[VT] new rims and bolt thread seems longer on front than back

[Helmo645]

Well was driving today after freshly putting some new rims on and the back wheelstarted shaking like crazy... Had a look and most of the nuts were lose as f&@$ on it... Then got home and used the socket set to do up tighter and realized it only does up as tight as going flat with the top of the bolt as oppose to the front ones which seem to let the nut go down an extra cm... Would there e any reason for this or do I need longer threaded hub or something??? Really dot want to go driving and have this happen again
hard to see but top of bolt flat with top of thread on back wheel

As oppose to front wheel