Bicycle frames are stiff truss structures with little vertical compliance. As we've seen in my
recent video about frame comfort, the majority of the vertical deflection at the back of the bike
is actually found at the rear tyre, seatpost and saddle. Today, we'll be diving into the world of
seatposts, and more specifically, suspension seatposts. Given that cyclists often have 60
to 70% of their body weight on their saddle, I don't know if there is any other component that
offers as much of an improvement in ride comfort - that's assuming you've already optimized your
tyre width and pressure. The best bit is that a suspension seatpost upgrade is as little as $100,
and it's very easy to install yourself. Here are my six reasons to use a suspension seatpost.
#1 You can improve your comfort. A suspension seatpost both absorbs bigger hits. as well as
damping vibrations coming up from the road. The less strain your body experiences when you ride,
the fresher you'll feel at the end of the day. #2 You can stay seated for longer. Suspension
seatposts allow you to pedal while seated on terrain that normally requires standing up.
Compared to a rigid post on the same bumpy climb, I find that my legs often feel fresher
with the suspension seatpost simply because I'm standing up less. #3 You can reduce or alleviate
lower back pain. It's not uncommon to hear people with back injuries say they couldn't ride a bike
without a suspension seatpost. By isolating vibrations and bigger hits from your body,
you will put less strain on your lower back when you ride. #4 They make narrow tyre bikes much more
capable. A suspension seatpost allows you to take bikes with narrower tyres on rougher terrain than
you normally could. Obviously, this isn't an ideal situation, but you'd be surprised how off-road
you can go on 38mm tires. #5 The performance is not height or weight dependent. The comfort of a
regular seatpost is dependent on your body weight, as well as the amount of exposed seatpost sticking
out of your frame. As smaller riders often have less body weight and less exposed seatpost,
they have the most to gain with a suspension seatpost upgrade. #6 They are lighter,
cheaper and more simple than a full suspension bike. Rather than using a full-suspension bike,
you can fit a suspension seatpost to a hardtail and enjoy similar levels of comfort, without the
extra weight, price and complexity. Here are four reasons NOT to use a suspension seatpost. #1 The
weight. You can expect a 100 to 500-gram weight penalty over a conventional aluminium seatpost. #2
The suspension bob. When you pedal, your body movements create forces that can activate the
suspension. This bob will occur to varying degrees depending on the seatpost model and setup. #3
You have a full-suspension bike. If your bike has rear suspension, your saddle is already suspended,
so you do not need a suspension seatpost. #4 You have a fat bike. If you're riding a bike
with four to five-inch wide tires those tires are likely deflecting 30 to 60mm over bumps,
which means that the benefits of a suspension seatpost are significantly reduced. With the pros
and cons out of the way, let's closely examine the role of suspension seatposts. There are two
things they're looking to achieve: a larger amount of vertical deflection (which takes the edge off
bigger hits), and a higher level of damping (which increases vibration absorption). 'Deflection' is
the total movement that a seatpost will move after an impact. A seatpost with more deflection will
reduce the fatigue on your body, as it protects you from harder jolts like unexpected potholes
or dirt road corrugations. It'll also allow you to keep pedalling through particularly bumpy terrain.
'Damping' is the speed at which the seatpost will move over repeated bumps. A seatpost that dampens
vibrations effectively will help to insulate you from road buzz coming up through your bike.
High exposure to vibrations can actually increase the risk of various injuries. including lower
back pain and spinal degeneration. This is why vibration exposure is often regulated in
industries that require driving or operating heavy machinery. When we measure seatpost vibrations in
a laboratory setting, we find that some seatposts can absorb 15x more vibration than others.
