Upside Down Forks - What are the advantages?

What is the go with upside down forks?. Are they particularly any better
then normal forks, in normal riding conditions and perhaps some track days?

 

Less unsprung weight? Looks cooler? Dunno, I'm just making an
uneducated guess, someone will know the real reason

 

Stiffer. The disadvantage is supposed to be an_increase_in unsprung weight
due to a long, skinny slider doing the bouncing up and down instead of the
shorter, fatter one you get with a rwu fork. To be honest, I'm far from
convinced, and can't really see why manufacturers just don't send the rwu
fork off to join the sidevalve engine.

 

Well there you go, thanks IK. You should see the forks on my RZ though,
resplendent with anti-dive technology no less, and a 16 inch front wheel
for that authentic GP look! I know how you love that '80s technology ;-)

 

80's techno, you mean...

("They said there is no hope, they said no UFO's...")

 

Stiffer. The disadvantage is supposed to be an_increase_in unsprung weight

Why would a skinny (hollow) slider bouncing up and down have more mass
than a fatter, oil filled one? USD forks have lower unsprung mass, but
have greater total mass since the oil filled uppers are of a large
diameter and longer than the equivalent RWU oil filled part.

Jules

 

days?

Makes 'em easier to drain but a bastard to fill.

Doug Cox.
Work to ride, Ride to work...

 

Let me ask you a counter-question... how do you figure the slider (the
moving part, the one the wheel and the brakes attach to, just to ensure
we're on the same page) to be full of oil in a rwu setup only?

Another reason to consider why this might be true, and not the opposite, as
mags will often argue...

My 6R is quoted as having a fork diameter of 46mm. The forks on it are rwu,
hence the 46mm refers to the stanchion. Sliders, which are about 350mm long
from wheel axle to dust seal, have the outer diameter of, as measured 5 mins
ago with a set of calipers, 55mm...

That raises a considerable wtf in my mind, as it implies the slider wall
thickness might be anything up to 4mm. That amounts to a hefty lump of metal
on any scale.

By comparison, the couple of sets of usd forks I've pulled apart (on my R1,
once, and on the YZ, about 87 times) have both had exceedingly thin walls on
both the stanchion and the slider; for the R1 (41mm-dia), maybe ~2mm for
both the stanchion and the slider, and for the YZ (massive-arse 46mm
treetrunk-things) ~2mm for the stanchion on the YZ, and possibly even as
little as 1.5mm on the slider.

There is no way on earth I can see either of those coming anywhere near to
the weight of the sliders on the ZX6, so how the hell can anyone in their
right mind claim that using rwu on a bike offers an unsprung-weight
advantage?

All forks are filled with oil from ~top to bottom, the volume being
~cross-section area of inner tube (slider for usd, stanchion for
rwu)*(length of entire forkleg-air gap at the top-space for axle mounting
etc at the bottom), so a 43mm rwu fork holds ~the same amount of oil as a
43mm usd fork.

 

How about the 2003 ZX6R (uSd) vs the 2003 CBR6 (rwu).

 

Short and Long Answer: No.

 

What stops the oil succumbing to the law of gravity and departing the top
bit in favour of the bottom bit?

 

IK,
Question,:do you think that my 'Briggs& Stratton' motormower motor, being
sidevalve, would really benefit from RWU forks, and if so, how much more
forking power will it produce ?

 

only if you match it to a ohlins rear shock

 

Getting Slower & Slower ! wrote:

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

 

Maybe because
the tube [skinny (hollow) slider] is made of a more dense material than
the larger alloy [fatter, oil filled one] bit.

But I'd put my money on more $$ being spent on the upside down parts ...
spend more money and some times you get a better product.

 

My USD white power extremes have to be inverted to drain the oil out...
fillin is easy.

 

In short, what is the first year the ZX9 had USD forks?. And would they be
backward compatible with my 98 model with RWU forks on them? If so, is there
any great advantage to doing this or not to bother?

 

The ZXR750 made me think of it. I seen one at uni a few weeks ago and
noticed it had USD on it. And that alot of the newer bikes were being
released with them. Im very happy with the way my ZX9 handles now, and the
previous owner had the suspension perfect.

 

They use negative weight oil.

-----sharks

 

It's actually the last year... the first ZX9's, the B's, roughly shared
forks with the ZXR750 (different lengths), which were usd's; big, fat ones.

The 98 model was the big seismic shift; everything changed then, and it's
stayed alarmingly similar ever since.

Depending on whether the steering head dimensions changed, maybe. If they
hadn't, then you'd do a straight transplant, forks, wheel, brakes, triple
clamps and bars, which could lead to some strange steering behaviour.
Otherwise, you're looking to mill up a set of triple clamps, which costs
$$$$$.

Well, one advantage is that they would make your bike about 30kg heavier,
making it less likely that it'll blow away in a cyclone... that's something
of a factor for someone living in Brisbane.