I think I've got it all forked up!

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XTINCT

XTINCT

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Everything I've read on this forum says that a stock commando fork has 4.5" of travel. Is the compression stop caused by the spring being bound?
When I lay all the components out on the table and line them up next to a ruler, it looks to me like the little piston which is the rebound stop when it tops out in the dampener tube with 4.5" of travel does not even get close to the old or even the new holes in the tube. How does this provide a hydraulic stop? What am I not getting?
I think I've got it all forked up!
 
Duh yep seems Norton couldn't afford new correct length springs or just wanted to use up over stock so shorted damper rod so top out clanged short of full 6" potential on under side of tube cap instead of hopping clear off spring tops 2" free to slam back down again going out of control. Greg Fauth at Decent Cycle has just the kit your trying to re-invent. While apart work the parts with say 2" longer rod to see what happens. Prior longer damper rod attempts all put in a solid spacer re-limiting to 4+" but softer top out. Just scroll down a few more threads to catch the low down on Fauth kit and other options.
 
XTINCT said:
Everything I've read on this forum says that a stock commando fork has 4.5" of travel.
Click to expand...

Edit. The fork travel can be less than 4.5" if it is assumed the hydraulic buffer actually prevents the fork from bottoming out completely.

XTINCT said:
Is the compression stop caused by the spring being bound?
Click to expand...

No, but the spring is close to coil-bound at maximum fork compression.
The somewhat crude hydraulic compression buffer stop is provided by the stanchion running up against the taper at the lower end of the damper tube.
I think I've got it all forked up!



XTINCT said:
it looks to me like the little piston which is the rebound stop when it tops out in the dampener tube with 4.5" of travel does not even get close to the old or even the new holes in the tube. How does this provide a hydraulic stop?
Click to expand...

The piston doesn't provide any hydraulic stop on the downward stroke, not only is it still some distance away from the end of the damper tube at full compression but the piston valve is open as long as the fork is on the compression stroke so wouldn't do so even if it extended far enough to cover the holes in the damper tube.

The damper piston only begins to come into play as the fork is extending when the piston valve is closed.
 
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I think I've got it all forked up!

Right damper body is featherbed-ignore
Seems you are reading (and believing) the wrong posts.
I see your damper bodies are modified/ruined.
One of the mods as far as I've analyzed is to convert the center (early) damper body with bottom holes and no bump stop into the (later) left hand damper which does have a bump stop action due to holes being above apex.
http://atlanticgreen.com/forks.htm
 
Commando stanchion tube on full compression does not reach below the taper so holes below that edge always free flowing so no hydro stop possible. The hole on the taper is still too low as by time its covered forks already stopped by hard metal clash. This bottoming soft stop was solved decades before hobot by sealing all factory holes by various means and making new holes above the tapper. I'd made new holes of slightly less flow area than factory, one similar large factory size hole ~3/4" up and 2 smaller ones ~1/2" & 3/8" up for progressive slowing before final 'sealing' with indefinite soft/silent end point before rebound. I'm the only one I know of to experiment with lessor damper holes flow size and staggered in travel closing off but mostly luck out to like thinner fork fluid. Those with more desire can experiment creeping up on hole sizes vs fluid viscosity. As extended damper rod 'valve' can travel past the higher holes, over doing hole sizes would be much harder to seal and resuface than just beating alu plugs in the factory do nothing holes. Btw Alu damper tubes take some sprung mass off slider assembly as do Alu rods.

Its miss leading for Norton to label the damper end as a valve as its way more just a syringe plunger so most the flow dampening restriction occurs through gap of rod and damper cap. Pretty slipshod for Norton Commando to use the cap threads impact as top out stop instead of prior Roadholders soft top out via the top stanchion holes covering. To restore top out, old school extended top bushes as one piece or by add on collars "Convent" which both retain 4" travel limits though. The plungers can be turned into more proper valves and some have but still open for better valve action redesign.

