For most bikers, the seatpost only fulfils the purpose of holding the saddle securely and permanently in position. However, much more can be gained from the rigid tubes. Clever designs and the targeted use of materials provide damping comfort where hardtail riders previously had to endure the whims of the ground unfiltered. The early approaches to this had more disadvantages than advantages - nervously bobbing suspension mounts with complex parallelogram designs tended to make bikers seasick. Modern comfort seatposts take a more subtle approach and limit themselves to absorbing vibrations and minor bumps that occur on forest roads or gravel tracks as effectively as possible. On hardtails in particular, good comfort supports can be a benefit for many riders - especially on long tours and marathons.
The development of the comfort seatpost has benefited from increasingly advanced manufacturing techniques, especially when it comes to carbon fibre. It is therefore hardly surprising that six out of seven seatposts in our test are made from the black gold. Canyon goes even further with its S25 VCLS and builds the post in two parts - like two parallel leaf springs. It promptly took the top spot in the comfort rankings. No other model offers such a clear increase in comfort thanks to the damping of tiring vibrations, but the others also perform remarkably well. Titanium as a metallic material is also represented in our test in the form of the USE Sumo, with equally high comfort values.
However, as with all load-bearing components, stability and safety are of paramount importance, and it is precisely here that there is potential for optimisation. We therefore tested the seven seatposts, which the manufacturer claims have comfort-optimised flex behaviour, not only for their increased comfort in the laboratory and in practice, but also for their durability. With some surprising results.
These comfort seatposts for mountain bikes are tested:
- Cannondale Save2
- Canyon S25 VCLS
- Easton EC90 Zero
- Ritchey WCS Carbon Link Flexlogic
- Schmolke SL
- Syntace P6 Hiflex (BIKE tip: test winner)
- USE Sumo Titanium
This is how we tested
Practical test The practical impressions were gathered over several months by various testers. Each seatpost was always mounted and ridden on an identical hardtail. In addition to the riding impression, the experiences regarding the assembly effort and handling of the seatpost were also noted. Despite the subjective component of the practical test and the wide spread of the tester pool from 70 to 90 kilos, the statements on comfort are very homogeneous. There were no safety-related anomalies or even failures.
Laboratory test The tests on the fatigue behaviour of the supports and their flex behaviour were carried out at the Zedler testing institute (www.zedler.de) in Ludwigsburg. Each support first had to fulfil the requirements of the ISO 4210 standard. This is 100,000 load changes of 1200 N behind the centre of the saddle clamp. The test samples then underwent a practical test collective specially developed by Zedler-Institut, which applies higher forces of up to 1700 N as well as individual loads to the saddle nose. The loads are intended to simulate several years of use of the seat post in intensive touring use by a rider weighing 90 kg. A realistic extension length of 27 cm was selected. The test run was completed when the sensor system detected an event indicating a defect (from cracking to breakage) and switched off automatically.
If the results of the fatigue test of the two test samples were unobjectionable and conclusive at a constant level, or if both samples passed the test without any abnormalities, the two tests were retained. If there were any abnormalities, a significant value dispersion or critical failure behaviour, a third test sample was tested.
"Failure cases of seat posts are almost a daily occurrence in our expertise practice. There are basically three damage mechanisms. The most common is failure of the bolted connection. The movements of the saddle sometimes lead to improper loading. In this case, the reserve is small and even a slightly too low torque can lead to failure. Breaks at the exit of the post from the frame are less common. The main causes here are insufficient compressive strength of carbon tubes and unfavourable clamping mechanisms on the frame. The clamps on the frame are often tightened too tightly. The rarest fractures are in the centre of the tube or at the head. In the fatigue strength test, the torques were adhered to and the seat posts were not clamped unfavourably or too tightly. The test criteria are above the ISO standard, as its minimum requirements do not cover hard sporting use. BIKE's real-world data collection has shown that a rider can be pressed into the saddle with up to four times the acceleration due to gravity when riding into a compression. Depending on the position, a rider weighing 80 kilos can put a good 50 kilos on the saddle, which corresponds to a short-term load of up to 2000 newtons. With our test loads, we stayed well below that." (Dipl-Ing. Dirk Zedler, expert)
The test assessment of the comfort seatposts
The evaluation takes into account several factors - durability, handling, weight and flex behaviour - and is always based on the test sample with the worst result.
As a load-bearing and safety-relevant component, the Durability has the greatest weighting. This aspect therefore accounts for 50% of the overall assessment. However, it is split into the load cycles up to failure and the fracture pattern. The load cycles are therefore included in the test judgement with 25 % and the fracture pattern with 25 %. If a support has passed the ISO 4210 standard, it automatically receives half the score. The full score is awarded if it passes the entire fatigue test without any anomalies.
