Let's offroad / mountain bike / mtb / ride dirt

Ouch! I'm running (I think) 56GI and I would say that is about right to verging on a bit high for flat stuff, irrelevant for downhill stuff and far too high for climbs. Unless you are racing then there is no need to blast the fireroads. Especially if you are in a group, the fireroads are where people take it easy and chat. For flat single track then (hopefully!) the trail is too twisty, rocky, rooty, etc to blast at speed anyway. Yes, there are trails where I could go faster with a higher GI but there are a lot more where I am pushing hard to go the speed I'm going.

That may be part of the reason why I use such high gearing, fireroads are probably my favourite part of off-roading, hence choosing a high enough gear to pedal fast enough for them.

And i'll definitely be going to Swinley on Sunday, first time i've had a Sunday off in ages and i'm not going to waste it!