KEEPING YOU POSTED: A GUIDE TO SEATPOSTS

In some respects, a seatpost just needs to hold your saddle at the correct height and not fail. However, there are a wealth of designs and materials to choose from and upgrading can offer more than a few grams shaved. They can have a surprising effect on comfort, too.

Materials

Aluminium alloy, titanium and carbon fibre are the three main contenders and come in at various price points. This latter largely reflects weight, finish quality and to some extent strength. Choice of material will also depend on your intended/style of riding. For example, stick to metal posts if you’re going to be mounting Q/R racks, trailers or tag alongs etc. Wedge packs aren’t a problem but I’d shy away from fitting SQR type luggage, including the Carradice Carradry  to carbon fibre

 

Aluminium Alloy 

Aluminium Alloy posts tend to be either 7005 or 6061. Sometimes marketed as “Aircraft” grade, this is a marketing thing, rather than a tangible measure of its quality. Wall diameter will influence weight and compliance.

Fluted models were popular back in the late 70s and 80s. I can fully appreciate why someone might want to go this route, to preserve a classic bike’s authenticity. However, they were notorious for channeling water inside the seat tube. In steel framesets, this often led to internal corrosion, and galvanic seizures between tube and post when fitted with lithium-based greases.

To some extent, comfort will depend upon the host frame’s material/quality. However, a budget aluminium alloy post and plain gauge frameset can prove a slightly unforgiving mix-especially over longer distances and/or off road. Prices start at £15 (cheaper, if you scour the sales bins of online stores, or go the unbranded Far Eastern route).

Polished, or silver anodised finishes age most gracefully and the former can be polished to remove light to moderate scratching/oxidisation. Automotive cutting compounds will usually achieve good results but I’ve also been impressed by Crankalicious Mayo Jaune .

 

Carbon Composites

Depending on your weight, a budget carbon post may prove a more cost (and weight)-effective upgrade than a decent quality suspension model (A subject discussed later in this feature). Basic, though serviceable models bonded to slightly workman-like aluminium alloy heads come in at £30. Sure, you wouldn’t put one on a Stork but I’ve used them to good effect on cyclo cross and winter training builds.

There’s not much of a weight advantage, over aluminum alloys, at this price point but they have more, tangible “zing”. Get to £100 and we’re talking a much lighter, better finished product.

Durability will depend on factors such as rider weight/riding style, but I still have high end models going strong some ten years on. Check for weight limits; 90-110 kilos is not uncommon. Exceed that and there’s no claiming on a warrantee and an overworked, underpaid A&E nurse will not appreciate pulling slithers of composite from your buttocks. 

While a keen eye is always advisable, it’s particularly important to inspect carbon/composites and not just if you’ve had a crash. Inspect the cradles and shaft for any cracks, or unusual blistering of lacquer. Install them using a torque wrench AND a gripper paste (NEVER GREASE) to prevent unnecessary clamping force, which will likely hasten fatigue. Here’s our review of Muc-Off’s Carbon Gripper Paste.

 

Similarly, employ a carbon fibre friendly release spray, such as Efetto Carbo Move, should your composite post prove stuck/stubborn. Releasing the clamp bolt and turning the post a little bit every 6 weeks or so, is another simple, preventative measure.

Titanium

Titanium remains relatively expensive and tends to be most popular with riders of Ti framesets looking to complete that unique aesthetic. Branded examples come in at around £140.00 upwards. Unbranded examples from the Far East are of variable quality and considerably cheaper (sub £40) 

 

Some, in common with carbon/composites have maximum payloads -110 kilos, or thereabouts. On the plus side, they do offer a subtle, springy ride quality that takes the sting out of intrusive, lower-level vibration. Better quality examples, in keeping with other titanium products are extremely resistant to fatigue and of course, corrosion.

Ti builders tell me these don’t require specialist greases/assembly pastes. A good quality polymer, Ceramic, or indeed, PTFE infused grease should be fine, regardless of the metal host. That said, steer clear of old-fashioned lithium based preps, if you are pairing with a steel, aluminium, or magnesium frameset. Otherwise you run the risk of galvanic corrosion and ultimately, seizure.

Diameter

Getting the right diameter for your host frame is imperative and may restrict your choices. These days 27.2 and 31.6 are the standards. As a result, there’s plenty of choice at each price point. 

However, things get trickier with older frames. Luckily, a lot were 27.2 (including my beloved 1950s Holdsworth). Plenty weren’t though, so if it’s not stamped on the original (or you don’t have a post to measure) measure the seat tube very carefully, using a calliper.

Getting the seat tube inspected by a frame builder or experienced shop mechanic might be a good move, if you’re in any doubt as to its integrity. Sometimes it’s possible to ream a seat tube out, for example, from 27.0 to 27.2. Or there may be some residual paint, following a re-spray.

