Commando suspension setup

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Rohan said:
Carbonfibre said:
I seem to remember a post from someone suggesting progressive springs were all the rage on MX bikes? Could this person have perhaps been mistaken........................lol
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This spring is available now for your KTM.
Not an insignificant name.
One of just a large range.

Commando suspension setup
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This shock spring is for the PDS system that has no linkage for progression. Progression comes from the spring. Straight weight springs are the norm for linkage systems as the progression is in the linkage.
 
Ludwig, I think you are wise specifying a softer spring than what Wilbers suggest. I bought a Wilbers for a canterlever mono shock and went with what they recommended but it was too hard. I have it wound out nearly as far as it will go to achieve the sag I like. It may be ok for a smooth track but not the road. They are very well made and work very well. graeme
 
Very easy to check whether a spring is truly progressive. Remove spring from damper, and compress damper and measure the travel ( adding 50% of length of bump rubber). Then you need to safely compress the spring the same amount as max travel, and this can be done quite easily using a length of threaded rod and a couple of large washers. Its then simply a matter of taking note of whether or not any coils are touching, if they are its a progressive spring, if not its a linear spring wound to look as though its progressive.

For custom rear units filling out a spec sheet such as this: http://www.maxtonsuspension.co.uk/files/twinshock.pdf will mean the supplied units are pretty close to whats required, as things like the correct spring rate for a particular purpose can be worked out mathematically, and then the damping characteristics can be set to work with the spring rate chosen. Fine tuning is then carried out on the bike by first adjusting the spring pre-load, and then adjusting compression and rebound settings to suit rider and riding style perfectly.
 
The reason for threaded rod relates to this being the safest way to compress a spring. Main things though are having the correct spring rate for rider weight and suspension geometry on particular bike, with the damper settings appropriate for this spring rate. Damper settings which work fine on a 120lb spring wont be as good on a 100lb one, and as most off the shelf dampers are all set up the same no matter what spring rate is being used, they never tend to work that great.
 
Carbonfibre said:
Main things though are having the correct spring rate for rider weight and suspension geometry on particular bike, with the damper settings appropriate for this spring rate. Damper settings which work fine on a 120lb spring wont be as good on a 100lb one, and as most off the shelf dampers are all set up the same no matter what spring rate is being used, they never tend to work that great.
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Koni dampers came with 5 different damper settings - with springs off you pushed them down to the limit of travel, and rotated the shaft through 5 different clicks. Later ones have a little thumbwheel, 5 clicks on the move even, although this is supposed to be a bit fragile - mine still seem to do something. Afraid I don't recall if this was compression damping, rebound damping, both or all imaginary - a while since I looked at them.
 
Pistons on properly made custom shocks are selected to suit spring rate of that particular shock, and will generally also have adjustable compression and rebound damping with about 20-30 click adjusters fitted.

The relatively crude adjustment system on the old Koni shocks was primarily intended to compensate for wear during the service life of the shock, and was not fine enough to help with tuning the suspension to any degree. A good idea all the same, and far superior to much of whats around today, most of which cannot be adjusted in any way or rebuilt.
 
Carbonfibre said:
most of which cannot be adjusted in any way or rebuilt.
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Back then you relied on Girling or Koni to produce a setup suitable for what you were fitting it to - Commando got a particular setup of Girling - or Koni, and springs. One size suits all certainly, but at least in the ballpark.

Recall a test of a hypersport bike recently, with 1000s of settings. commented 2 or 3 clicks off factory setting was noticeably not better...

As folks have saying repeatedly,THERE ARE PLACES which can rebuild 'sealed' shocks - I had a sealed monoshock rebuilt* about 15 years ago. They cut it open, rehardchromed the shaft, fitted all new seals and workings, gased oiled and rewelded it up. 15 years later, still good.

Been toying with getting a set of old Girlings redone.
Probably better than new, and reasonable $$.

*P.S. Monoshock blew seal and dumped all its oil, so a rebuild was rather necessary...
 
Mate of mine who manufactures shocks can rebuild just about anything, but no real point in lots of cases as rebuild cost is sometimes not that far away from the cost of a new shock.
 
ludwig said:
xbacksideslider said:
..what I get now is that the SHAPE of the bump is what compression damping can adeptly handle..
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Only adaptive compression damping can . Fixed orifice damping can't..
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Yes, exactly. So, I have to conclude that compression damping, in the general absence of adaptive compression damping on our Nortons, is no different than spring, especially if your springs are on the stiff side to start with. Only if your compression damping can react, or adapt, to a very sudden, quick, increase in the rate of acceleration, does it offer anything that a spring doesn't. And even if you have adaptive compression damping, and if it is too harsh, then it's the same thing as bottoming, provoking a loss of traction/skid/patter. The same could be said of too stiff a spring.

Perhaps it is a fault but I tend pay more attention to the front suspension, particularly under braking and for that reason I like a stiffly spring front end.
 
Carbonfibre said:
Mate of mine who manufactures shocks can rebuild just about anything, but no real point in lots of cases as rebuild cost is sometimes not that far away from the cost of a new shock.
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Said from the point of view of someone who is entirely rooted in the modern era. ??
You forget that we are dealing with a 40 year old classic here, and some folks like them entirely original.

