Choosing the Right Thread for Outdoor Gear Repairs

Why the thread matters more than you think

When a seam fails on a rucksack or a tent flysheet, it is almost never the fabric that gives up first. It is the thread. Stitching lives a hard life: it flexes every time you stuff a sleeping bag, it grinds against grit on a bike frame, and it sits in UV light for months at a time. Yet most of us reach for whatever bobbin is already in the machine.

The thread in your everyday sewing box is usually a cotton-wrapped polyester, designed for hemming curtains and patching school trousers. It is fine for that, but it is a poor choice for gear. What you want for outdoor repairs is a continuous filament thread — a single unbroken strand rather than short staple fibres spun together. Filament thread is stronger for its thickness, sheds water better, and does not fuzz up as it runs through the machine.

Beyond that, four families of thread cover almost everything a hiker, camper or bikepacker will ever need to repair.

Bonded nylon: the dependable workhorse

Bonded nylon is the default for heavy gear. Several plies of nylon filament are twisted together, then coated with a resin bond. That coating stops the plies fraying as they pass through the needle, cuts friction, and slows water wicking along the stitch line.

It is exceptionally strong and takes abrasion well, which makes it the right call for rucksacks, webbing, straps, tool rolls and anything that gets dragged over rock. The one real weakness is ultraviolet light: nylon degrades in sunlight noticeably faster than polyester, so a repair stitched with bonded nylon and left on a sunny tent for a full season will lose a good chunk of its strength.

Sizes are usually quoted in Tex numbers. Tex 40 (often sold as V-69) handles most pack repairs, while Tex 70 (V-92) is for load-bearing seams, haul loops and webbing. Heavier still, Tex 105, is for serious strap work.

Polyester: the UV-resistant all-rounder

Continuous filament polyester is slightly weaker than nylon and marginally less abrasion resistant, but it shrugs off sunlight and absorbs very little water. For anything that lives outdoors, that trade-off is usually worth it.

That makes polyester the sensible default for tents, flysheets, tarps, guy lines and bike luggage that spends its days strapped to a frame in the sun. It also holds up better in damp, mildew-prone storage. For lightweight tents, Tex 30 or Tex 40 is plenty — a heavier thread on thin silnylon can actually pull through the fabric before the seam itself fails, so match the thread to the cloth rather than going as strong as possible.

Aramid and PTFE: the specialist options

Para-aramid thread is enormously strong and heat resistant, and it turns up in safety-critical kit. It is also poor in UV, dislikes repeated flexing, and is brutal on a domestic sewing machine because it chews through needle plates. Unless you are repairing something genuinely safety-critical and know exactly what you are doing, it is not worth the expense or the hassle.

Expanded PTFE thread is the opposite extreme: effectively immune to UV, rot and most chemicals, which is why it is used on boat covers and shade sails. It is slippery, though, so knots work loose and tension needs careful setting. It is expensive, and for camping gear it is almost always overkill.

Matching thread to the job

A quick reference for the most common repairs:

• Tents and tarps: bonded polyester, Tex 30–40, in a colour close to the flysheet or a mid-grey that will not show dirt.
• Rucksacks and haul bags: bonded nylon Tex 40 for general seams, Tex 70 where straps and haul loops meet the body.
• Sleeping bags and quilts: fine polyester or nylon, Tex 16–30, matched to the shell weight.
• Bikepacking bags: bonded nylon Tex 40 for most work, polyester if the bag bakes on the frame all summer. Reinforce high-wear corners with bar tacks.
• Waterproof clothing: fine polyester, with the seam sealed afterwards.

Needles, tension and a few workshop habits

Thread choice is half the job; the other half is how you run it.

• Match needle to thread. A Tex 40 thread wants a size 90/14 or 100/16 needle; Tex 70 wants 110/18 or 120/19.
• Use a sharp or universal needle on woven nylon, and a ballpoint on knits and stretchy fleece so you push between the fibres rather than cutting them.
• Change the needle at the start of every project. A blunt needle causes skipped stitches and snagged fabric.
• Aim for roughly 8–10 stitches per inch (about 3 mm). Shorter stitches perforate light fabric and weaken the seam.
• Backstitch at both ends, then melt the cut tails with a lighter. Nylon and polyester both melt; polyester behaves slightly better in a flame.
• Hand-sewing? Draw the thread over a block of beeswax first. It stops tangling and adds a little water resistance.
• Never use thread that has sat in a box for a decade. It goes brittle, and it will snap at the worst possible moment.
• Always test on an offcut of the same fabric, with the same number of layers, before committing to the real repair.

Get those habits right and a repair will outlast the rest of the garment — which is exactly what you want from gear you have to trust in the hills.