Seatposts: Often Overlooked Yet Critical For Your Comfort (Lab Testing)

A good seatpost is the key to achieving a comfortable ride. That’s because along with your tyres, seatposts actually make up the bulk of your bike’s comfort – in fact, according to the data available, a well-designed carbon seatpost flexes at a rate 100x greater than a steel frame.

The Ergon CF3 carbon seatpost requires 69N of force to flex one vertical millimetre (0.04″). In comparison, a typical bike frame may require more than 7000N of force to flex one vertical millimetre, demonstrating how much a seatpost (and how little a frame) plays in the comfort equation.

In short, flex seatposts are a great way to achieve a super comfortable ride as they:
(a) Reduce high-frequency road vibrations, and;
(b) Take care of the bigger impacts (think rough dirt roads) thanks to their 20mm+ (0.89″) of vertical flex.

In this article, we will discuss the different seatpost types and materials, before looking at the difference between vibration damping and seatpost deflection. We’ll then check out some of the lab testing that’s been completed and will finish up with my seatpost recommendations.

Note: This article was originally published July 2015, but has been updated in May 2019.

Niner Seatposts

The Most Overlooked Bike Component

Very few people think about the ride quality of a seatpost, which is precisely why I think they’re the most overlooked bike component. They’re arguably even more important for bike travel as touring and bikepacking bikes are usually set up with higher handlebars, resulting in a larger proportion of our body weight on our saddles (normally 80%+). Couple that with our penchant for seeking rough roads, and seatposts really are the key to unlocking all-day comfort on your bike.

Bikes fitted with narrower tyres have the most comfort to gain from using a flex seatpost. This is because a larger proportion of the overall shock and impacts will need to be taken up by the seatpost. Bikes with wider tyres still have a lot to gain too, as flex posts help to take the edge off bigger impacts.

You can learn about the relationship between seatpost and tyre comfort by reading about the springs in a series HERE.

Trek’s IsoSpeed Decoupler allows the seat tube to flex independently of the top tube.

Over the last decade, bike manufacturers have been optimising their bikes around comfort, and the seat tube has been the main focus. Trek have developed what they call an ‘Isospeed Decoupler’ which is integrated into their seat tube, offering around 20mm of vertical compliance. Giant created a unique seatpost shape called D-Fuse which will flex around 12mm underneath you. And Cannondale has stuck with something a bit more traditional, using a smaller-than-usual seatpost diameter paired with a flat-section carbon layup to achieve a super comfortable ride.

The good news is that you don’t need to buy a fancy new bike to achieve a high degree of comfort. A handful of aftermarket seatposts can match the vertical flex and vibration damping of the Trek, Giant and Cannondale designs, allowing you to transform whatever you ride into something that rides ultra smooth.

The Different Types of Seatpost

Carbon, Aluminium and Titanium Seatposts
Seatposts are manufactured using three different construction materials. The majority are made from aluminium which is lightweight, reliable and very cheap to manufacture. Titanium seatposts are much less common and are typically paired with titanium frames for a nice aesthetic. Carbon seatposts are lighter and more expensive, but more importantly, they can be optimized using different layering techniques to achieve an unparalleled ride quality.

Suspension Seatposts
There is a handful of suspension seatpost manufacturers, but perhaps the most common is Cane Creek. The advantage of a suspension seatpost is that it will help absorb big hits and other impacts from the ground below, allowing you to pedal through bumps while also reducing the fatigue on your body. Suspension seatposts have been measured to be multiple times more effective than any rigid seatpost. The main disadvantage is the increase in weight.

Elastomer Seatposts
Specialized has been incorporating elastomers into their flex seatposts for over a decade so that they can achieve their desired ride characteristics. The latest-generation carbon elastomer post (pictured on the right) is said to offer 18mm of vertical flex, is reasonably lightweight and is also reliable as there are no moving parts.

Straight and Setback Seatposts
Seatposts are available in different offsets ranging from 0 degrees to 35 degrees. A setback post puts you further behind your crankset and a straight seatpost moves you closer. The amount of setback or offset is best determined through a basic bike fit at a participating bike shop. They will look at the relationship between your knee and pedal axle, as well as your hip angle/mobility and will determine how far you should sit behind your crankset. You can read more about bike geometry HERE and about getting a personalized bike fit HERE.

Seatpost Damping

Microbac Laboratories’ test jig for comparing the different characteristics of seatposts. Image: BikeRadar

Damping is the speed at which a seatpost will move over repeated bumps, and it’s the most important characteristic for cycling on smoother surfaces.

