uralik

Hey everyone, I have always wanted a folding bike with a belt and hub motor such that it has more or less standard parts in it and I like working on my bike so I went this path:I figured I may share this in case someone else will search info about it and especially what was the final cost for me.

1. Bike: Downtube 8H, bought it new before price increase in the beginning of 2021. Coming from MTB world I was a bit surprised by overall higher price ranges for folding bikes and downtuibe was getting at least close to whatever you get for your money with normal sized bicycle.I Instantly changed tires to Schwalbe marathon as I live in Brooklyn and puncture protection is necessary. $938

2. Battery: used 28AH EM3EV 52V battery. I like the quality of EM3EV product as they actually tell you what cells they use and they put a fuse for every cell so I am less worried about any accidents. It is a triangle battery which nicely fits onto the rear rack. $400

3. Motor: used Bafang front hub, 350W nominal, 36V. This was a motor taken off from a batch of bikes which arrived with wrong motor-controller pair, pretty good deal. $90

4. Grin technologies Baserunner controller + Cycle analyst V3, rim, spokes, wiring harness. Grin controllers and Cycle analyst is a game changer for me. You can control and fine-tune all parameters of your ebike e.g. modulation between your throttle and how fast controller discharge the current from the battery. Basically I have build the bike just because of this as you can not get such control in general ebike from a store. $577

Extra:

5. Used rigid fork. After setting things up I have realized how crappy is the zoom fork on Downtube, it is a joke of suspension forks, although I am a bit spoiled of the air fork I have on my other bike. I was lucky to find a *new*, *unused* rigid fork for iZip E3 Compact bike which is suspiciously similar to my downtube hahaha. $35 With that fork I enjoy the ride much more since there is no this spongy feeling which I had before.

6. Brooks saddle, my old saddle so I didn't pay for that. $0

7. Old MTB pedals as I didn't like the folding wellgo pedals much. $0

Installation process was pretty smooth. I was surprised to see that the gates belt ring was installed incorrectly on Downtube bike (on the outer side of the system) and it was not aligned with the belt thus producing weird noise during ride. Placing it on the inner side fixed all issues.

Nice thing about this build is that once I want to change the bike I can sell the bike and move the 'ebike' parts to my next one, and I really enjoy tweaking the controller, but I think this maybe not everyone's kind of thing.

Battery range: On my typical commute to NYU two-ways (~30km) I spent about 5-7Ah depending on how much I assist with pedals, so 28Ah battery may be an overkill, but I like the fact that I never go below 50% of the battery and I only charge up to 85%.

Let me know if you have any question! Will be happy to answer!

Wanted to post a picture but my account is too empty for that
This is the imgur link: http s://imgur.com/ a/XPjrbCQ (remove spaces)

DVC45

Looks nice. Thanks for sharing.

uralik

thanks for posting the picture here!

Buckethead808

Well, since you offered.. I just bought an 8H and I'm wondering if you can expand on this:

My 8H arrived the same way but, not knowing all that much about bikes, I don't know whether this installation is correct or not. I was wondering how you determined that it was installed incorrectly. There's a photo of the crank and belt ring on the Downtube site showing the ring mounted the same way mine is mounted, the belt ring on the outboard side of the crank, away from the frame. (I also can't post photos, it's at imgur.com/a/sxPqq9Q). So it seems that all 8Hs are assembled this way and it's not specific to your bike (or mine).

After reading your post, I took a closer look at my bike and it *does* look like the belt is not running perfectly straight between the hub and the crank, and that moving the belt ring inboard of the crank would make it straighter. I just wanted to find out more about how you figured that out before I make the same change on my bike.

anga

Why not ask Yan, owner 9f Downtube?
Belts are sensitive to beltline and expensive enough to consult him.

uralik

Right, I think its a good idea to ask him if you are reluctant about the installation. I am simply sharing my experience here, because that is why we have a forum haha. In fact before this alignment issue I had multiple issues which I told about Yan over email, they are all minor if you have tools:

1. Front wheel was untrue so rim was clearly unbalanced so I had to tune the spokes tension (I have video recording which I sent to Yan).
2. The rear wheel was so misaligned in dropouts so you can actually see that, here is a pic: http s://imgur.com/a/5kmMORp (still cant post images sorry). This misalignment was already producing some tear between the belt and teeth on rear cog.
3. The tension of the belt was *way* over the normal, which I believe due it misalignment.

Buckethead808, coming back to the belt thing:

After I have fixed this stuff and got it for a ride I was surprised to high frequency sound from the belt and front ring as the belt was not ideally coming onto the tooth on the chain ring. As you can see on the pic above the chain ring was installed on the outer side. I had a different expectation in mind because when I tried belt before it was really a `silk` smooth feeling from the drive-train. When I got home I put the bike on the stand and after some eyeballing I noticed that chain ring and rear cog teeth are not aligned very well, there is like a parallel shift. First I was a but frustrated, then I realized that I can put a ring on the inner side which would either decrease the shift or eliminate it. Fortunately, after I did this the drive train bacame so smooth, the only sound you hear is the IGH sound. This is where the chainring stays now: http s://imgur.com/a/vot75hn

Even if the belt was supposed to be installed such that it tears, makes weird sounds etc, then screw that -- I will do it my way haha. And actually this is what I liked about downtube: the entire unit does not require any specific tools to work on it. I can only wish it to have some better version of horizontal dropouts as Bike Friday do with their frames (I know I know they do steel frames..)

Buckethead808 , overall I would recommend you to check everything there just to make sure that its all aligned and spokes tension is good etc.

In addition to that, the chain tension thing on 8H could be better in terms of thread step and overall quality as the current one does not allow fine-tuning as I would like it to be. I have checked after market chain tensioners and the main issue is that IGH no-u-turn nut makes it very hard to adopt other tensioners.

Let me know if you have any more questions, I am happy to discuss this bike as I really enjoy riding it.

Buckethead808

Thanks uralik , I appreciate it. I was thinking of starting an 8H/11H owner's thread, several people on the forum have bought 8Hs in the last month or so and it would be nice to share adjustments, customizations, etc. and I'm pretty sure the 11H uses the same frame and most of the same parts. anga I didn't think to ask Yan about the belt ring mounting because from what I can tell, all 8Hs are assembled this way and I have to assume if he wanted the belt ring to be mounted on the other side of the crank, that's the way it would be.

My 8H had similar issues out of the box: rear wheel misaligned, belt tension too high. I checked the things I knew to check, and went through the setup checklist on the Downtube site, but I've never ridden or even seen a bike with belt drive before so I had no idea what to expect in terms of sound or "feel" when riding it.

uralik

That would be cool to have the owner's thread. For instance I wonder what was other's experience about using kanga rack or so which attaches on the front. I have also seen some adaptors for brompton bags which is also interesting... but no real feedback towards using those on downtube as I have checked last time.

Buckethead808

That's some of the same stuff I'm interested in. FYI the Kanga rack (and its Klickfix-branded version, the Vario rack) are both discontinued and out of stock everywhere as far as I can tell. I did order the Tern G2 luggage truss (with Klickfix mount) for the front of the 8H, I had planned to get the Kanga rack as well before discovering it's no longer available.

Doc_Wui

Wow. Nice bike. It's written in the DIY ebije bible that suspension forks and motors don't mix well, so I think you did right as far as safety by going rigid fork. .

I've got a front motor 20" minivello that just turned 1000 miles yesterday. We also have a Downtube 8FS and Nova with rear motors. I bought the bare motors and spoked them into hubs. We''ve accumulated 3000-3100 miles on the folders. Great fun, and just under 40 pounds per bike with smaller batteries.
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