I just recently wrote a bit where my heroine was involved in a wild bicycle chase. So here are some Victorian bicycle terms:
Penny-farthing: the large-wheeled bicycle popular with young men from the 1870s to mid-1880s. Was called an "ordinary" bicycle until this term came into use in the 1890s, first as a perjorative. Most weighed about 40 lbs., and you picked your wheel size based on your leg length.
To take a header: To go flying off headfirst. A very real danger with the penny-farthing, many of which had poor or no brakes and were prone to tipping.
Scorcher: Someone who rides fast (and probably recklessly).
Safety Bicycle: a bike with two wheels of equal or near-equal size and a chain drive. First available in the mid-1880s. Once these were widely available, the bike was no longer a toy but a practical vehicle for anyone.