Tech: Anti-dive braking is back
Faster processor offers the latest KTM a clever solution to an age-old problem
‘If it senses a bump the fork won’t lock up’
KTM’s new 1290 Super Adventure S has WP’s latest semi-active forks, which, thanks to a new brain, are claimed to offer better response to inputs. That means they are quicker at making changes to the damping, which should offer a more natural feel. One of their most interesting bits of tech is an anti-dive function (that can be turned off, if desired). The idea is that when you apply the brakes, the computer senses this and is able to resist the dive. But how does it do it – and why?
First up, some basic physics. When you apply the brakes, the bike continues trying to go forwards. As this happens weight transfers towards the front wheel, which is the part of the bike trying to slow down. This increase in weight at the front-end causes the forks to compress. In some ways this is a good thing: the extra weight on the front wheel increases traction, so you can continue braking harder and slow down faster.
It has some disadvantages too: the rear wheel goes light and under very extreme weight transfer the fork’s suspension travel can be reduced considerably. This means that should you encounter a bump while the forks are compressed, they’re less able to deal with it, which could end in a calamity. To help solve this, engineers have come up with all sorts of anti-dive solutions over the years.
All anti-dive functions work on helping the forks resist the forces that make them want to compress. Forks already have compression damping, which works by restricting the flow of oil from one chamber to another, helping to slow the speed that the forks compress. In early antidive systems engineers rigged up extra hydraulics, so that when the brake was applied pressure from extra oil at the bottom of the fork stopped the forks compressing. This brought with it other issues – under hard braking the compression damping could get so high that the forks locked solid. In KTM’s semi-active system, when the computer senses the front brake being applied, it can quickly close magnetic valves in the fork, restricting the flow of oil, and thus resisting the dive. Not only does this system mean the fork can increase compression damping quickly and accurately, it also means that if the fork senses a bump the damping can be reduced by the computer without upsetting the front wheel. Nifty eh?