SAPIM STAINLESS HM CONCAVE ROUND NIPPLE WASHER

Design and construction

An eyeleted rim spreads nipple load through a stainless insert; an eyeletless rim, which is most modern rims, puts the nipple head straight onto the rim bed, and under 120 kgf of tension a nipple head can deform an aluminum bed or crack a carbon one over time. A washer spreads that load. The HM concave round washer has a spherical dish that matches the Polyax seat, so the nipple can tilt and the spoke runs straight; the concave oval washer does the same on rims with oval holes or strongly angled drilling; the flat round washer spreads load on rims that already have a countersink. All three are stainless steel, and Sapim sizes them to the 14-gauge Polyax.

Many rim makers now supply their own washers, such as DT Swiss PHR washers, and we use those where the rim specifies them; on rims that do not, the Sapim washer is what we fit.

How it rides

You will never feel a washer, but a wheel built with the right washer on an eyeletless rim holds tension longer and does not develop the cracked or bulged spoke holes that end a rim's life. It is the least glamorous part of a wheel and one of the most important, which is why we put it on a page. We fit the HM concave washer on every eyeletless alloy and carbon rim that does not ship with its own washer system, which is most of the rims in the catalog.

Sizes, fit and compatibility

The Sapim Stainless HM Concave Round Nipple Washer fits the 14-gauge Sapim Polyax nipple and any eyeletless rim with a standard spoke hole; the configurator fits the washer automatically on rims that need it and skips it on eyeleted rims and rims that ship with their own washers.

Building it at ProWheelBuilder

Sapim makes the washers in Belgium; ProWheelBuilder is an independent wheel builder in Georgia, not the manufacturer. We fit washers on every eyeletless rim that calls for them, build with spokes cut from the measured ERD of the rim, bring the wheel up in stages with a gauge, stress-relieve it and true it before it ships.

The configurator includes the right washer in every build that needs one and prices the wheel live.

Building it well

Rims are measured before they are built. We check the ERD of every rim with a gauge rather than trusting the catalog number, because two rims from the same box can differ by a millimeter and a spoke cut to the wrong length either bottoms out in the nipple or runs out of thread. It is the least glamorous part of building a wheel and the one that decides whether the wheel stays true.

One more thing

A word on tubeless. Every tubeless-ready rim we sell leaves the shop taped and with a valve fitted if you ask for it, and we tape to the rim maker's recommended width rather than whatever is on the bench, because a tape that is a few millimeters too narrow is the most common cause of a slow leak. Add sealant, seat the tire and ride.

And another

Spoke count is worth a sentence. A modern rim on a modern hub does not need 36 spokes to be strong, but it does need enough spokes for the rider and the riding: 28 for most road and cross-country wheels, 32 for trail, gravel with a load, heavier riders and e-bikes, 36 for touring and tandems. The configurator recommends from your weight and bike type, and we will talk you out of a count that does not suit the rim.