Commando suspension setup

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Rohan said:
L.A.B. said:
Randomly selecting a parts book ('61-'62), under the heading: "FRONT FORKS WITH SIDECAR TRAIL" I find: "19506A Fork spring.....2..."
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Yes I have that one too.
Doesn't appear in the Commando lists though. ?
Nor in any of the Dealers offerings ?
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The factory specifically stated that sidecars should not be fitted to Commandos-so there wouldn't be any Commando sidecar spring option! :roll:
And by that time, hardly anyone would have wanted to fit a sidecar anyway.
 
Carbonfibre said:
Interestingly enough many users of "progressive" suspension springs are not aware of the fact that they only provide progressive action, when parts of the spring become coilbound.

In most cases so called progressive springs are wound in this way to enhance sales, and if they were truly progressive the forces involved when the spring becomes coilbound would greatly increase the chances of failure.

Easy to check this out, by simply compressing the spring the same amount as suspension travels, and taking note of how many coils are touching..........if none are touching, then the spring isnt progressive and wont work as well as a normal linear type part.
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Well, they work fine, and show no signs of the sudden stop you will get when truly coil-bound, so I am happy. Progressive springsfitted are those sold by British Spares, NZ. Tried ATF as fork oil first, God knows why, too light, topping out, damping too light. 20W motul fork oil sorted it nicely.
 
ludwig said:
Cheesy ,
whatever you decide to do , the first thing you should do is to check the setup of your forks .
Read this :
http://w6rec.com/duane/bmw/fork/chapter5.html
It is about BMW telescopics , but most of it aplies to roadholders too .
You might be surprised what you find .
Secondly , try to understand how your forks ( and forks in general ) operate , so that you know where you want to go .
Not too many know what is exactly happening inside their forks .
A correctly set up roadholder fork is not so bad as some want you to believe ..
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This seems a really complicated way of checking your forks/yolks.
Perhaps one should ask if the fork sanctions and the yolks were straight in the first place to require all this malarkey?
Checking fork sanctions trueness only requires a pair of V blocks and an engineer’s flat surface plate and mounted clock gauge to measure any run-out. They should be true to .002 inch.
Fork yolks ideally should be removed and checked by eye with straight fork sanctions inserted and a couple of long parallel bars that are in line on the sanctions to se if thy seat all true and square.
 
ranmar850 said:
Carbonfibre said:
Interestingly enough many users of "progressive" suspension springs are not aware of the fact that they only provide progressive action, when parts of the spring become coilbound.

In most cases so called progressive springs are wound in this way to enhance sales, and if they were truly progressive the forces involved when the spring becomes coilbound would greatly increase the chances of failure.

Easy to check this out, by simply compressing the spring the same amount as suspension travels, and taking note of how many coils are touching..........if none are touching, then the spring isnt progressive and wont work as well as a normal linear type part.
Click to expand...

Well, they work fine, and show no signs of the sudden stop you will get when truly coil-bound, so I am happy. Progressive springsfitted are those sold by British Spares, NZ. Tried ATF as fork oil first, God knows why, too light, topping out, damping too light. 20W motul fork oil sorted it nicely.
Click to expand...


So called "progressive" springs generally have the coils closer together on one end of the spring. Only when the coils are touching is true progressive action provided. All in all progressive springs are a little bit silly, as most are cosmetic only, and tend to mean suspension action thats not quite as good as with linear springs fitted.
 
I went down this route when i first looked at upgrading my front end, progressive fork springs jumped out of the catalogue page at me, but on further research with 'Nez' in Wellington (New Zealand)who has a lot of experience with Nortons including racing, advised against the progressive path and explained why not to use them , same reasoning as is in the above threads.
So with that I mind I ordered a set of Landownes, just yesterday ,and John gave me a Xmas price including postage to New Zealand
 
ATF was used , primarilly as it was ' Anti Foaming ' , the race boys boiled their oil or just pumping through it airated ( filled with bubbles )
this made it 50 % air , viscosity wise . STP was the ' thickener ' to desired resistance . Then they invented fork oil . largely motocross oriented.

' Progressive ' springs are more ' dual rate ' , as they were . Subtle diferance . Often not diferentiated .

