I did the Rhyd Ddu descent at the beginning of October. When the rest of the country was enjoying a freak heat wave Snowdon was covered in cloud and the winds were gale force at the top.
The first part of the descent is not really ridable and neither is the first part of the ridge. In gale force winds with a bike in one hand when you really need two to stop you falling down the sheer drop to your death it’s not much fun.
After that it’s a big wide open moon scape of a drop where you simply have to pick a line. It then levels out and passes over what I believe are old mine workings, some of it’s ridable but some of the boulders have to be climbed over. Expect some big hits, I knocked the back wheel out of the frame.
Getting to the bottom the final descent is just a wide firm track to the station.
My plan that day was to go back up to the top and do the Rangers descent too but the combination of the Rhyd Ddu and climbing the first switch backs of the Rangers up to Maesgwyn was exhausting.
A better ride 2 weeks later (to get over the feeling of being defeated) was up the Llanberis to the summit then a very quick descent down the Llanberis to the gate at the top of the tarmac, then back up Llanberis to the top of the Rangers, then down the Rangers and finally up over Maesgwyn and back into Llanberis itself. Just under 5hrs and loads of fun.
Short version: the Rangers and the Lllanberis descents are a lot more ridable and a lot more fun than Rhyd Ddu, and Rhyd Ddu is not advaible in crap weather.