The short version
- Butyl — cheapest, holds air for weeks, easy to patch, heaviest. The correct default for almost everyone.
- Latex — fastest and most supple, but needs inflating before every ride and hates rim-brake heat.
- TPU — a third of the weight, packs tiny, expensive, awkward to repair.
- Mousse — cannot puncture, at the cost of weight, heat and a service life in the tens of hours.
The property that decides everything: gas permeability
Air does not leak out of a good tube through holes. It diffuses through the rubber wall itself, molecule by molecule, driven by the pressure differential. Every elastomer is permeable to some degree, and the differences between them are enormous.
Butyl rubber (isobutylene-isoprene rubber, IIR) is the outlier. Its backbone carries dense gem-dimethyl side groups — two methyl branches on alternating carbons — which pack tightly and severely restrict the segmental chain motion that gas molecules need in order to hop from one free-volume site to the next. The result is a permeability roughly one tenth that of natural rubber. Halogenated versions (chlorobutyl and bromobutyl) add cure flexibility and adhesion while keeping the barrier property, and they are what the inner liner of every tubeless car tire is made from too.
| Material | Relative permeability | Typical pressure loss |
|---|---|---|
| Butyl (IIR / halobutyl) | 8–12 | 1–3 psi per week |
| TPU (thermoplastic polyurethane) | 25–45 | 3–8 psi per week |
| Natural rubber / latex | 100 | 15–40 psi overnight |
| Silicone rubber | ~600 | Unusable as a tube |
The four options, compared
| Butyl | Latex | TPU | Mousse | |
|---|---|---|---|---|
| Weight | 95–120 g (70–85 g lightweight) | 70–85 g | 25–40 g | 800–1,900 g |
| Air retention | Excellent | Poor | Good | N/A |
| Rolling resistance | Baseline | 1–3 W/wheel better | 1–2.5 W/wheel better | Much worse |
| Ride feel | Slightly damped | Notably supple | Supple, slightly harsher than latex | Dead, heavy |
| Puncture behaviour | Small hole, slow-ish deflation | Stretches around debris; when it fails it tears fast | Small hole; resists pinch flats well | Cannot puncture |
| Repairable | Yes, universal patches | Yes, with latex-specific glue | Only with brand-specific patches | No |
| Heat tolerance | Good | Poor — avoid rim brakes on long descents | Poor — softens near 100°C | Generates its own heat |
| UV / ozone / oil | Very good | Degrades in storage | Good | Good |
| Cost | $5–10 | $15–25 | $25–40 | $90–180 |
Butyl: the correct default
Butyl wins on every axis that affects daily use. It holds pressure for weeks, tolerates heat, resists ozone and UV in storage, patches with any universal kit, and costs almost nothing. Standard butyl tubes are typically 0.8–1.0 mm thick; lightweight versions drop to 0.45–0.6 mm, saving 25–35 g at the cost of some puncture margin. Heavy-duty and thorn-resistant tubes run 1.5–3 mm — genuinely effective against thorns, and slow enough that you will feel the weight on every climb.
Tubes are dusted with talc so they can slide freely inside the casing rather than binding and abrading. If you fit a tube without talc into a tacky new tire, friction at the contact patch can wear a hole from the inside over a few hundred kilometres. A light dusting of talcum powder inside the tire on fitting is a two-second job that prevents a genuinely annoying failure mode.
Latex: fast, supple, high-maintenance
Natural rubber latex tubes are dipped rather than extruded, giving a thin, extremely elastic wall. Two properties follow.
First, low hysteresis. Every rotation, the tube is compressed and released at the contact patch. Some of that energy comes back; some is lost as heat. Latex loses less than butyl, and independent rolling resistance testing consistently shows 1–3 watts per wheel saved at 40 km/h. Over a 40 km time trial that is real, and it is why latex remained standard in professional road racing long after tubeless arrived.
Second, extreme elongation. Latex stretches enormously before it tears, so it often deforms around a small piece of glass instead of being punctured by it. Once it does fail, however, it fails fast — a latex blowout is loud and instantaneous, with none of the gradual deflation a butyl tube gives you.
Rim brake heat. Sustained braking on an alpine descent can push an aluminium rim past 100°C. Latex softens and can burst. Disc brakes remove this problem entirely — one reason latex became more viable, not less, as disc brakes took over.
Sunlight and ozone. Latex degrades in storage. Keep spares in a sealed opaque bag and replace them after a couple of years even unused.
Petroleum products. Chain lube, degreaser and mineral oil attack natural rubber. Keep them apart.
TPU: the weight-weenie's answer
Thermoplastic polyurethane tubes arrived commercially in the 2010s and matured quickly. A 700×28c TPU tube weighs 25–40 g — a saving of roughly 150 g across a bike, which is more rotating weight than most riders will save anywhere else for the money.
