Why fit a Suspension Seatpost?

• You can’t afford a full-suspension bike, but want the comfort of suspension;
•  You have a perfectly serviceable hard-tail and can’t justify the cost of adding a full-sus rig to your stable, or the second-hand value of your hard-tail would barely cover the deposit on a full-sus bike to replace it.
• ·You prefer the light weight and simplicity of a hard-tail, less to maintain and less to go wrong.
• You prefer the performance offered by a hard-tail, especially for racing; instead of absorbing power in compressing the rear suspension, a hard-tail transfers the power more efficiently, especially when standing on the pedals to accelerate or climb.

Suspension Upgrades

Front suspension helps to keep control on rough downhills and helps build confidence, this enables anyone to go faster down hill and tackle drops that they would never dare to attempt on rigid forks.

The problem is that the faster you are going the harder the tail hits you in the butt, unless you are out of the saddle. Sometimes you want to remain seated and peddling, or can’t avoid coming down on your saddle, this is when a suspension seatpost comes into its own.

This would be even more important on an aluminium hard-tail, because larger diameter aluminium tubes are stiffer and give an even more unforgiving ride than steel [or titanium] frames which tend to flex more.

So are suspension seatposts any better in practice?

An article in MMB stated that “They are different from having rear suspension, because they are suspending you and not you and the bike. So they work well for making you more comfortable, rather than making you go faster or stick to the ground better.”

This is the crux of the issue: suspension seatposts do not help to keep the rear wheel in contact with the ground over rough terrain.

Where this is achieved, such as on Paul Lazenby’s cross-country winning Marin, the extra traction of full suspension can compensate for the power-absorption resulting from compressing the rear suspension.

Alternatively, some full-suspension rigs have lock-out to prevent ‘bobbing’ when climbing out of the saddle to get the power down.

Advantages

There is no doubt that the suspension seatpost does make the ride over rough surfaces, particularly rocky tracks, more comfortable.

On fast rocky down-hills riders usually stand up, so a suspension seat-post doesn’t give much benefit – except when you land hard on the saddle.

Where seat-posts also help you to go faster is where you want to stay seated and keep pedalling, but the discomfort caused by repeated hits slows you down.

The best example of this in the area where I do most of my riding is a level rocky track known locally as Pro-Flex Alley, where a suspension-post makes it easier to remain seated and pedalling. It also makes long, or even all day rides more comfortable and consequently less tiring.

Drawbacks

There are some drawbacks: the main one is that, like any other suspension, there is an initial amount of ‘sag’ that has to be taken up. This is the amount that the suspension compresses just as a result of sitting on it, before it has to absorb any shocks.

The problem is that, to keep the saddle-to-peddle distance the same when sitting on the saddle, the seat has to be set slightly higher than normal when not sitting on it. This makes it a little more difficult to get back over the saddle when you need to get your weight back over the rear wheel, especially if you haven’t had time to lower your saddle before a steep descent…

On the USE seatpost the saddle clamp is a little bit fiddly to fit. It works perfectly well, once it is fitted, but looks a bit Heath Robinson compared to some other neat seat-clamps.

Ideally, a seatpost should fit the frame seat-tube exactly, without the need for any shims. Some seatposts are available in a variety of diameters and there may be one to fit your frame, but many of them, including the highest-rated USE XCR only come in one or a limited range of sizes and need shims to fit other sized seat-tubes.

In practice the shims for the USE are long enough to give good support over sufficient length and grip well, so there is no problem with them.
More of a problem was finding shims to fit a seatpost mounted RaceGuard [thanks to Cheltenham Cycles for helping out with this one] and reflector!