Steering head bearings & swing arm bearings
It is possible the bearings at the steering head and / or the swing arm are worn
enough to allow slop which should not exist. Such slop can cause a high speed
head shake which can be exciting. The change in weight distribution caused by
adding the panniers could exacerbate the potential for head shake by shifting the
weight bias toward the rear of the bike, thus "unloading" the front end of the
bike and allowing the steering head a bit more freedom to move about.
So I'd look at the steering head bearings first of all, then check the swing arm bearings.
After that, check ride height both without a load and with a load. You may need
a rear spring which has a higher rate to compensate for the added load of panniers.
The shock has much less influence on ride height than the spring does, whether it
is a high-pressure nitrogen filled shock or not.
In any case, best to go through the entire bike and check everything, including wheel
balance and all other suspension-related items. Adding a steering damper might mask
the symptoms but will NOT cure the cause. You need to find the root cause because
the safety of the bike could be compromised by whatever is causing the shake.
And have a very close look at the front forks where the axle passes through. Some
of the front forks on some of these bikes have had "issues" ( they fail structurally while the
bike is under way ) and that is potentially disastrous. Look for cracks in the lower fork leg
near where the axle passes through the lower fork leg.
It'sNotTheBike screwed with this post 01-23-2013 at 08:39 AM