The soft initial resonce is supposed to prevent all the jarring and chopping , from minor irregularities .With the hard rate under it for all the major stuff . The L W Triton had External progressive rate both ends , couldnt complain about them really .
Once people thought if the wheels / suspension moved the least possible , it was ' safest ' as it was all so horrible , wobbly ,and awkward .
Thousands of years of development :p saw control & dimensional stability approached with the Superior Norton chassis and ' Roadholder ' forks .

Norton " The Worlds Best Roadholder " the badges on the front suspension read . AND NOW they want to turf them . Times have changed , :shock:
 
Here is a quick little exercise, a Commando in various states of suspension sag with roadholders and 19inch Dunlop's (well halfway between what I measured and what the manual says). Shock sag makes quite a bit of difference here so Hobot may be onto something with his long travel units. The bottom two pictures are a modern set of clamps, first with 19inch wheels then 17inch, it looks like they will not work to well with the Commando neck angle....

Commando suspension setup


edit, the bottom one has longer shocks as well
 
Quote; So called "progressive" springs generally have the coils closer together on one end of the spring. Only when the coils are touching is true progressive action provided. All in all progressive springs are a little bit silly, as most are cosmetic only, and tend to mean suspension action thats not quite as good as with linear springs fitted.[/quote]


I don’t want to get into an argument but the old Girling rear shocks that are no longer available had progressive springs and were preferable by the racing boys and were saved where possible by a lot of racers from shot Girling dampers.
 
Bernhard said:
Quote; So called "progressive" springs generally have the coils closer together on one end of the spring. Only when the coils are touching is true progressive action provided. All in all progressive springs are a little bit silly, as most are cosmetic only, and tend to mean suspension action thats not quite as good as with linear springs fitted.
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I don’t want to get into an argument but the old Girling rear shocks that are no longer available had progressive springs and were preferable by the racing boys and were saved where possible by a lot of racers from shot Girling dampers.[/quote]

Springs are very complex ,wire gauge,coil gauge ,material and section shape and dia of coil all effect how the spring reacts to load, I think stock 30 inch lbs Norton springs did a "job" good enough for most daily user's , But as brakes got better the compressive forces increased ,plus riders where getting more frisky :!: Bottoming out [coil boundness]became more common. so someone designed the progressive, its a spring that is wound with increasing "space" between the last few inchs, thus increasing the springs resistance to become coil bound, But as the springs first compressive stage is exhausted [coil bound] it then demands that the last section doe's the rest. Spring designers recommend that springs never become coil bound.
I designed the Lansdowne kit to assist the springs compression resistance by building in a proper compression damper. enabling stock springs to be employed.
As reported by Reggie and Lab on this forum, they experianced less dive.

The Lansdowne kit in effect assists the springs from sudden compression. which is allways returned with the same "modified force"
 
ludwig said:
Many springs sold as "progressive" aren't , because under normal operation , the closer coils never get coil bound .
This is the case for the progressive springs I bought from RGM and Norvil (Les Emmery) .
I use them only because they are lighter ( less windings) .
The springs sold by IKON are relly progressive :
Commando suspension setup
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Interesting, what is the wire dia :?:
 
The use of truly progressive springs is uncommon, as the stresses involved when the springs become coilbound (those that dont arent progressive), makes failure a lot more likely.

Have tested several so called "progressive" springs, and none of them provided progressive action as the coils were not touching when compressed the same amount as max suspension travel.

A lot of people get taken in by marketing BS relating to these springs, and often pay more for progressives that arent, when linear springs of the correct poundage will provide better suspension action than costly progressives.
 
The replacement coil springs on my (now former) car were progressively wound, and were way superior to the oem linear springs. A light initial movement, with increasingly stronger take-up (good for towing too).

As mentioned, the springs on Commando Girling rear shocks are not linear. Nor are the springs on the Koni replacement shocks - they go from noticeably very wide spacing to very tight spacing.

I haven't tried, or even seen, the Progressive springs offered for Commandos, but am mystified by the comments. Widely used, and I've seen only good comments about them compared to stock... ??
 
ludwig said:
What we need is not progressive springs , but progressive , or rather regressive compression damping :
firm at low ( slider ) speed and softer at high speed compression ..
Click to expand...

So the race tech cartridge emulators are probably a good idea for roadholders and probably a bit simpler to DIY than a cartridge transplant. Then again machining a new set of triple clamps and fitting some modern forks and using 18in rims could be even easier and give better results.

