"Downhill" mountain bikes is a term of art and, as an avid mountain biker, I'd guess not actually the type being used for conversions to commuter bikes.

You're much more likely to target a "trail" full suspension mountain bike or fixed tail bike. You'll have a lot more cost options and they're more suitable for a commuting purpose, they'd still have plenty of travel and braking compared to a standard commuter or utility E-bike. As a note, my mid-level trail bike came with a better set of brakes then my high end cargo hauler e-bike which weighed about 10 times as much.

Yeah there’s no way you could use a DH bike as a daily rider, even with an electric conversion. The geometry and shock travel is just wrong (when you try to pedal a DH bike on the flat, you look like you’re riding a chopper with the added bonus of your knees going up to your waist)

The implication is that most DIY ebikers don't bother with pedalling. Hand throttle keeps you at 50km/h fine.

Long seatposts that bring you up to a typical height are fine. The suspension is doing the work, no need to leave the saddle.

DIY downhill ebike is around $4000 NZD, while the cheapest, lowest spec downhill ebike from manufacturer is $6000 or so. There's a sizeable savings to be made.

Yeah I think you don't need to do this to an expensive bike. Mechanical disc brakes and just a front shock are probably fine if you want to go 50km/hr. A heavier sturdier frame and burlier tires are ok because it is powered.

I wouldn't recommend converting a road bike as they are more fragile.

I’d love a utility ebike but afaik they just don’t have enough weight and hence - the grip at high speeds to be safe.

I’d guess e-scooter/moped is next best thing tho parking is an issue in some places.

Mechanical grip is entirely a function of tire compounds. In fact, ebikes can have even more tractive grip because you can make them AWD! This makes them much safer in snow and ice compared to other two wheeled vehicles.

They are fine at 45-50 km/hr. That keeps pace with car speed on residential roads fairly well. Any faster and I agree you could look at scooter or moped.

What is this "shock" thing you speak of? Is this a nasty side effect of "e" bikes?

A "cheap" bike is just a rigid frame with rigid forks.

In the US midwest at least, almost everyone who buys a cheapo bike from Walmart, Target, etc buys what is basically a terrible hardtail mountain bike. Front fork suspension, wide knobby tires, etc.

My assumption is that people buy them since they are a touch more comfortable than a full rigid bike frame.

Imperfections in the road at 30mph are very different than at 15mph. Especially on a cheap frame.

A fat tire can stand in for a shock, but "cheap" bikes don't usually fit 3" of rubber either.

Relatively cheap electric fatbikes like [1] are currently very popular in Italy, as far as I have seen on a recent holiday:

[1] https://elettrica-bike.it/en/product/fat-bike-vulcano-s-tipe...

Shock absorbers = Suspension

I don’t see any ebikes being sold without at least a 50mm front shock. The added weight of the battery+motor makes it essential

I have a Trek Allant+ 9.9S that is shockless.

Wow carbon fibre, and the tyres don't seem too thick.. How does it ride?

Ahhhh I think I understand - it's a "speedbike" right? So only for driving on roads like a car, so there's no question of forest tracks or gravel walkways.

I upgraded from a Trek xm700+ with a front shock. Both served me well but I don't miss the shock.

Yep, they're both commuter/cruiser type bikes, so probably not best offroad.

Both have the top end Bosch Class 3 motor, so they're usually against the rules on trails in my area.

Being pedantic, the suspension of the xm700+ doesn't have a shock. Its a simple coil spring that gives the wheel some room to wiggle. Shock absorbers actually dissipate that energy with oil/air/rubber.

If you ride it like a bicycle and try to avoid potholes and curbs, simpler designs work great.