In the past I have done as Gazza suggested and loose-fitted the tyre on the rim, then balaced it, observed the result and then rotated the tyre to the most favourable position.
It didn't seem to work for me this time though.
No matter where I positioned the loose-fitted tyre it seemed to be quite a bit out of balance.
In the end I popped the beads on in what I thought was the best position, but found that 60g was necessary to achieve balance.
I was clutching at straws from that point and only tried rotating the tyre by 90 deg out of desperation really, because there was no way I wanted 60g of lead on there.
I was most surprised that it worked.
My balance method is "off the bike" using a proprietary "spindle and cones" and a pair of adaptors which convert my paddock stand into a balancing stand, each equipped with two bearings to run the spindle on.
So, pretty reliable kit, I would say.
I think the error must be creeping in when I attempt to balance the wheel with the tyre only loose-fitted on the rim.
I'm slightly surprised by this but I can't see much alternative possibility.
I'm not sure that fitting your own tyres is worth the trouble .... unless you have carbon wheels which kinda forces the issue.
It does mean you can by tyres nice and cheaply from the likes of Oponeo though, and not then have to squirm and beg the local fitter to put them on for you.
Or, if you're going through a skint phase you can do like I did and search out a brand new PR4 rear on ebay for seventy quid .. plus the petrol to fetch it.
I paid even less for the PR4 front but I'm not going to divulge the shameful details of that deal on a public forum.
There is also the satisfaction of doing it yourself, as well as the knowledge that you only have to trust your own work .. the Joey Dunlop syndrome, if you will.
It also gives you the opportunity to take the time to clean up the brake calipers and suchlike while you're in there
I use 370mm cable ties from B&Q, but doubled up cos they're not long enough on their own (for the rear at least .. can't remember about the front but I'll know in a day or two).
They're nice and thin but only just strong enough and I do break the occasional one.
I also only cable tie around half of the rim, usually five positions. Then I slip each bead on or off singly rather than both together like the guy in the vids.
I usually nip the central 3 ties up tight but leave the two outer ones slightly looser.
Its all about getting both beads into the very deepest part of the well on one side of the wheel, thus creating maximum slack diametrically opposite.
I have a pair of 3 inch plastic levers from a bicycle puncture kit on hand, but seldom need them much if at all.
And I use a proprietary dilutable tyre lube (like Gazza says, one purchase lasts pretty much forever) and I use it sparingly.
I also use an Abba bead breaker .. a piece of kit which I can recommend most highly, not just for its effectiveness (and gentleness) but also for its relative compactness and ease of storage in the shed.
I'm not sure that your kitchen scales method to find the heavy spot would be very accurate, Rob.
..... but I'll give it a go, or maybe adapt it, using a spring balance to lift the tyre off the ground at the bead.
Oh and as for balance weights .. I did buy some once but I also have a bit of roofing lead that I can cut into the required weight and attach using sticky rubber pads from the pound shop.
Its a neat and tidy method.