A seatpost that dampens vibrations effectively will insulate a rider from much of the road buzz coming up through their bike. Seatposts with the best damping characteristics have been tested to be more than twice as effective than those which perform poorly.

We currently have two damping lab tests to draw some conclusions from:

Seatpost Damping
Velo Magazine’s damping test results with 14 different 27.2mm seatposts.

Velo Magazine’s 2012 test results show that:
– Almost all carbon seatposts performed better than the aluminium or titanium options.
– Straight seatposts (carbon, titanium & aluminium) are worse at damping shock than setback seatposts.
– The Cane Creek suspension seatpost was surprisingly not as effective at mitigating road buzz as two carbon seatposts.

Microbac Laboratories collected data on many of the newer flex seatpost models. This test includes the Ergon CF3, Ritchey WCS Carbon Flexlogic, Canyon S13 VCLS, Specialized CG-R and Syntace P6 Hi-Flex. Image: BikeRadar

The Microbac Laboratories’ 2016 test results show that:
– The Ergon CF3 leaf-sprung seatpost absorbs 2-3x more shock than other flex carbon seatposts.
– The only aluminium seatpost in the test (Thomson) is simply no match in terms of damping.
– The Specialized post is somewhat underwhelming on the road considering its radical design.

There is a caveat here! This data only applies to bikes without luggage fitted. Why? Rear panniers and bikepacking seat packs are highly effective at mitigating vibrations, so you won’t notice a huge difference between a carbon or aluminium seatposts when travelling with luggage.

Seatpost Deflection

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 pedal through bumps on rougher terrain.

When testing seatpost deflection, two axes of measurement are usually taken – vertical and horizontal – but they almost always track proportionately. The Velo Magazine lab test data shows that under the specific force applied, some seatposts were able to deflect twice as much as others.

Seatpost Flex
Velo Magazine’s deflection test results with 27.2mm seatposts.

The results are a bit hard to read, so let me type that out:
1. Cane Creek Thudbuster ST (13.7mm, 19.3mm)
2. Ritchey Carbon Straight (5.8mm, 4.8mm)
3. Ritchey Carbon Setback (5.5mm, 5.0mm)
4. Cannondale Carbon (5.4mm, 4.3mm)
5. Zipp Straight Aluminium (4.9mm, 4.2mm)
6. Ritchey Setback Aluminium (4.8mm, 4.5mm)
7. Specialized FACT Carbon (4.8mm, 4.4mm)
8. FSA Straight Carbon (4.8mm, 4.2mm)
9. Thomson Straight Aluminium (4.8mm, 4.2mm)
10. FSA Setback Carbon (4.3mm, 4.2mm)
11. Moots Straight Ti (4.3mm, 4.2mm)
12. Moots Setback Ti (4.2mm, 4.0mm)
13. Zipp Setback Aluminium (3.9mm, 4.0mm)
14. Thomson Setback Aluminium (3.5mm, 3.6mm)

The conclusions we can draw from the Velo Magazine test:
– The best performing regular seatposts offer 50-60% more flex than the worst performing.
– Carbon is able to deflect more than both aluminium and titanium.
– Setback seatposts tend to be worse performing, making up places 10, 12, 13 and 14 in this test.
– In another league altogether is the Cane Creek Thudbuster suspension seatpost which offers 3-4x more flex than a regular seatpost. It’s also worth noting that this is under half of what it can flex (33mm).

The Microbac Laboratories deflection test using the minimum and maximum seatpost insertions at different rates of force.

The conclusions we can draw from the Microbac Laboratories test:
– There is a linear relationship between deflection and force (for a small range), helping us to predict flex at different force rates.
– Lighter riders are better suited to the Ergon/Canyon seatposts and heavier riders the Syntace/Ritchey.
– The minimum (high seatpost) and maximum insertions (low seatpost) affects the amount of deflection by 1.5-2x.
– The Ergon CF3 is the king again, outperforming all other seatposts at the maximum and minimum insertions.
– The Ritchey and Syntace seatposts rely on a high seat height to achieve their flex (2x greater flex).
– The Specialized CG-R was again quite underwhelming, flexing under half as much as the Ergon CF3 and Canyon S13 VCLS.

Do You Want More Damping or Deflection? Or Both?

If you’re looking for a firm ride on the road (less saddle movement), you’ll want to select a seatpost with a lower deflection but a higher damping ability. According to the Velo Magazine results, that’s something like the FSA K-Force, while the Microbac Lab results suggest the Ritchey WCS Flexlogic is the go. That said, this information is applicable mostly to road riding – you’ll find a bikepacking seat pack or rear panniers will dampen road vibrations appropriately with whichever seatpost you choose.

