A "scorcher" in costume in an 1896 parade in Washington DC
The phrase "scorcher" was well enough known that someone dressed as a devil riding a bike would be understood to be spoofing the idea of being one. This scorcher, however, is sitting up nicely. From the Washington DC Morning Times of July 15, 1896.
A woman could also be a scorcher
Note her aggressive position on the bicycle, not to mention her mannish attire, as portrayed in Dr. Neesen's Book on Wheeling.
And we have this poem from an 1896 issue of the L.A.W Bulletin and Good Roads.
THE INTROSPECTIVE SCORCHER.
I am the scorcher!
That appertains unto my spine!
With head ducked low
O'er man and beast, and woe
Unto the thing
That fails to scamper when I ting-a-ling!
Let people jaw
And go to law
To try to check my gate.
If that's their game!
To kill folks, but I'll do it just the same,
They clear the track for me;
Because, you see,
I am the scorcher, full of zeal,
And just the thing I look like on the wheel!
The problem with this fellow is his less than upright posture
A rider's "incorrect position" as shown in The Bicycle: Its Selection, Riding and Care from 1892.
Yes, as much as anything, the problem with scorchers seems to have been their aggressive posture, although why it was OK for the race track but not OK on city streets is a mystery.