The other real advantage is packability. A TPU spare folds down to roughly the size of a matchbox, which changes what fits in a saddlebag or jersey pocket. Even riders who run butyl day to day often carry TPU as the emergency spare.
The trade-offs are practical rather than performance-related:
- Repair is proprietary. Standard vulcanising patches do not bond to TPU. You need the manufacturer's patch kit, and success rates are mixed.
- Heat sensitivity. TPU softens well below butyl's limit. Rim brakes on long descents are a real risk.
- Valve interfaces vary. Some early TPU tubes had fragile valve bases; check reviews for the specific model.
- Cost. Four to six times a butyl tube.
Mousse: the nuclear option
A mousse is a solid ring of closed-cell nitrogen foam that replaces the tube entirely. It is standard equipment in off-road motorcycle competition — enduro, hard enduro, and much of rally raid — and has appeared in downhill MTB and cargo applications.
| Property | Behaviour |
|---|---|
| Effective pressure | Simulates roughly 12–13 psi (0.8–0.9 bar) when new; softens with use |
| Puncture immunity | Total. A nail through a mousse changes nothing. |
| Weight penalty | Roughly +1 kg per wheel versus tube and tire |
| Service life | 15–25 hours of hard enduro; longer at low intensity |
| Heat | The foam's internal hysteresis generates significant heat at speed; sustained high-speed road use degrades it rapidly |
| Fitting | Difficult; requires dedicated mousse lubricant, which must be reapplied at intervals |
| Cost per hour | High — but so is a DNF in a race |
The decision logic for a mousse is unusual: it is not about performance, it is about eliminating a specific failure mode. If a puncture means the end of your race or a walk out of a remote valley, a mousse is rational despite every metric being worse. If a puncture means a fifteen-minute roadside stop, it is not. The same reasoning appears in industrial settings — see our guide to solid, foam-filled and pneumatic tires, where downtime economics drive the same conclusion.
What about going tubeless?
Tubeless removes the tube and seals the tire directly to the rim, with liquid sealant plugging small punctures as they happen. It is a genuine improvement for most off-road and gravel riding, and increasingly for road.
| Tubed | Tubeless | |
|---|---|---|
| Small punctures | Stop and fix | Usually self-seal while riding |
| Pinch flats | Common at low pressure | Effectively eliminated |
| Minimum usable pressure | Limited by pinch flat risk | Much lower — more traction and comfort |
| Rolling resistance | Baseline | Typically 1–4 W/wheel better |
| Setup | Trivial | Needs tubeless rim and tire, tape, valves, sealant |
| Maintenance | None | Sealant top-up every 2–6 months |
| Roadside failure | Swap tube | Plug, or fit a tube — carry one regardless |
| Mess | None | Meaningful |
Note the last row of practical advice: tubeless riders still carry a tube. Sealant handles small holes; a sidewall cut needs a tube. Which brings the choice full circle — the best emergency spare for a tubeless setup is usually a TPU tube, because it weighs nothing and takes no space.
Choosing, in one paragraph
Ride to work, ride at weekends, do not want to think about it: butyl, standard weight. Race on a disc-brake bike and count watts: latex front and rear, inflated before every ride. Care about weight and packability, or want the smallest possible spare: TPU. Ride off-road at any pace on rough ground: tubeless, with a TPU tube in the pack. Race enduro where a flat ends your day: mousse, and accept every penalty that comes with it.
Frequently asked questions
Why do butyl tubes hold air so much better?
Dense methyl side groups along the isobutylene backbone physically obstruct gas diffusion through the polymer. Butyl's permeability is roughly a tenth of natural rubber's.
Are latex tubes really faster?
Yes — typically 1–3 watts per wheel at 40 km/h, from lower hysteresis. You pay for it with daily inflation and incompatibility with rim-brake heat.
How often should I inflate latex tubes?
Before every ride. Losing 15–40 psi overnight is normal behaviour, not a leak.
Can I patch a TPU tube?
Only with the manufacturer's own patches — standard vulcanising patches do not bond. Carry a spare rather than relying on repair.
Do heavier tubes prevent punctures?
Thick thorn-resistant butyl genuinely helps against thorns and small glass, and does nothing against pinch flats or sidewall cuts. It also adds 100–200 g of rotating weight. For most riders a good tire casing plus correct pressure is a better investment.
What is a mousse and should I use one?
A solid nitrogen-foam ring that cannot puncture, behaving like a tube at 12–13 psi. Worth it only if a flat would end a race or strand you somewhere remote — it is heavy, hot, expensive and short-lived.