The Santa Cruz Superlight. One of the classic MTB desigs of all time

So we want a bike that's light enough to pedal uphill, without getting a hernia. Fast enough downhill, to beat your mates to the bottom. Strong enough not to break, if you sometimes get big air and doesn't cost more than a small family car. Yeah, I know, pretty tall order. If we've already thrown out the need to win races (a specialist requirement) full suspension is surely the way to go. It can make both climbing and descending more enjoyable (no, really) and it's definitely more fun on descents. Horror of horrors, don't we usually have most of our fun on the descents? If you have most of your fun on the climbs you need a race bike. The down side with suspension is two fold, the expense and the maintenance. The maintenance isn't the problem it used to be, as many of the new designs work for a long time without much interference. However most of the new shocks need servicing by a specialist when the time comes and this can cost about sixty pounds. So you end up with two possible candidates for best bike, the tough hardtail and the light(ish) cross country full suspension. These could be made of almost anything (ok so spaghetti would be no good) but aluminium is a front runner for reasons spelt out in Frame Materials.