Better Headset Spacers

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Spacers with a flat surface on the inner diameter can help prevent your headset from loosening. Just to clarify: If your headset stays put as it is, then don’t change it! It’s just that my headsets kept loosening on two different bikes, and so I was looking for a solution.

Classic headsets use a locknut at the top to maintain the headset’s adjustment. It’s essential to prevent the upper headset cup and locknut from turning together, as this would loosen the headset. A keyed washer between the top cup and nut stops that rotation – in theory. In practice, this system does not always work: The keyed washer tends to turn anyhow, because the key is too small. And you cannot make it bigger without weakening the steerer tube.

When the washer is made from steel, it can mess up your steerer tube’s threads if it turns (very bad). With an aluminum washer, the steerer tube simply cuts new threads as the washer turns (not good). In both cases, the key is not sufficient to stop the washer from rotating.

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The solution is simple: Use a flat surface on the steerer tube, and a matching flat surface on the spacer, to provide more material area than a narrow key. French bikes (and some British ones) used that system, and it worked better. The headset cup doesn’t turn with enough force to cut threads into all that aluminum.

Compass made the spacer taller than a simple washer, which provides even more material to resist the turning torque. And since the spacer is so effective in preventing the system from rotating, it’s not necessary to tighten the headset locknut with force. A little more than finger-tight is sufficient to keep it from loosening. You can use a single headset wrench: Tighten the top headset cup first, insert the spacer, then (lightly) tighten the locknut. Don’t overtighten the locknut, otherwise, the spacer can jam.

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It’s easy to retrofit your bike with this system: Machine or file a flat on the back of the steerer tube that matches the inside of the spacer. This doesn’t weaken the fork: You only remove the raised portion of the thread, which didn’t add any strength to the steerer.

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I’ve used prototypes of these spacers on my Mule for thousands of miles and dozens of Rinko disassemblies. They have performed great, and they’ve solved the loosening of the headset on this bike.

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We now offer the spacers in 5 mm and 10 mm thickness. If you need an in-between thickness, just add standard headset washers (without tabs) to make up the difference. Or cut a few millimeters off your steerer tube to match the spacer, as I did on my Mule.

Click here for more information or to order these spacers. As I said before, if your headset works fine, don’t change it. But if it keeps coming loose, this may be the solution.

About Jan Heine, Editor, Bicycle Quarterly

Spirited rides that zig-zag across mountain ranges. Bicycle Quarterly magazine and its sister company, Compass Cycles, that turns our research into high-performance components for real-world riders.
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32 Responses to Better Headset Spacers

  1. Christian Bratina says:

    I ad no idea anyone was using threaded headsets on new bikes! All of our old ones had a notched steerer with a tanged washer. Threadless is so much easier to tighten.

    • There are a number of advantages to threaded headsets: Easy adjustability of the bar height is one, but perhaps the biggest reason to use them is aesthetics. The stem is less bulky, which keeps it more in proportion to the slender tubes of a steel frame, especially one made from standard-diameter tubing.

      • Ken B says:

        Your preferred decaleur system attaches to the stem bolt(s). It would seem that once you mount the decaleur attachment to the bar bag, you lose the ability to adjust your handlebar height–moving the bars up would lift the bag off the rack, and moving them too far down would mean that the pins would not insert far enough.

      • Cloth bags have quite some “give” to them, so adjusting your stem up to an inch (25 mm) up or down won’t affect the bag.

  2. Have you tested these spacers on a variety of bicycles?

    • Yes. The idea of a flat surface on the steerer is nothing new. Millions of French bicycles used that type. The only thing we changed is make a thicker spacer with the matching flat, rather than just a thin washer. (Most headset spacers are just round and have nothing to prevent them from turning, so only the thin washer tries to resist the forces.)

      The project started 7 years ago, when I custom-machined a thicker spacer with a key to prevent it from turning, but that wasn’t enough. Then I had the idea for this, and I’ve used it on several bikes for more than 2 years now.

      Again, it’s only for bikes with threaded headsets, and I recommend it only if your current headset is having trouble.

