triple trees

hey guys. i'm restoring an older bike. tryng to make a mild custom with
little or no framework. i've heard raked trees are dangerous, so what
about extended trees where the fork holes are set forward an inch or
two, both top and bottom, with no rake? would this work? would it be
safe?

 

CAUTION
ANYTHING that affects steering geometry is not for amateurs to play
with.
Those fork holes MUST be bored parallel to eachother and straight to
within
thousandthsof an inch.
You'd better have a lot of faith in the materials you use because a
failure
of the tree will kill you and it is a highly stressed part.
Moving the holes forward changes the relationship between the pivot
line
and the contact patch.
You might expect more stability, you might also get a wobble.
MadDog
"No Fear??? - Its whats kept me in one piece all these years."

 

mad dog is dead on .
don't mess with them that way.
good luck, sammm

 

That's would have the same affect as raked trees.

 

Hey, David. My shift key works.

i'm restoring an older bike. tryng to make a mild custom

No, David. You're not "restoring" an older bike, if you're trying to
make it into a "mild custom". Restoring is when you make it look just
like it looked when it sat on the showroom flooring, begging somebody
to buy it, DOT stickers and reflectors and all...

You're trying to say that you don't want to cut and re-weld the
steering head. You're not trying to say that you're building an exotic
custom with almost no frame, like a Britten.

I know a guy that used to do that to motorcycles which had sidecars
attached. While it raked the forks out slightly, it also reduced the
trail a bit and reduced steering heaviness.

If you bore out the rear hole of the upper triple clamp, and install a
special eccentric sleeve there to move the upper clamp backwards
without changing the steering stem angle, the upper triple clamp is
weakened, but that's not where the heavy load is concentrated.

You can lose the rear upper clamp bolt and still ride around, as long
as the
steering head bearing nut is tight. I know this, because that bolt fell
out once.

The lower triple clamp will have to take an extra bending load because
the fork stanchion tubes have to go through them at a slight angle when
you sleeve the upper triple clamp.

Steel lower triple clamps are pretty tough, but I sure wouldn't
recommend doing the raked tree modifcation with a cast aluminum lower
triple clamp. It might break.

Maybe you're a custom builder and you don't plan to ride much, you just
want a converstion piece sort of motorcycle. Then you can get away with
almost anything...

Motorcycles have been built for a hundred years with offset triple
clamps and they are not unsafe when the engineer designing the chassis
understands that rake has less effect on steering feel than trail.

The whole idea of offset triple clamps is to kill off the excess trail
and reduce steering heaviness.

You need to study rake and trail and understand why motorcycles have
raked out forks to begin with.

Every would-be custom builder thinks, "Whoa-a-a! Raked out forks look
so kewl!"

But, what is the alternative to raked out forks, when trail has much
more effect on steering feel than rake?

The chassis designer could just as easily design a front end that had a
*vertical* fork that moved straight up and down, and have 4 to 6 inches
of trail, and the front end would caster like the front wheels on a
shopping cart.

Enough caster (trail) would ensure that the motorcycle was self
stabilizing.

But what would the chassis look like, if the steering head was a foot
further forward than it is with a raked fork and the steering head was
where the head light is now?

Wouldn't that be a weird looking motorcycle? But, maybe some motorcycle
"stylist" would like the looks of the arrangement and popularize some
customization of it...

 

I guess it's possible and in certain circumstances almost safe.
Generally it is dangerously misleading information.
A tight and true steering system is critical and even small
defects can make a bike lethal.

You forget to mention what this will do to the steering head
bearings. Another part of the critical steering system.

Old news, Tony Foal (sp?) made one of these decades ago. Worked
well as far as steering was concerned. The downside was that even
moderate braking made the forks bind (the ones he used were not
very advanced or strong).

 

so i'm guessing no?

 

Tony Foale. Of course, the vertical telescopic fork is going to have
problems with clearances on the sliders. But there is probably an ideal
compromise between a 45 degree raked out fork that cannot comply with
small pavement irregularities and a vertical fork that binds under
braking.

 

I recommend that you quit guessing and google up some websites that
discuss the effect of rake and trail and how offset triple clamps or
leading axles affect steering feel.

You also need to know about how front tire diameter and width and
profile affect steering feel and turn in.

You need to find out what "out tracking" is and you really need to know
how countersteering and chassis stability works before you start
dicking around with this mild custom you're working on.

But, you can also learn the hard way, by buying a lot of different
wheels and tires and playing around with pulling telescopic forks up
and down in the triple clamps.

 

Yes Sir; You Puttnucker's Check www.tolle.se and get on with'it....

My regards "DG"
..