I've been doing my indoor workouts on a 20-year-old Racermate wind trainer. The bearings are starting to go, so I jumped into the 21st century and bought a fluid trainer.

On my old wind trainer my RPE, HR and "speed" matched up pretty well with what I experience on the road, at least for tempo-like efforts. But I'm finding that the effort level on the fluid trainer is waaaaay off from what I'm used to. It seems like I need to be about three to four teeth larger in back to get my RPE and HR to match, and even then my "speed" is several MPH lower than I would expect. Also, it seems like I'm getting a lot more leg burn on the fluid trainer for a given cadence and speed than I would expect.

Is this common - this need to drop a few gears when you are on a fluid trainer? Or is there something else going on I haven't considered?