However, solicit their advice and don’t attempt to persuade them to do something they feel is dangerous/will not work. For example, my road bike hailing from 1991, is made from Reynolds 531c (Competition). This is a particularly thin-walled variant. Reaming from 27.0 to 27.2 would compromise the frame’s structural integrity. In this instance, I used a lathe to reduce a 27.2 Thompson post to 27.0.

Similarly, it is trickier (although certainly not impossible) to find good quality posts for older mountain bike frames. 26.6, 26.8 and 26.4 being common choices. In these instances, this means aluminium alloy.

Some suspension posts, such as this Cane Creek Thudbuster come in 25.4 diameter, with a choice of shims to accommodate these sizes, so all is not lost. Dutch brand BBB offers an affordable and aptly named (400mm in length) Skyscraper post in most diameters. I used one on my Univega to very good effect, for several years. I only retired it because of cosmetic damage (the seat collar’s binder bolt fractured unexpectedly, causing it to sink into the frame and scarring the post’s dun finish).

Length

Length is another consideration. As semi/compact geometry framesets have become the dominant design, so seat posts have become longer. Time was when posts started from 220mm to 400mm. These days 300-400mm is the norm. Adequate for most rider’s needs but either measure carefully to avoid unnecessary length (and weight) or something too short. My Univega runs a 400mm post and I’m a safe distance from the limit mark. If you’re at the limit mark with a 400mm post, then chances are, your intended frame is too small. Never exceed the insertion mark either. Doing so runs the risk of post/frame failure and potentially serious injury.

Layback/Inline 

A seatpost with layback, such as this Torus places the saddle further back, thus increasing the reach (distance) between the handlebars, resulting in a more stretched position: an obvious choice for competitive road and cross-country mountain biking. However, it won’t suit everyone. I am proportionately short in my torso, much longer in the leg than my height and gender might suggest.

While this has been largely addressed with semi/compact geometry frames and stem choice. I still err towards inline designs, which place me a little further forward. Inline posts are also an obvious choice for TT bikes, since they place you further forward, for higher pedalling efficiency.

On the flip-side, this can also result in a harsher, less compliant ride, which may influence your choice of material. If you are in any doubt, it’s well worth investing in a bike fit consultation.

Cradle

 

The cradle (sometimes referred to as the clamp) holds the saddle rails and allows fine tuning of the saddle angle/position. Twin bolt models have become the norm, since they’re more secure. Nonetheless, single bolts are pretty reliable. My Univega’s Selcof  uses a slightly agricultural but very effective single bolt cradle and I’ve seen no reason to change.

Again, apply a stoical, good quality grease to the threaded hardware, especially if you’re marrying metals of different parentage. Failing that, some heavy-duty wet lubes also make reliable stop-gap substitutes.

Suspension 

In common with other suspension technology, posts have come a long way. They still present a weight penalty, so research carefully. I’m very fond of the Cane Creek Thudbuster, which comes in both short (ST) and long (LT) travel versions. It’s been around for many years and seems very effective at ironing out the bumps. Rebuild kits and similar spares are also readily available.

Mountain bikers might be the obvious market but they’re good options for tandem stokers and gravel riders seeking a little more refinement. Performance orientated road riders might find Redshift Sports Dual position an excellent choice. I also used a Nitro Pro Gas Suspension unit some 15 years back, which used a mixture of springs, oils and Nitrogen gas. It also offered a very progressive and predictable 2.5 inches of travel.

At the other end of this market, budget boingers tend to be quite crude and heavy but functional enough for lighter riders doing less demanding riding. I’ve also used them on trailer-bikes, with much success and happy stokers.

 

Personal Favourites 

When it comes to aluminium alloy models, the Thompson is an iconic design and justly so. It’s staying on my traditional road bike. Again, if you’re looking for an inexpensive but very cheery model, especially for older machines, BBB Skyscraper is a smart and relatively lightweight (280g) option. I’m also very fond of the Genetic Syngenic, and of course, the Cane Creek Thudbuster ST Suspension Seat post .

Maintenace/ Care

Strip and re-grease (or apply gripper paste) at least annually. More frequently on mountain bikes and others in hard service (especially those shunning mudguards).

Making a protective “boot” from old inner tube and slipping it over the seat collar slot helps protect against ingress, seizure and extends service intervals. Take these opportunities to inspect for any hairline cracks/similar signs of stress fracture, such as this crease, above.

Replace as required.

 

Where appropriate, remember to grease collar bolts. Some Allen heads can also prove quite soft. Sometimes a Torx driver will offer sufficient bite, permitting extraction. However, more obviously “chewed” examples will need drilling out. 

Micheal Stenning

PUBLISHED APRIL 2020

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