For many motorcyclists, an upside down fork (USD) is the absolute must have. But only a few bikers know what the differences of a USD fork to a conventional telescopic fork is and what technical advantages it brings. So is an upside down fork really better than the conventional fork! You will know after reading this…
USD-fork vs. Telescopic fork – The differences
The uprights of upside-down forks are arranged so that the inner tubes lie down and bear the axle of the front wheel. The fork bridges, where large lever forces act, thus lead to the more flexible, outer tubes with the larger diameter. Also, a larger clamping diameter in the fork bridge is thus made possible.
Although the inner fork leg tubes are less stiff, because they are not required to be fixed firmly by the fork bridges due to the reverse installation, they can be guided as sliding tubes in sliding bearings spaced further from each other so that overall a higher stiffness of the fork leg is achieved.
Furthermore, this design has lower unsprung masses, since the thin tubes show downwardly, which basically improves the wheel guidance. However, the overall weight of an upside-down fork is larger due to the construction and the steering angle is lower because of the thicker tubes. In addition, fork sealing are theoretically subject to more severe wear due to soiling.
Telescopic forks are therefore slightly lighter, but they are less stiff and the sealing rings are better protected against dirt.
Upside Down Fork = Better Driving Behavior?
Short answer: No! An upside-down fork definitely does not have an extremely improved driving behavior, as mentioned above, in normal operation. In racing, motorcycles with an USD fork benefit from low unsprung masses, a slightly higher stiffness, as well as a resulting better wheel guidance that probably only race drivers can feel.
Can you feel the difference between an Upside Down Fork and a Telescopic Fork?
Now that you know what features a USD fork brings with it, you are sure to ask yourself if the difference in driving is noticeable and we have to say honestly: NO! If you would even send a professional driver with closed eyes to a test round, he could not say 99% with certainty whether a USD or conventional telescopic fork is installed …
In general the big different are making the used components in the fork and there are big differences in both conventional forks and USD forks. In both classes, everything is possible from absolute scrap to the finest stuff!
Why is a USD fork installed in modern bikes?
To be honest, a USD fork over the years seems to have risen from a trend to “state-of-the-art” status. A manufacturer has begun to mount USD forks into his bikes (especially the supersport bikes) and the others have followed. The small advantages that a USD fork brings with it are probably only possible to feel on the race track. The rest is probably prestige … On cheaper and smaller bikes for the city, however, regular telescopic forks are still used in the classical sense. As already mentioned, they bring the advantages such as the higher steering angle and a lower weight with it.
So if you are thinking too much about your bike really needs an USD fork, you can rest assured. You will probably not notice the difference in the end, USD only sounds great in the advertising brochure!