tool
drive kit calculator
Compare the kit on your motorcycle with a new one: ratio, gearing change, the links the chain needs and whether the speedometer changes.
final ratio
3.00 3.00
Same ratio as now.
Chain: about 120 links (now 118). The rear axle stays where it is now.
The calculator needs JavaScript. Worked by hand with the same maths:
| size | teeth | ratio | chain | |
|---|---|---|---|---|
| now | 428 | 14 / 42 | 3.00 | 118 links |
| new kit A | 428 | 15 / 45 | 3.00 | about 120 links; axle stays where it is |
| new kit B | 428 | 14 / 45 | 3.21 | 7.1 % shorter; about 120 links; axle about 2.6 mm further back |
how it is worked out
The final ratio is the rear teeth divided by the front teeth. A higher ratio is shorter gearing: stronger pull and more engine revs at the same speed, with a lower top speed.
The chain length uses the standard roller-chain formula in pitches, L = 2C + (N1 + N2) / 2 + ((N2 − N1) / 2π)² / C. The distance C between the sprockets comes from your present chain, so the suggestion keeps the rear axle about where it is now, rounded to an even number of links.
The chain and both sprockets must share one size. 4xx chains have a 1/2 inch pitch and 5xx chains 5/8 inch; a different width of the same pitch does not seat properly.
| size | pitch | inner width |
|---|---|---|
| 415 | 12.7 mm | about 4.76 mm |
| 420 | 12.7 mm | about 6.35 mm |
| 428 | 12.7 mm | about 7.94 mm |
| 520 | 15.875 mm | about 6.35 mm |
| 525 | 15.875 mm | about 7.94 mm |
| 530 | 15.875 mm | about 9.53 mm |
send the exact list, get one quote back
Write the motorcycle, each part with its size, the quantity and how soon you need it. PRISMA MP replies with availability and prices.