Size Information

Sizing can look complicated but the basics are:

Traditional numbers - examples are - 24" x 1" or 3.00-4. Most tyres have a traditional size but some may not. A 24" tyre will not measure 24" in diameter. Only the ISO sizing is exact. 

ISO - When in doubt follow the ISO size. All tyres will have an ISO size and they look like 50-559, where 559mm is the diameter of the tyre where it fits into the bead of the rim, and, 50mm is it's width.

Note some makers may use 50x559 instead of 50-559.

Manufacturers may label their tyres in traditional, ISO or both sizes.

Wheelchair Tyre Sizes

1. Rear (Drive) Wheels
• 20" (451): ISO 37-451, 40-451
• 22" (501): ISO 37-501, 40-501
• 24" (540): ISO 25-540, 37-540, 40-540 (most common)
• 26" (559): ISO 50-559
• 25" (559): ISO 37-559 (used for sports)
• 28" (622): ISO 32-622
2. Front (Caster) Wheels
• 3" (75): ISO 50-75
• 4" (100): ISO 100-25, 100-32
• 5" (125): ISO 125-25, 125-32
• 6" (150): ISO 150-25, 150-32
• 7x1 3/4 (177): ISO 47-177
• 8" (200): ISO 200-32
• 8x1 1/4 (203): ISO 32-203
3. Specialized Off-Road or Sports Wheels
• 25" (559): ISO 37-559
• 28" (622): ISO 32-622
4. Small Pneumatic Tyres for Manual Wheelchairs
• 12-1/2 x 2-1/4 (203): ISO 62-203

Scooter Tyre Sizes

1. Small Mobility Scooters
• 3.00-4 (260): ISO 260x85
• 3.50-4 (260): ISO 260x90
• 8x2 (200): ISO 200x50
• 12-1/2 x 2-1/4 (203): ISO 62-203
2. Medium Mobility Scooters
• 4.00-4 (280): ISO 280x100
• 4.00-5 (310): ISO 310x100
• 10x3 (254): ISO 254x76
3. Large Mobility Scooters
• 2.5-8 (220): ISO 220x65
• 3.00-8 (260): ISO 260x85
• 3.50-6 (350): ISO 350x100
• 3.50-8 (300): ISO 300x90
• 4.10/3.50-6 (350): ISO 350x105
• 4.00-8 (400): ISO 400x100
• 5.20-10 (460): ISO 460x130
• 6.00-12 (480): ISO 480x150
4. Specialized or Other Tyres
• 7x1 3/4 (177): ISO 47-177
• 8x1 1/4 (203): ISO 32-203
• 10x2.5 (254): ISO 254x65
• 11x4 (280): ISO 280x100
• 12-1/2 x 2-1/4 (203): ISO 62-203