My new to me 2021 Tern Vektron D8- Bafang m400 motor


Well-Known Member
Got a great deal on a tern D8 with 70 miles, this is the tern that has the bafang M400 motor

have put 40 miles on it the past 2 days , battery still shows 12 miles range and i have not been conservative
wanted to climb some big hills with it to see how it would do

cannot remember what the torque is supposed to be but think 80 or 85nm
been a long time since i owned my haibike yamaha but my instinct is too say they are pretty close in climbing, maybe the yamaha was a little better

the bike is fine, it is efficient, smooth pas
but i will add the throttle - not sure how many hoops i will be jumping through to make that work but i will get it done

it rides very nice for a 20 inch folder and i did not have my suspension seat post on yet

when this battery eventually goes will put in the 48 volt controller and run it off my 48/52 volt batteries
am prepared to swap out parts etc if needed in the future, may even stock up on a few parts in advance in case i cannot get parts 7 years from now
but i dont ride hard and have never had to do a motor repair

this bike is definitely going to be a 5 or 8 speed igh in the next few months, hopefully with belt drive but if that wont work ok
has 2.0 big apples now and will go to 2.15 big apple or a 2.3-2.4 tire in the future

this bike is not heavy but not light either- 50 lbs i think
i take battery and seat off any bikes i am lifting so it is manageable

the biggest highlights on this bike are how easy it is to fold, how stable it is folded
obviously tern does a great job on all folding stuff and i am very impressed - some of these ebike companies building folders could learn a lot from this bike

been folding it up and hauling it around in my subaru and just love the nice folding

putting this up against the evelo dash with the same motor- not sure how evelo has their motor set but think they would be close- i personally do not like the frames with the battery inside because i often leave a bike locked up on the rack at home and bring the battery inside
hoping i will be able to copy the awesome 5 speed igh and belt on the evelo

will update this as i change/upgrade things
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Whoops! I dont know why i was the thinking the evelo came with the m400, maybe the old one did..
forgot this new one has a dapu
would be really interesting to compare these 2 bikes at some point if anyone has an evelo dash in az
Whoops! I dont know why i was the thinking the evelo came with the m400, maybe the old one did..
forgot this new one has a dapu
would be really interesting to compare these 2 bikes at some point if anyone has an evelo dash in az
Is that a Vektron? It would be inconvenient for me to swing by your place just now, but I'm sure willing to check out the bikes for you up here! I will post a full report! ;)

I guess the battery inside the frame of the Dash is supposed to be elegant, maybe even intended as a win-win by making use of a large and structurally strong frame member in that location. The welding and frame members are really nicely faired and finished. But to my eye the oversized frame member with the battery inside still ends up looking a bit kludgy. Of course, I cut my teeth on the lugged-steel frame aesthetic of the 60s and 70s. 🤷‍♂️

I never remove the battery from the Dash, even when we have folded the bikes to put them in the car, as it's a bit of a nuisance and we are doing a team-lift anyway. But yes, in the ideal world, I would like to be able to just grab and remove it from behind the seat or under the rack even when the bike is not folded.

Tern seems to do a nice job of making their bikes a manageable, cohesive package when they are folded. The Dash is not so refined in that respect; it wants to come apart, and to tip and fall over. It's kind of like that scene with Ray Bolger playing the Scarecrow in the Wizard of Oz where he's all shaky. I'm sure you read the Dash thread where I talked about the bungee cords and cardboard I use to bundle ours for travel. Over time I'll make up some padding and velcro or some clever thing, but it's also something that Evelo could improve on.

Looking at the wheelbase on the Vektron, it looks like it's 41.5 inches, a bit more than our Expressways at 40", but less than the Dash at 45.25". I'd be interested to see how that works out for riding. Yes, I think I'll need a few weeks to make a good job of comparing them. Let me know when you can drop it off here; I'm already excited!
Lol are you in phoenix? Would love to compare the bikes if you are!
Yes it is a D8 vektron

My problem is the heat here , need to be able to take the batteries inside, sometimes I leave the bikes under the car shade outside overnight but need to take the battery in, I actually like the looks of the dash and in frame batteries like that better, think they protect the batteries good etc
But I have had a couple of bikes like that and it is a hassle for me

The tern is at the shop hopefully getting the 350 watt controller and throttle put on but when I get it back will take pics of the 3 things tern puts on the bikes to hold it together, I have had a lot of folders and these three small things make a huge difference

And I think they could be easily duplicated

Seems we could buy the parts from tern…
Naw, we’re up in the Pacific Northwest, in the Puget Sound area.

That makes sense about the batteries! Swing by and come see us when that heat gets a bit much down there. Up here, 100 degrees makes the NEWS!
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Well I spend most of the summer in flagstaff :)

But if I ever get out that way would love to visit!
Sounds good. But, hey, we gotta quit talking about the weather and start hearing more about that bike here!
I agree!! Hope the shop gets it done soon

Will definitely write up some more impressions once I get it going
Have Tern Vektron that my wife mostly rides. I really like it.
Can you tell me more about the process to add a throttle?
Sorry guys I’ve gotten sidetracked with other projects and that is still at the shop waiting on stuff to do the IGH, my guess is it’s going to be another 2 to 4 weeks before I work on the electronics and see if that’s going to work or not but I’ll definitely update this
In theory changing the controller and getting the main electric harness with a throttle should work but I’ll definitely let everybody know
Small update on this

Nuvinci igh is in and working good
Bike is at the shop for a repair right now and we are going to put the 350 controller and wiring harness in

On this bike the 350 wiring harnes with throttle is slightly too big to fit into the motor compartment, so I had a choice
Barely dremel the frame a little to get it through or cut and solder 6/7 very very fine wires- decided to dremel the frame out a little , it is a very small amount

Don’t know if this will be the same on other bikes

Will update this next week when it is done hopefully
Got the bike back, now has the nuvinci 380 and m400 350 watt controller with throttle wiring
throttle works but is slow, not sure if this is because it is turned down in the controller or just because the bike is 350 watts
would get me home if a problem i think
keep in mind this bike is like the M600 motor and throttle does not work until 5-6mph

have not looked into programming it, too many bike projects but at some point will put my eggrider on it and see if it can turned up a little

i had 2 options to get the 350 controller wiring harness to fit, it is bigger than the 250 harness that was in it because it has added throttle wire and brake cut off wires, the sections where these come together in the wiring harness were too big
Side note- this bike does not come with brake cut offs on the hydraulic brakes, it is like most low power mid drives i think
i am not planning on using these wires since the throttle does not start from a stop

To make the harness fit in the frame we could cut and solder all the very very small bafang wires in the wiring harness or barely enlarge the hole in the frame, i decided to do the frame because did not want more places for potential wiring issues later

bike shop got it back together and everything seems fine, small power increase but i think the controller went from 14a to 17a so not much

do think this is an easy upgrade for someone who works on their bikes, i just chose to have the shop do it

Bubba just realized that you have a vektron but did not say which model- this one i have is the bafang m400 mid drive and is not the most common one, most are bosch and you wont be able to put a throttle on the bosch bike
let us know if you have the bosch or Bafang motor

i will change the thread title to clarify that

this is a pretty easy swap out on this bike, wiring harness is a complete match, all the lights work etc
i have plenty of bafang mid drive throttles so just stuck one on there and works fine

bought everything from greenbikekit and had excellent help from Anna
just looked up my receipt , got the new wiring harness and controller with 35 in shipping it was 157 so not bad
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So, I might be a bit slow on the uptake here, but would you mind posting your goals in changing out the gearing, the controller, and adding a throttle? As I understand it you've replaced the derailleur freehub and cassette with an IGH, and replaced the controller to accommodate a throttle and a higher-voltage battery. Is that correct?

I'd like to get back to messing about with bikes, but I've got too many other projects going as it is. I haven't sold our Giant Expressways because I thought it might be fun to convert them to mid-drives, but I don't know if or when I'll even have the bandwidth to do something like that.

For what it may be worth, the Dash does have motor cutoffs. I am a bit surprised they didn't put any on the Tern. Not that the Dash has any terrific power band, I'm glad to eliminate any opportunity for the battery to expend its energy warming the brakes. ; )
would not have put this much money in this bike if i paid for it new, but got a REALLY good deal on it so could justify modding some stuff for fun

I personally hate derailleurs, if every bike I owned could have igh and belt that would be awesome, so just did that because i wanted it

so far really like it, will post back with more feedback on the nuvinci after more miles

and even though there is a tensioner thing on it feel like it will be less like to get out of alignment or have problems when folding which i plan to do a lot with this bike
should clarify i was unwilling to spend the 400 plus labor to try a veer split belt, maybe sometime in the future but right now it is a chain

the price for the parts for the 350 watt controller and throttle was pretty low, spent a little more for labor than i wanted but it is what it is
it is still a 36 volt motor, really and no use for a 36 volt battery anywhere else plus it is brand new battery so did not swap it yet

this bike can be made 48 volt and 5-6 years from now if the battery is dead will probably do that , should just require a controller swap out i think

90% sure my haibike yamaha did not have brake cut offs, not sure if this is true of a lot of low power mid drives or not...
my harness does have the brake cut off wires and i could swap out for some brake handles that have them but wont do it right now

hope that got most of your questions answered, at this point i still have way less money than a dash in it and imo from watching the threads on that forum i think this M400 is more reliable than the dapu on the evelo, but who knows