For example. the Thomson Elite seatpost was tested by Microbac Laboratories to absorb just .025 gs of
vibrations while the Ergon CF3 was absorbing 0.375 gs. But interestingly, data recently collected by
the University of Exeter suggests that once a seatpost is installed on your bike, it may not
reduce vibration exposure. That said, this test was conducted using rigid carbon and aluminium
seatposts, so it'd be interesting to find out whether suspension seatposts are more effective
using the same test protocol. Let's now take a closer look at the different damping systems
of suspension seatposts. First, we have spring damping. The best way I can describe these
seatposts is that they're very springy! This makes them exceptional on off-road
terrain as they're super-responsive to bumps. But there is a cost to this high reactivity:
I've found that when spring posts are perfectly set up for rough terrain, they bob more than I'd
like on smooth surfaces. The easiest way to reduce this movement is to adjust the spring
preload (or the amount of force required to cause the saddle to start moving). This will stop the
saddle bob, but will also reduce the seatpost's ability to take the edge off small bumps.
If smooth roads are your thing, you'll likely find spring seatposts a bit too active. This brings me
to elastomers. Elastomers are the quiet achievers, as they're much less noticeable underneath
you. This is the result of elastomers having an inherently slower rebound speed after an impact,
which is particularly beneficial while riding on fast bumpy surfaces like gravel roads. I tend to
prefer the more muted feel of an elastomer post it feels more 'natural', for lack of a better word.
The downside to elastomers is that they can firm up in cold conditions, rendering them
less effective, so skip this design if you need it to work well in sub-zero conditions. I've also
found they require lubrication around the edges of the elastomer, although this maintenance is
essentially solved with a simple seatpost cover. Lastly, we have air damping, which is sometimes
used in telescopic seatposts. The main advantage is that you can adjust the spring rate to a higher
degree of accuracy. Now, let's look at the two different suspension seatpost designs.
Linkage-driven suspension seatposts move in the same direction as the forces coming up from the
rear wheel. This allows them to very effectively counteract, and even neutralize bumps, reducing
the impact forces travelling through your back and bum. In addition, linkage posts ensure that
the saddle-to-pedal distance is mostly maintained. When the seatpost is compressed, a telescopic post
is usually considered inferior, as the angle it compresses is different to the direction of force
coming from the rear wheel, resulting in a less reactive seatpost system. Telescopic posts also
end up with a shorter saddle-to-pedal distance when you are riding over bumps. Despite their
flaws, telescopic posts are still very common, as they're often lighter cheaper, more subtle, and
have a lower installation height. Let's move on to the data. To see how these different seatpost
designs compare, Krzysztof over at GravelBikes.cc has been using his smartphone with a vibration
meter app to compare the vibration absorption of different bike components, on both a rough trail
and a fast gravel road. On the rough trail, the spring seatposts are, by a large margin, the most
effective at mitigating vibrations. Meanwhile, the elastomer Cane Creek eeSilk offers around half as
much vibration improvement. However, it's worth noting that this seatpost only has around half the
suspension travel. It'd be interesting to see how a longer travel elastomer seatpost compares here.
And finally, the air seatpost improved things a bit, but clearly requires a higher bump force
to activate. The gravel road with fast repetitive bumps narrows the difference between an elastomer
seatpost and a spring seatpost - despite the variation in suspension travel. This is
because the bump force is lower on gravel roads, which means that the spring post is likely only
using half its travel anyway. The air seatpost showed little difference from the typical carbon
seat post in this test. Suspension seatposts are available with anything from 20 to 90mm of travel,
so how do you choose the best travel for you? Rougher roads warrant more suspension travel.
