Use two straps minimum on anything strapped to a bike, cross them, and check that the combined working load limit is at least half the weight of what you are tying down. Then re-tension after the first thirty minutes, because webbing beds in and everything you tightened in the car park is looser than you think. Bungee cords are for holding a jacket in place at walking pace and nothing else — they store energy, they fail suddenly, and the hook goes somewhere.
The forces you are actually restraining
Motorcycles are not covered by commercial cargo securement rules, but the physics is the same and the commercial numbers are the only published, tested figures available. The US Federal Motor Carrier Safety Administration's performance criteria, at 49 CFR 393.102, require securement systems to hold cargo under 0.8 g deceleration forward, 0.5 g acceleration rearward and 0.5 g laterally without exceeding the breaking strength of the devices — and to stay within their working load limit at 0.435 g forward, 0.5 g rearward and 0.25 g lateral.
Translate that. A 10 kg roll bag under a hard 0.8 g stop is trying to travel forward with roughly 8 kgf behind it, and a motorcycle stops considerably harder than 0.8 g in an emergency. The forward direction is the one that matters most, and it is the one riders secure least, because the natural instinct is to strap downward rather than forward.
The aggregate rule from the same regulations is the useful shortcut. Under 49 CFR 393.106, "the aggregate working load limit of tiedowns used to secure an article or group of articles against movement must be at least one-half times the weight of the article or group of articles". A strap that passes over the load and attaches on both sides contributes its full working load limit; a strap that runs from a vehicle anchor to a point on the load contributes half. That is why over-the-top straps do more work than corner straps, and why two properly routed straps beat four badly routed ones.
The same section also states the principle that governs everything else: cargo "must be firmly immobilized or secured on or within a vehicle by structures of adequate strength". Immobilised. Not merely held down. A bag that can rotate or creep is not secured, however tight the strap feels.
Strap types, and what each one is for
| Type | Right use | How it fails |
|---|---|---|
| Cam buckle strap | General luggage securing; the default choice | Slips if the tail is not fed straight; webbing frays where it crosses a sharp rack edge |
| Ratchet strap | Heavy or awkward loads, transport tie-down | Over-tensioning crushes soft luggage and can bend racks; the handle can foul when packed |
| ROK-style stretch strap | Soft bags where a little compliance is wanted | The stretch that helps it grip also lets the load move; wrong for anything dense |
| Rubber bungee with metal hooks | Holding a jacket in place while parked | Stores energy, releases suddenly, hook whips toward eyes; ages and perishes invisibly |
| Cargo net | Stopping small items escaping, over a strapped load | Not a restraint on its own; hooks pull off under load |
| Voile-style ski strap | Bundling, securing small items to a rack | Limited length and load; not a primary tiedown |
How to strap a bag so it does not move
- Find real anchor points. Subframe loops, rack rails, pillion footrest hangers, grab rail. Never indicators, never bodywork, never the number plate hanger, never anything plastic.
- Compress the load first. A half-empty roll bag will settle and go slack no matter how well you strap it. Squeeze the air out and roll it down before the straps go on.
- Run the first strap over the top, anchor to anchor, side to side. This is the strap doing the most work under the aggregate rule, and it resists lift as well as lateral movement.
- Run the second strap forward and down, crossed against the first. This is the one that resists the 0.8 g stop. Most riders skip it and then wonder why the bag creeps forward onto the seat.
- Protect every edge the webbing crosses. A rack rail with a machined edge will saw through a strap over a few hundred kilometres. Wrap it, or route around it.
- Deal with the tails. Loose tail ends flap, then find the rear wheel or the chain. Roll each tail, secure it with a small elastic band or tuck it back through the webbing, and check nothing hangs below the seat line.
- Load-test by hand. Grab the bag and shove it hard forward, then sideways, then try to rotate it. If it moves more than a centimetre in any direction, it is not immobilised.
- Re-tension after 30 minutes. Webbing beds in and knots settle. This single stop prevents most roadside repacking.
What goes wrong, and how it goes wrong
The strap that touches the exhaust. Nylon webbing against a hot silencer parts in under a minute, and it does it silently. Check the routing with the bike on its wheels and the suspension compressed, not on the centre stand.
The strap that reaches the tyre. A tail that hangs down finds the rear tyre or the chain and gets pulled in. On a chain-drive bike this can lock the rear wheel. Deal with every tail, every time.
The bungee that lets go. Perished rubber gives no warning, and the hook travels toward whoever tightened it. Cheap bungees also stretch enough under load that the item they hold is never actually still.
Straps over a hard case lid. Compressing a case lid against its gasket in the middle bows the lid and breaks the seal at the corners, so a strapped case leaks in ways an unstrapped one does not. Strap around the case, not across the lid, or use the case's own mounting points.
Everything strapped to the pillion seat and nothing forward. This is the load placement error more than a strapping one, and it puts mass exactly where a bike least wants it. The distribution logic is in pannier and top box load limits.
Straps as consumables
Webbing has a service life and riders treat it as permanent. Retire a strap when any of these appear:
- Fuzzing or cuts on the edge of the webbing, particularly where it crossed a rack rail.
- A cam buckle whose teeth no longer bite, which shows up as a strap that needs re-tensioning every stop.
- Chalky, stiff or faded webbing. UV degradation is invisible until the strap parts.
- Any strap that has been through a chain or under a wheel, regardless of how it looks.
- Stitching that has pulled at the buckle end, which is where the load concentrates.
- Any strap you have knotted to shorten it. A knot in webbing is a stress concentration and cuts its strength substantially; shorten by folding and clipping instead.
Store them dry and out of sunlight. A strap left coiled on a rack through a summer loses strength invisibly, and the failure happens at motorway speed rather than in the car park. Marking each strap with the year you bought it takes ten seconds and removes the guesswork about which ones are past it.
Carry two spares. They weigh almost nothing, they are the single most useful improvised repair item on a bike, and they cost less than the fuel to get to a shop that sells them.
For which luggage should be strapped rather than bolted in the first place, see hard versus soft luggage. For keeping the strapped load dry, the layered method in waterproof packing assumes the bag stays put, which is what this article is for. And add a strap check to the routine in your pre-ride check — it takes ten seconds and it is the check that stops a bag reaching the road behind you. A bar-mounted remote is worth having when your hands are the only thing free with a loaded bike and gloves on.
Frequently asked questions
How many straps do I need for a roll bag?
Two as a minimum: one over the top from side to side, one crossed forward and down. Four is common on larger bags. What matters is that something resists forward movement, not just downward.
Are ratchet straps too strong for a motorcycle?
They can be. It is easy to over-tension a ratchet enough to crush soft luggage, bow a case lid or deform a light alloy rack. Cam buckles give plenty of tension with much less risk of that.
Why do my straps go slack after an hour?
Webbing beds in and the load settles as air escapes from soft bags. Re-tension at the first stop, roughly half an hour in. If it keeps happening, the buckle teeth are worn.
Can I strap luggage on top of a hard case?
Only within the rack's published limit, and never with the strap compressing the lid across its middle, which breaks the gasket seal. Route the strap around the case or use its designated tie points.
Are bungee cords ever acceptable?
For holding something in place while parked, or over a load that is already properly strapped. Never as the primary restraint. They stretch under load, perish without warning and the metal hook travels when they let go.
