Soma B-Side V.2 Belt Drive BBS02 750W/48V Custom Build

[MIKEinNC]

Hi Rider, and ncrkd, thank you both for your responses.

Also, thank you both for pointing out that the S-A CS-RK3 is the best choice because of the belt line adjustability it's cassette mount offers.
I had registered that point, but somehow lost sight of it.

Rider, I'm glad to hear that you were able to use the same belt with different pairs of cogs.
I'd surmised that, if you added roughly the same number of teeth to one cog that you subtracted from the other cog, you could stay within the range of adjustability of the rear sliding dropouts.
I'll use your experience as a much appreciated cross check for my measurements.

When I asked the question about 26" wheels, I was actually wondering if that might cause a change in geometry, which could have a negative effect on the bike's handling.
I'm not too concerned about the increased potential for pedal strikes, because I'll install shorter cranks along with the mid-drive.
I've done that on two other BBSXX builds I've done, and I find it gives me a little more comfortable pedal cadence at higher speeds.
It makes things a bit easier on my old knees.

Thanks Again !
Mike

[Rider]

Good afternoon Rider, I've been fascinated reading your posts on the belt drive conversion.
I have a Soma B-Side (18.5") frame on order, and plan to follow in your footsteps, using the SA 3 speed IGH and a BBS02.
I want to use the 55T x 24T sprocket combo, and wondered if you were able to use the same 118T belt when you changed ratios ?
I'm thinking of using 26" wheels, with 2.5" Hookworm tires.
Are there any particular negatives you can think of, in downsizing from 27.5", with the Soma frame, which I know is spec'd as 27.5 ? (Other than the less plush ride.)
Any thoughts on 3 speed vs 5 speed IGH ease of installation and riding impressions, would also be appreciated.
Thank you,
Mike

Hi Mike

I was able to use the same belt with all the ratios I have tried to date on the B-Side and Wolverine stated in the thread, but I paired the front and rear belt rings with my existing belt length in mind. The Gates site has a belt length calculator you can use.

The Soma B-Side seemed to have very good pedal to ground clearance, so I think you will be fine with 26x2.5 and stock Bafang 170mm cranks.

I don’t think I would have ever sold this B-Side if it was an XL frame. I bought it before I knew what geometries fit me best. It a great frame and versital geometry.

As for 3spd (33% gear gaps) vs. 5spd (25% gear gaps), I like the 33% gears gaps better for street use and 25% gear gaps better for off-road use. You get more range with the 5spd at the expense of shifting more. Not sure you will be able to align the belt on a 5spd without a custom made front belt ring. The great thing about the S-A CS-RK3 is the ability to adjust the belt line on the cassette and if you want to run a chain and derailleur you can setup a 21spd through 33spd.

[ncmired]

Good afternoon Rider, I've been fascinated reading your posts on the belt drive conversion.
I have a Soma B-Side (18.5") frame on order, and plan to follow in your footsteps, using the SA 3 speed IGH and a BBS02.
I want to use the 55T x 24T sprocket combo, and wondered if you were able to use the same 118T belt when you changed ratios ?
I'm thinking of using 26" wheels, with 2.5" Hookworm tires.
Are there any particular negatives you can think of, in downsizing from 27.5", with the Soma frame, which I know is spec'd as 27.5 ? (Other than the less plush ride.)
Any thoughts on 3 speed vs 5 speed IGH ease of installation and riding impressions, would also be appreciated.
Thank you,
Mike

Hi Mike - if I may butt in till Rider comes back - here's the Gates Belt length calculator: https://www.gatescarbondrive.com/~/m...tor.xlsx?la=en and the currently available belt tooth counts.

CDX - CenterTrack Belts (12mm wide)
Teeth	Length	Part Number
174	1914mm	11M-174T-12CTS
168	1848mm	11M-168T-12CTS
166	1826mm	11M-166T-12CTS
158	1738mm	11M-158T-12CTS
151	1661mm	11M-151T-12CTS
143	1573mm	11M-143T-12CTS*
137	1507mm	11M-137T-12CTS*
132	1452mm	11M-132T-12CTS
130	1430mm	11M-130T-12CTS
128	1408mm	11M-128T-12CTS
125	1375mm	11M-125T-12CTS
122	1342mm	11M-122T-12CTS
120	1320mm	11M-120T-12CTS
118	1298mm	11M-118T-12CTS
115	1265mm	11M-115T-12CTS
113	1243mm	11M-113T-12CTS
111	1221mm	11M-111T-12CTS
108	1188mm	11M-108T-12CTS
	* Available Fall 2019

I doubt you'd be lucky enough to reuse the belt after changing ratios, even after changing both belt pulleys. You'd have to run the calculator against your effective chain stay slider min/max, to see. Fiddling with belt drive ratios gets expensive, fast.

