I am currently assembling a turbo bike from the spares in my garage, it’s an eclectic mixture of bits…

Last big decision is what sort of bars to fit, I have both risers and drops to choose from.

Anyone have a reasonable case to make for either option?

Aero.

Riser with drop bar ends. 😉

Seems logical to go for the one that gives the closest fit on the turbo bike to the bike you want to get fitter and faster on.

Drops, more positions, which on the turbo is a good thing as you don’t tend to move around as much.

Whatever you are used to for your road bike, obvs.

Seems logical to go for the one that gives the closest fit on the turbo bike to the bike you want to get fitter and faster on.

This. Or drops.

Don’t bother with either, just ride no-hands.

There’s no traffic to worry about and its very hard (but not impossible 😳 ) to fall off a Turbo 😀

If I had the choice I would directly replicate the position of the bike I race on.

what ernie says

I go even more, just use the bike I want to go faster and use for events. Its the thing that makes most sense. Get used to time in the position you’re going to use the most

Aero.

If aero is a position you use in real life this isn’t such a stupid comment. Being able to train in the same position can be useful or at least give you something else to take your mind off the tedium.

As a recreational MTBer who only turbo trains for fitness I use drops on the turbo because more positions is better when you are in such a static position so much of the time. I’d use flat bars if it was what I had though

Can recreational MTB use ever be condoned?

What kind of frame is it? Road bike frames can have really short top tubes, so you’ll need a snooker cue for a stem to make the risers fit 🙂

Having spent a fair amount of time on a turbo trainer, I suggest dropping out the rear wheel of your mountain bike and fitting your 700c std roadbike wheel (with TT tyre) and voila, you have the perfect position!
I kept a road bike for years on the trainer and fettled with the position of bars, stems, seats etc, even went as far as fitting aero bars to mimic the mountain bike.
Just swapping wheels is the best solution in my book.

I already have a spare old MTB frame and yonks ago I bought a 26″ turbo tyre… Might as well use them for something.

It’s a proper hodgepodge of bits, an old road fork and front wheel, 1×8 speed drive, it’s got the drops fitted now looking like it will work quite nicely…

I am in no hurry to assemble it, but I would prefer to have a dedicated bike living on the turbo by the end of summer…

I have my old Trailstar on the turbo with a 26er Tacx turbo tyre on it. I figured that if I’m going to use the turbo, it needs to be as close to the bike i ride most outside as possible.

So I’d say risers (if you have those on your MTB – and are training for MTB…).