  3. Jon Blum says:

    I have not had loosening problems (with my headset), so I am curious what might cause this. Rough roads or hard braking? I remember you mentioning a loose headset after very hard braking in a previous post. Can’t say I understand the forces involved.

    Seems like threadless headsets would have less trouble with this. I agree they are less attractive, and present issues with adjustment (esp. as we grow older and stiffer, and want to raise the stem). Some say they make a more rigid connection between the bars and the fork, but I don’t perceive any difference, nor do I feel my wheel flopping around due to the traditional stem and steerer.

    • Headsets loosen from all kinds of forces. The headset is under tension to pre-load the bearings. So it always wants to loosen. Vibrations will do this, but also the fore-and-aft movement of the fork when braking. Headsets on threadless actually are more prone to loosening, since all that keeps them in adjustment is the friction of the stem on the steerer tube. You remember correctly – when we tested brakes and did full-on emergency stops on a steep slope from 30 mph, we found that the Ahead-type headset (and front quick release!) had loosened after multiple runs.

      As to the stiffness of the connection between stem and fork, the threadless headset actually is stiffer. With a traditional quill stem, you get some windup in the quill. We noticed that when we tested truly heavy loads on porteur racks. With low-riders, the load isn’t offset as far from the steerer axis, so the polar moment of inertia is lower, and a quill stem works fine. With lighter loads, it isn’t an issue, because you don’t use much force on the handlebars anyhow.

      On my Urban Bike and my René Herse, I used a threaded steerer with a short tube brazed into the top, to which a direct-clamp stem attaches – similar to many older French constructeur bikes. This combines the advantages of both systems, plus it leaves the inside of the steerer tube empty, so I can install a headset switch there.

  4. Rick Thompson says:

    Jan – I know you offer that neat little rinko headset wrench, but just saw this – a posting by Peter Weigle of his version of Natsuko’s bike with Hirose design headset nut having a brazed on tube for allen wrench tightening: https://www.flickr.com/photos/49353569@N00/14614167535/in/faves-64917772@N00/
    Combine that with the new spacers and you really would just need a couple of allen wrenches to rinko. Any thoughts of offering headset nuts with similar wrench tube brazed on or machined in?

  5. Mark says:

    Will you make the notch key version so users don’t have to file out the notch out in your spacers for the rest of the world that uses JIS quill headsets?

    • I prefer to file a flat on the fork, rather than a key into the spacer… I did make a prototype keyed spacer, but the steerer just cut threads into the aluminum. At that point, you are back to a standard headset spacer with nothing to keep it from rotating. If you made the spacer from steel, it might work.

  6. Peter Mullin says:

    I do experience the loosening headset problem on both of my threaded-fork bikes. In one case, it’s because (I think) the original fork is just a bit too short, necessitating omitting the keyed washer altogether. So, what I really need is a 1″ threaded fork with a longer steerer, fender eyelets, rack bosses, and preferably fork-crown brake mounting (so no canti bosses). Oh, and made out of proper steel (not Hi-ten)…and black. Does such a thing exist anymote?

    • Gugie says:

      Custom, yes. Alternatively, you could find a fork that has a long enough steerer and the fork blades you want, and are sized to fit the tire you want to run along with proper fender clearances. Adding on all the eyelets and bosses you want is a simple thing for a framebuilder to do. BTW, if you’re looking at wider tires and fenders, brazed on centerpull posts are a wonderful addition. Compass sells the bosses, I’ve purchased several sets for frame upgrades. Jan has many of the hard to find bits to enable recreations of the constructeur style bikes we love to drool over in BQ and the books they sell.

  7. Ray Varella says:

    Hmmm, perhaps there are philosophical differences at play here in how to properly adjust a headset. I have always treated threaded headsets the same way I treat locknuts on an axle or lockrings on cup and cone bottom brackets. In order to properly set the adjustment, the upper and lower nut are each held with a wrench and then tightened against each other. Having a spacer or two in between does nothing to change the principle. In many decades of use and numerous miles on dozens of bikes in many conditions, I’ve only had one headset come out of adjustment and that was from a frame I purchased where the “expert” mechanic installed the headset. Even after years of benign neglect riding on baked washboard clay, my headsets don’t come loose. I suspect that traveling with bikes and not having proper tools to adequately adjust the headset would make these spacers useful. I’ll be sure to try them on a build where I remove my fork frequently. Knowing how much is at stake if a headset came loose under hard braking, I’m not likely to ever set any nut “finger tight”, that just sounds like a recipe for an accident.

