Specialized Demo 8 BBSHD

[Stewinnz]

Here are a few photos of my Demo8 BBSHD DH bike. In the photos I am running a lekkie 36 with an 11-25 cassette, the chain line is pretty bad on the low ratio gear so I have since swapped to a lekkie 42 which has a better chain line offset, and gone with an 11-36 cassette giving a perfect chain line and better low gearing for uphill climbs.
The BB on these bikes are a PF30, 83mm width. I used an eccentric bb to get a better clearance between the axle and bb shell, this allowed me to rotate the BBSHD further foreward getting better ground clearance.
BBSHD is 100mm width.
I have noticed with the extra width of the bb, the pedals are sitting quite a bit further out from the bike centre and I have found that I am getting pedal strike quite often. Im pretty sure I will get used to this and adjust my riding to account for it. I am running 170mm lekkie cranks, not sure if there are options for shorter cranks that fit the BBSHD.
I am running a luna 17.5 ah battery in a backpack, which seems to be going well. I have set everything up so I can switch to another bike If this one doesnt work out. So far it seems really good though.
I will be using it for a combination of riding:
1, local tracks i can ride to from my house where there is an access road to the top of trail heads (no public driving access) then single track grade 2-5 downhill only trails
2, general exploring on cross country trails/farm access tracks/coastal tracks
3, going to my mates place to brew beer where we have one or two beers so dont want to drive the car.
There is a possibility of getting a trailer to tow the kids around on camping trips etc too.
Hopefully this info helps anyone else looking into converting a downhill bike into an electric bike using a BBSHD.

Stew

[BucWilD]

how fast can you get that Demo 8 up to?

[Stewinnz]

Around 40 kph on the road. Could go faster if the front chainring was bigger but I want to be able to climb hills so need some low ratios.

[TaylorN]

Hey Stewinnz, sick ride!

I am going to be building a 2010 Banshee Legend with BBSHD 100mm here shortly and was curious about your selections. What are your thoughts on the Lekkie 42t with the 11-36 cassette? Is it using a lot of power going uphills?

In comparison, I have another semi-downhill/freeride bike with a BBS02 motor. I am running a 30t front chainring and 11-34t cassette. Even on the steepest climbs in the 34t I am only using Pedal Assist level 1 (out of 5). As the battery runs low and I become fatigued I might start using Pedal Assist 2 for brief steep parts of a climb. I have a 6ah battery to cut down on weight as much as possible, and can easily get 15-20 miles taking laps up and down a quite steep local mountain. The gearing combo is super efficient with the motor.

I haven't really looked at the chainline yet on the Banshee, but my other bike had a 68mm bottom bracket, so the chainline isn't really bad in my mind (I will need to take a photo).

Can you snap a photo of the chainline on your bike with the Lekkie 42t in the 36t cassette gear?

On your bike, I think if the chainline was still not great, the Luna Eclipse 42t is slightly more offset @ 24.8mm vs 20.4mm from the Lekkie 42t. That's probably like shifting the chainline over by almost 1 full cog/gear on the cassette, right?

And regarding efficiency, based on your experience so far, do you think it would be worth having a little large granny gear with the 42t chainring, say a 11-40t, 11-42t, or possibly even an 11-46t cassette in the rear? I think 11-40t would be doable on the 9speed Banshee, but I'd have to get a new derailleur with longer cage(?). If I wanted to go to a larger cassette than 40t, I think I'd have to switch to a 10-speed to have access to the 11-42t or 11-46t cassettes. Is any of that worth it, or is the 11-36 ample with the 42t chainring and BBSHD, since the BBSHD supposedly has much more torque?

I'm including a picture of the gear ration combinations. Options 2 - 4 were what I was thinking about. You'll notice the some annotations for "Remove Gear" or "Disable Gear". Remove Gear would be taking a cassette and physically removing gears, then adjusting the derailleur to limit gear selections to the "first" 6 gears, making the gear ramp up is much greater, but the chainline would be better in the lowest gear (ie 34t), all while having a small front chain ring gear (ie 30t) which doesn't have the offset of the lekkie or luna eclipse. The Disable Gear theory, would be to get a bigger Cassette and again set the limit of the derailleur so the last 1 or 2 gears (say the last 40t and possibly 36t) wouldn't be accessible, so the chainline would be just slightly better in the 36t position (or the 28t position if disabling 2 gears).

What are your thoughts?

Thanks!

[Dee]

I'm running a 36t with a 1600 watt BBSHD from Lunacycle. I live on the front range in Colorado so I built this to climb those hills.

Total weight: 75 Lbs.
BBSHD motor: 15 Lbs.
48v 24AH 1.1 Kilowatt Battery: 11.5 Lbs.
Range: 50 to 70 miles
ABS plastic Battery Enclosure: 6 Lbs.
Console: 1.7 Lbs.
Bike: 36 Lbs.
Frame Material: 4130 Chrome Moly
Frame Make and Model: Mongoose Hilltopper
Frame Year Made: 1996
Bottom Bracket: 68mm

No spacers were used between the motor and the bottom bracket.

Prior to adding the custom chain guide / bash guard and a return chain guide from Amazon, I had frequent chain drops. The chain dropping always happened around shifting and I finally had enough and built a custom chain guide.


I'm on top of the very first ridge on the Front Range on the western edge of Fort Collins, CO. Made of limestone, this ridge is home to unique plants species not found anywhere but this single ridge.

