So in the process of building up a cheapo TT bike off ebay parts that while get some outdoor use but will probably be on the trainer 95% of the time.
For the type of outdoor riding I have planned 1x will likely be spot on with a normal range cassette/mech and bigger rings seem to be a little easier to track down in 1x, so I’d probably go 1x if only using outdoor but generally the advice is ride ERG in the small ring right?
What’d you do in my situation? Obviously not a huge outlay either way but got that kind of decision paralysis we all get some times!
I use my cross bike with 1x on a kickr core and NEVER change gear.
Recommendations for chainring choice are likely based on flywheel inertia as Chad eluded to. But that optimisation is suggested because most people have 2 chainrings, not because a particular chainring is necessarily 100% optimal. The most optimal chainring size could be 75t but that’s not realistic because most bikes don’t have that.
So I say, buy the bike you want and if it works for you outdoors then it can work for you indoors.
having said that, if the bike will spend 95% of the time on the trainer then why are you speccing it based on the outdoor terrain?
The Drivo 1 is a decent trainer with plenty of high and low power capability, so I don’t think you will experience issues unless you have a very low FTP.
Per ERG, this is the Achilles heal of the trainer. It works but has a tendency to be slow to change resistance, as well as bounce around instead of holding a tighter target like other trainers. If you are doing more steady state stuff (a guess since you are talking about TT stuff), you will probably be fine.
I’ve been using my 1x bikes in erg mode for the last year and have had no problems. The only issue I might foresee is doing VO2 intervals in resistance mode. In 1x you either need to adjust the resistance or shift a bunch when moving between the 120% and 40% sections. In a 2x shifting between chainrings would replace some of the shifting in the back needed for the 1x. But I do everything in erg so it hasn’t been a practical problem for me.
I run a 48t front and outside an 11-36 cassette. Inside I have a 12-25 or 12-28. I started with a straight chainline but now sit in the 21 because my trainer is better able to control and adjust resistance with a slower flywheel speed. If you want to simulate flat outdoor riding (high inertia) be in one of the smaller cogs. If you want to get closer to climbing (low inertia) be in one of the larger cogs.
Even in your largest gear, the inertia of trainers is much less than outdoors, even when compared to climbing slowly. The only reasons to change gears on a trainer are therefore 1) to spread the wear around, and 2) to keep within the trainer’s speed vs. power limits.
Set your gearing - In order to maintain smooth, even power across all of your power zones, you should maintain a mid-ring gearing in the rear cassette, and either a mid (if you have three) or inner (if you have two) front chainring. Your chain should follow a straight path from rear to front. This will also help you avoid hitting a wattage floor.
Yeah this is a good point I do quite a bit of Zwift racing, too much if I’m honest, though picking up trainer road imagine I’ll be doing far less, and could always switch to the road bike on the trainer in those instances where it’s going to be using a wider gear range, probably makes the racing experience more realistic than doing a crit on a TT bike.
However, I believe that recommendation is based partly on the “wattage floor” but also on chain alignment. For example, the gear selected by choosing a mid-cassette cog and the small chainring could also be achieved with the big chainring and a bigger cassette cog. The chain wouldn’t run as straight a path but would still be perfectly functional. It’s nothing different to what the chain would be doing out on the road.
I’ve had no issues with zwift racing and free riding with my 1x. I have trainer difficulty / realism set around 40% and you can always adjust it as it is effectively ‘virtual gearing’ to get the low end you need for the steeper parts. I thought about getting an 11-36 for a vEveresting attempt as you are supposed to run the difficulty at 100%, but that is the only reason I’ve thought of for replacing my 11/28 / 11-25 aside from wear.