Road seatposts

How to choose a road bike seatpost

Three measurements determine what you need, and none should be guessed: diameter, length and setback. The first two depend on the frame; the third depends on your riding position.

The diameter

27.2 mm is common on road frames, including recent ones, because its slim profile provides a little vertical flex. You can also find 30,9 and 31.6 mm, and more and more frames require a proprietary-shaped seatpost, which can only be replaced with the manufacturer’s part. Measure your current post or read the size engraved on it: an error of half a millimetre makes installation impossible or unsafe. A shim lets you fit a narrower post in a wider tube, never the other way around.

Setback

• Zero setback (inline) : the saddle sits in line with the seatpost. For frames with a slack seat tube angle, triathletes and riders who want to move their saddle forward.
• 20 to 25 mm of setback : the standard option, moving the saddle back and opening up the hip angle.
• Setback works together with the fore-aft adjustment on the rails : together, these give you around 5 cm of adjustment. If your saddle is at the front or rear limit, change the seatpost rather than forcing the adjustment.

Carbon or aluminium?

• Thealuminium is robust, forgiving when clamped and inexpensive. At 27.2 mm, it already absorbs vibrations reasonably well.
• The carbon saves 60 to 100 g and absorbs more vibration. It does, however, require specified tightening torque and the assembly paste : an overtightened clamp crushes the tube.
• In both cases, observe the minimum insertion mark engraved on the post.

One bolt or two?

The two-bolt clamp (Two-Bolt) allows fine, continuous tilt adjustment without preset steps. The one-bolt clamp (One-Bolt) is lighter and quicker to adjust, at the cost of a little precision. Above all, check that the clamp fits the cross-section of your saddle rails : 7 mm round for most metal rails, or 7x9 or 7x10 mm oval for carbon rails.

Suspension and dropper seatposts

This category also includes two distinct options. A suspension seatpost such as the Cane Creek eeSilk offers 20 to 35 mm of travel and transforms comfort on rough roads or gravel, for around 50 g of extra weight. A dropper post (dropper post) lowers the saddle on the move: rare on the road, but useful for more demanding gravel riding.

To find out more: How to choose a road bike seatpost

See also: Road bike saddles · Seatpost clamps and saddle clamps · Road bike handlebars