Suspension part 6

Damping (continued final of the series)

As mentioned in the last issue, there are no hard and fast measurements with which to set the damping on the suspension. We also stated that most riders don't know what their bike is really doing when they're riding it. So the question must be asked...how do you know when it's right? And how do you know when it's wrong?

I've seen suspension technicians bounce a bike up and down and make a decision as to what changes to make to the suspension. Mere mortals like ourselves may observe this and, seeing what decision they arrive at, start to base similar decisions of our own on this information. The problem is that we haven't had the technical training they have.

We probably haven't bounced a couple of thousand bikes up and down before, feeling for what the suspension is doing either. Therefore, chances are we haven't gained a 'feel' for what good damping should 'feel' like on a stationery motorcycle.

It should also be noted that this is usually not the only source of information that the technician will base his decision on. As a matter of fact, to be as accurate as possible, they will use several sources of information. So in combination with 'feeling' the bike by bouncing it up and down, they will look at how the bike is wearing the tyres, if at all possible (especially in a racing situation) the technician will try to observe for himself what the bike is doing, along with getting the riders perspective.

Obviously if you are not racing and you come to a suspension expert, they will probably not be able to observe what the bike is actually doing, and will have to base their decision on the other factors. This should be enough for someone who has the skills to decipher the sometimes incomprehensible babble that we (as riders) offer, and what he 'feels' the bike doing.

Our job as riders then is to give the technician accurate information. In other words we need to observe what the bike is doing and report it. If you are going to be your own technician, that's fine, just recognise the different roles you play. On the bike you are the rider, gaining the information needed to base a decision on. Off the bike you are the technician and your job is to take that information and base a decision on it. Don't expect every decision to be correct. Chances are you'll have to repeat the process of changing these 'hats' more than once to get it right.

So...what exactly are we looking for? The damping can only be one of three things. Too hard. Too soft. Or, just right! To help you understand what effect each of these have let's look at them individually.

Too hard - as a rule, if the damping is too hard, the bike will feel unstable. If it's too hard in the compression damping the suspension will not comply with bumps, as the transferring of the force is too slow, meaning the wheel will tend to skip over the top of the bumps rather than follow the contour of the road surface. If too hard in the rebound damping the bike will tend to 'pack down' or 'squat'. This is caused by the suspension not allowing the bike to raise back up to it's original position quickly enough. The end result of this is sometimes referred too as suspension "chatter." Although the bike will feel unstable, it will tend to feel quite 'stiff' or 'taught.'

Too soft - the interesting thing here is that if the damping is too soft, the bike will also feel unstable. Only this time, rather than 'chattering' it will tend to feel 'sloppy,' and possibly 'wallow' in corners. (wallowing means that the suspension will oscillate without anything seeming to start it off, like bumps for example) It may also feel a little like a pogo stick, continuing to transfer the force up and down the length of the travel. This is particularly noticeable on bikes that have done a lot of miles.

Just right! - if the damping is working correctly, you probably won't notice anything! The suspension will keep the wheels moving up and down as required to keep the tyres on the ground and the bike stable.

Who was it that said "the more I know, the less I understand"? The interesting thing about reading information on a technical subject like suspension is that it will tend to raise more questions than it answers. I'm sure that over the last few issues we have been focussing on the subject of suspension, that has happened for you. That's okay. In fact that's what's supposed to happen.

It's now up to you to use this information and apply it. Doing so will answer some of your questions, and the ones it doesn't need to be directed to someone who knows what they are talking about. And...just in case you're wondering...that's probably not your brother in law or next door neighbour...

Good luck with your riding...