Hydraulic steering damper

I agree with this article as regards stability. However very few articles mention self-steering effects. Most motorcycles are not completely neutral steering, they usually tend to run wide slightly as you brake in corners when cranked over and hold their line as you accelerate or roll without brakes or power. Very few seem to oversteer much as you accelerate. :

Mike. That's a bit of a bastard of a thing to happen. I have just ordered some so hope I don't have any problems when I get them. Coming from Oz at the moment seems dicey. Hope someone who has them can chip in here and help you set the adjustments right. Any suggestions David!

kerinorton said:

Mike. That's a bit of a bastard of a thing to happen. I have just ordered some so hope I don't have any problems when I get them. Coming from Oz at the moment seems dicey. Hope someone who has them can chip in here and help you set the adjustments right. Any suggestions David!

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I am not David, but here is what I would ask, and some of the answers.

So why did Mike have tank slappers?
It is possible that there was a problem with the shocks, not made correctly etc, but I would call that very unlikely.
So what causes "tank Slappers"?
Instability, usually set off by little weight on the front such as a wheelie of hitting a bump.
Why did it start when the shocks were changed? What can change stability?
Rear Ride height.
It is possible even if the shocks were the same length, the springs or the preload on the springs may have been More than the stock shocks.
Causing the rear ride height to increase.
Any increase to the rear ride height is a decrease in trail. Trail is the biggest factor in determining stability.
In Mike's case, as far as we know, only the shocks were changed.

Before installing the new shocks I would measure the static sag and the rider sag.
Start with the new shocks at the same rider sag. Which is adjusted by the preload on the springs.

Of course check the the new shocks are the same length as the OEM shocks, you can either measure them, or install them one at a time, with the one stock shock still in place, the new shock should mount up with ease if it is the same length.

After riding with the rider sag set the same as the stock shock, if all is OK, I would try and set the rider sag at 30 mm.
After the rider sag is set to 30 mm check the static sag, it should be between 5 and 15 mm.

As to the springs being infinitely adjustable, that may be true based on the amount of threaded area, but you should keep the installed preload between 10 and 35 mm. If you are having to use any more or less it means you should have a different spring rate.
Hope that helps.

kerinorton said:

Mike. That's a bit of a bastard of a thing to happen. I have just ordered some so hope I don't have any problems when I get them. Coming from Oz at the moment seems dicey. Hope someone who has them can chip in here and help you set the adjustments right. Any suggestions David!

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What Dan said.

It was quite useful using those Ducati charts i have posted, too. Start at soft settings, and only add one type of change at a time.

I have the three preload clicks on mine, and with the stock IKON spring (i validated that with IKON for my riding weight) i run on the first click normally, or second loaded with paniers or pillion.

I think i came in at about 25mm of rider sag.

I think i run 1.5 or 2 on the rebound damping.

In my case, the only change was the shocks. Nothing else was changed; wheels and tires are OEM. The Ikons are a bit shorter than the Hagons. With the Hagons, and the bike on the centerstand, the rear wheel will still be 'just' touching the ground on a level surface. The Ikons hold the wheel clear of the ground. Frankly, I really liked that part! AGAIN, I don't want to come across as saying the Ikons are not good shocks, ONLY that I didn't want to fool around with the adjustment that much because it was a PITA to do it, ride 10 miles or so to the twisties in question and then do a bunch of testing/adjusting

Also, the fact that the shocks are threaded for the spring adjustment means you have to carefully measure the position of the adjuster nut on each side to be sure you have each one at the same preload.

gortnipper said:

What Dan said.

It was quite useful using those Ducati charts i have posted, too. Start at soft settings, and only add one type of change at a time.

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I agree - that approach has worked for the Nitron R3s... so far
I started with mid-range on rebound (12) and low speed compression (8) but set the high speed compression to minimum (1) and reduced the spring preload to achieve compression 13mm (bare bike off centre-stand) which gave 28mm stationary with me sitting on it.
After 300 miles I have used all but 10mm of the 85mm stroke - so I’ll leave it like that for now - plenty of adjustment left if I need it.

On most road bikes, the steering is neutral, so they tend to run wide if you gas them too early in corners. When you raise the rear end, you decrease the trail and they will tend to run wide earlier in corners. . If you increase the trail, the bike can oversteer if you gas it when you are cranked over. Stability is another issue. Your bike can be unstable both as you brake into corners and as you accelerate out. Instability does not matter as long as you do not run out of road. Instability is controlled by the steering damper. I've had tank-slappers happen due to locking the front brake and also by putting a footrest on the road which lifted the rear wheel - when I threw the bike vertical, I got the tank-slapper. In both cases I did not have the hydraulic steering damper. At one race meeting, the scrutineers ordered me to remove the damper as it was out of character with the bike. Not having it almost cost me my life - I dislocated my collar bone and not my neck - I went down the road on the top of my head.
You should not have to reverse steer to get your bike to tip into corners. When that happens, you probably don't have enough trail. (Even if that sounds counter-intuitive). When I had insufficient trail on the Seeley, it tended to stand up vertical as I braked into corners - tried to go in the wrong direction.

