The chain calculators below do not have allowances in the calculations for the chain slack required by the geometry of the rear suspension. They rely on the allowance for slack BMW allowed in the standard chain and sprocket set.

Basic Sprocket Dimensions

The chain is 112 links of 520 (5/8" x 1/4")

There are minor differences in roller and pin diameters

between manufacturers and chain types so be warned.

Distance Between Sprockets

When calculating the number of links needed in a chain, the centre to centre distance between the sprockets is needed. For the standard sprocket set BMW calculated the number of links needed and allowed for chain slack to suit the suspension geometry. This length can be used to make calculations for non standard sprocket sizes

Enter the front and rear sprocket sizes and the number of links to calculate the sprocket centre to centre distance.

Front Sprocket

Rear Sprocket

Number of Links

inches

Distance C to C

Distance C to C

Number of Chain Links Needed

The distance between sprockets for the standard GS chain is 24.966 inches. This figure can be used to calculate the number of links needed in a chain when using different sprocket sizes. Add 0.75" when fitting an 18" rear wheel.

Enter the front and rear sprocket sizes and sprocket centre to centre distance to calculate the number of links.

If your result is an odd number of links add one link to get an even number

Front Sprocket

Rear Sprocket

inches

Distance C to C

Distance C to C

No of Links

Chain Length in inches and Millimeters

The calculation of chain length is easy and measurement is worthwhile in determining chain wear.
Regina Chains

are more forthcoming than other manufacturers on wear and technical data. Some of the mild steel rear sprockets
supplied with kits will wear out well before the chain and front sprockets. There are circumstances where
replacement of the rear sprocket only is appropriate. The initial length of a chain can be calculated below.

Enter No of Chain Links

Inches

mm

TR650

The Terra chain length is stated as 114 links but it is unknown if this is for the 17" ABS model or the 18" non ABS model.
If it is the 18" then the ABS model would have 112 links as per the 650GS.