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  1. #1
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    Any tips for aligning disc brake rotors/calipers?

    I have a couple of disc road bikes, and generally speaking, don't have much trouble adjusting the calipers so the rotor is centered (doesn't rub).

    However, one particular bike/wheelset is giving me some grief.

    The bike is a BMC RM-01 with Shimano flat mount hydraulic disc brakes. The wheels are White Industry hubs on HED Belgium Plus rims. Brake rotors are Shimano RT-99 Centerlock.

    I'm able to get the rear lined up ok, but for some reason, the front is far enough out of the center of the rotor, that I can't compensate within the amount of 'play' I have in the caliper mounts. No matter what I do it still rubs on the inboard brake pad.

    As a test, I cut a thin piece of plastic (.5mm) into a shim of sorts and put it between the brake rotor and the hub, effectively moving it out away from the hub by .5mm. It's not something I'd trust riding on, but it did the job in terms of centering the rotor in the caliper.

    This isn't a pictire of my bike, but the front brake mount looks like this.




    I haven't had a chance to stop by the shop and ask the mechanics about it, but I will. I'm sure this is they have run into this before.

    Anyone here have any suggestions?

  2. #2
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    I have yet to see shims for center lock rotors. I'm sure they are coming. I think this is one of the downsides to flat mount rotors. THe frame mfg's are not giving us enough movement in the mounting hole calipher to adjust to diffent hubs.

    I had the same issue on some Bitex hubs except mine had the rotor too far out (opposite of your issue). I ended up putting a shim behind the left side end cap to create more stack. Worked like a charm.

    FWIW, finding a small thin metal shim should work. Shimano used ot have a thin 1.8 mm shim they put behind the cassette on 10 speed, I wonder if that would fit.

  3. #3
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    1-3/8" ID x .001" thick shims from McMaster work great as center lock shims.

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    I just went thru every shim I have, a Cassete spacer inside diameter is too small. Nov. Dave's suggestion may be our only choice at the moment.
    Last edited by Enoch562; 04-23-2017 at 07:04 AM.

  5. #5
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    Shim stock... get a feeler gauge at the auto/hardware. Cut the thickness u need from the unit. Not so cheap, but if it is perfect, it is perfect.
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  6. #6
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    Quote Originally Posted by Enoch562 View Post
    I just went thru every shim I have, a Cassete spacer inside diameter is too small. Nov. Dave's suggestion may be our only choice at the moment.

    Something else must be going on. 0.5mm of machining error between hub and fork I can believe.....but 2mm+? The equivalent of 12AWG wire? Something sounds really hinky, and not seeing pictures I'm stumped.

    (Note-I'm using Bitex BX106F/R hubs, 15x100mm front and 12x142mm rear, post-mount discs on my unpavement bike)
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  7. #7
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    Quote Originally Posted by November Dave View Post
    1-3/8" ID x .001" thick shims from McMaster work great as center lock shims.
    Thanks Dave,

    I figured you might have some ideas here. I almost emailed you, but thought getting it in here might help others as well.

    I love it when a plan comes together.

  8. #8
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    Quote Originally Posted by duriel View Post
    Shim stock... get a feeler gauge at the auto/hardware. Cut the thickness u need from the unit. Not so cheap, but if it is perfect, it is perfect.

    How would you propose accurately cutting .5mm shim stock to the right dimension to fit over the centerlock mount but not slip over the hub? Note that I'm not a machinist and don't have the machinery to do this.

    I suppose I could go to a machine shop and ask for this to be made, but probably at significant cost compared to just ordering the oversized stainless 1 3/8" .001 shims from McMaster that Dave suggested.

    I made a 'test' piece out of a thin piece of plastic (cut the bottom out of an old tupperware container). From a spacing standpoint it worked, but it was not pretty.
    Last edited by Migen21; 04-23-2017 at 03:15 PM.

  9. #9
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    Rotor/ hub spacing is one thing that really needs to get sorted (or a better way of dealing with it on the fly) if neutral service is ever going to be able to deal with this.

    I think I needed about 6 shims (6 bolt) front and rear to get my new Hope hubs to line up with whatever hubs are in my Roval wheels.

  10. #10
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    Quote Originally Posted by Migen21 View Post
    How would you propose accurately cutting .5mm shim stock to the right dimension to fit over the centerlock mount but not slip over the hub? Note that I'm not a machinist and don't have the machinery to do this.

    I suppose I could go to a machine shop and ask for this to be made, but probably at significant cost compared to just ordering the oversized stainless 1 3/8" .001 shims from McMaster that Dave suggested.

