Effects of a steering dampener

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maylar

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Anybody have any experience of mounting a steering dampener to a Commando, and can say what the effects are? I'm experiencing some front end shake with hands-off and getting a bit desparate. Need to have the old girl ready for the Rally, which will be a 500 mile ride for me.

drc
 
The steering damper as far as I am concerned is for side car use. The modern hydraulic damper fitted to race bikes is to try and stop a tank slaper situation at some point where the machine has a progressive over correction, a bit like a bad trailer load on a car. every machine has a harmonic point where this will happen. race bike design tries to move this point outside the range of race machine where it will be a problem . The hydralic damper seems to help get through the harmonic , the screw down steering damper for solo work probably best put on for show only. Nortons are well known for their design for road holding, and not allowing a slap, that is why the frame is so popular, If you use the screw down type with any force on solo work you may create roadholding problems instead of solving them.
 
The front end shake could be due to a loose yolk bearing, or badly worn forks, worn wheel bearings. If its not them it must be further back, something loose cracked or worn. Try soften the front tyre pressure this sometime works till you can find the problem.
 
I assume this wasn't a problem before you swapped out some parts. Any chance that when the bike went down it damaged something that you didn't notice? I am sure you have been through this yourself but what exactly did you swap out and what might have been bent or damaged that was not swapped out? Are you sure this is speed related and not RPM related? You didn't lose some of your balancing weights off a wheel or something?

Russ
 
Here's most the facts of the matter.
The steering damper as far as I am concerned is for side car use. The modern hydraulic damper fitted to race bikes is to try and stop a tank slaper situation at some point where the machine has a progressive over correction, a bit like a bad trailer load on a car. every machine has a harmonic point where this will happen. race bike design tries to move this point outside the range of race machine where it will be a problem . The hydralic damper seems to help get through the harmonic , the screw down steering damper for solo work probably best put on for show only. Nortons are well known for their design for road holding, and not allowing a slap, that is why the frame is so popular, If you use the screw down type with any force on solo work you may create roadholding problems instead of solving them.

#1 Reason I now shun steering dampers is they make the light almost thoughtless Cdo steering action a wearing down labor chore just cruising around.
#2 Reason is it prevents a Cdo from self correcting faster than pilot reaction and also fast pilot action to avoid a hazard or save a slip up.
#3 Reason a fully fettered Commando has no need of any steering dampening than
innately designed in.
#4 Reason is damper on Cdo's can tempt you into tank slap power lean changes even a damper can't handle on an untamed-unlinked chassis.

Modern super elites need them as their innate design makes them either fight throwing down to lean or fight picking back up to save - horribly. While a faulty Cdo shakes at rates humans can handle and damper a good bit, modern stiff chassis wait to shake at a blurring speed beyond what humans can handle or perceive. There is a long list of things that urge Cdo's to shake their nose but tire condition front to back - tops the list.

My essentially new fully fettered '72 Trixie but still wearing an original half worn k81 front tire shakes to crash state coasting down into 40's - in about 3 seconds if I let go to fiddle something. My past Ms Peel, new everything but minus the rear link also shook a good bit in 30s mph but with link could be ridden almost to a stop hands off. Uncanny to me. Rod links are not factory so I'm in same mystery camp as everyone else to try the few things I can alter on a factory Combat for least head shake hands off but don't expect to totally eliminate it.

While rest of the world is worrying about hands off head shake I attempted stoppies on Peel only to lean how to ride a locked front tire many yards to a stop.
Its way easier than trying to stay upright with locked front on THE G...
Peel will have my Scott's damper mounted for side car use and some events that rules require them, but will be set to zero, except if it eases side car handling. But even set on 0, this damper still feels sluggish so even if mounted on Peel will not be hooked up for most my flinging fun, on and off road. Two things I glance at to see if worth teasing up a contest is chicken stripes and fork damper showing. Race bikes don't show unused patch area but sport dampers so don't consider them fair game anymore.

Effects of a steering dampener
 
Dave — there has been at least one thread on steering dampers that you will find in the archives if you search. I can only tell you my experience of riding many bikes, old and modern, on bumpy back roads, and racing. Steering dampers mask handling problems — they don't solve them. Front end shake is not just generated from the front end but also from the rear, as BMW found out in the 1970s. This is why they got Continental to make a rear tyre with a stiffer carcass for the their bikes. I found that the most common cause of front end shakes was hard suspension (front or rear), which was sometimes made worse by not having enough weight over the front. I agree with Malfosse, Commandos don't shake their heads when well set up. Things to check:

Tyres: how old are your tyres and what type do you have? If in doubt, bin them
Tyre pressures: Try 30 front 32 rear, and add a few psi if you have heavy luggage
Rear suspension: Try backing off the preload a bit
Head steady rubbers broken/loose?
Isolastics: shim or adjust to, say, 8 thou clearance front and rear

If you lean forward, does the shimmy diminish or disappear?
Does it shimmy with your hands ON the bars?!

Unless you fit a damper that is horribly expensive, like an Ohlins, you may find it makes the steering ponderous unless it's backed off so much that it can't damp any shimmies.
 
If the shake is at low speeds, then this is normal for a Commando. They all did it.
 
suppose the bike just feels a "just" bit "twitchy" (from the use ofan 18" front wheel) with all other handling attributes just fine... i.e. no head shake, no wobble, no instability, straight tacking etc..... just that the bike might feel "just" a bit sensitive to steering input. Could a damper just take the "edge" off a a too crisp steering ride?

