Adjustable preload???

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So, is it possible to adjust the preload on stock MKIII forks? I think I heard that you could adjust them by the postion of the nut on top of the fork damper rod VS the big nut that threads into the top of the fork tube, but I can't find any info now. I have a HORRIBLE bottoming out knock. I just ordered new damper end caps (from Clubman)... I guess I'll try 30wt oil till then.
 
To adjust the preload you have to add a spacer above the spring and below the thick washer. I believe that the bottoming and topping issues are addressed by modifying (or buying modified) the damper bodies and using longer top bushings. The 30 wt oil will be very unpleasant...

Greg
 
gjr said:
To adjust the preload you have to add a spacer above the spring and below the thick washer. I believe that the bottoming and topping issues are addressed by modifying (or buying modified) the damper bodies and using longer top bushings. The 30 wt oil will be very unpleasant...

Greg
The Lansdowne Kit address's these issue's....preload and compression control. Mr John Dunn, Tec adviser Norton owners as found these control the forks ,and produce "Knock" free suspension. Read is comments just posted.
 
Is there any way to make a stock fork not bottom out so hard (aside from me loosing weight...I've grown attached to my 200lb :oops: )? Every time I hit a bump while cornering or go up a driveway curb I cringe and wait for the whack!
 
The bottom of the fork tubes on the inside is a close fit to the bottom of the taper O.D. of the Dampener tubes. This close fit has a lead in as the form of the taper you see at the bottom of the dampener tubes. There were variations in the location of the holes used for oil flow in and out of the dampener tube. If you’re willing to take it down you can begin to play. You need to take the wheel off and take the front end apart to get the springs out than put it all back together minis the wheel, fender and springs. Now you can slide the sliders one at a time to check how it’s all working. If you don’t like it you can plug and move holes and tighten other clearances to get it working well as can be. The springs are just too much to fight and you need to feel the results of your tuning.
 
Captain B said:
Is there any way to make a stock fork not bottom out so hard (aside from me loosing weight...I've grown attached to my 200lb :oops: )? Every time I hit a bump while cornering or go up a driveway curb I cringe and wait for the whack!

As a fully paid up member of the 'robust weight' brigade, I can highly recommend the Lansdowne kit to get the forks to behave like they should.
Although it's years since I rode a Commando with stock forks, I believe what you're describing is pretty much what they do :?
 
gjr said:
The 30 wt oil will be very unpleasant...
I've been hearing that often, but it would be cheap to atleast try. :| The INOA Tech digest and my factory manual both reccomend 30wt???? But my neighbor, who gave me the INOA digest, runs 10wt :?
 
or go up a driveway curb I cringe and wait for the whack!
--------------------------------
I'd be more concerned about the unknown damage being done to the tyre!
 
Captain B said:
I think I heard that you could adjust them by the postion of the nut on top of the fork damper rod VS the big nut that threads into the top of the fork tube, but I can't find any info now.
So, has anyone heard of this?
 
As you move the rod down into the dampener tube and relocking the nut you will get just that much more travel but there is not enough there to make any difference as to bottoming out. To fix this you have to get into it and understand how it works. There are no pat "do this" type answers sorry. Only hard fought knowledge found by working with the system you have and reaching your own conclusions. I have written some of what we have found here. You have to get the oil working without the springs and than get the springs working how you like them.
There were three guys working on this kit. We talked and looked,
and looked some more.
First stage, strip down forks to one
fork stanchion, one slider, one steel bushing with clip to retain,
one high hat bush, one seal and one seal retainer assemble dry
at this point. Check travel, got six inches plus with no dampener tube,
valve, rod or springs.
Ok second stage, add stock dampener tube
with valve supporting rod, tube cap, spring, stock spacer, jam nut.
No fork cap nuts or fluid so when you slide this back and
forth the spring assemblies are coming in and out of the top of
the fork stanchions tops. The travel was four and one half inches.

Note that in this state the springs are loaded against the top of
the dampener tube cap and are trapped by the jam nuts and the
spacer on the other end so the dampener valve is tight up to the cap.
Until the bike is full assembled with the dampener rod jam nut
tight to the fork caps and the weight of the rider is felt the
valve is always going to stay there up against the cap.

The stock length of the rod is limiting the distance the
sliders can move. Do the same test with two inch longer rods and
an extra set of springs for preload and you get back the
six inches of movement. The true limit, the max to be had,
is when the top of the steel bushing hits the bottom of the
high hat.
Now you don't want to ride the bike in this state with
the two bushes tight to one another there's just not enough
support and the front tire will bounce back and forth at
stop lights. So we came up with the two inch longer modification
for the one and one half inches of travel gain so that under
no circumstances could the dampener valve be used
to limit the travel for this we wanted a fluid stop and not a one and
one half long loose fitting bushing between the two
bushings already in the front end like the covenant kit has.

