Bike tyre pressures
To change the rim size on a bike you should consider a 1.5" drop in tyre width for every inch bigger you're making the tyre. As you increase the size of the tyre, the width of the tyre will increase too, so reducing this will make the tyre fit within the frame. Moving down in size is much easier and will allow you to fit wider tyres on the rims, increasing comfort and rideability. However, it's always worth checking out the clearance of the frame, and whether there is any adjustment needed in the brakes.
Please find below a list of the recommended and maximum tyre pressures for most widths. Italics in grey are Halfords recommendations and not Schwalbe's.
| Tyre width | Schwalbe rec. | Mavic max. | Rim size |
|---|---|---|---|
| 18 mm (0.71 in) | 9.5 bars (138 psi) | 10.0 bars (145 psi) | 13C |
| 20 mm (0.79 in) | 9.0 bars (131 psi) | 9.5 bars (138 psi) | 13C |
| 23 mm (0.91 in) | 8.0 bars (116 psi) | 9.5 bars (138 psi) | 13C-15C |
| 25 mm (0.98 in) | 7.0 bars (102 psi) | 9.0 bars (131 psi) | 13C-17C |
| 28 mm (1.1 in) | 6.0 bars (87 psi) | 8.0 bars (116 psi) | 15C-19C |
| 32 mm (1.3 in) | 5.0 bars (73 psi) | 6.7 bars (97 psi) | 15C-19C |
| 35 mm (1.4 in) | 4.5 bars (65 psi) | 6.3 bars (91 psi) | 17C-21C |
| 37 mm (1.5 in) | 4.5 bars (65 psi) | 6.0 bars (87 psi) | 17C-23C |
| 40 mm (1.6 in) | 4.0 bars (58 psi) | 5.7 bars (83 psi) | 17C-23C |
| 44 mm (1.7 in) | 3.5 bars (51 psi) | 5.2 bars (75 psi) | 17C-25C |
| 47 mm (1.9 in) | 3.5 bars (51 psi) | 4.8 bars (70 psi) | 17C-27C |
| 50 mm (2.0 in) | 3.0 bars (44 psi) | 4.5 bars (65 psi) | 17C-27C |
| 54 mm (2.1 in) | 2.5 bars (36 psi) | 4.0 bars (58 psi) | 19C-29C |
| 56 mm (2.2 in) | 2.2 bars (32 psi) | 3.7 bars (54 psi) | 19C-29C |
| 60 mm (2.4 in) | 2.0 bars (29 psi) | 3.4 bars (49 psi) | 19C-29C |
| 63 mm (2.5 in) | 1.8 bars (26 psi) | 3.0 bars (44 psi) | 21C-29C |
| 66 mm (2.6 in) | 1.6 bars (24 psi) | 2.8 bars (41 psi) | 21C-29C |
| 71 mm (2.8 in) | 1.5 bars (22 psi) | 2.5 bars (36 psi) | 23C-29C |
| 76 mm (3.0 in) | 1.2 bars (18 psi) | 2.1 bars (30 psi) | 23C-29C |