The seatclamp is another of those unsung heroes on your bike’s list of components – a small, simple but vital part which has an important role to play. A circular metal collar located at the top of the seat tube, as the name suggests its job is to firmly clamp down on said tube to hold the seatpost in place, preventing the saddle from rotating or the post from sinking into the frame.
For many riders the only time they are conscious of their seatclamp is on the occasion when they first adjust their saddle height, but should you need to replace yours – due to damage such as stripped threads, or even just for aesthetic reasons – there are a few things you need to know.
Read on to find out more about the different kinds of seatclamps and to help decide which one might be right for you.
Seat clamps for road and MTB bikes fulfil the same function as BMX seat clamps and are typically made of the same material (aluminium), often CNC-machined and anodised for extra resistance to damage.
However there are a couple of considerations to take into account when replacing a seatclamp, the foremost being internal diameter and quick-release or bolt closure.
• Diameter: The internal diameter of the seat clamp must correspond with the external diameter of the seat tube – too big, and the seat post may move in the frame, with the risk of cracking; too small and the collar can’t fit on the top of the tube (and you might damage your frame in trying to force it on). There are five standard seat tube diameters on the market: 28.6mm, 30.0mm, 31.8mm, 34.9mm, and 36.4mm, so once you know the size of your seat tube (measure with a calipers or check your manufacturer’s specifications) make sure to buy a seatclamp that matches.
Note: The seat clamp diameter needs to match the diameter of your seat tube rather than your seatpost, which is a little smaller. For example, a 27.2mm seatpost (a size commonly found on road bikes) fits inside a 28.6mm diameter seat tube, so it’s a 28.6mm clamp you need.
• Quick-release closure: A quick-release or QR seatclamp uses a small lever to close the seatclamp collar, as with QR wheel skewers allowing the mechanism to be easily opened and re-closed without the necessity for tools. This is useful for riders who wish to frequently raise or lower their saddles, as with MTB bikers who might want to drop the saddle for better body positioning on a technical descent, and raise it again for pedalling efficiency when going back up the hill. However QR seatclamps have fallen a little out of favour in recent years, owing in part to their sometimes less-secure grip (making post slippage a problem) and also to their propensity for being inadvertently knocked by knees. Additionally, many commuters have long bemoaned the fact that QR seatclamps make saddles an easy target for thieves. The advent of dropper posts for MTB riders has also eroded their appeal.
• Bolt closure: These use a simple, short bolt with a hexagonal head to close the seatclamp collar. Bolted collars have long been favoured by gravity riders for their secure grip but are also now more often seen on road bikes as the advantages of a rock-solid grip (once the optimum saddle height has been set) outweigh those of the QR collar.
BMX Seat Clamps
Many BMX bikes on the market today use an integrated seatclamp, where the clamp collar and threaded holes are part of the seat tube. However if you don’t have this type of frame you will need a sturdy BMX seatclamp, which likely as not will sit inobtrusively under the saddle for its lifetime and only be adjusted in the event that your saddle is knocked out of whack by an impact.
BMX seatclamps are made of tough aluminium alloy that is often CNC-machined for optimum strength-to-weight ratio. BMX seatclamps are closed via bolt rather than quick-release (as most BMX riders won’t generally have a need to raise or lower their saddle), with the vast majority having an internal diameter of 25.4mm (as per standard BMX seat tube diameter).
Look for a smooth model with no sharp edges or corners that can catch knees or other body parts.
After that, the only decision to be made is… what colour?