Im still surprised that no one sets sag, is it not such a big issue on a road bike? I guess the range of sag settings on an MX bike have a much bigger affect on trail and rake.
 
ludwig said:
What we need is not progressive springs , but progressive , or rather regressive compression damping :
firm at low ( slider ) speed and softer at high speed compression ..
Click to expand...


Which is the exact reason for dampers having shim stacks, and high and low speed porting in the pistons! However when you are using dampers which are not adjustable, and have not been custom made for specific application, the basic settings may be way off for the spring rate required, and not suitable for the suspension geometry of the bike they are fitted to anyway.
 
Cheesy said:
ludwig said:
What we need is not progressive springs , but progressive , or rather regressive compression damping :
firm at low ( slider ) speed and softer at high speed compression ..
Click to expand...

So the race tech cartridge emulators are probably a good idea for roadholders and probably a bit simpler to DIY than a cartridge transplant. Then again machining a new set of triple clamps and fitting some modern forks and using 18in rims could be even easier and give better results.

Im still surprised that no one sets sag, is it not such a big issue on a road bike? I guess the range of sag settings on an MX bike have a much bigger affect on trail and rake.
Click to expand...


Fitting modern cartridge internals will certainly make a big difference to any bike fitted with crude poorly designed internals dating back to the 1950s! However this is generally quite an expensive process, and results which are almost as good can be achieved by looking at having a cassette fork conversion done, which entails fitting used modern forks into Norton sliders. The advantage of this is proper high and low speed damping, and forks which in most cases are easily tunable for specific applications.

But anyone going to the trouble of getting front forks that work, also needs to look very carefully at rear dampers, as those which are not adjustable, and have not been custom designed to suit specific application perfectly, may not perform anywhere near as well as a proper custom set up with the proper spring rate and the correct damping for rider weight and suspension geometry being used.
 
However these were the best in the world in the 1950s , a advance of a few decades on the competition , and seldom equaled until the 80s .
regarded as a intregal part of the machines character , one would not neccesarilly have a machine capable of operating
entirely as it might .

Having at the Intreped age of 18 been adjusting the front brake with both hands right simultaeneously testing the adjustment, the swine went way over right , front wheel locked under , on the old SLS at 50 odd , face first .
The onwitting quick reaction in releaseing the brake , understandable in the circumstances. :? Alowed the
antiquity to reasert itself vertically . Or put itself back upright .

So , theres a line somewhere there ,

We need to start a ' Handling Characteristics ' / Roadholding ' thread methinks . For descritions of characteristics or
impressions of stability / cornering / self alignment under duress , predictability in responce , and the like .

Tecnique in operating per conditions etc . Prefered requirements , and officer Prune , Do Not Do's .

Right . 1000 words Ea. of You . Om my desk , wednesday P.M. , . :p :roll: :mrgreen:
 
Fitting cassette type front forks (appear completely stock) and rear suspension that works properly, are things which will greatly improve any bike with OE suspension parts which dont work that well. However on a bike such as the Commando where the chassis design has been compromised to some extent by rubber mountings fitted to reduce vibration, the positive effects of a good suspension set up, are likely to be reduced somewhat by the lack of feel related to the rubber mountings.
 
Cheesy Ludwig

Sag, I know about it, read about it, but like many others never bothered to do anything about it! Using the Race bike last season threw up a couple of basically obvious suspension questions. On my original bike, I used the standard forks & the correct quantity of oil! Not as per the book said. No fork brace or mudguard. NJB shocks supplied by Norman. Bloody good & cheap items that he forwarded based on the information he asked for.
Now, as the bike was it handled well. The exhaust dragged. :D The front forks could be seen twisting yet the bike tracked pretty well. People kept saying the forks are like poles & I updated. The Maxtons eventually arrived, at Brands this season the bike handled poorly compared to before. Why? I believe it all to be rear end. Sag. The shocks are too compressed when I have my not too insubstantial mass on the bike. Changes of direction & on/off the throttle felt choppy the smoothness was not there. I noticed it!!! that tells you how well it handled compared to before. The shocks are 20mm shorter than the NJB's. I need to read more about setting up the Maxtons. I need to measure more. Then actually try any changes on track, back to back. But I believe my shocks are too short.

Chris
 
If you find NJB's work better than Maxton, then why not just stick with the NJB's and save yourself a great deal of money?
 
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