This article will assist with identifying the source of play/looseness in rear hubs. 

Notes:

• As a first step, ensure that the play is isolated to the rear hub. Oftentimes frame linkage looseness can mimic a loose rear hub. This is best done by replicating the play when then wheel/hub is clamped in a different frame or trueing stand. 
• SL hubs using alloy axles will have a 3-5mm of axle freeplay when the wheel is off the bike. This play will go away once the wheel is clamped in the frame. See this FAQ

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Potential Issue:  Loose bearing press in drive side hub shell.

In some cases play can develop if the drive side bearing bore in the hub shell has slightly opened and the bearing no longer presses in place but rather sits loose inside the bore. 

Verification Procedure:  Check integrity of drive side hub shell bearing press. This can be done by removing the bearings and checking if the driveside bearing presses into place with minimal force or if outer bearing race can be moved when installed in hub shell. See images below

Solution:

• Remove the driveside hub shell bearing and clean outer race and hub shell bearing bore interface. Reinstall using Loctite 638 or similar type sleeve retainer. 
• File warranty claim here.

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Potential Issue: Steel Boost 148mm Axle with too short grind location.

Note: Only applies to hubs with steel axles - not applicable for alloy axles

A small batch of early boost hubs had an axle grind distance which was too short and stopped before reaching the drive side hub shell bearing which could result in a small amount of play. See photo below (Note measurements are without endplugs installed). 

Verification Procedure: Measure axle grind distance. Verify using image below.

Solution: Replace Steel Axle. If under warranty, file warranty claim on our support site. If not under warranty, replace with HBS20-101