The Flex behaviour corresponds to the practical comfort gain and is rated at 30 %. The judgement is made up of the deflection values in the laboratory measurements and the collected practical impressions of the test drivers.
At the Handlingwhich is weighted at 10 %, the handling of the seat post during assembly and adjustment is taken into account just as much as the adjustment range of the saddle on the seat post. For example, some posts only allow a very narrow adjustment of the saddle forwards and backwards due to the wide clamping, while others allow much more. Any abnormalities during riding are also taken into account here.
The Weight is also rated at 10 %. The categorisation is based on the standard weights of other comparable seatposts today.
Static deflection with 270 mm extension and 100 kg
The comfort posts made of carbon and titanium (USE) flex significantly more than the two aluminium reference models from Thomson and Syntace. Canyon is the most comfortable, Cannondale the most unyielding. In practice, the dynamic flex behaviour is decisive. The USE and Syntace are noticeably more comfortable than Easton, Schmolke and Ritchey.
Weight and length
The design makes all the difference: a kink in the Cannondale SAVE2 post creates a fairly large offset, but also has a stiffening effect. Although it is by far the longest post, it flexes the least. But just being light doesn't bring any noticeable comfort. USE, Syntace and above all Canyon show that the intelligent use of materials can lead to the desired result.
Static deflection with variable extension and 100 kg
The deflection depends on the extension length. The Syntace P6 Hiflex Carbon yields 8.17 mm at the maximum extension length (310 mm). The shorter the extension length (here: reduction in 2 cm increments to 190 mm), the less flex. Even with the thin post, comfort is only felt by those who can pull it out far enough.
Comparison of diameter - static deflection with 270 mm extension and 100 kg
The diameter determines the flexibility. The comfort measurements with the Syntace P6 Hiflex Carbon in various diameters show the non-linear relationship between diameter and deflection: Compared to the thin 27.2 mm post, the deflection of the thick 34.9 mm version decreases disproportionately.
Durability - a complex issue
But how do the individual supports fare in the durability test? We know from past fatigue tests: Just because one test sample lasts, doesn't mean the next one will. And if something does break, it is better to have an early failure that is recognisable than a late but sudden collapse. Read the statements of some manufacturers on the next page.
Statements from the seat post manufacturers
Canyon
"We take the safety of our components very seriously and are certainly one of the pioneers in the industry when it comes to component testing with our specially developed component test benches and load profiles. We have been constantly optimising these in cooperation with universities and colleges for years. Especially at the interfaces, such as saddle clamps, the non-standardised clamping and connection conditions of the test stand have a major influence. This crack characteristic shown here is not known to us from reality, although many thousands of supports have been used in the field for years. It should also be noted that this type of crack does not lead to total failure of the prop and our customer is not at risk at any time. If this type of crack were to occur several times in our service department, we would of course initiate changes immediately." (Dr Michael Kaiser)
Schmolke Carbon
"Our seatposts are designed in such a way that the bolt slowly presses further and further into the carbon under heavy overloads, as happened in the two test samples with the silver bolt. This allows the rider to feel the saddle slowly loosening before a fall can occur. In reality, however, our SL seatposts broke exactly 0 times. Unfortunately, such failures are more likely to occur in test bench trials, where the component has to go through its entire, otherwise multi-year life in a very short time and therefore 100% realistic fracture patterns can never be achieved. (This is also shown by the unrealistically frequent breakage of stem bolts in our handlebar tests). Nevertheless, in future we will dispense with the slight milling, as with the broken black bolts, and only use bolts like the two non-broken silver ones. (For heavy riders who also put extreme loads on their bike due to their riding style, we will reinforce the carbon tube again over its entire length, as we customise our components on request). The loads of up to 170 kg in the 2nd test simulate heavy loads on the saddle and the bike. However, our extremely light seatposts do not have to withstand this several hundred times. In return, we offer very accommodating crash replacements even beyond the 3-year warranty period." (Stefan Schmolke, owner of Schmolke Carbon)
Bacebasics/Idworx
"We have been using the USE Sumo titanium seatpost in many of our Idworx bikes for several years and USE has been producing seatposts with this head for around ten years. Hand on heart, we have never seen this type of damage in practice. This does not necessarily mean that the loads in the test are unrealistically high. Either it is an extremely rare material defect, or it means that the load spectrum that led to the breakage in this one specimen contains forces that are at the upper limit of what can be achieved in practice by very heavy riders. With a rider weight limit of 100 kg, we still consider the support to be safe due to our large experience base, but will commission further tests in consultation with USE to find out whether the support may need to be reinforced for this maximum rider weight." (Gerrit Gaastra)
