Tern HSD P9 Review

This review was provided for free, but BOSCH provided two nights of free hotel stay in Vail, Colorado so that I could attend an event and test ride the bike. My goal is to be transparent and unbiased with you, this video and writeup are not meant to be an endorsement of Tern products. I welcome your corrections, additions, and feedback in the comments below, and the Tern Electric bike forums.

Observations:

• Tern is a leader in the folding bicycle space, and an early adopter of electric bike technology. They helped to pioneer folding ebikes and compact electric cargo bikes known as “midtail” cargo bikes. The HSD models blend some folding capability with strength and utility. It’s available in four different flavors as follows, please note that prices reflect timing of this review and are subject to change:
• $5,499 Tern HSD S+ with Bosch Performance Line motor and Enviolo Sport 380 continuously variable transmission (CVT) drivetrain with AUTOMATiQ auto-shifting with Gates Carbon belt drive. Also includes a Thudbuster suspension seat post.
• $4,499 Tern HSD S11 with Bosch Performance Line motor and Shimano Deore XT 11-speed derailleur (11-36 tooth cassette) with traditional chain. Also includes a Thudbuster suspension seat post.
• $4,099 Tern HSD S8i with Bosch Active Line Plus motor and Shimano Nexus 8 internally geared hub with Gates Carbon belt drive.
• $3,499 Tern HSD P9 with Bosch Active Line Plus motor and Shimano Alivio 9-speed rear derailleur (11-32 tooth cassette) with traditional chain.
• The most affordable model in the group is the HSD P9, which features the simplist 9-speed derailleur + cassette drivetrain. It’s fairly lightweght at 56.5lbs vs. the S8i that weighs 55.9lbs because it uses a belt-drive. As an active rider who prefers fast shifting and isn’t afraid to get my hands dirty for the occasional derailleur adjustment, the P9 is my favorite of the group. The big upside for internally geared hubs and CVT hubs is that they can usually be shifted at standstill and are less vulnerable to physical damage from curb strikes and other trail debris. This can be more common on a cargo model, especially with smaller 20″ wheels that bring the derailleur closer to the ground.

Pros:

• Tern is respected company with years of folding bicycle, folding electric bicycle, and electric cargo bike expertise and leadership. They spun off of Dahon years ago, another well-recognized folding bicycle company. Their folding handlebar design, proprietary Andros adjustable stem, and unique telescoping double-seatpost hardware feel sturdy and safe. The fact that they sell four versions of the HSD says a lot to me, it’s capable and desirable.
• Most electric bikes are rated to carry 250lbs or maybe 300lbs but the HSD can handle up to 375lbs! That’s enough for an adult rider and child or small adult passenger. The bike offers great utility for getting groceries, lumber for a project, or school gear, and the sturdy front thru-axle and premium tires (with puncture protection) offer peace of mind. The rear wheel offers quick release, and that makes it easier to service than many hub-motor ebikes… the front wheel uses a hex wrench bolt since it’s a thru-axle.
• Safety is a big deal to me because I sometimes ride in the early morning and late evening, surrounded by traffic. So, I love the bright color options here, as well as the reflective tires, reflective stickers on the frame and optional pannier bags, and the premium integrated lights that run off of the main battery. The headlight is especially great, being positioned high up at the handlebar vs. low on the fork and having an independent on/off switch.
• Some electric cargo bikes feel flexy because they are so long, and lack the proper materials or reinforcement. Some position the battery or motor at the rear vs. the center of the frame, but the Tern GSD feels very solid and stiff. They did a great job balancing approachability and stiffness with a mid-step frame that has extra cross members.
• The motor used here is one that I have reviewed hundreds of times before on other electric bikes and it has earned my trust as being reliable. Both the Bosch Active and Performance Line motors offer smooth controlled power delivery, and they measure your pedal input over 1,000 times per second! The motor controller listens for rear wheel speed, pedal cadence, and pedal torque. If you get the P9 version of the HSD (with a 9-speed derailleur), the Bosch motor controller also offers shift detection, to help reduce stress on the chain, sprockets, and derailleur.
• I like that Tern chose the Alivio shifters from Shimano because they offer a three-shift low lever, to quickly drop gears and climb, along with a two-way high lever for comfortable press or pull shifting. This shifter is my preference to most SRAM and some low-level Shimano shifters :)
• The narrow-wide chainring reduces drops and slop in the drivetrain while the aluminum alloy guard protects the chainring teeth and acts as a bash guard for the motor casing. The sleek plastic chan guard keeps your pants or dress from getting dirty or snagged.
• While the HSD S8i and P9 only come with a Bosch PowerPack 400 batteries (verses the PowerPack 500 on the S+), this is still a great battery pack in terms of weight, durability, and replaceability. You can even upgrade to a PowerPack 500 later on, because it’s compatible with the same interface. These batteries are compact enough to store in backpacks and bike bags, and they have a loop at one end to make carrying easier.
• I love how the battery pack can be charged on or off the bike because it’s convenient for those who commute to work and need to fill-up for a long ride home or errands along the way. I appreciate that the S+, S11, and S8i models get the faster Bosch 4 amp charger for quick fills vs. the P9 which only gets a 2 amp charger… but it’s still a great charger that’s lighter, smaller, and the plug interface is cross compatible so you can use the faster charger too, if you have another Bosch powered electric bicycle.
• Power and range are important but so is stopping, especially with a heavier bike and potentially more gear or multiple passengers. The Shimano hydraulic brakes used here are great, they feature adjustable-reach levers to fit different hand sizes. The front disc brake rotor is 180mm vs. the rear 160mm, which increases the mechanical advantage and cooling properties. This is great because more stopping power actually comes from the front brake as rider and cargo weight shifts forward. Just be careful not to bend the rotor at bike racks since it’s so low on the 20″ wheels and large.
• Good kickstand choice and position, while it’s not a double-sided kickstand like the GSD has, it helps to cut down on weight and should be easier to deploy and stow for most riders. I expect that it would work fine for most cargo and even a child passenger… though the bike will tip to the left side vs. being perfectly level. One benefit of the side stand is that it doesn’t hang down as low and won’t drag or make contact with obstacles as easily.
• So many awesome accessories! Whether you’re taking people or cargo, there are plenty of ways to stow gear. You could start off with a baby seat, then upgrade to a padded child seat with handlebar, and continue to transport a young adult (as long as you don’t exceed the max rack weight of 132lbs). I liked the big pannier bags that were strapped onto the demo bike, as well as the locking plastic front basket with its carrying handle :)
• The front rack design is excellent, note that the optional tray and basket mount directly to the head tube and won’t impact steering the way cheaper fork and handlebar mounted racks and baskets might. This is important for carrying heavy loads, and when parking due to the side-mount kickstand design.
• The promotional videos show a man riding with a dog trailer, and Tern has designed a dedicated trailer mount for the HSD! This is wonderful, because sometimes it can be difficult to get a trailer setup with ebikes that have unique frame designs and disc brakes (due to caliper mounting position).
• The swept-back handlebar, Ergon ergonomic grips, and plush Velo saddle make the bike a lot more comfortable than it could have been. I especially enjoyed the suspension fork, which offers compression adjust, lockout, and preload adjust (to pre-load the spring for heavier riders). For even more comfort, you can lower the tire pressure a bit (just don’t go too low or it could cause a pinch flat, they recommend 30 to 55 PSI).
• With a very approachable 18.5″ stand over height, you can easily step-thru the frame vs. having to swing your leg up and over the saddle or over the rear rack (which might be loaded with cargo or a child seat). I like that the top tube and portions of the side stays have clear plastic stickers to keep the paint looking nice. I also appreciate that Tern has added a bottle cage mounting point on the top tube with three bolts positions so you can position the cage perfectly!
• Tern chose premium ABUS locking cores for this electric bike, and included a frame lock to secure the rear wheel! This frame lock is also made by ABUS and uses the same key as the battery pack, so you won’t have extra clutter and confusion each time you need to access the locks.
• The fenders are extra wide, sturdy, and fairly quiet. The Bosch Active Line Plus motor is also extremely quiet! For me, the chain and derailleur is appealing simply because it’s so tight and quick for shifting. Hubs don’t shift as quickly and the ENVIOLO CVT isn’t as tight or efficient as the Nexus 8 or 9-speed cassette derailleur combo. All things considered, even though the P9 uses a weaker motor, it’s still very capable and drains the battery more slowly.
• Being able to fold the handlebar allows you to stow the bike on its side to save space… this could make sense in the trunk of a car, RV, or the bed of a pickup. I noticed that the pedals were not folding, so consider some quality metal folding pedals like these to make the bike even flatter… or to reduce scraping and gouging that a protruding pedal can cause.
• The four stand points at the rear of the rack allow this ebike to stand upright, saving space in an elevator or closet. This is a feature that many of the Tern products now offer, and it works pretty well… just be careful about where you park it so nobody gets hurt if the bike is bumped and tips over. I was amazed that it stood up on the uneven dirt path I was filming on!

