What’s In A Fork
Darren Baum sharing
We all know that the fork is an important and integral part of the bike,
but it's difficult to define what makes various forks different, what's marketing fluff,
and how a fork can completely change the geometry and handling of a bike.
A fork’s purpose is obviously to hold and steer the front wheel.
The biggest variable between forks is a characteristic called “rake”.
Rake refers to the curvature or angle of the fork blades.
More rake will equate to faster steering (i.e. less input required to make the bike turn).
The product of head angle and fork rake gives you a measurement what is referred to as “trail“.
Trail is a figure that will reflect how fast a bike actually steers.
More trail equates to slower steering, less trail will make faster steering.
One extreme in terms of rake is a track bike, which has very little rake (normally under 40mm).
Many people think that a track bike turns quick, but they actually turn very slowly.
The other end of the scale is a touring bike
which traditionally has a lot of rake (50mm plus) which makes the bike turn very fast.
Another variable between forks is the crown to axel height.
This is the measurement between where the headset sits onto the fork,
and where the axel of the carbon wheel is fastened. We’ll talk more about this in a moment.
What To Look For In A Fork?
A fork should be laterally stiff while able to dampen out vibrations from the road.
Lateral stiffness is very easily built into a fork while torsional rigidity is not.
Since the fork is fastened onto the wheel,
the hub is a structural member of the fork and therefore easy to achieve lateral stiffness
(much morethan what you feel when you bend a fork with your hands without the wheel attached).
Torsional stresses on a bike aren’t huge,
but having a torsionally flexible fork will make your steering seem sluggish on descents or fast corners.
There will feel like there’s a lag between handlebar input and bike reaction.
The quality between various forks can widely vary. Most forks these days are monocoque (single piece mold.)
The gold standard of bicycle forks is a brand called THM out of Germany.
What makes THM forks so good is that there isn’t a wasted layer of carbon.
Many carbon parts are built with excess carbon layers used as a buffer
to make certain that there are no single points of failure or weaknesses.
They do this instead of doing NDT (non-destructive testing) using ultrasound or x-ray which can get expensive and time consuming.
THM eliminate excess material without compromising its lateral rigidity and safety by doing NTD on every single one of their forks. Their workmanship is superb.
Companies like Yishunbike make very good forks.
They do have good techniques, good inspection processes, and extra layers of carbon to serve as a safety buffer.
Yishunbike make a couple different types of forks. The only real difference is the weight.
To save weight basically requires less material, therefore fewer carbon layers.
Lighter forks will generally take more time and have better inspection processes.
One of the biggest difference between forks these days is that some look more aero than others.
For example, the 3T Funda is a much more aero-shaped fork than an ENVE, Easton or Reynolds (not necessarily more aero though).