The hire company sometimes charge an 'admin' fee of around 25 euros on top of the fine.
If you don't pay the fine you will not be able to hire a car with the same company again.
You can only easily avoid paying if you are not a Spanish resident.
If you are a resident they may be able to "embargar" your bank account.
If you are not a Spanish resident then it is easier not to pay.
To avoid paying you will have to cancel your card, however this may be inconvenient.
Once the money has gone out it may be hard to reclaim especially as the offense will be documented with photos so if you are going down that route it may be best to block your card straight away.
The best thing to do is not get a fine in the first place.
Apparently Granada council earn over 30 000 euros per day in traffic fines.
If you see any big yellow sign in Granada with the word "prohibido" on it don't go down that street.
By the way: the Guardia Civil set up many radar traps in order to earn extra income from speeding motorists so when in Spain always drive within the speed limit. Especially when the speed goes down from 80 to 60 around traffic junctions.
For more info about driving in Spain visit this pagehttp://granadainfo.com/driving-spain.htm
This page has driving distances from other cities to Granadahttp://www.granadainfo.com/distances.htm