Much like the term ‘arm pump’ is thrown around various track day paddocks to explain a little achiness or fatigue in the forearms, chatter is also a term that is used in a variety of different circumstances.
When people refer to chatter, they are often referring to a fast vibration or juddering from the front or back end.
But such results can be caused by a variety of different things, and while one person’s chatter may be the result of a brake system issue, another’s could be the result of something like the suspension bottoming out.
However, when talking about the most known use of the term chatter, it is predominantly found in the highest tier of motorcycle racing – MotoGP.
To understand what causes chatter, first we need to take a quick look at how suspension works best.
Both the forks and shock on a motorcycle move on a vertical plane in relation to the bike’s frame. The more upright your motorcycle is, the better the suspension can do its job of soaking up the bumps and forces that are thrown at it throughout any given lap.
As the motorcycle begins to lean over, the suspension become less and less efficient and it begins to struggle more and more to deal with and soak up these forces.
That’s one of the reason why traction isn’t as plentiful while leaned over, because the suspension can’t track the road surface as well.
When you start to get to the extreme lean angles that we see in MotoGP, you’re going past the point at which the suspension can work properly.
As a result the tyre can potentially begin to slide. But it’s not just a simple slide that once is let’s go, that’s it.
In this instance because the tyres are so incredibly grippy and they’re under considerable load, the tyre starts to slide, but then milliseconds later it regains grip before heading into a tiny slide again.
When talking about chatter, it is this micro sliding and gripping that shakes both the bike and rider to pieces, making it impossible for the pilot to ride at their full potential.
Here’s the biggest example of chatter you’re likely to see. Watch Ben Spies travelling through the right hander about 22 seconds into this video:
In this particular GP he struggled to 11th place because his issue was so bad.
Yes, but it’s by no means a one-time solution for every rider and bike combination.
Riders will tell you that they have fixed it by one means on one bike in the past, but years later couldn’t fix it the same way on a different bike.
Being that there are so many things that go into making a bike feel the way it does when moving through a corner, it could be any one of those things that causes (or fixes) the issue.
From geometry, to wheel weight, suspension settings, wheel base, tyre stiffness, chassis flex, even engine components used, as well as a whole lot more.
Not only do teams struggle to find the exact cause, but even if they do manage to stop it, by changing something else on the bike later down the line or even just when visiting a different track it can come back again.
The solution tends to come from the engineers finding a way to upset the frequency of the chatter. Once the frequency is neutralised the chatter goes away.
But as I said, there’s no guarantee that it won’t come back in the future.
It’s something that teams in MotoGP have been struggling with for many years since they broke the lean angle barriers of previous generations.
Even in some high level domestic championships you won’t see the issue, not because the riders aren’t capable, but because the bikes aren’t able to go to the same extremes.
Back in the days when there were multiple tyre manufacturers creating tyres specifically for different bikes and teams, the manufacturers could create a tyre to suit the motorcycle.
Nowadays though with a single manufacturer, the whole thing has been flipped on its head where bikes are now having to be changed a lot more to work with the tyre.
This is why you’ll see more issues arise as new tyres come in, because they upset how the bike was designed to work based on the previous one.
Whether it’s the tyre size, construction or compound, a small change in any of those factors can undo a lot of hard work the engineers put in to squeeze every last ounce of performance out of their current bike.
Colin Edwards has commented in the past that the introduction of a new, larger rear tyre upset the balance of the bike by making the rear contact patch bigger, therefore meaning the bike had a tendency to run a little wider.
This meant that more steering effort was needed to hold the line, in turn adding more load to the front. All because the rear tyre was made a little bigger.
I think it’s safe to say that when talking about chatter, it’s something that is only really experienced by the motorcycling elite.
If you ever feel a juddering (more likely from the front end) it’s highly unlikely to be the same chatter the guys on TV are referring to.
Instead, depending on where you are experiencing the juddering think what facets of the motorcycle are being used in that moment and you’ll probably find the root cause is something like a faulty part, an incorrect setting, or even poor technique.
Photo by Raniel Diaz
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