How to prevent flat bike tires

The evidence here is moderate: real tests, but not many of them. 13 sources, listed at the end.

What the tests say

What causes flats. Sheldon Brown groups them into three causes¹:

• punctures from glass, wire and thorns
• pinch flats (“snakebites”): two small holes from hitting an edge while underinflated
• rim tape failures that expose spoke holes

He names goathead thorns as a notable hazard in the Southwestern US. He recommends liners, “thornproof” tubes with a thicker outer wall, or sealant¹.

Goatheads. Goathead, or puncture vine (Tribulus terrestris), is native to warm parts of southern Eurasia and Africa and has been introduced to North America². Each fruit splits into five burs, each armed with two large spines and sometimes two smaller ones¹²; Wikipedia gives a spine length of about 10mm². Extension and weed-board sources say the burs puncture bicycle tires¹²¹³. Seeds can remain viable in the soil for up to five years¹¹¹², and one city summary says 5–7 years or longer¹³. Wikipedia lists the plant as a noxious weed in some US states and recommends removal before or during flowering². Nobody has studied how often goatheads cause flats.

Liners (BRR lab test). Bicycle Rolling Resistance tested liners in a Schwalbe Kojak 35mm tire at 60 psi. The bare tire scored 73 points for tread puncture resistance³:

Three of the four liners also cut wet grip by 5–6 points; the FlatAway left it unchanged. BRR judged both Mr Tuffy liners the best balance, and said Tannus Armour “will prevent virtually all punctures” at a big speed cost³.

Tubeless and inserts. Going tubeless removes the inner tube, which is what gets pinched in a classic snakebite, and lets sealant close small holes. It’s also faster: across eight gravel tires, tubeless averaged 3.9 W less than butyl tubes at low pressure⁴. In BRR’s insert test, a 40mm tubeless tire without an insert failed at 9 psi, running on the rim edges. With a CushCore (122g) or Vittoria AirLiner (56g) insert, it completed the test. Both inserts added little rolling resistance down to about 27 psi⁵. Sealant has to be kept fresh, especially in heat (see). Stan’s is reported to say its sealant stays liquid for 2–6 months depending on temperature and humidity⁶.

Tubes. In BRR’s 2026 update, latex was the fastest tube material (9.5 W at 100 psi). The best TPU tubes were close behind (9.7 W), and standard butyl was slower (10.5–12.4 W)⁷. BRR didn’t systematically measure TPU puncture resistance, so claims that TPU tubes resist punctures better are untested⁷.

Casing and belts. Sheldon Brown says puncture belts add a little weight and rolling resistance, but “probably have some value” against hazards like broken glass⁸. BRR’s road-tire tests report a “Total Puncture Score” that combines sharp and blunt puncture force with total tire thickness, which makes tires directly comparable⁹.

Pressure and pinch flats. Berto’s 15% tire-drop rule and wider tires both reduce how far the tire squashes, and so cut snakebite risk¹⁰. Sheldon names underinflation as a major cause of snakebites¹.

The numbers

• Goathead burs carry two large spines (sometimes two smaller ones); seeds can stay viable in soil up to 5 years, and 5–7 years or longer by one account¹¹¹²¹³
• Mr Tuffy liner: puncture score 73 → 136 for +1.9 W³
• Tannus Armour: 73 → 245, but +13.6 W and 221g³
• Panaracer FlatAway: +14.4 W, the largest penalty tested³
• Gravel tubeless vs butyl: −3.9 W per tire at low pressure⁴
• Without an insert, a 40mm tubeless tire failed at 9 psi. With an insert, it held⁵
• Tubes at 100 psi: latex 9.5 W, best TPU 9.7 W, butyl 10.5–12.4 W⁷

Myths and disagreements

• “Tubeless means no flats.” Sealant dries out, and large cuts or burps still happen⁵⁶.
• “Liners are basically free.” Penalties ranged from +1.7 W to +14.4 W³.
• “TPU tubes are more puncture-resistant.” Not measured by BRR⁷.
• Gap: real-world rates. Lab puncture scores use a fixed probe³⁹. There’s no field data comparing puncture rates for tubeless, tubes, liners or tire models.

Stopping flats

• Desert gravel or MTB: run tubeless with fresh sealant (BRR’s gravel tests used 30ml per tire) and check it about monthly in summer. Carry plugs and a spare tube⁴⁶.
• Staying with tubes in goathead areas: use a thornproof tube plus a Mr Tuffy-type liner, the best trade-off in BRR’s test¹³.
• Rocky terrain at low pressure: consider an insert⁵.
• Pick tires by puncture score: compare protected and race casings on BRR’s road and gravel puncture scores, not marketing names⁹.
• After a goathead stretch: stop and check your tires. Pulling a thorn out of a tubeless tire lets the sealant work. That’s practical advice, not a tested method.

Sources