    I made a 'test' piece out of a thin piece of plastic (cut the bottom out of an old tupperware container). From a spacing standpoint it worked, but it was not pretty.
    Scissors (how heavy duty depends on thickness). McMaster might have a minimum order point, I'm not 100% sure on that I order from them a lot through work but I'm not the buyer. I want to say that there is a minimum though, just an FYI. But none the less shim stock is easy to cut, it doesn't have to be pretty it just has to work (<- obviously subjective).
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  11. #11
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    Just so everyone understands what we are doing here.

    What we are talking about "cutting with scissors" is effectively a metal washer that would fit over the notched centerlock mount, and rest on the flange just beyond it. The ledge there is about ~1mm proud of the outside of the centerlock notches, and the washer has to sit on there so that when you tighten down the rotor lockring it doesn't squeeze out. It's a pretty tight tolerance and it's not something you want to get wrong.



    As November Dave pointed out, McMaster sells 'bearing shims' for micro adjusting machinery. The 1 3/8" ID shims will be a tight fit over the centerlock mount (depending on their manufacturing tolerances), but should do the trick. You can buy them in boxes of 5 to 10 depending on the thickness. I'll order a few varying sizes so I can experiment.

    This is a good picture showing what we are trying to accomplish. Spacing the disc rotor about so that it's centered between the disc pads.



    I'm not sure if this problem exists because there is no agreed upon standard, or if the hub and/or frame manufacturers just aren't following them, but I'm finding swapping wheels with different brand hubs to be a challenge. Hopefully these shims will be a permanent resolution to that, at least until this stuff is being made within the necessary tolerances.

  12. #12
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    Quote Originally Posted by Migen21 View Post
    Just so everyone understands what we are doing here.

    I'm not sure if this problem exists because there is no agreed upon standard, or if the hub and/or frame manufacturers just aren't following them, but I'm finding swapping wheels with different brand hubs to be a challenge. Hopefully these shims will be a permanent resolution to that, at least until this stuff is being made within the necessary tolerances.
    I swap between two sets of wheels, one is shimmed, one is not but the spacing is now identical. Wheel swaps are a breeze, don't even have to worry about swapping pads between carbon and alloy rims.

  13. #13
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    Quote Originally Posted by Enoch562 View Post
    I have yet to see shims for center lock rotors. I'm sure they are coming. I think this is one of the downsides to flat mount rotors. THe frame mfg's are not giving us enough movement in the mounting hole calipher to adjust to diffent hubs.

    I had the same issue on some Bitex hubs except mine had the rotor too far out (opposite of your issue). I ended up putting a shim behind the left side end cap to create more stack. Worked like a charm.

    FWIW, finding a small thin metal shim should work. Shimano used ot have a thin 1.8 mm shim they put behind the cassette on 10 speed, I wonder if that would fit.
    1.8mm isn't 'thin'...that's huge for this application.
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  14. #14
    tlg
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    I've shimmed centerlocks. It does work. No one makes them though which I'm kinda baffled about. I had them made at work on the CNC punch.

    Quote Originally Posted by craiger_ny View Post
    Scissors (how heavy duty depends on thickness).
    I'd like to see you cut a ~1-3/8 hole in shim stock with scissors.
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  15. #15
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    Just throwing this out there, but I know you can get centrelock to 6 bolt adapters, (I don't know these effect rotor spacg) but is it an option to convert it to a 6 bolt rotor and then shim it to the desired spacing with 6 bolt shims?

  16. #16
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    Is the problem with just this particular wheelset or is it present on the original wheels too, but just not as bad?
    If the hub is out, call up White Ind and they will help you out. It may be something as simple as an axle or endcap swap. If you look up how to measure hub dimension for wheel building, then measure the setback of the rotor mount face to the endcap is the same. They should be able to provide you with a number to look for.
    If it's not the hub, then get with your LBS and have them contact BMC.
    I agree with what's been said above, shimming a few thou's is one thing, nearly 2mm is something else entirely.

  17. #17
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    The McMaster shims I linked work well. We've used them and have recommended them to a bunch of customers who have used them to excellent result.

    Despite being a tiny bit undersized compared to a center lock hub's splined section, they are easy to install in basically the same way you install a tire. This sizing may in fact be preferable as it maximizes the contact area between the shim and the rotor.

    A pack of 5 costs $7.75. Minimum order is one pack of 5 shims. This is a turn key solution that is half the cost of the equivalent pack of 6 bolt rotor shims ($15 from Wheels Mfg).

    I honestly don't know what more of a solution someone could want. We'll be happy to bag them and resell them if that makes them more palatable to the bike market, but they 100% work for exactly the OP's needs.

  18. #18
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    Also, FWIW, I built the wheels in question. Migen21 bought them unused from a customer who bought them and wrecked his back basically as they were delivered. We connected the two parties but weren't part of the transaction between them.

    Without having spoken directly with the OP about this, there is fundamentally no chance that the hubs are 2mm out. I've just measured a bunch of WI CLD front hub shells and they are all exact to within .02mm of one another.

