What is the ideal shaft diameter for heavy duty trekking poles?

When you carry a heavy backpack (15 kg / 33 lbs or more) or tackle rugged, rocky terrain, standard trekking poles may feel flimsy. The shaft diameter plays a critical role in strength, stiffness, and durability. For heavy‑duty use, the ideal shaft diameter is 18–20 mm (0.71–0.79 inches), combined with thick walls (1.2–1.5 mm) and 7075 aluminium alloy. Here’s why.

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Why diameter matters for heavy loads

A trekking pole’s resistance to bending and buckling is proportional to the fourth power of its diameter (for the same wall thickness). A thicker shaft is exponentially stiffer and stronger. An 18 mm pole is about 40% stiffer than a 16 mm pole of the same wall thickness. For heavy‑duty applications – where you may lean hard, catch a fall, or jam the pole between rocks – this extra stiffness prevents bending and failure.

The problem with thin shafts (14–16 mm)

Ultralight poles (14–16 mm) are designed for low loads and smooth trails. Under a heavy pack, they flex excessively, absorbing energy and feeling “whippy.” They also bend permanently more easily. A 16 mm aluminium pole can bend under a 100 kg lateral load; an 18 mm pole of the same alloy might withstand 130 kg. For heavy users, thin shafts are a safety risk.

Why 18–20 mm is the sweet spot for heavy duty

• Strength: 18 mm poles, especially those made from 7075 aluminium, can support heavy lateral loads without permanent bending. Many expedition‑grade poles (e.g., Leki Khumbu, Black Diamond Alpine Carbon) use 18 mm lower sections.
• Stiffness: A thicker shaft provides a solid, confidence‑inspiring feel. No wobble or flex when you plant hard.
• Durability: The larger diameter dissipates impact forces over a wider area, reducing the risk of denting or cracking.
• Weight penalty: An 18 mm pole is only about 30–50g heavier per pole than a 16 mm model – a small price for reliability.

What about carbon fibre?

For heavy‑duty use, carbon poles with 16–18 mm diameters can be strong, but they are more brittle. A high‑modulus carbon pole (e.g., Black Diamond Alpine Carbon) can be excellent, but lateral jams can still snap them. Most heavy‑duty users prefer 7075 aluminium for its ductility (bends instead of snaps). If you choose carbon, look for the thickest walls and largest diameter (at least 18 mm).

Real‑world examples

• Leki Khumbu: 18 mm lower section, 7075 aluminium, designed for high loads and technical terrain. Weight ~290g per pole.
• Black Diamond Trail Pro: 17.7 mm (effectively 18 mm), aluminium, very stiff. Popular with backpackers.
• Komperdell Expedition Alu: 18 mm, reinforced lower section, heavy‑duty lever locks.

Avoid for heavy duty:

• 14–16 mm carbon poles (ultralight, fragile).
• Any pole with a diameter under 16 mm, regardless of material.
• Twist locks (they slip under heavy loads regardless of diameter).

How to measure and verify

Measure the lower shaft (just above the tip) with a caliper. Many manufacturers list the diameter in specifications. If not, you can estimate: 18 mm is roughly the diameter of a UK 5p coin (18 mm) or a US nickel (21.2 mm – a bit larger). Look for explicit “18 mm” or “19 mm” specs.

Final verdict

For heavy‑duty trekking – carrying loads over 15 kg, hiking on rocky Alpine or Lake District terrain, or if you are a heavier hiker (over 90 kg) – the ideal shaft diameter is 18–20 mm in 7075 aluminium. This provides the stiffness, strength, and confidence needed for demanding conditions. Pair with lever locks and carbide tips. Avoid thinner shafts; the small weight saving is not worth the risk of failure. Invest in thick, robust poles – they will last for years of hard use.