As we just saw in the test, if you're riding on rougher terrain with larger forces coming
from the rear wheel, you will benefit from more suspension travel as it can dampen
more vibrations. I'd say most rough roads can be comfortably cycled with just 35mm of travel,
but 50mm or more may be required if you're hitting bumps at higher speeds. More upright
riding positions are also better suited to longer suspension travel. This is simply due
to the higher percentage of weight on your saddle. Conversely, if you have more weight on your hands
because you ride in a more sporty position - you can get away with less suspension travel. Finally,
let's now take a look at the best suspension seatpost products. The Kinekt 2.1 and 3.1 are
among the most active seatposts on this list, offering 35mm of travel. There are five spring
rates to choose from, suiting riders right up to 145 kilograms. The carbon model is the lightest
coil-sprung seatpost money can buy at 471 grams. These seat posts are particularly active in their
initial part of their travel, so they tend to be better suited on rougher trails rather than
smoother roads, in my experience. That said, you can quickly firm things up without using any tools
via the preload control knob, which is an optional extra for $16. The Redshift Shockstop is the best
coil-sprung post I've tested, as it seems to do a great job of absorbing off-road bumps without
bobbing too much on the smoother roads. However, it still isn't perfect. When I got the preload
right for off-road terrain, I found there was more bob than I'd like on the road. Unfortunately,
the preload bolt is not particularly accessible as it's at the bottom of the seatpost, so it's not an
adjustment that you'd want to make too regularly. The Shockstop weighs 547 grams and can be used by
riders up to 110 kilograms. The By.Schulz G.2 is a very highly-rated seatpost. There is a
short-travel version with 30mm and a long-travel version with 50mm of suspension. You can choose
from five different spring rates, which will suit riders all the way up to 150 kilograms. There are
10 different diameters too, making them suitable for almost every bike. The downside to this
seatpost is that there is no preload adjuster, so you might find it feeling springy sometimes,
and it's heavier than most at 700 grams or so. The low-cost suspension post of choice
is the Suntour NCX. At under a hundred dollars, it's a complete bargain, but there are downsides:
it's pretty heavy (around 800 grams) and it comes with only one spring rate out of the box
(although softer and firmer springs are only $15). The maximum rider weight is 120 kilograms. I've
spent years on the previous version of the Cane Creek Thudbuster. With its slower rebound speed,
I think it's a great option if you ride a larger percentage on smoother surfaces. The 50mm of
travel is ample for off-road use too. There are four spring rates to choose from, suiting riders
right up to 150 kilograms. If you ride a mix of gravel and tarmac roads I don't know if you can do
any better than the Cane Creek eeSilk. At half the weight and half the travel of most squishy posts,
it performs closer to the best carbon seatposts available. But the key difference to a carbon
post is that the spring rate isn't determined by how much exposed seat post you have, allowing you
to perfectly tune it to your body weight using the five different elastomers available. Regular
dropper posts have very little vertical flex, which is an unfortunate consequence of their
telescoping design. If you love dropper posts, but also want to maximize your ride comfort - there
are two suspension options available (and a third in the works). The best performing model is the
Byschulz D.2. It costs a small fortune, but this coil-sprung option will stay incredibly active on
bumpy roads. Like the regular Byschulz post, there are multiple spring rates to choose from and 30mm
of travel. The other dropper option is the PNW Coast, which has 40mm of suspension, and is the
best-value dropper by far. This air spring system has been tested by gravel bikes to be much less
active than the other suspension seatposts, but it'll still take the edge off those bigger hits,
and performs well on gravel roads too. In summary, a suspension seat post is a great comfort upgrade
as it will both absorb bigger hits as well as dampen vibrations coming up from the road. This
essentially means you'll feel fresher at the end of a long ride. For anything slow and off-road,
you cannot beat a spring-damped seatpost. These posts are incredibly active underneath you, and
will allow you to stay seated on rough surfaces for much longer. If you ride a decent percentage
on smoother surfaces or are sensitive to suspension bob, you'll prefer elastomer seatposts,
as they're less noticeable underneath you. The Cane Creek eeSilk is what I personally use and
recommend. It's great for if you have a sporty ride position like me, or if you mostly ride on
smoother roads. Given it only has 20mm of travel, you will have to compromise on the rougher roads,
but I still find it offers a significant comfort improvement over a regular post. Plus it doesn't
bounce, it's light and it's elegant. If this video has inspired you to pick up a suspension seatpost,
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