AND, 15 years ago, monoshock repair was about $200, as against ~$800 for a new one, as I recall. $%%$$# dealer margins....
 
willh said:
Progression comes from the spring. Straight weight springs are the norm for linkage systems as the progression is in the linkage.
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I think you are the first to say that in plain english. Only took 11 pages !
 
xbacksideslider said:
ludwig said:
xbacksideslider said:
..what I get now is that the SHAPE of the bump is what compression damping can adeptly handle..
Click to expand...
Only adaptive compression damping can . Fixed orifice damping can't..
Click to expand...

Yes, exactly. So, I have to conclude that compression damping, in the general absence of adaptive compression damping on our Nortons, is no different than spring, especially if your springs are on the stiff side to start with. Only if your compression damping can react, or adapt, to a very sudden, quick, increase in the rate of acceleration, does it offer anything that a spring doesn't. And even if you have adaptive compression damping, and if it is too harsh, then it's the same thing as bottoming, provoking a loss of traction/skid/patter. The same could be said of too stiff a spring.

Perhaps it is a fault but I tend pay more attention to the front suspension, particularly under braking and for that reason I like a stiffly spring front end.
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Xback — I think you are right to concentrate on the front suspension, because of the absence of proper compression damping, as we know it, on unmodified Roadholders. I had one or two 'moments' under hard braking with both standard and softer springs, and I am sure I'm not the only one!

Ludwig — do I understand you correctly that by adaptive damping you mean shims (or a shim stack) which regulate the flow of oil through the damper piston, the flow of which can increase when the shims are deflected?
 
Rohan said:
Carbonfibre said:
Mate of mine who manufactures shocks can rebuild just about anything, but no real point in lots of cases as rebuild cost is sometimes not that far away from the cost of a new shock.
Click to expand...

Said from the point of view of someone who is entirely rooted in the modern era. ??
You forget that we are dealing with a 40 year old classic here, and some folks like them entirely original.

AND, 15 years ago, monoshock repair was about $200, as against ~$800 for a new one, as I recall. $%%$$# dealer margins....
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The person I was referring to manufactures suspension for a wide range of classic bikes, and has been doing so since the 1970s. I can see that people want to keep bikes original looking, but not sure if I would want to put up with things like poor suspension and even worse carburetion, on a bike that was ridden regularly?
 
Carbonfibre said:
but not sure if I would want to put up with things like poor suspension and even worse carburetion, on a bike that was ridden regularly?
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Again, your off-the-cuff rubbish statements again demonstrate that you have not even ridden a Commando ??

A Commando in good condition is quite a capable bike in modern traffic - I'd pick the front brake as the first weak point, although pretty much any bike from the era or earlier is about the same - some anticipation in riding goes a long way here.

Sure, you can modernise all these things into a modern sport bike - but where is the point in that ? You'd replace practically everything to get there.
Guess thats where modern Triumphs come in - DOHC, EFI, leccy starter, etc etc .
 
As each new series of each model of each Japper is a decided improvement over its predecessor , its fairly obvious
They Never Get Them Right , straight off . :mrgreen: :wink: :p
 
Matt, each subsequent model being an improvement over the previous model goes back to the dawn of motoring. Motorcycles, trains, ships, airplanes, rockets, etc etc.

You can generally date old motorcycle photographs fairly accurately by the yearly features shown.
A 1896 de dion bouton is as different as a 1902 model as a prewar Norton is to a postwar model, as a 69 Commando is to a 1975 model as a first year GSXR is to the most recent.

Trabants perhaps being the exception....
 
Rohan said:
Carbonfibre said:
but not sure if I would want to put up with things like poor suspension and even worse carburetion, on a bike that was ridden regularly?
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Again, your off-the-cuff rubbish statements again demonstrate that you have not even ridden a Commando ??

A Commando in good condition is quite a capable bike in modern traffic - I'd pick the front brake as the first weak point, although pretty much any bike from the era or earlier is about the same - some anticipation in riding goes a long way here.

Sure, you can modernise all these things into a modern sport bike - but where is the point in that ? You'd replace practically everything to get there.
Guess thats where modern Triumphs come in - DOHC, EFI, leccy starter, etc etc .
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As I used to work as a motorcycle mechanic in the 70s I rode a fair few Nortons when they were still current, and was able to compare them directly against the various Jap bikes which most buyers seemed to prefer back then.

If you want an old bike to look at or take to shows, then putting up with crap suspension, brakes, carburetion etc etc isnt much of a problem, but if its going to be ridden and used on a regular basis it makes a lot of sense to improve those areas...............as a fair number of forum members seem to do!
 
I agree with Carbonfibre. It's pretty tough to put up with a stock Commando if you want to ride it very much. I would venture to say the stock Commando disc brake was the worst performer from the era. The list gets pretty long when it comes to modernizing the Commando.
 
Most people bought Toyota Corrollas instead of Six Litre Bentlys too . Does this mean the Toyotas better .
The Honda boys whined about the British stuff , in the 70s .But they fell over laughing about the Italian stuff .

General opinion was that the eytie job needed dismantling and rebuilding brand new . You got what you paid for.
The best handling machine available . At that price , what did you expect , Perfection ? .

For Transport , a whizz bag mayve been reliable ( perhaps ) but as far as a motorcyle went , most of them were Toy ones .

Do the Jap entusiasts rekit there old rubbish , or just fit new suspension / frames . :roll: :mrgreen:
 
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