Rear Axle bolt

[Notch000]

Can anyone tell me what size the rear axle bolts  are?  My socket set only goes to 20mm which is too small so need to get a new socket head to tension chain

[limax2]

Nut is 27mm across flats and the spindle head is 24.

[Notch000]

any idea what that is in socket, spanner size

[limax2]

A socket or spanner will be marked "27mm" and "24mm".
I wouldn't use an open ended spanner but a ring spanner would be o.k. except you can't tighten it to the correct toque with one.
You should use a socket and torque the nut up to 117Nm.
In the absence of a torque wrench that is best described as jolly tight.