Mike. I instigated this talk because mine are costing $875.00 NZ. Yours must have cost the same so its a waste not using them. Hopefully you have the time to sort it out. In my case, I have a second commando so wont mind disabling the 850 if I need to. I hate not having one to ride.

Yep - same price range converted to USD. At the moment they are on the shelf. We are in the UK and probably won't be back to the Norton until at least January. So I have plenty of time to consider whether I want to try to tune the shocks or just sell them on Ebay. They have 160 road miles and about 50 yards of off-road!

Fast Eddie said:

I fitted the NYC Norton kit. I couldn’t bring myself to bolt on a piece of angle iron bracket, and his machined alloy brackets and fittings are the dogs... I also wanted a damper that’s easy to adjust and give a wide adjustability, although I tend to have it on a very low setting.

View attachment 17599

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Nigel
I have one of Kenny's frame brackets coming. With Matt's lower yoke design (internal brake manifold) I have to use a longer stroke damper.
Did you bolt your bracket straight onto the frame tube or use some kind of protection/shim?
Cheers
Rob

I clamped mine directly to the frame Rob.

But if I had a beautiful cNw build like you, I’d put a wrap of insulation tape on there first.

It’s a good fitting clamp. With powder coating and insulation tape adding to the frame tube diameter, take care not to over tighten.

I used one of these, just tapped out the outer hole to take a M8 for the damper.. Come in 1" diameter and fit perfect.

robs ss said:

Nigel
I have one of Kenny's frame brackets coming. With Matt's lower yoke design (internal brake manifold) I have to use a longer stroke damper.
Did you bolt your bracket straight onto the frame tube or use some kind of protection/shim?
Cheers
Rob

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If you use a stanchion clamp like below, you shouldn’t need a longer stroke, you can adjust the position of things to get a good stroke with no fouling anywhere etc.
That is, of course, assuming you have space for such a clamp with the fork travel on your particular front end.

Fast Eddie said:

If you use a stanchion clamp like below, you shouldn’t need a longer stroke, you can adjust the position of things to get a good stroke with no fouling anywhere etc.
That is, of course, assuming you have space for such a clamp with the fork travel on your particular front end.

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No - the hydraulic lines off the rear of the yoke mean the the front rose joint will have to be near the stanchion, hence extra stroke requirement.

gortnipper said:

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I had my first ride yesterday with this setup, and i am impressed with the difference, despite having not much of an expectation.

Yes, it is a cheap NHT damper and not an Ohlins. If i was doing any track time on this bike, I would probably popped for one - or something like a Toby or Hyperpro.

There were two things in particular I noticed on my four hour ride: first, the wind buffeting on the motorway was reduced quite a bit at 70+mph (i wouldnt call this "snaking" it wasnt that severe); second, in long fast swooping turns on our rough country roads, the front felt that much more securely planted.

I wish i had done this years ago.

My Commando had a damper when I bought it which it badly needed due to the badly mis-sized wheels/tires the PO had installed on it. When I removed them and replaced them with OEM wheels/tires, the need for the damper disappeared as far as wobbles/poor handling.

HOWEVER, there is an advantage to dampers in routine riding - they reduce rider fatigue, especially on long rides on relatively straight roads. That is the reason most bikes that come with dampers nowadays have them. On the down side, they can make operating in the twisties more work unless they are the adjustable type. I removed the non-adjustable OEM damper from my BMW R9T for that reason. The bike is easier to ride on twisty roads without it. OTOH, it is nice on a 90+ MPH run up a Cuota (interstate-type toll road) in Mexico. I sometimes think about buying an adjustable damper that I can turn on/off while riding but I haven't done it. I don't ride the 9T all that much anyway...

With my bike, when I ride it around tight circuits - I don't really have to steer it, because it oversteers when I gas it in corners. So it does not really matter if the damper is set a bit too hard. On public roads, it is different because you usually have to observe the speed limit and stay on the correct side of the road, so you don't ride your bike that way.

With Norton Commandos, I have always suspected the steering geometry Peter Williams specified for the first model , was correct - and the tank slapper problem could have been fixed with a damper instead of changing the yokes. Changing the yokes to get more stability changes the handling in a way which reduces flexibility. If your bike oversteers slightly as you accelerate, it gives you more confidence at the expense of stability. - The bike might shake it's head as you come out of corners or tip you off if you hit a bump, when you have no steering damper..

As with many things, designs are built to a range of loads, temperatures, angles, weights, even time of day. That applies to motorcycle suspension too. What range of speed? Wheel diameter? Tire pressures? Weight distribution?

In 1971, my brand new Commando had the high speed weave; chalked it up to combo of Avon GPs and SoCal freeway grooves; switched to K81s and never happened again. Forty years later, my '73 750 which never did it, all of a sudden, did it - at over 100 mph but associated with my switch to a wider rear tire. Found I could prevent it by tucking in and shifting my weight rearward. Wore that tire out, went down a width, no more weave. But . . . . . after the weave was cured, I did fit a damper anyway,