Joined: Aug 2008
Posts: 13,144
Likes: 2,167
From: Ann Arbor, MI
Bikes: 15 Kinesis Racelight 4S, 76 Motebecane Gran Jubilée, 17 Dedacciai Gladiatore2, 12 Breezer Venturi, 09 Dahon Mariner, 12 Mercier Nano, 95 DeKerf Team SL, 19 Tern Rally, 21 Breezer Doppler Cafe+, 19 T-Lab X3, 91 Serotta CII, 23 3T Strada
Depending on the type of rain and riding, yes, a cap brim is helpful to keep eyeglasses clearer and for longer. My preference is for running caps becausethey are lighteeight, thin, low crowned, use non-soaking and quick drying synthetics, and have longer brims.
I did give up using caps years ago in favor of another device, but since $20 was too rich to "experiment" with a cap, I won't waste the OP's time.