HI, i recently Got Some 17" Alloys for my 96 colt, and it just generally vibrates sometimes when driving? any ideas on why this might happen?

Just thought i should mention the drum brake screws on a colt are NOT countersunk.

Therefore i had to buy new screws and sand them down to smooth the wheel face flat, otherwise the wheel would be angled when it went on, im not sure if this is related though?

Any Ideas people?

does this always happen when you are driving, sometimes happen when you are driving, or only happens when you brake?

It Sometimes happens when im driving

Try making sure they are torqued down all the way. If this is the case, you can try rebalancing them. Also, pay attention to the tire wear. If they are wearing abnormally, it will cause a vibration. Is the wheel bent? If none of these things fix it, it might be something with your suspension.

Check to see if centering rings have been fitted.
The centre bore could be larger than your hub.
The wheel studs should not be relied on to centre the wheel. They are just function to hold the wheel on.