Unless you are in a race and seriously competing in said race - get off the damn bike and pee!
And, there is no need to go find a bush and get dirt in your shoes.

Instructions:
1. Get off the bike.
2. Turn back to road.
3. Pull out your wanker.
4. Pee
5. Put your wanker away - this is very important.
6. Get back on the bike.