    • You are right, a keyed washer works well enough on hub cones and locknuts. For the headset, the problem is that they key is not deep enough, because the walls of the steerer are too thin. The hub axle has a key that is deeper, especially when you regard it in relation to the diameter of the axle/steerer.

      If the headset loosens under hard braking, nothing bad happens. (I had this happen, usually on test bikes where the headset cups weren’t seated correctly until I braked hard a few times.) You’ll just notice that your headset is loose after you release the brake. It’s not good, but doesn’t carry the risk of an accident.

      • Nic says:

        From my bike shop experience the fit between threaded parts (steerer & headset parts) is often (always?) sloppy. One day I tried to cut threads on a steering column “too big”. The tool allows for this. The shimano headset ( along with its accurate threads) screwed beautifully right. Perfectly clean threads, ( I always finish my cleaning with dishwashing soap & hot water, dry with hair dryer…) add a tiny drop of Loctite and , you know what? self- loosening headsets is a thing of the past . I too have been enamored with the miraculous precision of cone & cup adjustment with quality metal & machining. Why do steerer threads have been treated by the industry as “second class” puzzles me. You understand that the so-called aheadset I just hate with its adjustment system that is simply not one: You “crush” your bearings and lock (or try to lock) with a clamp that will slip quickly, you get a self loosening and self destructing setup. This comptraption has been imposed to us cyclists by an industry that saw that skipping the threading operations and stocking one steerer length was economical for them. Just tell them it’s better! BTW I’m the inventor of the “ahead nipple”, the spoke nipple that clamps around the spokes, if it’s good for headsets….then.

  8. The solution is to grease the steerer threads and both sides of the traditional keyed washer. When adjusting, slightly over-tighten the cup, then when tightening the locknut, use two headset wrenches, tightening the cup and locknut against each other (the cup returning to the proper adjustment). The washer(spacer) then receives little or no turning force. Use the full length of the long headset wrenches for torque. Problem solved.

    I’ve been doing this in my shops for 45 years and have NEVER had a problem with loosening headsets after using this method.

    • It’s the same method I used to use, but it works only if you have exactly the same friction on both headset parts (cup and locknut). If one turns a bit less freely than the other, especially once it’s preloaded, then you will start to turn the keyed washer. If the key has a good interface with the groove in the steerer, that should stop it from turning further, but in practice, few have. Most are made to very sloppy tolerances and will turn past the groove…

  9. Rustilicus says:

    One problem is 5mm is too thick to fit into many headsets.

  10. Spacecowboy666 says:

    How did you mount your bell on your mule with Nitto NP stem?
    Do you drilled a hole (for threading it) like the brake cable stop on the stem extension?

  11. jasonmiles31 says:

    I don’t really understand why this spacer reduces the required torque on the lock nut. Isn’t the only thing preventing the locknut from loosening the friction between the washer/spacer and the threads of the steerer? If you reduce the torque you reduce the friction. I understand if the tab breaks off the washer there is no washer friction, but this can’t be higher than the total friction from both fully tightened threads right?

    Do you have any theories? Maybe the spacer has a tighter fit reducing relative motion?

    • The headset always wants to loosen, which means that the cup wants to turn. If you simply screw the locknut on top, then both parts can turn together, and they often do. (The only thing that prevents them from turning is the friction in the threads.) By inserting a washer or spacer that cannot turn in between, you prevent the two parts from turning together. Now you have the friction of each part (cup and locknut) against the washer/spacer that prevents these parts from rotating.

      All the locknut now has to do is hold down the washer/spacer, rather than preload the threads of the headset cup so much that it no longer turns. When you envision one of those old French headset cups and spacers with teeth, it becomes easier to understand. The headset cup wants to turn, but it cannot unless the spacer is lifted up. And the top locknut prevents that from happening.Stronglight P3 headset

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