A Guide to
Road Bike Forks
Full Carbon vs Aluminium Forks
Full carbon road forks have a completely carbon construction, including the steerer tube. These tend to be the lightest, but most expensive road bike forks. Make sure when you’re cutting the steerer tube that you use a proper carbon cutting blade. There are forks out there which have carbon legs, but with an aluminium steerer, giving almost the same performance as a full carbon, with a little added weight and less cost – the M:Part Rigid 700c carbon road fork is constructed in this manner.
If you’re just looking for a cheap replacement fork, then there’s no harm in looking at an aluminium fork - they might not be as light as a carbon fork, but they’ll cost a lot less.
Buying the Right Sized Fork
When buying a new road bike fork check that the steerer tube and brake mounts are compatible with your current set up. Most modern bikes will either need a tapered steerer tube (1.5” at the bottom, 1 1/8” at the top) or a straight 1 1/8” steerer tube. Older bikes may require a 1” steerer, as found on the Raleigh 1” A-Head and Threaded forks.
Most road bikes come with calliper brakes, but disc brakes are becoming more popular too, for which you’ll need a disc compatible fork, such as the Enve Disc fork.
Mountain Bike Forks
You need to select the correct forks for your bike based on how you ride but also how much travel and which steerer standard you bike is designed for. It's generally best to replace like-for-like. A frame that comes with a 100mm cross-country fork like the RockShox 30 Gold TK as standard simply won't be designed to take the stresses that a 160mm travel all-mountain or enduro racing fork will put on it, plus it will impact your frame geometry negatively and make the bike handle very poorly.
Coil Springs vs Air Springs
Forks offer their suspension travel via either an air spring or a coil spring. Coil springs offer predictable and smooth performance but air springs have an advantage in that they can be adjusted to suit rider weight. How much a fork compresses under your weight – known as 'sag' - is very important as it allows the fork to extend into dips as well as absorb bumps. Being able to adjust this is very important to get maximum performance. Air springs also tend to be lighter, which means they're the most common choice for everything but extreme downhill use.
The damper is a vital component in a fork, taking the energy from an impact and controlling how it's released. Many manufacturers offer forks that look externally similar but have different dampers, such as the Fox 32 Float which comes in either a cheaper 'Evolution' model or higher level 'Factory' spec. The difference is that the cheaper unit uses an 'open bath' damper where the damping oil can mix with air inside the fork, meaning that on rough descents the damping control becomes compromised. On the more pricey fork, a cartridge damper which isolates the oil from the air is used to give consistent performance.
There are also a number of different standards for steerer tubes, which is the part of the fork that inserts into the frame and is clamped by your stem. Many older frames use straight 1.125” steerers, but in recent years tapered steerers, which go from 1.125” at the stem end to 1.5” at the lower end have become more common. These offer much greater stiffness and strength but aren't compatible with older frames.