JD
 
Flo.

I'm with Dave on this one. Neither of my Commandos showed instability at any speed. If it shakes, somethings wrong and needs to be fixed.

Rick
 
jeffdavison said:
suppose the bike just feels a "just" bit "twitchy" (from the use ofan 18" front wheel) with all other handling attributes just fine... i.e. no head shake, no wobble, no instability, straight tacking etc..... just that the bike might feel "just" a bit sensitive to steering input. Could a damper just take the "edge" off a a too crisp steering ride?

JD

JD — I hear what you're saying but IMHO, I don't think so. Steering dampers are designed to damp out head shake and, as you say, yours doesn't shake its head. With 19 inch Avon Roadriders 100/90 x 19 inch front and rear on WM2 rims, the steering felt just right on my 850 — not too quick, not too slow. Does your bike have standard length shocks and forks? What make and width of tyres do you have? Has your bike always steered like that or since you changed something? It sounds like you have a sweet handling machine!
 
I've never had a twitch from my stock setup 'S', other than the time I went over some RR tracks, turned left on Rt.1 in Beltsville and hit an oil slick. I thought I was going down since I was accelerating hard, but as soon as it came out of the slick, it righted itself and went on straight as a pin. No Honda will ever do that.

Dave
69S
 
rick in seattle said:
Flo.

I'm with Dave on this one. Neither of my Commandos showed instability at any speed. If it shakes, somethings wrong and needs to be fixed.

Rick

It was a well known thing at the time. A stock Commando would shake at the front at about 30mph if you took your hands off the handlebars.
Mine does not do it now, rim/tyre changes etc. has got rid of it.
 
Had a steering damper on my Combat for most of its life. Took it off last month. I put on a Dave Taylor head steady and the bike lost any tendency to quiver on bumps in corners or go into a speed wobble on shut off, etc. No more need for the damper. As Hobot says you can't make any quick steering moves if you have it on. (Sometimes it is necessary.) It can only mask a problem not really fix anything.
 
just that the bike might feel "just" a bit sensitive to steering input. Could a damper just take the "edge" off a a too crisp steering ride?

Now Wait just a dang minute here, above has nothing to do with hands off head shake, but sure reminds me of bad tires or improper inflation ratio fr/rr.

Dave, the self correcting nature of cycles and Cdo especially is one of the most fascinating things in my life to understand and take full advantage of. If you had slid much longer though the full isolastic whip lash may of built up till a throw down. You've heard the help a top link can do, I consider it the least valuable, so imagine how fun it is to on purpose get bike to crash out for the automatic save that follows predictably.

The best tire combo is two 19xWM2 100's but for the rears poor center section.
Best ballet is done on tippy toe light shoes, but won't last long out shopping.
Tire pressure plays back into suspension stiff ness, so experiment and get back.

I think I got Trixie Combat slightly less head shake onset getting rim and spoked more ture and toned up but way more noticed me playing with tire PSI yesterday. Been though her factory forks completely a couple months ago.
 
I'm still trying to figure out why you would have your hands off the bars at 30? The only time I am traveling thirty is on my way to 60 or on my way to zero, unless I am in a restricted speed zone. In all three instances I need access to the controls on the bike!

Let's see, brake, clutch, throttle...yup need 'em all.

Russ
 
rvich said:
I assume this wasn't a problem before you swapped out some parts. Any chance that when the bike went down it damaged something that you didn't notice? I am sure you have been through this yourself but what exactly did you swap out and what might have been bent or damaged that was not swapped out? Are you sure this is speed related and not RPM related? You didn't lose some of your balancing weights off a wheel or something?

Russ

Damage was limited to bent handlebars and some cosmetics (footrest, kick lever, brake lever, muffler, blinker, fender). Right front blinker bent the headlamp mounting ear and ripped out of the headlamp shell. I did have to remove the right fork in order to replace the headlight mount, but everything went back together smoothly. It was a skid-in-the-sand-at-10 mph kind of fall.

Checked wheel balance, it's perfect.
 
daveh said:
Dave — there has been at least one thread on steering dampers that you will find in the archives if you search. I can only tell you my experience of riding many bikes, old and modern, on bumpy back roads, and racing. Steering dampers mask handling problems — they don't solve them.

Got that. Thanks.

Tyres: how old are your tyres and what type do you have?
Avon AM26 rear, Avon Super Venom in front. Both have very little wear.

Tyre pressures: Try 30 front 32 rear, and add a few psi if you have heavy luggage
That's what I run.

Rear suspension: Try backing off the preload a bit
Progressive shocks, preload is all the way down.

Head steady rubbers broken/loose?
I found one of the head steady rubbers loose, and replaced it with a new one (it had wear marks from clutch cable). No change. Though the new one was a bit thinner and I needed a shim washer to make it perpendicular with the steady. How important is it that they are both the same compound?

Isolastics: shim or adjust to, say, 8 thou clearance front and rear
I've recently loosened the front iso one "hole" (adjustable MKIII). I'll put it back and report.

If you lean forward, does the shimmy diminish or disappear?
Haven't tried that ... with hands off. But it's always been a tad unstable if I put my feet back on the rear pegs on the highway. That's not uncommon with Commandos.

Does it shimmy with your hands ON the bars?!
I feel "something", but it may be a figment of my imagination.

Thanks for the ideas.
 
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