On the wheel change, since the BBS motors cause a wide crank arm Q adding a motor PLUS dropping the tire diameter will raise pedal strike potential.

On 3 speed vs 5 speed, I don't know of a 5-speed IGH with a cassette mount - is there one? The cassette mount is crucial to adjust the belt line - as is the related external bellcrank. Hub rotary shifter mechanisms takes up too much room and hurt the chain line.

[MIKEinNC]

Good afternoon Rider, I've been fascinated reading your posts on the belt drive conversion.
I have a Soma B-Side (18.5") frame on order, and plan to follow in your footsteps, using the SA 3 speed IGH and a BBS02.
I want to use the 55T x 24T sprocket combo, and wondered if you were able to use the same 118T belt when you changed ratios ?
I'm thinking of using 26" wheels, with 2.5" Hookworm tires.
Are there any particular negatives you can think of, in downsizing from 27.5", with the Soma frame, which I know is spec'd as 27.5 ? (Other than the less plush ride.)
Any thoughts on 3 speed vs 5 speed IGH ease of installation and riding impressions, would also be appreciated.
Thank you,
Mike

[Rider]

My notes state that a BBS02B spider mounting surface is 22mm from the B.B. edge. The spider I used is not flat, it actual has an inset for the chain/belt ring taking it further outward to the right. A flat spider will get you closer to the B.B. or you can use a 1-2mm spacer on this spider. With a 68mm B.B. the best you are going to get with bolt-on parts is ~52mm; which puts th belt ring in Rohloff chain line territory. If you are using the SA CS-RK3, you align the belt line on the cassette mounting surface. The only way to get a closer belt line is to face the right edge of the B.B. (watching chain stay clearances - both sprocket and reduction gear housing) or a fully custom built/machined spider/beltring combo. It appears the best a custom made setup can achieve is ~46mm, because of the thickness of the beltring (whichout facing the 68mm B.B. edge). You have to do your own individual measurements to assure all is lined up properly. There is really no way around that. Don’t just take stated values and assume everything will line up. Even the Gates belt rings have slight offsets depending which side you mount. Good luck.

[scstusek]

Hi Rider, do you know what the offset on your French spider is? I have a Gates drive that I would like to convert to electric, and it appears that the inside edge of my belt ring is about even with the outer edge of my bottom bracket.I think I read somewhere in your posts that the Bafang motor housing will push that about 20mm to the right. I 'm just looking for ways to get the chainline right. Thanks!

[Rider]

Asking for some help:
Building BBS02 with Nuvinci N380 on a belt drive...
What pulley rings do I need?

If you are putting a belt drive ring on a BBS02 you can’t go smaller than a 50T or it won’t clear the reduction gear. You have to do the calculations for the belt line yourself based on the rear hub you are using.

[Ttreshh]

Asking for some help:
Building BBS02 with Nuvinci N380 on a belt drive...
What pulley rings do I need?

[Rider]

Things change and life moves on... Now that my Sulry ECR is dialed in I ended up converting this Soma B-Side into my belt drive 3spd pedal city ripper and beach cruiser. It's so nice having that 33% lower and higher gear on both sides of the single speed gearing that Soma recommends. Get a headwind or hill that is taxing you, grab first. Get a tailwind or decent and want pick up speed, grab 3rd. Sweet! All in complete silence.

I will be posting up my extra BBBS02B 750W 48V color display kit with full belt drive rings and adaptor, plus Avid BB7 brakes and rotors for $500 in the For Sale Parts section today.

HERE'S A LINK TO IT:

https://electricbike.com/forum/forum/for-sale/parts/73694-bbs02b-750w-48v-color-display-gates-belt-drive-kit-with-avid-bb7-brakes-rotors

Belt drives are sweet with E-assist or pedal.

Cheers all!

[Rider]

When you consider the cost of a Lekkie Bling Ring, the little extra cost to go Gates CDX belt drive isn’t that much if you shop on the net for the parts. The biggest issue is having the belt line straight. IMHO not having that right and using a BBSHD instead of a BBS02B is what caused the above belt ring adaptor to fail and maybe it’s weak designed inward offset.

