KNOW YOUR… FORKS
Unless you’ve got the wheelie skills of Dougie Lampkin (who managed a whole lap of the TT on the back wheel), you’re probably as needy as the rest of us on a bike’s forks. We caught up with suspension guru Michael at K-Tech to learn more about them…
FB: Are all fork legs the same?
MH: Essentially, you have two main types of fork systems which are open cartridge and closed cartridge – with many different types of system within them. An open cartridge fork basically means that the oil within the cartridge is the same as the oil on the outside with one common oil chamber, which is principally an easier fork to live with. The closed cartridge forks have a pressurised area at the end of the cartridge which is sealed off, and will essentially offer a more consistent damping that will work better in extreme conditions. The trade-off is that they’re harder to maintain.
FB: How do conventional forks work?
MH: Basically, you have both compression and rebound pistons within a cartridge with shims covering the pistons. It varies massively with different types of forks as some won’t even have a piston, but the conventional approach would be using the shims to adjust how the oil is fed through – altering the feeling from the forks as they compress and decompress.
FB: How often should you service forks?
MH: Most manufacturers will have a service time they work to, but as a rough guide for road riders that cover a lot of miles in a year, having a service every two to three years will keep your stuff working as it should. Suspension really isn’t that different from getting your engine serviced and you should see some of the oil we drain from old kits. If you’re riding on track and getting a fair few miles in then halfway through the season should be plenty, as well as after any big off and at the end of the season!
FB: How does a standard fork differ to an aftermarket fork?
MH: Massively… you’d need more than a thousand words for that question though! Essentially it’s the same as every aftermarket part as everything is built to a specific price on a bike. Some machines come equipped as standard with below par suspension, and although some come with quality kit everything can be improved. The difference between aftermarket and standard forks tends to be through the quality of build which relays into feel, and the degree of adjustability available.
FB: Are superbike forks entirely different again?
MH: A superbike fork is that next step up, created for a specific bike and its needs. You have a lot more adjustability and they’re created to deal with
the higher stress levels – think what a set of forks go through on a superbike around Cadwell Park for example! Unfortunately they also cost a fair whack more.
FB: What’s typically adjustable on forks?
MH: Some standard low quality kit may not have adjustability at all, but most forks will have full pre-load, compression and rebound adjustment on them. Pre-load essentially means the load that is applied to the spring, which will in turn change the amount of resistance the spring gives, affecting the break-out force which is the point where the parts will start to move. Compression essentially covers the rate in which the spring is compressed, like it would be under braking, while rebound controls the rate in which the spring will then return to the correct length – so when you’re jumping back on the power. This is very simplified though!
FB: Why is adjustability so important to a fork?
MH: Every single different aspect from adjusting the preload to even the amount and viscosity of the oil will make a monumental difference to the feeling of the bike. For example, if a bike is out of its optimum working range the chances are it will feel like an absolute dog to ride, and we find this on the bike setups we do on both used and brand new bikes. Even a few millimetres can make a huge difference, so you shouldn’t pass it up!
FB: Are springs and oil weights really that important?
MH: Essentially, the easiest way of getting a bike set up properly is using the correct spring that is suited to a particular rider’s weight, which will help to give a personalised feel on the machine. As far as oil goes, although you can change the amount and the viscosity, the easiest way of approaching it comes down to using a good quality suitable oil, in order to make the fork last longer between services.
FB: What kind of bikes do you guys tend to upgrade the most?
MH: It’s funny actually, as we’d generally say that the road side just about edges out the off-road segment – but not by much. We do a lot of road bikes, such as the MT-07, which really benefit from uprated suspension components alongside a whole host of sportsbikes and race bikes all year round, whereas we see more of the off-road guys at the start and the end of the year!