My dad and brother have e-bikes. My dad last summer and my brother just a few weeks ago- my brother got lucky though, as availability on bikes of any kind is basically non-existent right now and pre-orders are onto 2022.
Anyway, I demo’d my brothers brand new Trek Domane+ alr 6 for about 10km a couple weeks ago. Fairly enjoyable ride and quality bike with or without the electical component. Was quite surprised how subtle the boost was, but perhaps I was just not familiar with how to increase it. A good description might be that it was always like there was always a moderate wind at your back. You still have to work on the hills etc. And you are arent going to be totally screwed if the battery dies and you are in the middle of nowhere- you will just be on a slightly heavier road bike. Complete guess that I in no way can qualify, but as far as the domane+ alr 6, I would guess you are burning maybe 75-80% of the calories you would on a conventional bike. It has a very reliable groupset with Shimano 105s- you would obviously be getting a considerably better groupset on a regular road bike if you are spending 6K, but 105s are just fine in this case. And Im sure the higher tiered road ebikes are onto ultegra etc
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