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Update 2023-10-10: the issue with the bike shutting off was corrected by replacing the Bosch Purion controller under warranty.

Introduction

Last year my spouse spoiled me with a new cargo e-bike, the Tern HSD P9 Performance (Note: It's the 1st generation HSD – the 2nd generation has some major changes). I had been wanting a cargo e-bike to do school dropoffs and small errands. I've been commuting to work by regular “acoustic” bikes for years, but hadn't tried an e-bike until the Tern. Since then, we've put about 700 miles (~1100km) on the bike. Here are some thoughts.

“Folding” and Storage

The HSD is often described as a “folding bike.” Usually, when you hear folding bike, you think of a bike that folds in half for extremely compact storage or transport. With the HSD, it just means that the really long stem/headtube thing can fold. There's even an included rubber strap and This is helpful, because this part of the HSD is very long compared to “standard” shaped bikes, but not nearly as helpful as being able to fold the entire frame in half in the middle like some other folding bikes. Even with the handlebars folded down, it's not that easy to fit this thing in the back of a car.

Another storage feature: the HSD is designed so you can tip it back and stand it vertically on the back of the integrated rear rack. This is pretty cool and could really come in handy if you wanted to store the bike upright in a small space. In practice, I have been way too paranoid to do that. I fear that it would be far too easy for kids or others to tip over the bike from this position. I've considered attaching some kind of bungee anchor to the ceiling of my garage to prevent the HSD from tipping from vertical... maybe someday. In the meantime, we've just been parking it like a normal bike with the kickstand.

E-System

The HSD P9 Performance comes with a 500Wh Bosch PowerPack and a Class 1 Bosch “Performance” motor capable of 65 Nm of torque. You control it with a Bosch Purion display.

The battery can be removed from the bike (key required) and charged separately, or you can plug the charger directly into the bike, with a charge port on the battery mount, which is protected by a weather-resistant rubber flap. In practice I pretty much always take the battery off to charge it, because the cord from the Bosch battery charger brick is awkwardly short and I can't plug it into the bike in my garage without leaving the brick in dangling or in the way in the garage.

The bike has 5 assist levels, ranging from “Eco” to “Turbo.” I keep it on Eco most of the time, but my spouse likes to use Turbo almost constantly. With Eco, the bike feels roughly like a normal bike (no mean feat for a bike that weighs ~60 lbs (~27 kg)), or perhaps a bit easier than a normal bike. On Turbo you really feel the motor helping, making all but the steepest hills easy, even with kids or cargo.

This is a mid-mount motor pedal-assist bike. Meaning that the motor is mounted in the middle with the chainring and there is no throttle. Instead, the system has torque and speed sensors. Based on your assist setting and a measurement of how hard you're pedaling, the system adds some extra assistance automatically. I like this approach as it's more like a normal bicycle vs. some e-bikes with throttles that feel like they would rather be electric motorcycles, but just added pedals as a regulatory endrun.

In Eco mode on flat terrain, the battery is good for about 70 miles. In practice, around here, we can usually get around half of that, which IMO is more than sufficient.

Shifting

The bike is a 1x9 drivetrain. One chainring, 9-cog cassette. It uses an indexed trigger shifter, which I like. One of the derailleur/tension pulleys in the back hangs very low to the ground, so you want to be careful riding over rough terrain and keep in mind that this is no mountain bike.

Fenders

The bike comes with integrated front and rear fenders which are great. They don't rattle or make any noise and feel very solid. I think it helps that the wheels on this bike are pretty small, so the fenders can also be small and the fender stays thereefore have good leverage.

Brakes

The Shimano hydraulic disc brakes on the front and rear work well, though sometimes noiser than I would like. I think I have a sticky piston on the front caliper that I need to address. But these brakes seem to stop the bike well even with passengers or heavy cargo.

Lights

The bike has integrated front and rear lights. They can be turned on/off from the Purion display and are powered by the drive battery, which I appreciate. The front light is pretty bright, though perhaps not so bright as some of the brightest USB-rechargeable standalone bike lights. Overall, I'm happy with the lights and I haven't felt the need to bring another bike light along during nighttime rides.

Cargo Carrying / Accessories

The HSD comes with a built-in rear rack that is very stable/sturdy. And it has to be. Because whatever optional passenger seating you may want to install is supported by this rack.

The bike doesn't come with passenger seating or bike cargo-carrying boxes. Instead, you have to buy and install accessories to help carry whatever people or cargo you want. This makes sense, because there are many things you could do with the bike and there's no real one-size-fits-all solution that they could sell. But it's also a bit frustrating because the official Tern accessories are a bit pricy. We wanted to carry our kids, so we got the “Captain's Chair” and “Joyride Bars” and “Sidekick Footrests”. This is a good setup to carry one passenger or some cargo (in practice, we sometimes cheat a bit and cram two kids in the seat). But these accessories alone cost us a few hundred dollars.

Will it Bus?

There was actually a period of time when I was commuting to work with this bike, which included one leg of the journey on a bus. This bike actually fits (barely!) the Sportworks bike racks found on the front of many buses. Now, this bike is heavy. In base form without accessories, it weighs in at a bit over 55 lbs (~25kg). Lifting it on and off of the racks is not super easy, but doable. Also, make sure to check with your transit authority's rules/regulations on weight for bikes, and also check the rack manufacturer's specs. I checked all of this and made sure that the HSD was barely within the maximum length and weight limits if I took the battery off.

One gotcha is that the Sportworks racks our buses use secure the front wheel with a telescoing arm that you lift over the top. Because the HSD's wheels are so small, this arm doesn't have good leverage to hold the bike down and could possibly slip down the wheel while the bus is moving/rocking. When I first started taking this bike on the bus I had horrible visions of the bike sliding off the rack on the freeway. But then a bus driver had a good suggestion – to use a bungee or velcro strap to prevent the rack arm from sliding. I used a velcro strap for this and it provided a lot of peace of mind.

Misc Gripes

Update: Our local bike store worked with Bosch to replace the Purion controller (under warranty) and that seems to have resolved the issue with the bike shutting off.

• We've had a few issues with the bike turning off mid-ride and not wanting to turn back on. We've taken it back to the bike shop twice now. Most recently, the bike store has been able to reproduce the problem and they're talking with Bosch to figure out the problem.
• Otherwise, my only complaint is the price. It is an expensive bike. So expensive that you'll probably be paranoid about locking it up outside the grocery store, etc.

Conclusion

It's a good, if expensive, bike. We've got a lot of use out of it, eliminating many short trips by car. It rides like a regular bike but can carry a decent amount of cargo or passenger. The accessories are pricy but nice.

Would I buy it again? Yes. But I might buy ones of the bigger GSD models, instead, so that I can carry two passengers more easily. And I'd prefer one of the belt-drive models Tern offers now vs the traditional chain / derailleur setup on this bike.