Factory rod dia and cap hole dia. are too wide to provide much dampening w/o heavy fluids. Up graded longer 10 mm alu rod are a bit thicker and new caps by Greg Fauth or Jim Schmidt have smaller holes so rather thin space left that does distinctly dampen. In my Peel case, too much so sanded a bit of a waist on rod in cap at sag level with pilot on. Hardly any dampening for an inch or so of road texture absorbing compliance but progressive dampening either side beyond that.

If extending rods ~2+", gives ~6.15" travel before bushes clash, which leaves ~2" gap above factory springs to fill by old school solid spacers or extra spring section, stronger or weaker than main spring, as long as the spring stack does not coil bind on the extra travel compression.
 
hobot said:
Duh yep seems Norton couldn't afford new correct length springs or just wanted to use up over stock so shorted damper rod so top out clanged short of full 6" potential on under side of tube cap instead of hopping clear off spring tops 2" free to slam back down again going out of control. Greg Fauth at Decent Cycle has just the kit your trying to re-invent. While apart work the parts with say 2" longer rod to see what happens. Prior longer damper rod attempts all put in a solid spacer re-limiting to 4+" but softer top out. Just scroll down a few more threads to catch the low down on Fauth kit and other options.
Click to expand...

new stuff for me so just to be clear, sounds like like going with good fresh springs alone, isn't a fix?
 
84ok said:
new stuff for me so just to be clear, sounds like like going with good fresh springs alone, isn't a fix?
Click to expand...

That's right.

When refurbishing my forks a few years ago, I wanted to lower them as well. I decided that the best way to do this was to shorten the damper tubes.
I bought a new set of tubes, cut off the tapered end, and brazed on new tapered ends which I made myself.
This resulted in a 1/2" lowering of the ride height. It also reduced the travel by 1/2", but that has not been a problem for me, maybe because I don't weigh much.
I drilled the holes in the tapered section as per the new standard, but I don't think it matters much where they are as long as they're not BELOW the taper.

My biggest bugbear was the topping-out CLANG when the damper piston hit the cap. If you do some measuring, you will prove to yourself that the supposed hydraulic stop on extension cannot possibly occur; the holes in the stanchion are at least 1.5" too low. I made some nylon bushes to fit below the standard top bushes so that the holes become covered when the forks extend. What a difference! My front end now feels like a modern bike.

Oh and just to repeat an earlier rant of mine: why on earth aren't new stanchions made with the holes in the right place?
 
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New springs will not change anything as rarely do original springs loose much force as most their time is extended. Rust is about only thing that might require new springs.

Norton made 3 sets of spring available for Commando r-h's yellow red green IIRC but were on weak side or too harsh so attempts at progressive springs offered by vendors but they are often reported as even weaker over all rate than factory. It took me and world wide helpers detailing complete range of all rh history and components to realize Commando absolutely short changed on purpose or financially forced, ruining the prior rh behavior that made them so famous.

Depends on what you are seeking fork details to change for. It takes illegal risky behavior or panic moves to need more than low end Cdo rh's. I'm keeping my Trixie Combat bone stock for sane use. I've thoroughly explored fork limits and myself on rough surfaces, sharp to long turns and hard braking to know what large reserves required or SPLAT.

I'd say best bang for the bux would be slice 2 or 3 inches off factory spring then hunt for replacement springs harder or softer to fill in the gap till matching your mass and riding conditions. Get JMS green slick bushes and Frault kit for parts to modify damper bottom soft stop and cap gap dampening 'orifice' then slice down/thread longer rods, a bit longer than factory, to allow space for a short strong spring or rubber washer on top the damper 'valve' to nullify top out clank. Still only 4-ish" travel but likely a more secure comfy Roadholder disappearing act. Note shorting any spring raises its rate to keep in mind creating your own progressive springs. If ya thread top of rods about an inch further down can apply some pre-sag spring compression to get better sag level and earlier stronger spring engagement. Can vary dampening by fluid thickness and waisting rod a few 1000'th at sag height and inch or so, but needs very little to feel the difference so creep up on its depth and length relieved.

BTW roll both stanchions against each other for best way to tell if true or not.
 
