Which motorcycle tank mount fits and holds a 20 litre magnetic tank bag

Part of our guide on magnetic mounts and overheating

How to check fit for a 20 litre magnetic tank bag

Measure the bag base. Use a ruler or calipers to record length and width of the magnetic area or the pattern of magnet discs. Record the usable flat contact area in square centimetres.

Measure your tank where the bag will sit. Note local curvature and any seams, filler caps, or protrusions. Record the distance between the highest points across the contact patch.

Compare the two sets of numbers. A mount holds best when its magnetic plate or array covers most of the bag’s magnetic base. Gaps or mismatched magnet positions reduce effective hold even if magnets are strong.

If the bag uses multiple magnet discs, ask the bag maker for the disc layout. If a mount lists individual magnet positions, compare them once and only once here. That single check avoids repeating fit advice later. If that sounds like your situation, read up on qi2 and magsafe compatibility tips next.

How much a 20 litre bag weighs in practice

There’s no fixed weight for a 20 litre bag. Empty fabric bags can be under 0.5 kg. Packed with clothing, tools or camera gear they commonly weigh 1–6 kg. Heavy kit or metal tools push that toward 8 kg or more.

Use a luggage scale or bathroom scale to weigh your typical load. Pack the items you plan to carry and weigh the whole bag. That number is the key input for choosing magnet strength.

State any numeric guidance as an estimate. Manufacturer specs and real-world load will vary. Treat pull-force recommendations as a starting point, not a guarantee. We cover galaxy s23 magnetic mounts for 32 mm tubes in its own article.

Magnet pull force: what the numbers mean and how to verify them

Manufacturers often state pull force in kilograms-force (kgf). That figure is the ideal vertical pull on a flat, thick steel plate with full contact. Real-world conditions usually deliver less force due to paint, curvature, and thin tank metal.

Check the manufacturer’s spec sheet for 'pull force' or 'holding force'. If they list only magnet size or material, ask customer support for a pull-force figure.

Verify the spec yourself with a cheap test rig. Attach the mount to a flat steel plate that simulates full contact. Clip a luggage scale or a spring scale to the bag or to a hook on the mount and pull straight up. The scale reading where the mount separates approximates real pull force on flat steel. For the detail, see our notes on handlebar magnet mount that fits 31.8 mm clamp.

Do not rely on a lab number alone. Repeat the test with the mount attached to your tank (with paint protection in place) and with the bag loaded. The reading will be lower than the ideal spec. Record that value.

Measure your bag and tank, verify pull force with a scale, and test on a short ride before trusting a magnetic mount with a 20 litre bag.

Safe testing and fit checks before you ride

First test = static pull. Attach the mount and bag. Pull with a luggage scale until the bag starts to slide. Note the force. If the bag shifts below your loaded bag weight, do not ride.

Second test = short road test. Ride a short, slow loop on smooth roads. Use conservative braking and gentle turns. Stop and inspect magnet contact after the loop. Look for any movement, paint abrasion, or magnet separation.

Third test = weighted braking test. With the bag mounted and the bike upright, apply the bike’s brakes to simulate deceleration. You can do this safely in a controlled parking lot at low speed. Confirm the bag stays stable.

Place a thin protective layer between the mount and paint per the mount maker’s instructions. Many mounts include rubber pads or felt to protect paint and maintain contact.

Which mounts and products to consider

Many magnetic tank bags come with their own magnetic backing and do not need a separate mount. Brands that make magnetic tank bags or plates include Oxford and Nelson-Rigg. If you use a bag from one of those brands, check the brand’s recommended plates and accessories for best compatibility.

Some aftermarket magnetic plates and pad-style mounts are sold as generic 'magnetic tank adapters'. Look for products that publish pull-force numbers and list tank compatibility. Avoid any item that gives only subjective claims like 'super strong' with no numeric spec.

Examples to search for: 'Oxford magnetic tank pad', 'Nelson-Rigg magnetic tank bag', and 'magnetic tank adapter plate'. Use those search terms to find models with spec sheets you can verify.

If your tank is highly curved, prioritize flexible magnetic pads that conform to curves. If your tank is flat, a rigid plate with a larger magnetic footprint is acceptable.

Phone safety and other caveats

Most modern phones tolerate nearby magnets without lasting harm. Magnets can affect compasses and magnetic stripe cards. If your phone uses wireless charging or MagSafe, confirm the case and mount are compatible.

Magnet ratings degrade if magnets corrode or if the mount’s coating wears. Pick weather-sealed products or keep the mount dry when possible.

Strong magnets on a mismatched surface can scratch paint. Use the protective pad recommended by the manufacturer and inspect the tank regularly.

FAQ

I recommend you weigh your packed bag and test mounts on your own tank before long rides. Manufacturer numbers are a starting point; real-world testing confirms safety.