Monday, October 5, 2009

Bruiser Fork Expanding Steerer Plug

We have been hearing some confusion about the Bruiser fork expanding top-cap plug (included with every Bruiser frameset and Bruiser Aftermarket Fork order); from installation and use, to the plug pulling out of steer tubes when trying to tighten headset. We have illustrated the proper method to install and use this steerer plug.
This expanding plug is our replacement for the traditional star nut, because the heat treatment done to our forks does not allow a traditional star nut to properly bite the inside of the steerer.

In addition, we wanted to know how much force (in/lbs.) it took to pull the plug out of the steerer.
We clamped a stem securely to the steerer at the appropriate height (3-5mm) above the steerer top. Tightened a top cap and screw finger tight, then used a dial indicator in/lb torque wrench to load the plug / top cap until plug started to pull from the steerer tube.
In 5 separate pull tests, with 5 separate forks, it took approximately 80-90 in/lbs. of load to pull the plug from the steerer. This is 8 to 9 times the amount of force headset manufacturers recommend for proper bearing preload.

-Make sure stem's steerer bolts are completely loosened when preloading headset.
-Chris King states top cap preload 4-10 in/lbs. (15 max)
-Many other manufacturers state "Caution - Preload torque on top cap adjuster should only be enough to take the play out of the headset. More than that will cause headset binding and/or premature wear."


Anonymous said...

Hey guys instructions on this in the package with the bike would have been nice. I had no clue what it was for!

Ben's Cycle said...

Carbon forks have been coming with these for years. When your LBS installed your fork (as stated in the first bullet point of our product safety sheet included with your frameset and/or fork); they should have known.
Nevertheless, all future shipments will contain the instruction sheet.

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