    Though there exists a need to be able to shim rotors to be able to align them exactly among the wheels in your fleet, I've never seen anywhere close to this much variance with any strange combos (Hub A with Rotor B versus Hub D with Rotor E, for example). Most of the hubs I've ever used work with minimal-at-worst rubbing from one to the other even with mechanical disc brakes which have pathetic pad clearance (my cx bike still has mechanical disc brakes).



    So I don't think this is a case of hubs being so far out one to the other, nor could I recommend or feel comfortable with 2mm of shimming. That would compromise the center lock interface and clearly indicates something else that's out of kilter. Perhaps an axle isn't installed or adjusted properly, or some other thing. Happy to help with that off line.

  19. #19
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    Dave,

    Not sure where the 2mm thing came from. Likely a different post from someone else.

    I only need about .5mm to get into alignment without having to move the caliper.

    Part of my challenge is the proprietary front brake mount on the BMC doesn't allow me to move the caliper much, if at all, thus the need to shim.

    Edit for clarification: I hope no one is under the impression that there is something wrong with these wheels. I'm very happy with them. The build quality is outstanding. The problem I'm having is that the way the front caliper mount on the fork of the BMC RM-01 is designed requires me to remove the mounting plate, then loosen the caliper mount bolts to make an adjustment, then remount and test. It's a major hassle to try to align a rotor/caliper this way, unlike most situations where you would just loosen the mount bolts and make a small adjustment and re-tighten. It makes swapping wheels that have even a slight variation in rotor location a major PITA.

    The two wheelsets I have are a set of Enve 3.4 SES Disk with DT-240's that I use strictly for road, and the White Industries/HED Belgium Plus wheels that were built by Dave that I'll be using exclusively for gravel/all road.

    The shims Dave linked to should work. I need to move my rotor a total of about .5mm outboard to get it centered between the pads in the mounting position I use for my Enve's. I ordered a few different thicknesses of the spacers so I would have some flexibility.

    The nice thing about this method is, as Dave mentioned, once you have everything mounted, you can use the shims to get the rotor perfectly lined up on each wheelset and be done with it. Never have to loosen and adjust the caliper again.

    I just wanted to clarify that there is absolutely nothing wrong with the wheels that Dave built. The materials and the build quality are outstanding. My problem is the way the front caliper mounts is not user friendly.
    Last edited by Migen21; 04-24-2017 at 07:26 AM.

  20. #20
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    Quote Originally Posted by Migen21 View Post
    My problem is the way the front caliper mounts is not user friendly.
    Yup...this is probably one of the biggest hiccups in trying to get smaller / more compact, lighter, more aero disc brake calipers for road...you lose some of the adaptability that the mtb calipers have to adjust to slightly different rotor positions between wheels. I think Dave and others have it right, though....shim them to be the same and you'll be able to swap quickly. Might not be the greatest option for neutral support, but that's more of a concern for if you're racing.
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  21. #21
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    Quote Originally Posted by tlg View Post
    I've shimmed centerlocks. It does work. No one makes them though which I'm kinda baffled about. I had them made at work on the CNC punch.

    I'd like to see you cut a ~1-3/8 hole in shim stock with scissors.
    It depends on thickness of the stock but I've cut lots of shim stock into many different geometries with scissors and utility knives. You aren't thinking spring steel are you (I certainly wouldn't try that with scissors)? Perhaps part of the benefit for me might be the array of cutting implements that I have at my disposal (we cut a lot of mesh). Given that McMaster has them for the cost they do I wouldn't bother cutting anything unless there's an immediate need.
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  22. #22
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    Would this help if your local me has this: http://www.parktool.com/product/disc...tabbed-section


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  23. #23
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    Quote Originally Posted by ronf100 View Post
    Would this help if your local me has this: DT-5.2 Disc Brake Mount Facing Set | Park Tool


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    nope.
    use a torque wrench

  24. #24
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    Quote Originally Posted by ronf100 View Post
    Would this help if your local me has this: DT-5.2 Disc Brake Mount Facing Set | Park Tool


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    The mount surface is aligned - the other wheels I have work fine. It's just the spacing of the brake rotor is off by a half a mm or so. The spacer will solve the problem just fine.

    Thanks tho...

  25. #25
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    Well, this is a bit disappointing.

    I received my order from McMaster-Carr today, and some of the spacers were crumpled up inside of the zip-lock bags, and are damaged.

    These are the 316 Stainless 1 3/8" ID x .001 spacers I ordered. I ordered some that are slightly thicker that were unscathed, and will probably suffice to to do the job. Some of these might be salvageable, but I'm going to wait to hear from their sales staff before I open the damaged ones. I sincerely hope they don't insist on me sending these back. I emailed them pictures of the damage. Hopefully they'll ship some replacements post-haste...


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