Cannondale
"We were informed of the test results by Bike Magazine and are now analysing them carefully. The Cannondale brand has the highest quality standards and subjects its products to brutal tests during development. Our seatpost has passed all these tests and we have no reason to doubt the reliability of our product. We have carried out laboratory and field tests. We will now compare Bike's results with ours and also contact the test lab to analyse the exact testing procedure. This will take some time. In the meantime, we are 100% sure that our products work reliably." (Henning Schroeder, Vice President Product Management Cannondale)
Profile of the seatposts from this test:
Cannondale Save2
The SAVE2 seatpost is specified ex works on the Cannondale top bikes and is only available in 27.2 mm diameter. Its geometry is designed for the F-Si hardtails. Not only does it have a fairly large offset, it is also by far the longest post. It allows the saddle to sit up to 33.5 cm above the seat tube. However, due to the very shallow angle of the clamping head, the front of the two titanium bolts is difficult to access. This makes assembly and tilt adjustment a little time-consuming. Contrary to expectations, the SAVE2 proved to be a rather stiff "comfort support" and only fulfils the flex requirement at high extension. The high permissible rider weight is remarkable. Two of the three test samples broke at the front threaded bolt in the laboratory, albeit late.
Price/Info Original equipment only/www.cannondale.com
Length/offset 430 mm/20 mm
Diameter/weight Only 27.2 mm/221g
max. rider weight 138 kg
Assembly/handling 3 OUT OF 6 POINTS
Flex behaviour (laboratory and practice) 2 OUT OF 6 POINTS
Durability (Iso 4210 and Zedler) 4 OUT OF 6 POINTS
Failure behaviour 1 x no failure/2 x critical
BIKE judgement* SATISFACTORY
Canyon S25 VCLS- Easton EC90 Zero
The two-piece "leaf spring support" has been available for road bikes for several years, and from 2015 also for mountain bikes. No other suspension system was as comfortable in the laboratory and in practice. With its well-defined flex, it not only offers maximum vibration damping, but also functions almost as a micro-suspension. A small criticism in terms of handling: you have to dismantle the head to mount the saddle and remove the seatpost from the frame to adjust the angle. During the stability test in the laboratory, it developed a hairline crack quite early and always at the same point on the clamping jaws, but this is largely unproblematic in terms of safety and easy to recognise. Therefore very good-natured fatigue behaviour. After replacing the clamp, one support ran through the test without any problems. Just short of an even better judgement.
Price/Info 249,95 Euro/www.canyon.com
Length/offset 400 mm/+2 or -10 mm
Diameter/weight Only 30.9 mm/249 g
max. rider weight 110 kg
Assembly/handling 4 OUT OF 6 POINTS
Flex behaviour (laboratory and practice) 6 OUT OF 6 POINTS
Durability (Iso 4210 and Zedler) 3 OUT OF 6 POINTS
Failure behaviour 3 x uncritical
BIKE judgement* GOOD
Easton EC90 Zero
The Easton was actually intended to accompany the test as a carbon seatpost not designed for comfort. However, both the laboratory measurements and the practical test attest to its good comfort values - at least in the 27.2 mm diameter as tested. The bolts are easily accessible by tilting them, even if they are deeply recessed in the massive monocoque carbon head. With the short clamping jaws, the adjustment range of the saddle to the front and rear remains very large, and the rounded edges of the supports prevent force peaks and notch effects on sensitive carbon frames. Easton has always prided itself on its high stability, and the test samples also passed the entire test collective without any recognisable anomalies. The EC90 is also very light with a long effective length.
Price/Info 199,99 Euro/www.eastoncycling.com
Length/offset 405 mm/0 mm (also 20 mm)
Diameter/weight 27.2 (30.9 and 31.6) mm/214 g
max. rider weight unlimited
Assembly/handling 6 OUT OF 6 POINTS
Flex behaviour (laboratory and practice) 4 OUT OF 6 POINTS
Durability (Iso 4210 and Zedler) 6 OUT OF 6 POINTS
Failure behaviour 2 x no failure
BIKE judgement* VERY GOOD
Ritchey WCS Carbon Link Flexlogic
The Ritchey seatpost is a solid performer once you get past the initial assembly - the peculiar two-bolt clamp with the semi-circular carriage head earned little praise. You'll want a third hand to mount the saddle, and the saddle angle only remained fixed once we had tightened the clamp to almost the maximum torque (16 Nm!). On the other hand, the adjustment range of the saddle is very large. The increase in comfort compared to the aluminium seatposts was definitely noticeable and is easy on the rider on long pedalling sections. The Zedler fatigue test showed a very late failure, also due to the formation of a crack on the lower clamping plate, which is unproblematic in terms of safety. Due to availability, the seat post was tested in 350 mm length, but it is also available in 400 mm.
