In general, road bikes have non-suspension corrected forks while mountain bikes have either a rigid suspension-corrected fork, front suspension, or front and rear suspension.
At the highest level, bikes fall into two categories: suspension-corrected (typically mountain bikes) and non suspension-corrected (typically road bikes).
One can often deduce whether a frame is suspension-corrected or non-suspension corrected by looking at its fork.
Suspension forks having moving parts and extra space between the top of the tire and the fork crown so that the fork can compress without the tire hitting the fork.
Normal, non suspension-corrected forks are rigid (they have no moving parts) and are typically used on road bikes. Since they do not compress, these forks generally have less space between the top of the tire and the crown of the fork.
Rigid, suspension-corrected forks may look similar to a normal fork, but they are longer to more closely match the dimensions of a suspension fork. One visual indicator that a rigid fork is likely suspension-corrected is that it will have more space between the tire and fork crown, emulating the design of a suspension fork. In this way, a suspension-corrected frame can be switched between a suspension fork and equivalent rigid suspension-corrected fork without the bike’s geometry changing dramatically.
If you are uncertain whether a bike with a rigid fork is suspension corrected or not, it is usually possible to deduce this from the bike’s wheel size (Bead Seat Diameter) and Fork Axle-to-Crown.
For 622 BSD (700c or 29”) wheels, an Axle-to-Crown of less than 465mm is usually non-suspension corrected.
For 584 BSD (650b or 27.5”) wheels, an Axle-to-Crown of less than 455mm is usually non-suspension corrected.
For 559 BSD (26”) wheels, an Axle-to-Crown of less than 440mm is usually non-suspension corrected.
Bike geometry changes dramatically depending on the type of fork used so it’s critical to match the frame with an appropriate fork. Knowing the Suspension Type is important when considering a frame’s intended use case and configurability.
