Knowledge Level: Advanced
French manufacturer Mavic introduced their Universal Tubeless System (UST) in the year 2000 and, for mountain biking, tubeless set-ups are almost universally accepted. For cyclo-cross too, and amateur racers, they offer many of the benefits of tubular tyres, but for less cost and increased versatility. Acceptance on the road has been slower but, with more manufacturers now offering systems, there are some definite advantages that are worth considering.
What is tubeless?
Tubeless tyres are just that, a tyre without a tube. This is not a new idea, after all, it has been the choice of motorists since the early 20th Century. To hold air, bicycle tubeless systems have some essential elements in common: an airtight rim, an airtight bead and an airtight carcass. How each system achieves this is somewhat different. There is usually liquid sealant involved, which is held within the tyre to seal the bead, the carcass and to quickly seal small holes, should a puncture occur. To decide whether tubeless is for you, it is necessary to look at the systems and their pros and cons for different types of cycling.
Tubeless systems were first developed for mountain bikes, this is the form of cycling where you are most likely to see them used. There are a few different tubeless set-up options.
The original tubeless tyre system for bicycles, UST is widely regarded as being very robust. A UST-specific rim has an airtight rim strip running through its centre and a special, hook-like rim profile which engages with an equally special bead on the tyre. Getting the tyre to seal itself and retain air is straightforward, and air loss is rarely an issue, as the carcass has a thick, non-porous membrane, often making the addition of sealant optional (but desirable in the event of punctures). Of course, a solid system like UST comes at a premium; tyres are relatively expensive and you will need UST-specific rims. Most significantly, the non-porous carcass that makes the UST system so reliable, adds a significant amount of weight and once you have added a liberal dose of sealant, the weight of a cross-country designed carcass can be creeping into performance Downhill territory.
TLR tyres have a specially designed bead which creates a much tighter seal against the rim than a conventional tyre, but they have a porous carcass like a conventional tyre. A TLR tyre will mount on a conventional rim however, which means that the choice of rims available to you is much greater than that of UST, including some very lightweight racing options. A rim strip must be fitted to create an airtight seal over the spoke-holes, and a special valve is fitted, much like the UST system.
Fitting is somewhat harder than for UST; by design, the bead is very tight and some TLR tyre and rim combinations can be very difficult. Sealant must be added to seal the non-porous carcass. TLR offer lower weight than UST and a fairly reliable seal on a greater choice of rims. However, you may still find that your favourite tyre is not available in TLR format and you may find your choice of rim makes the fitting a bit of a challenge. This is particularly an issue for racers who may wish to change tyres frequently to match conditions.
Everyday tyres, without a tube
Running your favourite tyres without a tube is a very realistic proposition and something that riders have been doing for years. You will need a rim strip and valve, like the TLR system and lots of sealant, as the carcass will be very porous. Choosing the right tyre and rim combination is a matter of internet research or guesswork. However, this method of running tyres tubeless has developed considerably over the last few years, driven in no small part by the development of rims and rim strips specifically for this purpose, which have replaced unreliable and unpredictable DIY systems.
The benefits are clear: choose any tyre you like and mount it to a huge choice of rims. For the weight-conscious racer, this includes the most fly-weight tyres and rims available. Of course, adding the sealant will see the weight quickly increase. Reliability can range considerably, depending on the combination you choose. The experience of mounting the tyre can be measured in similar terms, with riders having to resort to the use of compressors to mount tyres in the worst cases, whilst others manage with just a track- or hand-pump.
By the time you have added sealant, the weight saving argument for tubeless set-ups is largely cancelled out and any improvement in rolling resistance is extremely marginal off-road. The real benefits are for puncture prevention and enhanced traction. With no inner tube, snakebites or pinch flats are virtually eliminated, which is a massive bonus is you ride on root filled or rocky trails. With no risk of pinch flats, this allows you to confidently run lower tyre pressures which greatly improves traction and handling. Additionally the sealant will instantly seal penetration punctures, even surprisingly large ones, often without you ever being aware that they occurred.
Set-up hassle, mess and cost are the most common reasons for not going tubeless. However, by following some simple tubeless set-up tips, much of this can be avoided. Many bikes are now being supplied with tubeless ready rims and, if you use these tubeless ready tyres, the results are usually excellent. Some riders also worry what happens if they suffer a puncture or sidewall rips that fails to seal. Simple, you can just put in a tube to get you home. This might involve you getting some sealant on your hands, but almost all mountain bikers find that going tubeless reduces their puncture count significantly or even completely.
For many cyclocross riders, the gold standard for grip and handling will always be tubulars. However, glueing is a messy time consuming process and, for most amateur racers, having multiple wheelsets with different tubulars, pre-glued for varying course conditions, is not an option. Tubeless set-ups give you the same low pressure, high traction and no pinch flat advantages as tubulars, but at a lower cost and with more flexibility for changing tyres. Any cross wheelset can be converted to tubeless using one of the commercially available kits, you can buy tubeless specific wheelsets and, like with mountain biking set-ups, you are not limited to tubeless compatible tyres. With a little online research, it is easy to find the best combinations. As with mountain biking, perceived set-up problems does put some riders off, but again, following some simple set-up tips, will help. Some riders also worry about the tyres folding over at low pressures, but with some research and good set-up, this can be totally avoided.
It is on the road that the adoption of tubeless systems has been the slowest. This is largely because the advantage of being able to run lower pressures to improve grip, without risking pinch flats, is perceived to be irrelevant for most road riding. However, more manufacturers are now offering road tubeless wheel-sets and tyres. Due to the higher tyre pressures, there are no conversion options on the road and using specifically designed rims and tyres is your only option. Having to buy a whole new wheelset undoubtedly puts a lot of riders off. However, these systems do work extremely well, set-up is far less hit and miss than with the off road tyres and, eliminating pinch flats is an advantage when pot holes are common. Also, the sealant will prevent small flints and thorns disrupting your ride and, on cold days especially, not having to stop for a flat tyre, is an attractive proposition.