Understanding new trike
So I have my new trike and there's something I'm not clear about. It's a 24 speed, microshift twist shifter. The right shifter has 8 gear indicators in the optical window. The left shifter has an "L" and a bunch of lines....I haven't shifted it all the way to see if there are other markings, but I've never seen a shifter without gear numbers. Can someone explain to me how this works? I'm used to 1x systems with no front derailleur on my 2 wheel bikes.
The other question I have is whether it's okay to swap out the rear derailleur. The trike has an Altus installed, and I have a brand new Claris. It seems Altus is mountain and Claris is road, but I don't know whether that means they are not compatible. Any idea?
Thanks.