If you have ever struggled with this I hope this little gadget that I've devised may be of some use to you. Its a template with common stud patterns show with pairs of holes, so you simply place the datum hole over one hole, line up a measurement hole with the opposite (or secon hole round for five stud) and you can then read off your measurement.
For more info go to
www.easypcd.co.uk
Mods - and as an appology for placing what is clearly an advert in your general section I'll give all Madabout Kitcars uses a £1.50 discount on a set of four (normal price £13.00). Just enter the coupon code
madkit when paying with google checkout and it'll give the discount.
Cheers, Mark.