Cons:

• Depending on the HSD version you choose, it can get pretty expensive… especially when you factor in accessories! This is a premium electric bike, with great dealer availability for setup and support. I appreciate that the HSD P9 is less expensive, but it still isn’t cheap ;)
• While I love that the seat raises so high, it wasn’t clear how you’d be able to raise the handle bars to match without some special accessory, the Andros adjustable stem helps a lot, but some other folding electric bikes have telescoping handle posts to address this. Tern followed up after I covered the HSD S8i a while back to explain that they do offer taller handlepost (the folding steerer column/stem piece) and that their local dealers can order and install them!
• Tern has chosen slightly wider 2.15″ tires (for comfort and stability), but the HSD can still feel jarring on bumpy terrain because the 20″ wheel size has a higher attack angle (running into bumps and falling into potholes vs. spanning them). By contrast, the GSD has wider 2.4″ tires… but even it can feel jarring compared to a larger wheel size. I have found that lowering the tire pressure can improve comfort a bit, and you can purchase a 30.9mm suspension seatpost to replace the upper rigid portion of the stock seat post. This will improve back, shoulder, and neck comfort for people with sensitivity or longer trips.
• The smaller 20-inch diameter wheelset makes this ebike easier to mount, load, and stabilize when starting or stopping, but it also brings the kickstand and derailleur lower (if you get the S11 or P9 models). The ground clearance on this bike is less than a full sized ebike and some cargo models with larger diameter wheels (24″+), so be careful when parking near a curb or other low obstacles.
• The Bosch Active Line motor can feel a little limited when facing a formidable hill and is best suited for city riding in my opinion. There is also a bit of a clunk when you stop pedaling, something that is common in the Active Line motors. For extra power, consider the S+ and S11 models with the Performance Line motor for faster 120 RPM cadence support (vs. 105) and even more power at 65nm of torque vs. 50nm with Active Line Plus.
• The Bosch Purion display panel isn’t removable and doesn’t have an active USB charging port like the Intuvia, Kiox, or SmartphoneHUB, but it’s much more compact and simpler to use. It might also avoid damage when folding the handlebars on the HSD.
• Interestingly, a lot of the wires and cables on this ebike are not internally routed. This is atypical for a premium purpose-built product, but may have been done to reduce pinching when folding the handlebar and to improve serviceability. Some of the cables stuck up and blocked the headlight a bit during my ride test. Not a lot, but they were there.
• It’s nice that they ABUS keys work for both the battery and frame lock, but it gets locked into position when the frame lock is open and you’re riding! This is a bummer if you have multiple keys on a keychain, because they will hang down and jingle around while the ABUS key is locked into position (with the potential to snag your pants/dress). You could just leave one of the two ABUS keys in the frame lock at all times, but then someone could lock your bike, remove the battery, or just or steal the key every time you stop… so you basically have to lock it every time. I would prefer to have the choice of removing the key whenever I want, as is the case for many alternative frame locks.
• The thicker gauge tubing on the rear rack may not be compatible with some standard panniers and clips. The thicker tubing was probably used for strength, to help support the official Tern pannier bags and increase the overall capacity for the optional child seat or Captain Chair that Tern sells.
• This is a very minor thing, but the headlight requires two steps to activate. You must first turn on the bike and hold the + button on the Bosch Purion display panel to then see a light icon on the lower left of the LCD screen, then you must make sure the slider switch on the back of the headlight unit is to the right. I can imagine that some users would wonder if the light was broken because the physical slider switch will not activate the light if the display panel is not first activated for lights. The rear light is either on or off based on the display panel + button steps.

Useful Resources:

• Official Tern website
• Local Tern bike shop directory to find a Tern dealer near you for fitting and test rides