RAKE AND TRAIL FOR TRIKES
JUST WHAT IS RAKE AND TRAIL?
Your front suspension geometry is defined by the following
six variables which are defined as:
OFFSET: Centerline of the top steering neck to the centerline of the top of
the fork tubes.
RAKE: The angle in degrees of the steering neck from the vertical cord.
FORK LENGTH: The distance between the top of the fork tubes to the
centerline of the axle.
DIAMETER: The diameter of the front tire.
TRAIL: The distance defined by the vertical line from axle to ground and the
intersection of centerline of the steering neck and ground.
HOW TO MEASURE CORRECT TRAIL
Raise the bike to an upright position, using a tape measure, hold the tape
straight down from the front axle to the floor. Put a mark on the floor at
that point. Then place the tape parallel to the steering neck, following the
angle of the steering neck all the way up to the floor. Put a mark here
also. Now measure the distance between the two marks and you have your trail
measurement. It should read between 2 and 4 inches. Note: If your bike is
equipped with a rear suspension, have someone sit on the seat when you make
the measurements to simulate your actual riding condition.
TOO LITTLE OR NEGATIVE TRAIL
With too little or negative trail (steering axle mark behind the front axle
mark), the bike will handle with unbelievable ease at low speeds, but will
be completely out of balance at high speed. It will easily develop a fatal
high-speed wobble. EXTREMELY DANGEROUS!
NORMAL TRAIL
Normal trail is somewhere between 2 and 4 inches. The bike will handle
easily at both high and low speeds. Flowing smoothly through curves without
swaying or wobbling. If you use a very fat rear tire, you should keep the
trail as close to 4 inches as possible.
TOO MUCH TRAIL
If the trail is more
than 4 inches the bike will handle sluggishly at high speeds. It will seem
almost too steady. You will have trouble balancing the bike at lower speeds
or on winding roads. It will feel generally sluggish and clumsy.
If the trail is more than 4 inches the bike will handle sluggishly at high
speeds. It will seem almost too steady. You will have trouble balancing the
bike at lower speeds or on winding roads. It will feel generally sluggish
and clumsy.
Just how does rake and trail affect a trike? Well, rake doesn't seem to have much of an effect with a trike, but that's not the case with trail. The more trail you have the front end will tend to steer harder at speeds over 30mph.
I asked a couple of known trike builders the question concerning rake. All the the answers all seemed to agree.......
I think you pretty well covered it. A VW trike with a long rake, in my opinion, looks better,
rides better and makes more sense because your front wheel in leaning into the turn.
This takes a lot of stress off the front end and front wheel.
On the other hand, a V8 trike or any other trike with a lot of weight on
the front end can't handle a long raked front end because of the
downward stress of the extra weight. They have to have a heavy front
end that is fairly vertical or you bend components in a hurry.
Another thing that determines rake-ability is the type of front end. If
you are riding on tubes there comes a point fairly early in the game
where the tubes will not operate correctly. I like springers for this reason
and LOVE girders. A 12 over girder leading down the road is hard to beat
and they ride like Granny's rocking chair.
For VW or other rear engine trikes the rake is a matter of choice and
esthetics. Too much is made of it. I've built two with stock Gold Wing
rake and they rode great. I built two with springers and they rode great and I looked BA_A_A_AD!!!!
Build it for you and get the look YOU want. Chances are good that it will
ride great. If it doesn't, fix it. It's called adventure!
Another answer:
From past experience in riding different models of trikes from bugs
to V8's..I've found that the straighter the forks (less rake) the
more front end wobble on low speeds and bumps, definitely a
steering damper needed there, although it is more prominent on
heavy front end machines like the V8's or front engine trikes. Long
rake also helps alleviate the washout sensation when taking off from
a start and turning. It also helps if the trike has at least a front
end weight of 10% of the total weight of the machine and rider
amount of rake. The longer the rake the more apt to go with
springers or girders as the motorcycle type forks were not meant to
flex parallel to the ground but to ride up and down in the sliders. As
for stability (and looks) I like the springers if ya can get a heavy
enough spring for them to not be susceptible to bottoming out on
speed bumps or potholes...jus my 2 cents worth...
