Rene Herse Threaded Headset Spacers (1 inch)

Spacers with a flat surface on the inner diameter help prevent the headset from loosening. Classic headsets rely on a keyed washer to prevent the upper cup and locknut from turning together, which loosens the headset. Unfortunately, this system does not always work: Keyed washer tend to turn anyhow. When made from steel, they mess up your steerer tube’s threads (very bad). On aluminum washers, the steerer tube simply cuts threads, allowing them to turn anyway (not good).

Using a flat surface on the back of the steerer tube prevents the matching spacer from rotating. Making the spacer taller than a simple washer provides more material to resist the turning torque. Since the spacer prevents the system from rotating, the nut needs to be only a little more than finger-tight. You can use a single headset wrench: Screw the top race and adjust the headset. Then insert the spacer and (lightly) tighten the locknut. Don’t overtighten the locknut, otherwise, the spacer can jam.

It’s easy to retrofit your bike with this system by filing a flat surface on the back of the steerer tube that matches the inside of the spacer. This doesn’t remove any strength from the fork: You only remove the raised portion of the threads; the solid diameter remains the same. This system was widely used on French and some British bikes and has proven itself over millions of kilometers. It can solve an issue often encountered with threaded headsets.

Pro Tip: The Rene Herse headset spacers are dimensioned for BSC and ITAL (1″/25.4 mm) steerer tubes. They will have a slightly loose fit on French-diameter (25.0 mm) steerer tubes.