Is it possible to do the Cliffs of Moher and Inishmore Ina day?
I'm not really sure about that, how long would it take you to get from one to the other? We stopped to see the Cliffs of Moher on our way from Dingle to Galway, and stayed the night in Galway. We spent an entire day on Inishmore and took our time to enjoy it. We rented a bike from the town and biked out to Dun Aengus which was really impressive. Inishmore was one of my favourite parts of Ireland, it's a place you can relax and take your time. There is a ferry to take to the island and ours was in the morning, I guess if you wanted to do both you would need to research the ferry times and see if it was possible. I think it would be too rushed.
How long did it take to bike to Dun Anghus?
I believe it was 6km from the ferry to Dun Aengus. When we got off the ferry there was a bike rental shop. Other people paid for a car to take them or horse and buggy. We stopped along the way at the Seal Sanctuary and saw many seals lounging around close to the shore. Our B&B in Galway had packed us a lunch which we ate while at Dun Aengus looking out over the cliffs. We took a different route on the way back and there was an old lighthouse we visited. There was also a shop/someone's house where a woman makes and sells Aran sweaters, my sister had visited a few years ago and told me to go there, she bought a knit hat. I think we must of passed it, there was a little house with a sign in gaelic on the side, I didn't think it was the place and missed it. I think it's also listed in the Lonely Planet guide. When we biked back into the village we stopped for a drink at a pub, it was great!
There were several people biking when we first started, but it quickly thinned and there was hardly anyone on the road when we biked, it was really nice.