Fork parts question

Hello,

I am in the middle of rebuilding my forks for my 1971 750. I have new bushes, seals, fork tube (stanchions) etc. I have been looking at the RGM site and see progressive springs and ally dampers "Improved damping":

http://www.rgmnorton.co.uk/buy/progress ... r_2300.htm
http://www.rgmnorton.co.uk/buy/alloy-fo ... o_2282.htm

I was wondering if anyone else has fitted these and noticed much difference?? I am considering getting these items for my forks.

Cheers-- Jerry

I had a set of rgms' progressives and yes they soften up the forks but only slightly. I couldnt honestly say they improved the ride on bad surfaces. Can't comment on the dampers though.

Alloy dampers tubes and rods are pretty but for a road going bike for every day use a wast of money. Of course I fully realise there are owners out there with money to throw away. You would be better in checking the fit of your damper tube caps (06-1347??) on the damper rods as the gap between the two controls the amount of oil that can pass between them as the forks extend and thus the 'speed' at which they do so. Personally I used caps which I believe were originally fitted to Manx forks as they were a fairly tight fit on the rods and had a much longer contact area. All the new std top caps I have ever seen are a crap fit on the damper rods but that was many years ago and I suspect those available from Andover Norton these days could be correct????? Dont Know as I still have a few old stock new ones.
Didnt they change the thread on the dampers and caps at some point ???

Dont forget when shoving your forks together that there is slightly more total movement in the damper assembly that in the main tubes - fork bottoms and you set up the damper rod in the top nut so that on full compression or extension the mechanical end stop does NOT take place within the damper tubes....... I have seen idiots with Dommy length internals fitted to Commando length forks such that the forks have nothing like full movement available...... Mind you having seen a few wideline framed motor cycles fitted with slimline frame (shorter) rear suspension units.......

John Robert here offers the Landsdowne fork internals.
If you search here, all will be revealed - apparently they are quite good.

John Robert himself is not going so good, hope things are OK with you....

I tried Progressive fork springs on my Commando, felt they were no better and in fact stiffer than stock springs, which are too stiff anyway in my opinion

took them out after about a year and put a new set of stockers in

J. M. Leadbeater said:

Didnt they change the thread on the dampers and caps at some point ???

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Yes, they did.

J. M. Leadbeater said:

Dont forget when shoving your forks together that there is slightly more total movement in the damper assembly that in the main tubes

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Actually there's considerably more stroke in the Commando damper than the fork leg.

J. M. Leadbeater said:

you set up the damper rod in the top nut so that on full compression or extension the mechanical end stop does NOT take place within the damper tubes.......

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Incorrect.
The standard Commando damper assembly always acts as the extension stop.

To prevent that from happening would require either the damper tube or rod to be extended in length by around 1.5 inches, far more than the available range of rod adjustment, alternatively a sleeve as in the Covenant kit or, an extended upper bush as sold by RGM Motors can be used. The damper assembly does not act as a compression stop-as it doesn't even come close to doing so before the fork leg bottoms out.




http://atlanticgreen.com/forks.htm

The fork damper rod tops out in the damper, 0.6"before the fork is extended enough to start to block off the big hole in the fork tube. This topping out action is also 1.25" short of reaching the smaller bump stop hole. The damper topping out limits the fork to 1.55" less travel than the bushes would otherwise allow.

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http://www.nocnsw.org.au/technical/norton-roadholders

If those of you with Roadholders don't believe me, remove the fork top nut from one side of your forks, (having first taken off your front wheel and mudguard) and fully extend the fork leg. You will notice that the damper rod disappears an inch or so below the end of the stanchion. In other words, when the top nut is in place, it and the attached damper rod stop the forks from extending as far as they otherwise would. For those doubting Thomases who are still unconvinced, have a look at the underside of the damper tube top and you'll see the tell-tale marks in the alloy where it has been struck by the damper valve.

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http://www.britbike.com/ubb/bin/ultimat ... tml#000008

norbsa48503
the dampener rod length controls the total movement of the sliders on Commando's. The dampener valve hits the inside of cap on the dampener tube. Knocking the travel from the six inches of potential down to 4 1/2.

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Jerry Doe said:

Hello,

I am in the middle of rebuilding my forks for my 1971 750. I have new bushes, seals, fork tube (stanchions) etc. I have been looking at the RGM site and see progressive springs and ally dampers "Improved damping":

http://www.rgmnorton.co.uk/buy/progress ... r_2300.htm
http://www.rgmnorton.co.uk/buy/alloy-fo ... o_2282.htm

I was wondering if anyone else has fitted these and noticed much difference?? I am considering getting these items for my forks.

Cheers-- Jerry

Click to expand...

Their damper kit is probably the replacement for the Covenant conversion they used to sell. The progressive springs are an improvement but save the stock springs is case you get the Lansdowne system of which progressive spring are not suggested.

pete.v said:

Their damper kit is probably the replacement for the Covenant conversion they used to sell.

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They still sell the Covenant kit. :?

http://www.rgmnorton.co.uk/buy/covenant ... g_2294.htm

pete.v said:

The progressive springs are an improvement but save the stock springs is case you get the Lansdowne system of which progressive spring are not suggested.