The springs that come with the kit are from ford tractors and are
the same O.D. and I.D. as Norton and progressive springs.
They start with a two and nine sixteenths free length and have
a bound length of one and nine sixteenths for one inch of travel
. From what we know the stocks springs have one half of an inch to go with
the slider bottomed out, that is the bottom of the stanchion hits
the bottom of the slider. We add one and one half of travel
with longer rods and the extra spring adds one inch and
the old springs had one half inch to go so the springs should
bottom out just as the fork stanchions do.
Now for the fluid control
if things were ideal one would have full movement with hydraulic
stops at each end that is nice and slow acting right at the
ends of travel. The best we have come up with so far
is using ATF for fluid and leak proof brand seals it works
on fifty bikes so far with no adjustments needed not
that there are no adjustments. I have one bike with stock springs
and one with progressive springs and i have to say
that I find the progressive better but the stock springs work
well too.
On the center stands these modified bikes don't
lift the wheels of the ground any more but still work for me.
The idea is to get the bike to go down from your weight
at least one and one half inches. Than ride around with four
and one half potential inches for bumps and the
one and one half for pot holes. Norbsa48503
_________________
Some things that make sense learned over time as of 2008.
The dampener caps will be worn on your old bike, and need replacing. They are a big
part of how the system works. If you’re using the aluminum dampener rods you should
be running bronze caps, they can be had from Clubman racing. Leak Proof seals and
full rubber gators with a little filing of the top hat bushing will provide long lasting non
sticking seals it needs to be part of the package with the kit.
And this is just what I found others have gone on from here.
 
Or get the LANSDOWNE and dial in what ever suits your riding style. Having the ability to adjust the pre load is like having adjustable springs,
The spring resists compression, The Lansdowne kit gives "vaiable" resistance all down the travel..Not JUST at the end, where its useless. Read John Dunns report ," NO pot hole could make the kit bottom out or top out." Best regards John Lansdowne
 
My kit at 65.00 U.S. will do that as well but I am trying to encorage captain B to do his own thinking and draw his own conclutions. Maybe he can uncover somthing new that's how I started this 12 years ago. In 2004 I had this pop up as a posted letter. We may find a new way yet.

A SUPERMILAGE RIDER ELEGANTLY EXPLAINS HIS KIT BELOW:
----------------------
I HAVE INSTALLED THE FRONT FORK KIT STEVE SHIVER (AKA HOBOT) IS WRITING ABOUT. THE KIT INCLUDES NEW LONGER DAMPENING RODS AND TWO SPRINGS. I BOUGHT IT FROM GREG AT THE LATEST NATIONAL IN OHIO.
PRICE WAS SOMEWHERE AROUND $65.

IT WAS EASY ENOUGH TO INSTALL. COMPLETE DIS-ASSEMBLY OF THE FORKS WERE REQUIRED. THE FORK BUSHINGS ON MY BIKE WAS WAY PAST THEIR "SELL BY DATE" SO THEY WERE REPLASED AT THE SAME TIME.

A COUPLE OF HOLES IN THE BOTTOM OF THE DAMPENING TUBES MUST BE PLUGGED (BY TAPPING AND INSTALLING PIPE PLUGS) AND NEW HOLES DRILLED FURTHER UP.

THE KIT’S SPRINGS ARE A COUPLE OF INCHES LONG AND INSTALLS ON TOP OF THE EXSISTING FORK SPRINGS. THIS MAKES THE FRONT END OF THE BIKE SIT SLIGHTLY HIGHER THAN BEFORE. IT IS NOTICABLE MOSTLY AT STANDSTILL. WHILE RIDING IT MAKES VERY LITTLE DIFFERENCE.

AS FAR AS BOTTOMING IS CONCERNED, WELL, QUITE FRANKLY IT IS NOT A CONCERN ANY MORE. I HAVE TRIED TO BRAKE REALLY HARD AND SUDDENLY AT LOW SPEED BUT NO WAY WILL IT BOTTOM. I HAVE TRIED TO PUMP THE FORKS UP AND DOWN HARD (AS HARD AS MY 185LBS BODY WEIGHT ALLOWS) BUT IT WILL NOT BOTTOM, NOT A CHANCE.

