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FlatRacer BMW Airhead Boxer steering bearing adjuster spanner tool

FlatRacer BMW Airhead Boxer steering bearing adjuster spanner tool

FlatRacer BMW Airhead Boxer steering bearing adjuster spanner tool

Designed and developed by us to enable secure and easy tightening and undoing of all the BMW Airhead Boxer steering bearing adjuster castellated nuts.

Our heavy duty castellated (4 prong) spanner tool is designed to be to provide the maximum contact area to these thin section nuts, something most C spanners including the original tool supplied with the BMW tool roll cannot do due to their hook design. Our spanner provides a safe and optimised access to all these castellated nuts.

The spanner measures circa 180mm in total length thus enabling it to be fitted in the original tool roll. Provision to fit a 3/8" drive breaker bar or torque wrench is provided, along with a small semi-circular cut out to enable it to be hanged centered on a tool wall/board.

This tool is made of heavy duty 6mm flat thick steel, precisely laser cut for maximum accuracy of fit so it does not damage the nuts' edges as force is applied evenly to all surfaces.


1 - Our tool is designed to work with the original BMW castellated nuts that are in good, usable condition. Nuts that exhibit distortion or burred/damaged edges should be rectified first as the tool may not fit as it is designed with tight tolerances. 

Nuts that are quite damaged (ie: subject to the use of chisels and other unsuitable tools in the past) should be replaced by new nuts. Please contact us as we can supply these brand new.

2 - Care should be exercised when handling as this is an heavy tool. Personal protection equipment is recommended when handling it (ie: gloves and steel toe cap shoes)

Similar spanner tools available for other sizes including the steering and fork top nuts of 36mm and 41mm, the BMW /5 fork bottom nuts (30mm) and the steering bearing castellated nut adjuster. Please see our other listings.

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