Well that makes sense. The problem I have with this design is that there
is no protocol for tightening these bolts since the torque required to
overcome the friction between the nut and the bolt is more than the
torque required to appropriately secure the mounting blocks. So we are
left with instructions like "tighten firmly" which has a different
outcome for the 120lb person with a short lever vs the 300lb person with
a 2 foot lever.
I think the idea is to tighten such that the two halves of the monting
block have clamped together evenly and rack doesn't move, so I found
that tightening the nuts to the point where I could no longer rotate the
bolts with the allen wrench was a good guide and then tighten them a
quarter turn more for luck. I do not detect any movement in the rack
with the wheels on the ground and pulling on the steering wheel. With
the rubber mounts I always saw a slight give during that test.
Thanks Vance as always for your insight.
As to the end result, these mounts are great. The front end feels very
tight and I don't detect any additional vibration or bump steer. I do
feel like I have full control over the steering for the first time in
years. All the vagueness has gone.
Stan
-----Original Message-----
From: Navarrette, Vance [mailto:vance.navarrette@intel.com]
Subject: Jam nuts on rack mounts
Stan:
You are correct. A "jam nut" is generally just a plain nut
that is torqued against another nut or threaded part
and prevents unwanted rotation by stretching the bolt
to provide a compressive force between the two nuts. Most often, the
jam nut is thinner than a regular nut but it can most any size.
The part you are discussing is a "lock nut" which also
comes in a variety of designs. The particular type you describe is
an "oval lock" design, where the nut is crimped to provide an
oval shaped thread. It relies on friction between the nut and
bolt threads to provide the locking action. There are a variety
of sub types, including top lock, center lock, hex collars, etc.
Of course, we are all familiar with the Nyloc style of lock nut
found on our LBCs.
Cheers,
Vance
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