USD vs Telescopic Forks
For the longest time ever, Indian motorcyclists have been buying motorbikes with telescopic forks. While the global market made this switch to USD forks on performance bikes a long time ago, we were still left wanting. Price sensitive, developing markets like India, were not considered receptive to costlier technologies, which were the norm in the western world.
Gradually we are seeing this change now, as more manufacturers are bringing USD forks to their premium motorcycles in India. Be it TVS with their Apache RR310 or KTM with all their bikes or even Bajaj with the Dominar. USD forks are here to stay and will only penetrate the market deeper and trickle down to lower spec motorcycles with time.
Which brings us to the question of this article, what exactly are the differences between the upside down and telescopic forks, and is it a big deal to buy a motorcycle equipped with this?
Before we jump into the juicy (or in the case of suspension, oily!) details of the two fork types, here’s a quick roundup of the various elements which constitute the fork. The front fork of a motorcycle is made up of oil, an inner stanchion, springs, an outer slider and seals. These components are by and large the same on both forms of forks under discussion here. Telescopic forks have been around on motorcycle for almost a century now, while USD forks were invented on race tracks in the 1980s. As many engineering revolutions in motorcycles, it came from the rigours and stresses that only race bikes produce on a track. The learnings of the track then gradually found its way onto production motorcycles.
USD (upside-down) forks and telescopic forks are two different types of suspension forks used on motorcycles. They both serve the same purpose, which is to provide a damping effect to absorb shocks from the road and improve the overall ride quality of the motorcycle. However, they differ in their design and construction.
USD forks, also known as inverted forks, are designed so that the stanchions are mounted below the slider. This design provides several advantages over traditional telescopic forks.
Telescopic forks, on the other hand, have the stanchions mounted above the slider. This design has been around for much longer and is still widely used on motorcycles. Telescopic forks consist of two tubes, the outer tube and the inner tube, that slide within each other to provide the suspension travel.
Advantages and Disadvantages
One of the main advantages of telescopic forks is their simplicity and ease of maintenance. They are also less expensive to produce than USD forks, which makes them more common on budget motorcycles. However, their design does not provide the same level of stiffness and precision as USD forks, which can result in a less refined ride quality.
In USD forks, the wider (outer slider) part of the fork assembly is connected to the triple clamp. When you brake super hard, the maximum stress is around the triple clamp. On conventional forks, the stanchion is what takes this deflection, which increases overall flex. But on the USD fork, the outer slider takes this excessive stress and flexes less. This allows the USD fork to be much stiffer, giving better control on the front end of the motorcycle. Increased front end control results in better handling and braking dynamics of the motorcycle.
USD forks also generally have greater overlap between the stanchion and the outer slider, which helps increase the overall stiffness. These forks are lighter than their older counterparts, even though it visually doesn’t appear to be the case. The stanchion is the component which makes up most of the weight of the entire fork assembly. USD forks have shorter stanchions which allow for a weight reduction.
But with everything engineering, it is never a perfect option. There are always trade-offs. And one of the main downsides of USD forks is gravity. On a conventional fork, when an oil seal breaks, you will see a minute amount of oil on the fork, which can be attended to at will. On a USD fork, a broken oil seal, sees gravity pulling the oil down the stanchions at a much higher rate of flow. Worse still, this oil is leaking very close to your disc brake assembly and tyres. Having oil on either of these two components can lead to disaster in very little time.
Another disadvantage of USD forks, is that the stanchion is closer to the road. Debris flying from the road tends to nick and scratch up the stanchions faster than on conventional forks where the stanchions sit higher up. Nicked stanchions will then destroy the oil seals and you are back to the problem described above.
So, which is better!
A difficult question to answer in absolute terms. But broadly speaking, if you are looking at performance motorcycles in which the riding is going to be highly stressed, as seen on the race track, then USD forks are no-brainers. But for motorcycles which are never going to push the performance envelope and are largely going to be used for pottering around town or the country, conventional telescopic forks are still the more sensible and economical choice.
Should you base your decision on purchasing a motorcycle dependant on it having a USD fork or not? Not entirely, as USD forks greatly improve a motorcycle’s braking and handling dynamics, but are still only one aspect of a motorcycle. You need to take a more wholistic view of your usage, and other characteristics of the bike, before putting down your money for these metal steeds!