I AM HAPPY WITH THE MODIFICATION. THE REAL TEST WILL COME IF I
EVER MAKE IT TO ARKANSAS AND TRY SOME OF THOSE GRAVEL ROADS HOBOT IS WRITING ABOUT. THEY HAVE SOME GOOD SIZE POT HOLES, NO? <GRIN>

BEST REGARDS
STEVE SNOEN
SURREY, BRITISH COLUMBIA
Just stay working on it and find your own way man.
 
Holy cow!!!
Adjustable preload???


Thanks for the great replys. I was really just looking for a yes or no. :lol:
 
IMHO the Norbsa kit is about controlling the symptoms while the Lansdowne kit will cure your fork problem :!:
 
Hey Ho Greg and Steve, hobot here,

There's are some other diddles to further tune Roadholders to suit.

Damper rod's top threads can be extended to crank in more
preload by about 1/2"+. Of course more washers too - you can't press
spring down to put the nut on.
[Slot/drill washer to allow port holes in the
fork cap nuts to drain in fairly fast and not spit back as much]

The above makes bike sit even taller as well as stiffer.
To regain stock height while retaining the 6" of silent stops,
put in a weaker spacer spring and lose some bottoming resistance
or
just stack as many lengths and rates of springs as you
can to get both the height and the # of progressive stages desired.
Only concept to keep right is no free spring slack in the ~6.14" travel
or it'd clank/ring/slap on top outs.

Might cut a small section out of stock spring to both shorten and
stiffen its spring rate. [shorten springs to stiffen rate]
Example- rail road track rider with short legs wants
to glide over smallish Gravel nuance but also ignore big x ties,
would keep tough valve spring spacer and cut say ~1" off
stock spring then add a 3rd rather weak easy to fully coil
bind spring, to take up the loose resting slack in whole spring
stack for top outs, and fully collapse to stock or desired height
un-loaded for center stand function yet further sag to preload
setting when mounted.

!0 mm rod is a tighter fit than stock one in damper cap.
It's OD can also be reduced or increased in sections by
sanding rod Al or added epoxy. I by guess by golly
took off a few thousandths tapered over 1.5" length
in the section of rod that was centered in damper
cap with me on the bike and some fuel too.
Made Peel so compliant I don't notice THE Gravel texture
till 50+ PSI yet no noise or definitive bottom stop to hit
gopher holes at speed or leap off edges or over crests.
Play with that and get back please.

Don't forget to increase the fork twist resonance up above
tire and rider sensing of it via a stout fork brace like RGM's.

Best fork oil for my varied conditions plus my Princess on a Pea
annoyance to jarring in wrists or ischiums, is plain ol
Power Steering Fluid.

For rest of the story maybe Greg will tell you how resistant
he was about a full 6" even existing.

hobot
Will use air supply to pump tires back up near 50 for pavement.
Ever water skied, ever ice skated, which is more precise?
 

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Well. I fixed my horrible bottom/top out probs in under 30 minutes.... I just put the stock springs back in. I guess I'm just too heavy :roll: Anyone want to buy some brand new Progressive Springs? $75 shipped anywhere in the lower 48. :|
 
Greg and crew, an extra feature I did on Peel was to have threads at top of damper rod extended down another inch, then I screw down the spring trap nut further for more preload and no extra washers to try to get power steering fluid past.

Two things may be confused on this thread, pre-loaded spring compression and sag height. Softer spring spacer will let bike sag down to stock height with standard factory spring rates with Greg's kit but still allow silent stops at 6" travel compliance.
Just cranking down on Greg's dual spring with both lower bike and stiffen up springing.

Road racing is not much a test, Gravel travel and beyond is. You may be surprised how fine a cheap DIY kit transforms Roadhoaders into disappearing act on or off road.

I staggered Peels new damper tube holes as well as their size. One ~factory size hole ~3/4" above top lip of damper taper and two more ~1/2 factor hole size,
1st at 1/2" above lip the 2nd ~3/8". Forks rebounding action is only way I know they have bottomed, as I can not feel/hear anything but soft indefinite change of directions. Let me know how the other kits handlr 50 mph axle deep gofer holes or landings from 6 feet high leaps or sideways tire skips on ripped pavement.
Sometimes a big limb fall encountered around a blind, if not over 8" I just power over it in glee, same as 4-5" roots hidden in grass. Ridiculous delight to follow
or lead MX bikes in scary places. They just love the sound of a heavy street twin over their chain saw like sounds in raw woods.

Not to worry, someday I'll have a shoot out on the various kits to find pecking order for me.

Steven 'hobot' Shiver
 
Two deer, one goat and an injured Great Pyrenees- so far in last 5 year interval of intermittent riding. No patches given for varmints lower than axle height.

Adjustable preload???
 
OK, I have to ask. Do you paint little outlines of the animials you hit, on your tank?
 
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