After grumpily complaining to myself about rotor alignment for the past couple weeks, a friend and the master wheel builder behind Light Wolf in Dresden reminded me that Syntace had my back, at least when it comes to 6-bolt hubs. Testing different cyclocross tires and wheelsets means a lot of swapping back and forth this season, and we’ve been reminded very quickly of the high tolerances required to keep disc brakes running smoothly and quietly, and of the wide variation from one hubset to the next. While there is a standard that defines where the rotor is supposed to sit in relation to the end of the axle, there is enough variation that almost every time we swap a wheelset I end up adjusting calipers. Conventional wisdom in cross has been to use the same hubs (and previously the same rims) on all wheels, but that is one luxury I don’t get while I am reviewing wheels for our readers. So to break down some of the hassle, hop past the break and see how Syntace’s shims can help center up braking across multiple wheelsets…

Syntace_Disc-Shim_6-bolt-hub-rotor-alignment-shims_rotor-without-shims Syntace_Disc-Shim_6-bolt-hub-rotor-alignment-shims_add-shims-to-fit Syntace_Disc-Shim_6-bolt-hub-rotor-alignment-shims_rotor-with-shims

While I’ve used individual shim washers in the past to try and align rotors, the hassle of lining up and installing a dozen or more tiny washers behind a rotor is such that I wasn’t too interested in trying it again. But with the Syntace shims it was an entirely different story. To use them, simply figure out which wheelset has the rotor closest to the dropout and use that as a baseline. Then stack the required number of spacers behind the rotor on the wheel (or wheels) whose rotors are farther away from the dropout to get them all in the same place, and bolt everything back up.

I’m not sure why, but with 3 or 4 wheelsets, the front rotors were all over the place and needed up to 3 shims on one hub, while the rear wheels were never more than 1 shim away from spinning drag-free. With the one-piece shims, I was able to easily stack them on the hub, drop the rotor on, and thread a couple of bolts in quickly without losing individual washers for a centered fit.

Syntace_Disc-Shim_6-bolt-hub-rotor-alignment-shims_pack-of-8 Syntace_Disc-Shim_6-bolt-hub-rotor-alignment-shims_actual-weight-7g-for-8

The shims come in a set of 8 from Syntace for just under 10€ and are each only 0.2mm thick to fine tune rotor placement. At just less than a gram per shim there isn’t much weight penalty for having the one-piece shims vs. individual spacer washers, and they are much easier to deal with. The only negative thing I can think about them now is that they won’t shim my centerlock rotors too.

Just another quick thanks to Felix at Light Wolf for gifting me these on my last visit and the peace of mind that they are already providing. I guess I owe him a beer or two now. Get your own shim kits wherever Syntace products are sold, or even directly from their web shop.


  1. Adam on

    …also useful for older IS mount brakes which lack horizontal adjustment. Have had a set of these for a week now waiting to fix my wife’s brakes 🙂

  2. Darryl on

    I searched for these before and could only find them in some obscure overseas bikeshop.
    Any one willing to sell these in Australia?
    Idealy they would come supplied with every aftermarket wheelset so changing wheels would not be such a pain.

  3. LAurent on

    Why would you want to use these? blindly put one behind your rotor and then it could be to wide, adjusting the calliper is much quicker.

  4. Quickie on

    LAurent- I thought the same thing until reading the article. These make sense if you frequently swap wheels and don’t want to adjust the caliper every time.

  5. WV Cycling on

    Strangely looking at these, then thinking about rimless revolver cartridge moon clips, I am infuriated for spending $8 for a single moon clip for my S&W 929……

  6. Handsome Dick Manitoba on

    This seems like a useful product. If you don’t immediately get it you probably don’t need it.

    Also, if I remember correctly Centerlock spline is about 35mm diameter which means you can get these shims for Centerlock.

    Might not be quite as pretty as a custom made product, and since there is an undercut at the back of the spline they may take a bit more effort to get installed nicely.

    Shimano (most) compatible freehub bodies are also 35mm OD so these might even be able to shim shimano cassettes to get both sides of rear wheels to swap perfectly all the time.

    It wouldn’t be hard for Syntace or someone else to make full custom centerlock spacers though.

  7. mes6073 on

    “centerlock is great… you can’t shim them.”
    Not as elegant, but I bet with a slight bit of modification/trimming, the 6-bolt shims can also be used for centerlock.

  8. Rod on

    I’ve shimmed Centerlocks. If I remember correctly, it was with very thin aluminium spaces for cassettes lockrings. They will slice you up if not careful, though.

  9. Andrew on

    Sounds like a great product to me…..agreed that if you don’t understand the point you probably don’t need it. I got a 2nd set of wheels for my cross bike this year (first time having 2 sets of wheels for a disc-equipped bike) and it was immediately apparent that shimming rotors would be necessary to make the wheels useful as pit-wheels. At CX nationals I flatted, and when I tried to use my wheels with non-shimmed rotors I ended up with rotors that contacted the pads through 80%+ of the rotation….. not ideal, and its not like you’re going to re-adjust your calipers when you’re trying to defend a top-3 placing. Some of these would make the shimming process a lot easier!

  10. James Cross on

    I have to say I am surprised these are just now getting the attention they deserve. I’ve had them for years now and are a valuable product. They work perfectly and allow you to swap wheels without having to touch your brakes period. I got them because I had a race bike with two sets of wheels, the training general use and the lightweight race day only set. With these spacers (same brand hubs mind you, still needed spacers for on one set) I was able to swap back and forth quickly and issue free. Example; before a race I had on a wheel with a road tire for use on the trainer for warm up and and then put on the race wheel with a proper tread for the race. This was quieter and saved me wear on the treaded tire.


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