. However, when it comes to braking down a long steep mountain, gravity doesn't care whether you are a racer or not.
    Yes and no. A racer will be doing everything a lot faster. S/he might actually develop less heat, as s/he would be braking more sharply but for less duration at each corner--or maybe coasting some corners non-competitive-non-crazy riders would slow for.

    But maybe not. I don't know which type of riding--quick casual, cautious casual, loaded touring, crazed competitive-- in that specific case, would actually cause more heat build-up .... I am equally uncertain about on- and off-road applications.

    Have you ever heard of rotors actually melting in Any application? (I have heard of road racers melting their tubular glue on very hot days on long descents .... I'd think metal had a higher melting point )

    CXWrench has .... but he deals with racers. I have Never heard of rotors actually melting anywhere else. So ... my assumption--not fact---is that it is pretty freaking rare in everyday use.

    I just put Shimano rotors on my TRP Spyre-equipped Fuji. Seeing as the nearest mountain to me is a day's drive away, I don't fear spontaneous combustion.

    If my rotors melt and I erupt into a two wheeled ball of flame and burn to a cinder, i will post here apologizing for believing that personal experience was a sound guide to making life-decisions.


  13. #13
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    I have mix-and-matched tons of different rotors on a mountain bike, I wouldn’t worry about it.


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  14. #14
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    Quote Originally Posted by milesw View Post
    I have mix-and-matched tons of different rotors on a mountain bike, I wouldn’t worry about it.
    There are many people who "get away with" things that aren't wise. Just don't come crying here when you end up on a gurney.
    “Statistics are like bikinis. What they reveal is suggestive, but what they conceal is vital.” -- Aaron Levenstein

    "Beware of geeks bearing formulas."
    -- Warren Buffett

    "Education is what you get when you read the fine print. Experience is what you get when you don't. -- Pete Seeger



  15. #15
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    Quote Originally Posted by Lombard View Post
    There are many people who "get away with" things that aren't wise. Just don't come crying here when you end up on a gurney.
    I guess you are a road biker and not very familiar with disc brakes?


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  16. #16
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    OP is complaining because these aren't available?
    Shimano XT-Saint RT86 Ice-Tech 6-Bolt Disc Rotor | Chain Reaction Cycles

    I'm also in the mix-n-match camp. I've never had any evidence of even the hint of a problem with my mixed systems.

    I don't see any significant advantage of the above part vs a nice aftermarket brand. Layers? Sounds cool, but that's just a marketing gimmick.

  17. #17
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    Quote Originally Posted by BlazingPedals View Post
    OP is complaining because these aren't available?
    Shimano XT-Saint RT86 Ice-Tech 6-Bolt Disc Rotor | Chain Reaction Cycles

    I'm also in the mix-n-match camp. I've never had any evidence of even the hint of a problem with my mixed systems.

    I don't see any significant advantage of the above part vs a nice aftermarket brand. Layers? Sounds cool, but that's just a marketing gimmick.
    Thise are 160mm rotors in the link you provided. I'm looking for 140mm.

  18. #18
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    Quote Originally Posted by milesw View Post
    I guess you are a road biker and not very familiar with disc brakes?


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    I am VERY familiar w/ disc brakes and you should never advise people to mix and match brake systems/rotors. It would be good if you just stopped giving advice in this section.
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  19. #19
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    Quote Originally Posted by cxwrench View Post
    If you use a Shimano Ice Tech rotor w/ an Avid/SRAM brake system you can end up w/ the aluminum core melting from between the stainless steel friction surface.
    As above, this is interesting. I'm not sure I'd attribute that failure to mixed parts, though.

    Shimano rotors seem to be a double-edged sword. The finned models dissipate heat faster than any other rotor, probably by a considerable margin. However, the melting point of aluminum is about half that of steel, so the total heat capacity of the rotor is far less. This implies to me that Shimano prioritized consistency in braking response for riders that brake properly (pulsing instead of dragging) over sustained stopping ability.

    I wouldn't expect to see wild differences in the heat capacity of pads and calipers between brands. Likewise, the boiling points of Shimano's mineral oil and DOT 5.1 are pretty close. If your rider melted a Shimano rotor, I'll bet they'd have done the same even if the rest of the system were Shimano.

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