Seat Posts

The seatpost is a simple tube that connects the saddle to the bicycle. Your seatpost can seem like a not so important part of your bicycle but it can have an important role to play in how comfortable your bicycle is to ride, and can also be a potential area for a weight-saving upgrade. A good seatpost will reduce vibration and absorb any shock or impact experienced while cycling. Seatposts are made from a metal, as this part needs to be strong and able to support the weight of the cyclist.

Things to consider while buying

There are a few things to bear in mind when choosing a new seat post. They all do the same job and look pretty much the same but take a closer look and you’ll see a lot of subtle differences. We usually take very little notice of seatposts but they can have a surprising effect on the comfort of the ride.


  • Material: Most of seat posts are made up of Alloy or carbon. Carbon fibre is generally regarded as being more comfortable due to its vibration-absorbing characteristics. Carbon seatposts are lightest, but they are costliest too. Many, trail and gravity MTB riders still favour premium alloy posts for strength and confidence. If ride quality is more important for you then saddle, and tyres have a far more direct influence on ride quality, you should primarily focus your efforts there. But if you are trying to build a super-light bicycle then there is no other choice than carbon for seatpost material.
  • Diameter: The most important dimension to consider is diameter. It must correspond to the internal diameter of your seat tube in order to have a snug fit. The majority of modern seat posts are 27.2mm (standard), 30.9mm / 31.6mm (oversized) wide. Older frames may have slightly thinner diameters (eg. 26.8mm) but these are becoming rarer. The diameter size for high-performance bicycle seatposts is larger because they are made of thinner-walled tubing. An oversize post is regarded as adding stiffness and strength for optimum power transfer as well as resistance to bending/failure. High-quality bicycles generally use seat posts with a 27.2 mm diameter. This is the most common size seat post in the industry, but is accepted as being more comfortable over rough surfaces.
  • Length: Length is another thing to think about, especially if you like to ride a smaller frame size. Make sure you have the correct length of seatpost for your needs. While a longer post is generally regarded as offering more comfort, the amount of post ‘sticking out’ of the frame will largely be dependent on your frame size/geometry and your own leg length etc. Seatposts are available in several lengths from 280mm to 400mm so measure the amount of post you have showing plus the minimum amount of insertion that needs to be in the seat tube before purchase. If in doubt, measure your old post. Basically, the line is there to make sure that the amount of post inside the frame can handle any load placed upon it during riding. If not, there’s a chance you could damage the post or even snap it in extreme circumstances.
  • Layback: Layback is the distance between the centre of the post and the middle of the saddle rail cradle. This can have quite an effect on reach and comfort. A post with a lot of layback will result in the saddle being further from the bars, putting you in a more stretched out position. If you feel the saddle is too far back or for efficient pedalling or for time trialling, an inline post with no layback is a better option.
  • Saddle attachment / Clamp type: The cradle or clamp at the top of the seat post which holds the saddle rails can tilt forward and back to allow you to fine tune the saddle position. The saddle clamp will be held in place with one or two bolts. Twin bolt systems are more common as they are more secure and spread the load better. The clamp bolts can be loosened to allow you move the saddle to your preferred position.
  • Colour: Colour for many riders is a crucial aspect while selecting a seatpost. You can chose a seatpost colour that matches your bars and stem ie. black and black, white and white.

Final words of wisdom

  • Leisure riders just need to make sure they’re buying a seat post with the correct diameter and in the correct length. If you’re in doubt, remove your existing seat post and have a look towards the end of the post and chances are it will have the diameter and length stamped on it.
  • Regular riders are well served with either a lightweight aluminium seat post or a carbon seat post. Stick with a reputable brand and a clamp head design that isn’t too wacky and you’ll be fine.
  • Racers should look for the lightest and stiffest carbon seat post that they can afford. So long as your reach doesn’t get compromised it may be worth trying an inline post too for increased pedalling power – especially on seated climbs.


There are a number of ‘non-standard’ specialized seatpost designs available in market. Some of the most important ones are aero posts and dropper posts.

Aero posts: These seatposts are specially made for road and TT racing. While most posts are circular in cross-section, many manufacturers are now making aero posts for road and TT racing, with an elliptical ‘blade’ cross-section which offers improved aerodynamic performance by offering less frontal area to the wind.

Dropper posts: These seatposts are specially made for trail and gravity MTB riding. In recent years, dropper seatposts have become a must-have item for mountain riders. A dropper seatpost will allow you to quickly and easily lower your saddle for improved control when you hit technical terrain, by means of a saddle or bar-mounted switch.

Leave a Comment