[Rider]

She's back on the road! Did a quick ride to the beach and back to test her new shoes and gearing out. Hit a nasty headwind all the way there (11+ miles) and it was sucking up 500-600 watts to keep it above 20mph. Although on the return it was only using 0-50 watts to keep it above 20mph; tailwinds are wonderful. Cruised about 2mph faster with the new gearing. Rode smooth, quiet and very soft ride with the 2.8/2.4 Schwalbe Super Moto-X combo front/rear. The belt drive is sweet.

[Rider]

Swapped out the 50T front sprocket for a 55T today. While the rear wheel was off I decided to swap tires once again. The WTB Byway 47c tires feel wonderful in a straight line on cement and all around on gravel roads and hardpack, but I'm turning this ride into more of a road only oriented city bike now. The WTB Byway knobby edge isn't the best for laying a bike down on the tires edge on cement and if you hit wet pavement with that knobby edge it has a tendency to slide out. The WTB Horizon is basically the same tire without the knobby edge, so I'd recommend that tire for a dedicated street ride over the WTB Byway, but I have other street tires already...

I had a pair of Schwalbe Super Moto-X 27.5" X 2.8" tires on this bike at one time, but got a 1/4" slit cut in one that required a inside tire patch and there wasn't much clearance for a tire that big in the rear (it did fit though). I returned a Schwalbe Super Moto-X 2.8" to the front Halo Vapour i21 rim for street use. It measures just under 2.6" on this narrow rim. I ordered up a matching Greenguard E-rated 2.4" Schwalbe Super Moto-X for the rear to get better tire clearance with the tire moving forward some because of the new 55T beltring. When this ride hits the rode once again with a little higher gearing for more speed it will be sporting 2.4" in the rear and 2.8" up front; probably netting about <2.4" and <2.6" width; right in the sweet spot that many MTB riders are finding offer the best compromise of traction, control and feel.

[Rider]

Thanks SM. Hope to see more belt drive builds over time as methods of belt alignment are discovered. IIRC the expensive Rohloff IGH is still the widest belt line out there and is the easiest to match a front belt ring to. Someday I will own one. I’m sold on IGH hubs in general. The ability to shift without pedaling is so nice. I usually downshift while coasting up to a light or even after I come to a stop. You can’t do,that with a derailleur setup.

[spinningmagnets]

Finally found a few hours to collect and format the info to publish this...[it still needs more links and other additions, but if I don't publish something now, I might never get to it...]

http://www.electricbike.com/gates-belt-bbs02/

[Rider]

Cracked the 3,000 mile mark with today's ride to the beach. Definitely a biking weekend here in sunny SoCal. The bike trail was packed and so was the beach boardwalk through Long Beach. Did 37.5 miles and averaged a rather fast for me 17.1mph. Top speed was almost 30mph; 29.8mph. I got in a jousting match with a couple roadies that didn't like me passing them at a light. I was simply cruising at about 21mph and they were stopped, but the light turned green when I approached. I lost them for a couple miles, then they caught me when I was waiting at a light. As I took off and quickly got up to speed, one of them jetted past me while I was going 22mph. His friend hung back, but eventually passed me as well. They were working hard to hold it above 23mph. I caught them at a light and we all had to wait. This time they took off as hard as they could and tried to drop me. I just simply clicked up the power a bit and caught their tail in no time. They kept looking back, switching lead position and sweeting bullets; all the while all they hear is silence, then a clicking whur over and over. I was just pedaling a few rounds, then coasting right in their draft. It reminded me of last mile of "their" road race. They moved left then right, still trying to drop me. Ain't gonna happen! They picked up their pace even more to 26mph. I clicked my power up from level 7 to level 8 and road their rear tires with my insistant coast clicking. I could have passed them anytime I wanted. We all got caught at another light and I just sat back a couple bike lengths with my foot on the curb; in my plaid beach shorts, button short sleeved shirt and straw beach hat with sunglasses (they were Roadied out in areodynamic bike apparel - LOL). When it went green this time, they didn't push it. My turn was coming up in two streets, so once traffic was clear I went to level 9 and pumped past them and across the street at an angle. then took it up to about 30mph and held it there until my turn. Needless to say, they weren't anywhere near me on the other side of the street. I don't know if they knew I was electrified. My bike is silent and it looks like a belt drive single speed, but I'm guessing they saw the black motor down there. Certainly they didn't know it was a simple 3spd inside that little cassette hub on the rear wheel. It was all in good fun...

The great thing is yesterday my 55T front belt drive ring arrived. That will add 5T to the front and more speed when desired. I can road this thing out a bit now that I have my Surly ECR build in the works for dirt roads and trail treks.

TO MUCH FUN!!!