altenator belt tention guide

anyone know what or how much tension you have to but on the belt before it is right as mine is flapping a little.

Assuming you're aware of the mechanicals of adjustment, 15mm deflection on the longest run. Or a generous half inch for us ancients.

Old thumb rule: if you can finger and thumb it relatively easily through 90 degrees on the middle of the long run, it's near enough for Longbridge.

9/16" is the closest fractional mesurement (that any of us old buggers can visualise) to 15mm

Cobber wrote: 9/16" is the closest fractional mesurement (that any of us old buggers can visualise) to 15mm

Yep, three gnats cocks over half an inch.