For dirt road use, deflection is king. Straight carbon seatposts offer the highest degree of vertical flex on big bumps, however, they tend to be a bit more jarring on the high-frequency small bumps. Suspension seatposts are simply on another level in all regards, with lots of deflection as well as excellent damping abilities.

Seatposts and Rider Weight & Height

Carbon seatposts are tuned with set spring rates.

For example, at 300lb force, the Ergon CF3 would theoretically flex its maximum amount of 20mm while the Specialized CG-R will only be halfway through its travel. Essentially, lighter riders will be far better suited to the Ergon or Canyon seatposts, while heavier riders should look towards the Ritchey, Syntace or Cannondale options.

Riders with less exposed seatpost will also benefit from the Ergon or Canyon seatposts. When these seatposts are deep in the frame, they are shown to flex twice as much as carbon posts from Ritchey, Specialized or Syntace at the same depth. But then again, less exposed seatpost on your bike significantly reduces the amount of flex, so a suspension seatpost is always the best option in this case (more on suspension posts below).

Tyre Width & Seatposts

best bikepacking bikes
There is little need to fit a flex seatpost to a fat bike because the tyres absorb the majority of the overall shock.

Tyres do an exceptional job of damping vibrations and absorbing bigger hits.

In the wider widths, tyre sidewalls will require much less force to deform than the best seatposts. If you’ve got tyres that are narrow (30mm to 50mm wide), you’ll benefit a lot from a seatpost with more flex like the Ergon CF3 or Canyon S13 VCLS. Between 2.0″ and 2.5″, flex posts are still really effective but you can usually get away with a little less flex if you like (eg. Cannondale SAVE or Ritchey WCS Flexlogic). The comfort effects start to diminish once you get into the plus-size tyre range (3.0″) or wider (4.0-5.0″) where the tyres are absorbing so much that aluminium posts work fine.

One cool thing about a flex seatpost (and matching Redshift Shockstop stem) is that it allows you to use narrower tyres without sacrificing any comfort. The benefit of this setup would be that you could reduce your rolling resistance and overall bike weight while still travelling in comfort.

Make sure to read my article about the springs in a series to understand whether a flex seatpost is useful on your fat tyre bike.

Carbon vs Suspension Seatposts

The Cane Creek eeSilk is a touch heavier than a carbon seatpost yet has five different spring rates available.

Ok, so both carbon and suspension seatposts are sounding pretty good here. But how would you go about choosing between the two?

There are two disadvantages to using a carbon post:
– There is only one spring rate available, and;
– The comfort is dependent on the amount of seatpost sticking out of your frame.

By having a set spring rate, a heavier rider will enjoy a more comfortable ride, while a lighter rider will feel more vibration and big hits. Carbon seatposts also perform much better with more exposed seatpost (2x more flex), which hands the better performance to taller riders.

A suspension seatpost is able to solve both of those issues. Most of the suspension options have four or five different spring rates, which allows both light (45kg/100lb) or heavy (150kg/330lb) cyclists to achieve the equivalent ride feel, no matter the seatpost height. With a suspension post, you can also tune the ride quality based on the surfaces you ride: a stiffer elastomer/spring for the road, or a softer one if you like rougher terrain. Most suspension seatposts have an adjustable pre-load too, which allows you to change the amount of force required to make the saddle start moving.

The main downside to choosing a suspension seatpost is the weight. Most of them tip the scales between 450-550 grams (1.0-1.2lb) which is more than twice the weight of most carbon seatposts available. That said, there is one truly lightweight suspension seatpost…

The Cane Creek eeSilk is perhaps the ultimate seatpost. At 295 grams, it’s barely heavier than many of the carbon offerings. With five different spring rates, riders of any weight can tune it to achieve the perfect ride quality. And it will work just as effectively whether set high or low in your frame. The price isn’t cheap – it’s around US $300, but then again, that’s the same price as a top-end carbon seatpost.

Flex: How Much Is Too Much?

There is certainly a point where you’ll find excessive seatpost flex, but that will depend on the terrain you ride, your body weight, your seatpost height and your personal preferences.

If you have a good amount of seatpost exposed, have an average body weight and want a flexible but firm ride, three suitable seatposts come to mind here: Cannondale SAVE, Ritchey WCS Flexlogic or Syntace Hi-Flex P6. These posts will still flex between 5-15mm on impact but are otherwise tuned to be reasonably firm.

