Upside Down Forks - What are the advantages?

"Getting Slower & Slower !" wrote

My Briggs & Stratton mower engine is OHV and it produces 14.5 forking
HP.

Suspension by coil sprung seat.

Theo

 

Mine's got the sprung seat but is a little old side valve with over 1800
hours on it. Blows smoke, leaks oil but still goes like a trooper. None of
them poofy, flimsy blade setups either. Get that big base plate spinning
and it'll mulch any forking branches you can drive over!

 

Sarcastic license, of course, but it wouldn't be far off it. Everything
about the B-Nines makes them seem to have been engineered for use on a
planet with gravity about three times that of Earth.

 

30kg heavier? Seems incredible. Or did you forget to take the
old forks off when you put the new ones on

-----sharks

 

And thats just his trike, you should see his mower!

;-)

big

 

paulh said....

pa> The concensus is that they're meant to be stronger/stiffer than
pa> conventional tele forks. This is somewhat obscured by the fact that as
pa> almost ALL hi-end sports are now Upside Down, so we dont have a top
pa> quality sports oriented 2003/4 'normal' set of forks to compare them
pa> with. Most normal forks these days are placed on budget, commuter and


Can't you compare the last of the RWU forked model GSXR/ZXR/CBR to the
first respective model with USD forks?

Or in all cases were each successive model so radically different?

 

"DoinitSideways" wrote

I would imagine the seals would be a lot more likely to leak.

Theo

 

Some sportsbike you've got there Frank, USD forks, single sided swingarm and
Fuel Injection.

AL

 

The fuel tank is a let down for a sportz bike, I'll have to get a
smaller one ... say less than 30 litres

 

You'll keep Big!

 

One problem about fitting stiff USD forks to a bike meant for RWU is that
because the forks are so stiff more road shocks are transmitted to the frame
causing it to crack where it joins the triple calmps as frames with USD
forks have thicker/bett braced headstems to cope with it.

A guy I spoke who did this to his early model GSXR said he ended having to
get the frame welded and strengthened.

Spend your $$$ on properly tuned goldvalves/wp sprins etc.


BTW can anybody explain to me why unsprung weight is so important. I mean
surely the different in unsprung weight between USD and RWU can only be
measured in grames not kg?

Or maybe the bike companies just do these little changes to get people to
buy next years bike instead of this years. The customer would want to feel
like they are getting a technically superior bike.

Just my $0.02 worth.

 

lemmiwinks said....

le> Dont worry about the forks, throw that filthy four stroke in the bin and
le> get a propper (two stroke) lawn mower ;-)

Is that opposed to a proper (one stroke) mower???

 

In simple terms.

Suspension's primary job is to keep the tyre in touch with the road surface
regardless of how uneven it is. Secondary job is distribute weight changes
smoothly (this can be argued against*)

Given it's primary job the less the mass that has to be moved up and down to
follow the road, the easier it is to keep the tyre in contact with the road
(less inertia)

JL
*In fact the need to distribute the weight smoothly is because of the design
"flaw" (can't think of a better word) inherent in forks that allow significant
movements of the centre of mass longitudinally due to the fact they compress on
braking and hence change the suspension characteristics. This is why there were
attempts to create anti dive in the 80s and why so called "funny front ends" ie
hossack, BMW telelever etc exist