In beautiful Glen Avon, you'll have little to complain about when it comes to the condition of the gravel roads; they're generally in perfect condition. A Scottish "Strade Bianche." Higher up in the glen, you'll encounter some rougher paths that are unsuitable for road bikes. In this glen, you'll be particularly affected by the sometimes blustery wind that can whip through the valley.
Fun fact: the water of the River Avon is among the clearest in the Scottish Highlands.