The Tuesday Tune Ep 8 - Why We're Riding Telescopic Forks Posted on 22 Nov 06:00 , 0 comments
For over 100 years, telescopic suspension forks have adorned the front end of motorcycles - and more recently, mountain bikes. For just as long, alternative systems have been proposed, built, tested, sold and usually also abandoned. Most of these alternatives have been some form of linkage fork, using short links, swingarms and pivots just like the rear suspension of your bike. These have invariably been touted as solving problems that telescopic forks have always found it difficult to address, the most notable of which is brake dive - so how did it come to be that we're almost all still riding telescopic forks in spite of their accepted shortcomings?
After all, if you could remove brake dive from the equation as a variable, it should be much easier to find spring and damping rates that allow for better bump absorption and traction since the need to compromise on sensitivity in order to support the fork under hard braking is eliminated.
This is a more complex question than it may first appear. After all, nobody is using telescopic forks for the rear suspension - that idea died with the old Manitou frames. Why is it that we can easily accept linkages as a viable system for minimising unnecessary motion of the rear suspension under acceleration/braking, but not for the front? What is it that linkage forks are yet to get right in order to achieve the level of performance and commercial success that their respective engineers always thought possible?
We suggest that the answer lies in two related aspects: the steering axis's relationship with axle path, and the number of design variables. This week's Tuesday Tune is about understanding how telescopic forks came to dominate the market in spite of their widely known and inherent compromises in performance.