We now live in a bankrupt 3rd world country with a devalued currency and we are all something like £20,000 in debt to the rest of the world, so in that situation I don't know whether we can expect surface erosion like this to be fixed or not. Instead, the necessary funds will probably be diverted to something like the Olympic Stadium, which we really can’t afford. I guess you could take the matter to the Small Claims Track of the County Court. The county council has said the rut does not warrant repair, so its position is clear. The rut did damage your motorcycle tyre, so that is also clear. A judge can decide. Your case will be much stronger if this happened at night when the rut could not easily be seen.