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I've also found the RGM progressive springs to be perfectly OK but perhaps not a drastic improvement over standard and are installed along with the Lansdowne damper kit.

L.A.B. said:

I've also found the RGM progressive springs to be perfectly OK but perhaps not a drastic improvement over standard and are installed along with the Lansdowne damper kit.

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John says that is a "no no" and would counter act what is engineered into his dampers. Not my words, his.

I cobbled my own solution to the problem of the forks "topping out" in the damper tubes at full extension by making nylon sleeves that fit below the top bushes in the sliders; sort of my own version of extended top bushes. It works.
But I can't help wondering why Norton never corrected the mistake.
My workshop manual clearly claims that the slider top bush blanks off the large then the small hole in the stanchion to provide a hydraulic stop. But anyone who takes the time to measure the components can see that the bush comes nowhere near the holes when the damper valve hits the damper tube cap.
I bought my stanchions in 1983 when building this bike.
It could have been corrected by simply placing the holes farther up the stanchion.
I'm still wondering...........

pete.v said:

L.A.B. said:

I've also found the RGM progressive springs to be perfectly OK but perhaps not a drastic improvement over standard and are installed along with the Lansdowne damper kit.

Click to expand...

John says that is a "no no" and would counter act what is engineered into his dampers. Not my words, his.

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That's not quite what John says, here: fork-tuning-rebound-oil-weights-viscosity-indexes-t22661.html#p297015

It appeared from feed back. many user's prefer stock springs, Progressive do drop the original ride hight. Andy from Germany stated the original springs give a better feed back...I guess it's who made the progressive springs and the start poundage ? Some riders like them,some dont..the variables are wide ranging ,spring type ,rider weight and riding style . Stock springs are a good start,with the system allowing some tuning.

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I'm not sure I actually agree that the RGM progressives lower ride height by any appreciable amount, in fact I would have said they did the opposite, although there are more than one type of "progressive" fork spring. :?

Stock springs with Lansdowne damper internals.

That's what I put in mine and the performance of the forks is just perfect in my humble opinion, road and track.

For the price point and average riders ability, there is no comparison.

All IMHO of course.

The std dampers damping effect is affected by the gap between the rod and the damper body cap. The steel rods corrode and pit and the oil then becomes a thin grinding paste so the damping dissappears. If you use 5/16" alloy rod you can easily make your own damper rods, the std damper body cap is also alloy so left as is it will gall like the Amal body and slide so I drill out the cap and fit PTFE lined thin wall bushes.

kommando said:

If you use 5/16" alloy rod you can easily make your own damper rods

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I made my own damper rods when initially building my bike. They are steel not alloy but are in good condition and the clearance to the cap is minimal.

I didn't understand why the forks topped out so badly until I read about such things as Covenant conversions and decided to study the forks more closely.

Best wishes to John Robert.

I recently ordered some dampers from Chris Cosentino. In our correspondence he mentioned that he will stop making these soon. Given JR Bould's illness, the future of decent front suspension on these bikes looks bleak.

steelcap said:

I recently ordered some dampers from Chris Cosentino. In our correspondence he mentioned that he will stop making these soon. Given JR Bould's illness, the future of decent front suspension on these bikes looks bleak.

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I'm sorry to say my emails to John at Lansdowne Engineering are getting delivery failure notices. I was hoping to see if possibly he had started a waiting list, as I was just ready to order his kit. From this thread, I am just learning of Chris Cosentino's cartridge kits. Are they comparable to the Lansdowne kits which have been so highly praised on this forum?
Bill

pantah_good said:

From this thread, I am just learning of Chris Cosentino's cartridge kits. Are they comparable to the Lansdowne kits which have been so highly praised on this forum?
Bill

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As with many topics, I think discretion is the best policy here. Using the Google search in the top right corner will get you more opinions on the subject than you could ever want.

Chris uses damper cartridges from Showa as his base. These are used on CBR600RR modern sports bikes and have rebound, compression and pre-load in both legs. More than non racing Commandos need, sure, but it's what I wanted and was willing to pay.

Thank you. In the meantime I did use the excellent search feature here and found a good discussion on them. Now just hoping they are available and not out of my budget range.
Bill

pantah_good said:

steelcap said:

I recently ordered some dampers from Chris Cosentino. In our correspondence he mentioned that he will stop making these soon. Given JR Bould's illness, the future of decent front suspension on these bikes looks bleak.

Click to expand...

I'm sorry to say my emails to John at Lansdowne Engineering are getting delivery failure notices. I was hoping to see if possibly he had started a waiting list, as I was just ready to order his kit. From this thread, I am just learning of Chris Cosentino's cartridge kits. Are they comparable to the Lansdowne kits which have been so highly praised on this forum?
Bill

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I can speak on authority that Chris is doing another run of his fork kits (his shop is next door to NYC Norton). What this means is... the kits will be available again, at least for a limited time.

We install Cosentino's kits in every high-end NYC Norton build, and stand by them. If Chris chooses to stop production you can rest assured NYC Norton will pick up where he leaves off.

That is good news