Skinnier seatposts are in vogue at the moment for the same reason skinny seatstays are popular: the theory is that they offer greater flex and therefore comfort. Since measuring often can’t be done to a 1/100 of a millimeter in accuracy, the next section gives a list of the most commonly used standard seatpost diameters. If a measured diameter differs, it can be assumed that the correct diameter is the standard one that most closely matches the measured diameter. Does the frame have some shims that reduce the seat-tube’s inner diameter, allowing such a narrow seatpost to be held in place? As is consistently the case, aluminium is perfectly adequate and will do the job. Carbon seatposts, however, offer greater dampening from road vibrations and are lighter.

supports the saddle, might be carbon on pricier models, but if you want to save a bit of cash, aluminium The Ascend II impressed us on the trails with a near-perfect return speed, impressively shaped and easy-to-use remote, and reliable action. Although the supplied cable didn’t last long in wet conditions, suffering from corrosion, simply replacing it with a better quality cable would solve that issue.

The same brand is also responsible for bringing dropper seatposts to the road audience: the Specialized Diverge, in its S-Works form, features a 'Command' dropper post. The theory is that those riding the adventure road bike, like mountain bikers, will want to be able to adjust their saddle height to suit the terrain. As far as we are aware, the BikeYoke Revive 2.0 is the longest dropper post on the market with 213mm of travel and a 582mm max length in its biggest size, which is good news for those with long legs. The latest Reverb appears to have hit the sweet-spot of performance, reliability and user serviceability.

preferable to have a handlebar-mounted remote. These tend to cost more money but also mean that you canThe longer seatpost length of mountain bikes means rigidity and robustness are important, whereas with the shorter seatposts on road bikes, compliance and ride comfort are greater priorities. 34.9mm seatpost The Crankbrothers Highline dropper seatpost is designed for cross-country cycling and gravel riding, so it comes in a narrow 27.2mm diameter and with relatively short stroke lengths at 60mm to 125mm. How to measure the seatpost diameter? The easiest and most accurate method is to use calipers (Vernier, or digital), as shown in picture 2. Measuring seatpost diameter using calipers. To help prevent mistakes when purchasing or changing seatposts, this article explains what kinds of seatpost diameters are most commonly used and how they are measured. Only diameter (width) is dealt with here. The length of the seatpost depends on frame geometry (design) and size – i.e. how much the saddle needs to be raised from the end of the seat tube. A separate article explains the maximum amount of seatpost extension from the frame (minimal insertion length). For seatpost height in terms of bicycle fitting, see: Setting up comfortable riding position.

There are a number of advantages to this, namely that the body of the post, which needs to cope with very heavy loads, doesn’t also have to be airtight and so lower-friction seals can be used for a lighter action.This post has a slightly more solid feel and smoother action, though. That’s due in part to less side-to-side shaft play, but also the stiffer and more positive-feeling forged-alloy, sealed-bearing ‘Blaster’ remote. there as well – like the Zipp Service Course SL. Aluminium road bike seatposts may not have the same level PNW’s Loam dropper post builds on an already extensive component range that offers good value across the board. Andy Lloyd / Immediate Media The Vario offers tool-free travel adjustment and an impressive remote (sold separately). Alex Evans

As with all aerodynamic upgrades in cycling, it is a culmination of marginal gains that will start to make noticeable differences to your riding. So, yes, seatposts can make a difference but, in most cases, aero seatposts will come in a proprietary design to fit a specific bike, making upgrade options considerably limited. Do carbon seatposts make a difference? Although the Ascend II is impressively cheap, it’s almost identical to Race Face Aeffect-R and Syncros post. If you’re after a bargain, then, look no further.

Whichever type of post you’re considering, you’ll need to decide on diameter, length, offset, clamp type, and construction material. Diameter is the most critical of these metrics, as it must be the right size to fit into your bike’s seat tube. The most common diameters are size 27.2, 30.9, and 31.6mm. Narrower diameter bike seatposts can help smooth your ride due to a minimal amount of flex, while wider ones are usually stiffer and thus enhance power transfer. If you do happen to have a seatpost that’s too small for your bike you can use a shim, but of course you can’t go the other way around. Mountain bikes typically have a lower standover height than road bikes, leaving more of the post exposed, so a wider post is preferred to improve strength. 31.6mm seatpost