Steering dampers

[z1000]

Watching the TT on M&M last night , and a bloke pulled out with a faulty steering damper. Why do some bikes have them and some not ? I have never felt the need for one on my Z , even on the track.

Are they fitted as some sort of after thought when it's realised the geometry is wrong , or what ?

[itchy]

Each model is different and there tends to be several factors which combine to determine whether a damper is needed.

You say "even on the track" but this has little to do with it. Head shaking and tank slappers are usually the product of a bike that is not upright combined with a lightening of the front wheel load and a bumpy surface. At the TT they are racing on public roads. How many public roads do you know of that are as smooth as a race track? The TT course is definitely not smooth. Added to which, a tank slapper in that environment is extremely dangerous. Hence the need for dampers.

[z1000]

Hmmm.. OK , point taken , bumps aside , and I saw a few last night on the tele , last time I was in the IOM , the circuit looked pretty much like a race track , that was twenty years ago , I,m sure it has improved since.

[rsvmilly]

z1000 said:

Hmmm.. OK , point taken , bumps aside , and I saw a few last night on the tele , last time I was in the IOM , the circuit looked pretty much like a race track , that was twenty years ago , I,m sure it has improved since.

Well the roads round my way certainly haven't improved recently

Thread about tankslappers here;

www.pistonheads.co.uk/gassing/topic.asp?t=170114&f=74&h=0&hw=damper

[victormeldrew]

I had an '85 GSXR750. This was a little lively, and a White Power steering damper was affixed pretty smartly. The '86 model came with one fitted standard. It had thicker wheels and a beefier frame too, which helped!

It's all down to geometry. If you want a bike that steers quickly then, much like a fighter aircraft, it needs to be naturally unstable. On a bumpy course like the IoM that will lead to all sorts of flapping about under power, and a steering damper would be almost mandatory there I'd have thought. As well as huge testicles.

Oh, and I have written off a bike as a direct result of a tankslapper, when I hit a set of ripples on a bend at just the wrong speed; the resonance set up a tank slapper that saw me flying over the bars and into the kerb on the other side of the road, directly across the path of an oncoming car. Plod was all for throwing the book at me, until an old boy who had been walking his dog vouched for me - "he was riding perfectly sensibly until it looked like his front wheel fell off". Sometimes people are just great!


>> Edited by victormeldrew on Friday 10th June 13:30

[z1000]

victormeldrew said:

As well as huge testicles.

Thats me then , I'll give it a go

Milly , you going to Le Mans? Where you camping ?

[rsvmilly]

Houx Annexe again this year. Didn't you mention you were in Houx?

Annexe is handy for the tomfoolery on the roundabout and local roads like this;

Nutter

(Warning - 10Mb so right-click and save)

[itchy]

z1000 said:

... the circuit looked pretty much like a race track , that was twenty years ago , I,m sure it has improved since.

Highway survey engineers record, among other things, a road defect called "variance". It is a measure of the degree to which a road rises and falls over a given length. For example, 10m variance is quantified over ten metres and is useful for determining whether low-speed road users will detect undulations which make for an uncomfortable road experience. 30m variance, on the other hand, is a useful measure on motorways because of higher traffic speed.

At speeds approaching 200mph, as at the TT, variance occurring over lengths in excess of 30m may well upset a bike's handling. But any significant 10m variance starts to appear as bumps at such speeds.

While on close inspection a road surface may look smooth, there's more to road quality than meets the eye.