There's an opportunity here for a little bit of fun, learning, and dare I say it, gamification.
The problem with showing distances is - it's just a number. It needs a relationship to make it real.
And if you use a relative percentage compared to the person who has ridden the longest distance for example, then you run the risk of tying the data too strongly to outliers in the range - for example if one extreme cyclist has ridden a huge distance, then everyone else's relative percentages will look tiny.
I'd recommend using a scale which is independent of other runners, and also introducing a little bit of fun facts into the visualisation - something that's meaningful or interesting - something that people can relate to.
So here's an example - you could show the distance as equivalent to riding the width, height, length, circumference of one or more of the US states, like in the example below.
This adds an element of interest in that it might be a challenge perhaps to do the equivalent of riding across the whole of the US. Or there could be an element of wanting to see what the next increment of distance might display. Will it be my favourite state? Will it be Florida? Is it were my brother lives?
And there's a sense of achievement of having ridden a distance that is akin to the real world. It could even be integrated with a twitter button: 'In the last year I've ridden the equivalent of ...'