Price/Info 269 Euro/www.ritcheylogic.com
Length/offset 340 mm/0 mm (also 15 mm)
Diameter/weight 27.2 (30.9 and 31.6) mm /166 g
max. rider weight 110 kg
Assembly/handling 2 OUT OF 6 POINTS
Flex behaviour (laboratory and practice) 4 OUT OF 6 POINTS
Durability (Iso 4210 and Zedler) 5 OUT OF 6 POINTS
Failure behaviour 2 x uncritical
BIKE judgement* GOOD
Schmolke SL
The Schmolke SL, handmade in Constance, was designed to show what a real high-end lightweight prop is capable of. At 135 g and a full 400 mm in length, it is unrivalled in the test field. The increase in comfort was more noticeable in the laboratory test than in practice. There are compromises in handling in favour of weight. For instance, the overhanging saddle clamp only allows little adjustment travel forwards or backwards. In addition, the range in which the tube can be clamped is limited by markings to approx. 7 cm. It is therefore essential to order the correct length. Even though the test samples passed the ISO standard requirements, they had to give up quite early at the BIKE/Zedler load collective. As an extremely lightweight support, it is therefore primarily recommended for light to medium-weight riders.
Price/Info 350 Euro/www.schmolke-carbon.com
Length/offset 400 mm/0 mm (also 20 mm)
Diameter/weight 27.2 (30.9; 31.6 and 34.8) mm/135 g
max. rider weight 95 kg
Assembly/handling 3 OUT OF 6 POINTS
Flex behaviour (laboratory and practice) 3 OUT OF 6 POINTS
Durability (Iso 4210 and Zedler) 3 OUT OF 6 POINTS
Failure behaviour 2 x uncritical/1 x critical
BIKE judgement* SATISFACTORY
Syntace P6 Hiflex
The P6 Hiflex from the pen of Syntace mastermind Jo Klieber once again stands out as the class leader. No other seatpost is so easy to use, offers such a large adjustment range for the saddle and at the same time has such stability reserves. Even after days on the test bench, the samples showed no weaknesses. The high permissible tightening torques that the carbon shaft and clamp head can withstand are nice details that prevent many a misuse. The Hiflex, which was one of the first carbon seatposts to include the topic of "vibration damping" in its specifications, also offers top comfort. All this makes the post a deserved test winner and earns it an unreserved recommendation - from marathon to all-mountain and for every rider weight.
Price/Info 250 Euro/www.syntace.de
Length/offset 395 g/0 mm
Diameter/weight 27.2 (30.9; 31.6 and 34.8)/239 g mm/239 g
max. rider weight 130 kg
Assembly/handling 6 OUT OF 6 POINTS
Flex behaviour (laboratory and practice) 5 OUT OF 6 POINTS
Durability (Iso 4210 and Zedler) 6 OUT OF 6 POINTS
Failure behaviour 2 x no failure
BIKE verdict* SUPER
USE Sumo Titanium
In typical British style, the Sumo Titan is an extravagant representative of its kind. Whether it's the shaft tube made of matt-brushed titanium, which impressed all the testers with its comfort-boosting flex properties, or the easy-to-use screw-in clamp head, which has to be completely dismantled to fit the saddle, but otherwise works really well. A support for individualists. Two of the three test samples passed the fatigue test unimpressed. The third also lasted a very long time, but then showed a sudden failure of the clamping head with sharp breaking edges - an indication of a material structure that had already been weakened during production. Hopefully this is an isolated incident, because otherwise the Sumo delivers a very solid overall performance. Only the tested support is available from Speedbasics, other sizes are available directly from USE.
Price/Info 199 Euro/www.speedbasics.com
Length/offset 395 mm/10 mm
Diameter/weight only 27.2 mm/252 g
max. rider weight 100 kg
Assembly/handling 5 OUT OF 6 POINTS
Flex behaviour (laboratory and practice) 5 OUT OF 6 POINTS
Durability (Iso 4210 and Zedler) 4 OUT OF 6 POINTS
Failure behaviour 2 x no failure/1 x critical
BIKE judgement* GOOD
You can find the detailed test of the lightweight comfort seatposts in BIKE 12/2015.
The complete issue
can be read in the BIKE app (iTunes and Google Play) or in the DK-Shop reorder:
