Tern HSD S8i Review

To run the forums, host the website, and travel, I charge a universal service fee for my reviews. This in-depth review was sponsored by Tern. My goal is to be transparent and unbiased with you, this video and writeup are not meant to be an endorsement of Tern products or Cit-E-Cycles who built the bike and provided support. 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. The HSD midtail cargo model blends folding with utility, and is available in three different flavors as follows:
• $5,199 Tern HSD S+ with Bosch Performance Line motor and Enviolo Sport 380 continuously variable transmission (CVT) drivetrain with AUTOMATiQ auto-shifting. Also includes a Thudbuster suspension seat post
• $3,799 Tern HSD S8i with Bosch Active Line Plus motor and Shimano Nexus 8 internally geared hub
• $3,199 Tern HSD P9 with Bosch Active Line Plus motor and Shimano Alivio 9-speed rear derailleur (11-32 tooth cassette)
• The lightest model is the S8i at 55.9lbs because it uses a belt-drive vs. a chain and cassette. It’s probably about as quiet as the S+, since that model also uses a belt, but weighs about 2lbs less because the ENVIOLO continuously variable transmission contains traction fluid and requires additional sensors for automatic shifting. My own preference for the HSD would probably be the P9, because I am an active rider who prefers fast shifting and I don’t mind doing a bit of extra maintenance. The Bosch motor controller provides shift detection for the derailleur setup, but not the ENVIOLO or Nexus hubs. Those drivetrains can be shifted at standstill and may require less maintenance overall. Still, in my experience, they aren’t as efficient or quick as a traditional chain with derailleur.

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
• 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 thick thru-axle and premium tires (with puncture protection) offer peace of mind
• Safety is a big deal to me because I sometimes ride in the early morning and evening, surrounded by traffic. So, I love the bright color options here, as well as the reflective tires, reflective stickers on the frame and 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
• 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 felt very solid and stiff. They did a great job balancing approachability with a mid-step frame and stiffness/strength
• 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
• While the HSD S8i and P9 only come with a Bosch Powerpack 400 (vs. 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, and it will work with the same interface
• I love how the battery pack can be charged on or off the bike, this is convenient for those who commute to work and need to fill-up for a long ride home or errands and then home. The battery has a built-in handle for easy-safe handing, and is shaped to make it easy to fit into backpacks and bags (if you want to bring two for extended journies). I appreciate that the S+ and S8i models get the faster Bosch 4 amp charger for quick fills vs. the P9 which only gets a 2 amp charger
• Power and range are important but so is stopping, especially with a heavier bike and potentially more gear or multiple passengers. The Magura hydraulic brakes here are fantastic! You get adjustable-reach levers and extra large dual-piston calipers which spread out force and improve cooling. The front disc brake rotor is 180mm vs. the rear 160mm, and it offers improved mechanical advantage and cooling as you stop and weight shifts forward on the bike
• 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
• 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
• The front rack design is excellent, note that the tray and basket mount directly to the head tube and won’t impact steering. 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 internally geared hubs 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!
• 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 have flexible mud flaps at the ends. The chainring guard offers full-coverage of the front sprocket, to help your pants or skirt avoid touching the belt or chain. In my experience, belts tend to be quieter, cleaner, more reliable, and longer lasting than chains. 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
• 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 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

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. The custom frame with cut-out for use with belt drives also adds to the cost. In general, this product is more expensive than some competing utility and midtail cargo ebikes
• 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 this review went live, explaining that they do offer taller handleposts (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 PSI 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 P9). The 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, there is also a bit of a clunk when stopping, something that is common in the Active Line motors. For extra power, consider the S+ model with a 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 it 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 and to improve serviceability. Some of the cables stuck up and blocked the headlight a bit too… not a lot, but they were there.
• It’s nice that they ABUS keys work for both the battery and frame lock, but they are actually locked into position when the frame lock is open! This is a bummer if you have multiple keys on a keychain, because they will hang down and jingle around (or possibly snag your pants/dress). You could just leave one of the two keys in the cafe lock at all times, but then someone could lock your bike and steal the key or battery… so you basically have to lock it every time you stop, and that sucks!
• The thicker gauge tubing on the rear rack may not be compatible with 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.

Useful Resources:

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