Puncture prevention sealants

The product you forget about, but that makes all the difference

Sealant is what makes a tubeless set-up work. It seals punctures as you ride, often without you noticing, and also makes the set-up itself airtight. But it has one property many riders discover too late: it dries out.

A consumable, not a permanent solution

Depending on the formula, climate and tyre permeability, sealant remains effective for two to six months. After that, it turns into rubbery clumps at the bottom of the tyre and no longer seals punctures, even though the tyre still holds pressure. This is the most common cause of ‘inexplicable’ tubeless punctures. The rule is to check and top up at each change of season, removing any dried residue as you go.

Latex or synthetic

• Formulas based on latex seal medium-sized punctures quickly and effectively. They dry out faster and do not cope well with freezing temperatures.
• Formulas synthetic, latex-free, last considerably longer and are better suited to a bike that is rarely used or stored in the cold. They are generally less effective at sealing large cuts.
• Sealants with fibres or particles are designed for mountain biking and larger punctures: the fibres bridge the hole. They do not pass easily through a narrow valve — add them with the tyre open.
• Sealants thin, particle-free, are designed for road and gravel riding, where punctures are small and the sealant is injected through the valve.

Amounts

Too little sealant will not seal anything; too much adds rotating weight and ends up sloshing around. The usual guidelines are: 40 to 60 ml per tyre for road and gravel bikes, 80 to 120 ml for mountain bikes, more for a high-volume tyre or wide rim. Both the tyre and sealant manufacturers specify the exact amounts.

Syringes and injectors

Two methods. With the tyre open : pour it directly into the tyre before reseating the bead — simple, but you have to remove the tyre. Through the valve : remove the valve core and inject the sealant with a syringe without disturbing the tyre. This is the method for topping up during the season, and it requires a valve core removal tool, which is built into most syringes.

Two precautions

The CO2 can cause sealant to coagulate : after using a CO2 cartridge for a roadside repair, check the condition of the sealant. Some ammonia-based latex sealants are also not recommended for untreated aluminium rims — check the label; it is worth reading.

To find out more: How to choose your sealant

See also: CO2 cartridges and inflators · Bike track pumps · Wheel and tyre tools