Steering Damper

[Longway]

Hi All,

Has anyone fitted a steering damper to the D900?

if so what make/model would be suitable and where does it mount

I saw one last year and thought it was perhaps a good idea to get rid of the 30 - 40mph wobble

Regards

Geoff

[eliminator]

Wobble? Might be down to something else, mine doesn't.

[amorti]

Fixing the symptoms is the wrong way to go mate. Look at head bearings, tyre wear and pressures, state of rear and front suspenders... masking the problem isn't correct or very wise.

[CD]

A steering damper can cause the bike to go into a really nasty weave so best avoided on all but a hyper twitchy sports bike. Sort the steering and all will be ok.

The 40mph wiggle is normal all bikes do it to some extent.

[amorti]

It's not normal, and not all bikes do it. My fireblade doesn't, my CB-1 didn't, no other bike I've owned or ridden ever did. But yes sir, they do all do that, apparently both D6's and D9's.

[Longway]

The bike is a very tidy 2002 model with only 14000 miles - surely the head bearings can't be worn, I had the swing arm off recently to get it powder coated and all was like new in that area with no wear evident, I've had it 2 years and its always had a slight wobble at 35 - 40 even with new Avon Storms, although they are just starting show some wear, the front one is starting to show signs of uneven wear, very little wear in the centre but more wear about a 3rd in from both sides, I run tyres at 34/36 psi, I have tried lower pressures but the wobble seems worse, any advise on changes I should make would be much appreciated or is this just a diversion design issue

Mods I have made is to lower the rear and and drop forks by about 10mm I would say the bike handles better for it giving it a lower centre of gravity, but the wobble still exists!

PS I also own a 29 year old CX500 and never experienced any wobble with that at any speed.

Regards

Geoff

[neilmud Lord Protector]

Mar 30, 2009 20:37:23 GMT Longway said:

PS I also own a 29 year old CX500 and never experienced any wobble with that at any speed.



/quote]

It wont go fast enough to get a wobble

Neil

PS low tyre pressure always made my D900 worse

[Longway]

oooh I asked for that - there's a few CX owners I know would not be impressed with such a comment

[CD]

All bikes do that slight shimmy. It's caused by interaction between the steering castor angle self centering the steering and the front tyre. It's a feature of a vehicle that has a substantial percentage of its weight ahead of the steering point. Some small bikes have us much as 20% of their weight in the front end (forks, bars wheel etc). Diversions I guess are relatively less than that.

Divvies wiggle it at about 40/45mph. 70's bikes at more like 30mph and sports bikes at as much as 60. However, if the shimmy develops into a weave there is something wrong with the steering most likely the head bearings have become knotched. Steering dampers cause the wiggle energy to transfer into the frame. If the harmonics between frame, steering, tyre and speed add up correctly this can become a full-on weave. Bike frame design has to consider this.

The wiggle is only felt when the bars are held lightly the rider's weight damps it out. Sports bikes throw so much weight onto the rider's arms the rider will probably never feel the wiggle. Divvies do it more obviously with bar risers.

This information came from a bike chassis design expert called Damian Harty of Prodrive.

[Longway]

Thanks for the info CD, I do have risers on hence not much body weight on the handlebars.
Yesterday I jacked up the front wheel, the steering feels OK, no movement and very easy to turn, no tights spots, perhaps too smooth

I seem to remember a previous bike I owned some years ago, could have been a CBX550, had a slight tight spot in the central steering position, it was only noticeable when the front wheel was off the ground but I wonder if this was to help stop the wobble

[CD]

With old steering bearings mine did a weave at 80 which was scary. New steering bearings fixed the speed weave and surprisingly made the wiggle less noticeable. The bike was also more responsive in corners. Perhaps worth getting an good MOT tester to take a look at it.

That said, the wheel bearings, tyres and rear suspension could all have an effect.