Raising Motorcycle Fork Tubes
the fork tubes in the triple clamp is a simple adjustment that can help make
a motorcycle respond faster to steering input and can lower the
This trick won't be
found in your owner's manual, because the manufacturers spend a lot of time
working out the best compromise for the motorcycle's suspension, and they
really don't want you messing with it. This old racer's trick changes
the bike's apparent rake and trail, usually enough to make a noticeable
difference on most motorcycles.
It also lowers the seat height slightly, although
depending upon the bike, the difference may be so small as to be
undetectable. But sometimes every millimeter counts, and the most
common procedure to lower a motorcycle involves three things: first, get a
lower seat of have the seat re-worked to lower the foam and make the front
of the seat narrower if possible. This can sometimes lower a
motorcycle by 25-35 mm (1" to 1-38").
Next, try raising the fork tubes in the triple clamp,
which can lower the bike another few millimeters. The third and most
complicated step is to lower the bike's rear suspension. This can
involve anything from shorter shocks to replacing suspension parts, and
often involves handling compromises. Try steps #1 and 2 first, and you
may find that the bike can be lowered enough to fit.
Motorcycles with cruiser-style rake, like the 1994 BMW K75 I owned once,
don't seem to respond to this trick, because the fork tubes would have to be
raised so far in the triple clamp to change the larger rake angle that the
bike would become impossible to ride and the front suspension would probably bottom
My old K75 had such lame handling that even raising the fork tubes to an
extreme amount didn't help much. However, the Triumph Thunderbird
Sport (TBS) seems to be very sensitive to fork tube height; after some
experimenting, I've found that raising the fork tubes on this bike
noticeably speeds up the steering.
After some experimentation, I settled on raising the fork tubes by 10 mm.
This seems to be just the right amount to make the steering more lively and
responsive without getting too radical. I suggest settings between 10
mm and 15 mm.
The steering becomes very quick when the tubes are
raised 15 mm, and certainly the bike is great fun in fast left/right
transitions. But that amount of change also causes the bike to develop
a slight tendency to fall in to the turn and feels like it's oversteering.
The handlebar inputs have to be very small and precise, or you'll find
yourself having to correct mid-corner. 15 mm might be good for a track
day, but it takes a bit of the fun out of riding this bike because of the
concentration needed to get through a corner. 10 mm seems just about
perfect and much more reasonable -- it's enough to noticeably quicken the
steering without making the bike feel too nervous.
You may want to experiment with your motorcycle to find a fork tube
height that suits you. It will depend upon the motorcycle, the tires
and the rider's preference. But it's usually a very easy project; on
most bikes, the fork tubes can be raised by loosening up the upper and lower
fork tube bolts that hold the forks in the upper and/or lower triple clamp.
Unless your TBS has the optional center stand, you'll need to raise the
bike up using a paddock, or swingarm stand (see the wBW
review of the Steel
Horse swingarm stand, a very well made stand which also works very
nicely on the Thunderbird Sport) for this project.
I suppose it could
be done with the bike on the side stand, but since I own a swingarm stand,
I've never tried it any other way.
You'll probably need to place a jack underneath the bike for this
project, because it's very easy to raise the fork tubes, but not easy to
lower them if you don't get it exactly right the first time.
I use a hydraulic scissor jack underneath the oil pan, and I place a flat
piece of wood between the jack and the engine to protect the aluminum.
Next, pry off the chrome plastic clamp bolt covers. You'll need a 5
mm Allen wrench (a 5 mm hex drive on a short ratchet extension works best)
and loosen the clamp bolts.
It's not necessary to completely remove
the bolts, just loosen them up enough so that the fork tubes will slide up
in the triple clamp.
Once the bolts are loose, a light push down on the handlebars should
easily push the fork tubes up above the top of the triple clamp.
You'll probably find that it's very easy to overdo it; in fact, it's
actually easier to get the fork tubes way higher than necessary, and then
slowly jack the bike up and tap on the top of the fork tubes with a piece of
wood until they're lowered to the desired height. As I mentioned
above, I suggest you start with 10 mm. It's easy enough to get both
fork tubes at an even height by using a metric scale graduated in 1 mm
Once you have both fork tubes at an even height, tighten up the clamp
bolts to the correct torque specifications for your bike and take it for a
test ride. Be careful at first to get a feel for the way the bike
This is a great way to brighten up the handling on the TBS
and other motorcycles could probably also benefit from raising the fork
tubes. It's easy enough to do and you can always put them back to
their stock position if you don't like the results.