Alrighty MFB you figured out how to restore hydro stops and get lower stance. You, me and a bunch of others also wondered why damper & stanchion holes so mis placed to conclude bean counters had final say with thought that screwing Commando was a temporary stop gap decision before fielding a modern cycle, so by time word got out wouldn't matter. I've tried Mx Endro and Trials bikes on severe off road but my forks allowed normal sitting busting though raw woods where they were all standing on pegs to handle and my own SV upgraded modern and Ninja semi race forks to like my own Roadholders better so ain't seeking any more even if better exists, likely couldn't tell except off road and restricted fouling lean angles. I'm isolated after family and buddy gone so get off on others successes sharing the highs before we die. I'm flabergasted how well such obsolete junk can be made to please us hot to trot riders.

XTINCT if anything like Exbackslider joy rider you'll be pleased if using the valve spring spacer from Greg for the extra tall fork lean its allows - also keeping front in steering effect longer when accelerating to fork extension through turns, if maniac to press that hard on un-tamed non tri-linked isolastic rubber baby buggy. I must alert you that each incremental improvement such as forks, just makes it that much easier to enter sudden hinging onset on mere let offs letting some oscillation slack develop into esculating tire lifting horrors that get worse before settling down if still not crashed by then. If not howling out loud about hinging onset ya' ain't got full education on Commando yet and maybe never should find out what I'm warning about. Head links don't do it, breast link don't solve this either, only down low rear 'rump' farhest away from iso mount by rod link or swash plate does. Once rump breast and head triangulated stabilized forks just hold front up when not road orgasming and have little to do otherwise umless just legal sightseeing cruise.
 
Lots of theories on different approaches out there.

Personally, I don’t have the mental capacity to spend on something where there’s a perfectly viable off the shelf solution readily available. I highly respect those that do re-engineer their forks and expend the required trial and error effort to reach success, but when it comes to forks n shocks, I prefer to buy the knowledge.

I fitted Lansdowne dampers with stock springs and excellent Falcon shocks on the rear, and for the type of riding I do, I’d say they are as good as Maxton kit I’ve had.

There are other, more sophisticated options, but the Lansdowne kit is inexpensive, easy to install and proven to work. Problem solved.

All only IMHO of course.
 
I'm with Fast Eddie. I'd tried the covenant conversion and all it really did was reduce the 'topping' of the forks, it didn't do anything for the damping. I fitted the Landsdowne dampers and they give a total transformation to the fork action. They are also easy to adjust and have a wide range of adjustment. Hard to see how any DIY solution is going to beat them and for the price they are a bargain.

Ian
 
ludwig said:
Ruined ??

How does one ruin a "damper" tube that has zero compression damping in the first place ?
The extra holes above the taper are of no consequence .
One of the more competent forum members posted (not all that long ago ) a way to get some compression damping with an easy mod , but apparently it went by unnoticed ..
Click to expand...

You are correct, "unimproved" would have been a better choice.
 
ludwig said:
One of the more competent forum members posted (not all that long ago ) a way to get some compression damping with an easy mod , but apparently it went by unnoticed ..
Click to expand...

Let me have an educated guess...... it was you that posted the easy damping mod. Well it would be much appreciated by forum members if you enlighten us again. Myself I didn't have that great results with the Lansdowne kit because my fork sliders weren't 100% (like most used original fork sliders) causing malfunctioning his Lansdowne dampers according the late Mr John Bould, so I sure would be happy to learn about that easy mod.
 
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ludwifg has also leaned factory damper 'valve' works better if made more a sealed syringe plunger for better dampening action via mostly through rod cap gap. Adjustable after market dampers with 2" extra travel with custom spring rates stack would be cat's meow. My sense of biased dampening is less for rebound extension to stick to road hollows better and more compression resistance/dampened to soften impacts compression

Mz Peel exeriment, her forks are now set up with an adjustable cartridge emulator for compression dampening in one leg while extension dampening handled in other by Roadholder plunger rod/cap & gap. Will use different oil viscosity in each leg to fine tune after mechanical means gets close to right.
 
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