RideDe juiste fatbike-band kiezen (20x4.0)
The tyre is the only contact point between your fatbike and the road. The right choice determines grip, comfort, rolling resistance and whether the tyre will even fit in your frame at all. This guide explains the size notation and helps you choose between treads, inner tubes and pressures.
The size notation: what does 20x4.0 mean?
The size is printed on the side of your tyre, usually in two notations:
- Inch notation, e.g. 20x4.0: a wheel diameter of 20 inches with a tyre width of 4.0 inches (about 10 cm). This is the common fatbike size in the Netherlands.
- ETRTO notation, e.g. 100-406: 100 mm tyre width on a rim with a 406 mm diameter. The ETRTO size is the most precise; 406 is the rim size that goes with "20 inch" fatbikes.
Note: "20 inch" also exists in other rim diameters (such as 451 mm on folding bikes). So preferably look at the ETRTO number on your current tyre. If it says 406, you're fine with the standard fatbike size.
Choosing a tread: knobbly or street?
- Knobbly tread (knobs): maximum grip on sand, grass, mud and snow. The classic fatbike look. Downside: more rolling resistance and a humming noise on tarmac.
- Street tread (slick or light tread): quieter, lighter-rolling and easier on your battery on paved surfaces. The logical tread if you mainly ride in the city and on cycle paths.
Honest advice: most fatbike kilometres in the Netherlands are ridden on tarmac. If you rarely ride off-road, a street tread will noticeably gain you comfort and range.
Frame clearance: will a wider tyre fit?
A wider or taller-profile tyre needs room between the fork, frame and mudguards. Before you order a different size, check that at least a few millimetres of free space remains all around — including suspension forks in their compressed position. Not sure whether a tyre will fit your frame? Send us the make and model and we'll gladly take a look with you.
Inner tube and valve type
If you're replacing the tyre, it's best to replace the inner tube at the same time — it's cheap and has often covered just as many kilometres. Mind the valve type:
- Schrader (car valve): a thick valve, the same as on a car. Standard on virtually all fatbikes and inflatable at any petrol station.
- Presta (French valve): a thin valve with a screw cap, best known from road and mountain bikes. Only fits a rim with a narrower valve hole.
Check which valve is currently in your rim and stick with that type; the valve hole in the rim is the deciding factor.
Tyre pressure: the PSI range
A permitted pressure range is printed on the side of the tyre, often in PSI. You deliberately run fatbike tyres at low pressure, and within the range you choose according to use:
| Pressure | Effect | When |
|---|---|---|
| Low in the range (e.g. 8-12 PSI) | Maximum grip and cushioning, the tyre flexes with the terrain | Sand, snow, loose terrain |
| Mid-range (e.g. 12-18 PSI) | A balance between comfort and rolling | Mixed use |
| High in the range (e.g. 18-30 PSI) | Low rolling resistance, more range, less wear | Tarmac and cycle path |
Always stay within the range printed on your tyre; the values above are indicative.
Recognising wear
- The knobs are rounded off or (in the centre) almost gone.
- The tread shows cracks, bald patches or visible canvas/carcass.
- The tyre keeps going flat or no longer holds its shape.
- Dry cracks in the sidewall — rubber can age even with low mileage.
If you spot one of these signs, replace the tyre in good time; on a heavy, fast fatbike a blowout is the last thing you want.