I liked staying with an 8 speed for the heavier duty chain. And I find the steel 8 speed cassettes readily at my local bike coop nearly unused in a bin for $1.25 per cog. Many cog sets you could buy online these days have spiders and or they're not steel, or they're designed to be super light weight. The cog sets at the bike coop are mostly already broken apart so I don't even have to punch a pin out to rearrange and 'retire' (disable) several cogs. You probably don't have to worry so much about the BBSHD, but these considerations might matter with a 3000 watt cyclone.


36t prior to custom bash guard/chain guide


Chain guide / bash guard with lower 'return' chain guide. No more dropped chains ever since.


I've laid a reasonably straight edge to show where the chain line would naturally be with the 36t


Sighting down the straight edge from behind the cassette which has a perfect chain line on cog 7


As you can see, I decided the first cog that had a reasonable chain line was cog 4. Retired cogs were placed in a reverse cascade.



I needed a longer limit screw to take out the travel to the first three cogs

Since the 36t has almost zero offset I find that the chain line is no good for the first three cogs.

Solution? Retire three cogs, use the limit screw on the derailleur to prevent it from accessing the first three cogs.

I took the cassette apart and placed the first gear (32t) in the cog four position.

I've opted to go with a larger step up to second gear (cog position five) which is 21t.

So, the cogs I'm using are: 32-21-16-12-11

the cogs I retired are: 28-18-14

I picked up an 8 speed cassette at the bike coop and rearranged it. The cogset numbers are now: 14-18-28-32-21-16-12-11.

With my battery at 80%, with no wind riding on flat ground, the 32t takes me to 14.5mph. The 21t gets me to 22.5. The 16t takes me to 27.5mph. The 12t I hit 32mph and the 11t maybe 33.5mph. On a 100% charge I hit 36mph with the 12t.

[TaylorN]

Thank you for the details and excellent photos Dee!

why did you end up going with the 36t chainring instead of the 30t luna might mini chainring? They have the same offset, right?

[Dee]

Thanks TaylorN!

Not sure whether or not the offset is the same. Seems like it should be.

I chose the 36t because I was worried I'd lose too much on the top end if I used the 30t.

Using the 36t it's a pretty good hill climber but the 30t, if you were doing a lot of that would be the better choice.

If I lived in San Francisco, I'd want the 30t for instance. I still pedal up the steepest hills but none of the regular roads up into the mountains forces me to pedal. I can usually just power up it in first gear, and sometimes 2nd gear depending upon the grade.

So it was an attempt at keeping most of the top end, while still having a serious granny gear.

I hit 35mph in fourth gear yesterday, that's the 12 tooth cog, with 48 volts in the battery so like 45% full or so.

[TaylorN]

Yeah, I don't really care about the top end very much since its not a commuter. This is strictly to go up the steepest hills using the least amount of battery and then ride back down. The 30t Chainring in the 11t rear sprocket seems to be plenty fast for me. If I need a little more speed when pedaling I will just give it some throttle :)

[Dee]

You will have a hill climbing monster! Let me know how that works out on the top end on a flat. I might have to buy a 30t just to see how zippy it is with that much torque.

[Dee]

TaylorN,

Our conversation got me thinking about that 30t.

So I bought one and slapped it on. I liked it a lot!

Chain didn't fall off once during the initial run. It did fall off the 36t frequently enough that I decided to end that with the DIY chain guide.

Lost about 3mph off the top end so the max I got out of it was 33mph. Not too bad really.

Thanks for giving me the 30t bug!

Edit: This thing is zippy! And I didn't change the cogset at all. So, with a 32t granny gear it's less than a 1:1 ratio. Had no problem hitting the top of that hill without pedaling. Battery stats show a definite improvement on miles per volt with the 30t.

[TaylorN]

Nice! Thanks for sharing Dee!

3mph loss is not bad. At 33mph I personally don't want to be going much faster without 4 wheels anyways ;)

Keep us posted on the battery stats you had before and after.

[rptarqui]

Hey Stewinnz,

What year is your Demo8? I'm thinking about doing the same with my 2015 Demo8. I'm a bit confused about the BB. I thought the BBSHD replaced the entire bottom bracket. Looks like you were able to use a eccentric BB shell with the motor. How do you like running the battery in the backpack? Any tips you can share with this frame?

Thanks,
Rich

[Stewinnz]

Rich

Its a 2015. The bottom bracket used in these is larger than that required of the BBSHD so you need an adapter. Your bike probably has an adapter already in there, just pull out the crank and measure the diameter of the hole to see if it matches the BBSHD.
This bike has been good but it really depends on what you will use it for, I would have liked to use it on grade 5 tracks but the motor hangs too low and hits the ground so I have to be careful which tracks i can ride.
If I was to do the build again I would use a GT force i drive as the clearance is a lot better.
Backpack battery is ok, i would run a smaller battery though, the mighty mini would be good, get two for if you want to do longer rides.

Stew

[rptarqui]

Appreciate the feedback. I'm concerned about the motor hanging low as well, though probably not really a problem for my local trails. The US National parks are opening up to e-bike use, so more incentive to give this a try. May take your advice an get two mini's. Thanks again.

[rptarqui]

Put a X1 Pro on my 2015 Demo8. Still working out the cabling. Not sure I can use the brake cut off sensors with my brakes. Hoping the battery rack works out..

[TaylorN]

Put a X1 Pro on my 2015 Demo8. Still working out the cabling. Not sure I can use the brake cut off sensors with my brakes. Hoping the battery rack works out..

Nice setup! Do you have more details on the X1? Where did you get it from, how much $$, what size bottom bracket do you have, what does it weigh, have you installed a Bafang motor before if so how does it compare, what is your overall height from the ground to the bottom of the lowest part of the motor/bracket, why X1 over BBSHD, is it rock stable when installed, how is the chainline, can you provide lots more detailed photos?

Thanks! :)