For lighter or shorter riders, a seatpost with a lighter spring rate will yield similar amounts of deflection. That’s where the Ergon CF3 and Canyon S13 VCLS are great. These posts are also suitable for taller/heavier riders that prefer more flex rather than less.

On particularly bumpy surfaces it’s fatiguing on your body to cycle for long periods of time. That’s why I fit my Cane Creek suspension seatpost to my bikes when I know the terrain will be rough – the extra 10-20mm of deflection is sometimes a godsend.

My Seatpost Picks For Comfort

Flex Post w/ Wider Tyres: Cannondale SAVE (208g/7.3oz)
I’ve used a Cannondale post in my mountain bikes for years, and think it provides the perfect amount of flex across all types of terrain, from smooth roads through to bumpy gravel roads. I think it’s the pick particularly if you’re using 40mm or wider tyres. If you’re coming from an aluminium seatpost, it will completely transform your ride! The SAVE is somewhat firm compared to a suspension seatpost, but it really does a great job of taking the edge off everything. Highly recommended for $199 on Amazon.

Flex Post w/ Narrower Tyres: Ergon CF3 or Canyon S13 VCLS (both 220g/7.8oz)
If you’re using narrower tyres (eg. 700x30c to 700x40c), it’s worth picking up a seatpost with a bit more flex to make up for the fact your tyres don’t deform as much. The Ergon CF3 (US $299) is certainly the best performer here as it has 20mm of vertical flex and weighs just 220 grams. A ‘flip head’ kit is available for the Ergon post, giving you the option to increase or decrease the setback to suit your needs. The Canyon S13 VCLS performs almost as well and is substantially cheaper (US $170), so it had to make the list too.

Vibration Absorbing Post: FSA K-Force Light (210g/7.4oz)
For something that offers a firm ride but still does a great job at absorbing road buzz, you can’t go past the FSA K-Force seatpost. This is the perfect upgrade for a road bike without any bike luggage attached. You can find the K-Force Light for $199 on Amazon.

Suspension Post: Cane Creek Thudbuster ST (454g/1.0lb)
My Cane Creek seatpost performed flawlessly on my big bike ride from Europe to Australia! While 250 grams heavier than a carbon post, you can take advantage of more than twice the vertical travel, plus five different spring rate options so you can tune your ride from soft to firm. It works out lighter than all comparable suspension post options and is also great value at $143 on Amazon.

Carbon Seatpost Options

Cannondale SAVE – My overall pick, a great performer for both vibration damping and absorbing big hits – $199 on Amazon
Canyon S13 VCLS – 2nd best deflection results, good at max insertion, great for lighter riders – US $170
Canyon VCLS 2.0 – Best deflection/damping results, great at max insertion, well-suited to lighter riders – US $299
Ergon CF3 – The same post as the VCLS 2.0 as it’s a shared product between companies – US $299
FSA K-Force – The Velo Magazine best-tested seatpost for vibration damping, great for road riding – $199 on Amazon
Ritchey WCS Carbon Flexlogic – Decent deflection results, great at damping vibrations, lightweight – $199 on Amazon
Specialized CG-R – The Specialized CG-R may be the go for heavier riders with its heavy spring rate – US $199
Syntace P6 Carbon Hi-Flex – 3rd best deflection results, but doesn’t perform well at max insertion – $198 on Amazon

Suspension Seatpost Options

Cane Creek eeSilk – 20mm of suspension travel, five spring rates, 295g – $310 on Amazon
Cane Creek Thudbuster ST – 33mm of suspension travel, five spring rates, 454g – $143 on Amazon
Cane Creek Thudbuster LT – 67mm of suspension travel, five spring rates, 540g – $127 on Amazon
Kinekt 2.1 Aluminium – 35mm of suspension travel, four spring rates, pre-load adjustment, 525g – $249 on Amazon
Kinekt 3.1 Carbon – 35mm of suspension travel, four spring rates, pre-load adjustment, 471g – $329 on Amazon
Suntour NCX – 50mm of suspension travel, two spring rates, pre-load adjustment, 765g – $114 on Amazon
Redshift ShockStop – 35mm of suspension travel, eight spring rates, pre-load adjustment, 497g – US $199

  1. Thanks Alee, I have a NCX, but I used for only 3 weeks, I still don’t travel with it, and I never had a suspension seatpost before.
    Thanks again and please continue writing articles like this, they are very good to learn about cycle touring.

