The 'centerbore' of an alloy wheel is the size of the hole at the back of the wheel which the 'hub' fits into. To help the wheels to seat properly this hole needs to be an exact match to the size of the hub.
Most modern wheels are what's called 'hub-centric' - this means that the hub which protrudes from your car [and mates with the equivalent sized hole at the back of your wheel] is 'load bearing'. All the studs or bolts do therefore is hold the wheel onto the hub!
If you have' lug-centric' wheels, the state of your studs or bolts is obviously more critical - be sure to replace these from time to time and always 3/4 tighten the wheels off the car to ensure they're centred.
The centre bore of the wheel is the location hole machined into the centre of the wheel. This helps locate the wheel securely onto the hub, see picture opposite. To help prevent electrolytic corrosion stick the wheels to the hub, smear some copper grease over this area to aid removal at a later date.
