For me a TT bike is worth, I reckon, around 60-80s over ten miles. TT bike is carbon, typical handlebar setup but without disc wheels. On an evening 10 I come in at around 24 minutes to 24:30 depending on the wind. Usually closer to 24 minutes.
Tonight I used a heavy steel roadbike (pretty poor frame- a Tange training frame, it is heavy and generally not very responsive), 8 speed, downtube shifters. Wheels/tyres however were the same as I use on the TT bike.
It's the worst bike I've ever ridden for a TT. It was a former commute hack, I'm retiring it and wanted it to go out in style.
25:20. It was a good night, warm and a bit breezy.