  2. I have been using USE suspension seatposts since the early 90s.They are fully servicable and the damping can be adjusted depending on which elastomers are used.I am using a USE Shokpost Vibe on my current world tour, and wouldn’t use anything else.Price wise they are comparable with the Thudbuster.Check them out at http://www.use1.com

  3. What about suspended saddles? I’m not talking about the classic leather saddle with springs, but more modern ones like the Selle Royal Wave.

  4. I just did my first ride with the Thudbuster ST, a 27 out-back mostly on chipped rock gravel. I’m older and been riding ~2 years; 10 miles is too short a ride and my first 32 miler trashed me. I’ve enhanced my 29er’s feel via a Serfas Rx saddle (substantial but not overly padded, and completely split down the middle, offering a bit of cush) and with a pair of Schwalbe Marathon Mondial touring tires which I can run at 45/50 front/rear psi (instead of the 65psi my OE WTB Nano Comps ran at); the Mondial’s are both cushier and roll noticeably easier. The ST’s result is unexpectedly profound: today, the day after, I’m not sore. Anywhere, anyhow. The ST just sucks up all the abuse formerly absorbed by my spine, musculature, viscera. Quite possibly the best, most important enhancement I’ve made.

  5. I’m considering putting either a syntace p6 or a fsa k light force on a trek superfly fs. I’m guessing that the proper seatpost will help with that part of riding trails that the suspension doesn’t kick in for as well, such as rapid little chatter. The bigger hits are what the suspension is for. So which of these two do you think would do a better job for what I’ve discribed?

  6. Vadim, because my routes are not very bumpy. I ride on paved surfaces and inter-town dirt/pebble trails. No mountain riding, no single track, no washboards, stumps, rocks, slopes. For this lightweight use it seemed that short travel would be enough, which I could only surmise from what’d I’d read and seen, having zero prior experience with this design (my old seat post was a cheap inner-spring design that cannot respond accurately to road input as the Thudbusters can). The other reason is that I need the seat post space for my seabag and fender to attach. For me any ride, esp those that take me 10-15 miles from home or car-base, are ‘tours;’ I want the things one would use for various circumstances and https://uploads.disquscdn.com/images/37a16bd3cad01fa9f5e9db8428be572fa638fdd248d452b679c2db1c5abed3d4.jpg conditions on board at all times.

  7. A prudent choice! Be advised that when energetically engaged it has the potential to slightly launch you off the saddle. It does a more focused job than rear suspensions so 🙂

  8. I would like to add a seatpost that is both suspension and setback for a small Haibike Hardlife that I can barely stand over. Does this exist?
    First, suspension because even though I’m on just pebbly trails, I feel every bump. (BTW, I’m an older, but enthusiastic rider, and I’m small (102 lbs.), but I’m strong and athletic.)
    Secondly, I barely fit the standover height, so that crossbar can really cause me some pain if I don’t stop carefully and slide my rear close to the seat. I’ve pushed the seat back as far as it will go.
    So I see there are setback seatposts, and I see there are suspension seatposts, but I can’t quite visualize one that does both. Thanks in advance if anyone has a suggestion.

  9. Hi Becky. All suspension seatposts have a significant setback (more so than a regular one). You should be fine with any of them.

  10. I have both models. St for road and trails. Lt for roughstuff. I prefer fizik arione saddles for on and offroad. Both work well. However you need a smooth pedalling action,as on an a full suspension bike,otherwise you will bob up n down like a yo-yo! Very effective for the high weight penalty. Have been using both for over ten years. The elastomers have shrunk slightly and feel a little harder. But replacements are reasonably priced. I can recommend them both for value and performance. I am 5’4″ about 64kg. So all my frames are short and stiff. The thudbuster really helps my back from excess jarring on our potholed British roads!

  11. You said titanium seat posts were only used on titanium frames (wrong) and didn’t mention them again. I love my titanium seat posts, they’re light, strong and flex, making them very comfortable.If you had included Ti in your tests you would see that titanium is better than all of the other seat posts you mention but you provide no data on them because you believe they don’t look good..

  12. You drew a lot of conclusions there! Generally, you’ll see titanium posts in conjunction with titanium frames… not because they aren’t comfortable or light or strong.

    There are two titanium posts in the test. They came (out of 14 seatposts):
    – 9th and 12th in the damping test
    – 10th and 12th in horizontal deflection
    – 11th and 12th in vertical deflection

  13. I noticed you use a Thomson elite on you surly LHT but I don’t see it listed here… would you recommend this for touring or does it not compare with the ones you have listed?

Comments are closed.

Related Posts