Please help me build my full suspension EMTB!!!

[sefunlekite]

Hi,

I'm new here so apologies if don't respect the etiquette. I currently live in Aberdeen (Scotland) close to some good trails and small moutains. I enjoy mountainbiking in them. As I have a 2 year old and work quite a bit I m not as fit as I used to be and don't have as much time.
My plan is to build a full suspension mtb with power assist to help climb those steep hills do do several rounds where I can only do one now or try to go further.
My requirements are:

1. Mid drive motor (centralised weight) which can:
- carry my weight (89kg) but I'm ok to pedal don't need thumb drive.
- gear and pedalling power sensor would be nice to manage technical climbs but i guess I could learn to ride differently. I have a background in enduro dirt bikes
- doesn't cost an arm as I will be spending quite a bit on a nice bike. I will either buy a downhill bike or an enduro one. Those bikes usually have bottom brakets which are 73°+ mm (most dwh are 83)
For example those are the bike I have my eyes on:
https://www.orangebikes.co.uk/archive/2013/alpine-160/
Here is their e version of the same bike (what I aiming for: https://www.orangebikes.co.uk/bikes/alpine-6-e-le/2018)
http://www.thebikelist.co.uk/giant/glory-dh-2009
Used bike like this are often 26'' wheels, whereas 27.5 are recommended to achieve better grip. MY plan is to use wider tires to make up the difference.
QUESTION 1: How much power do I need? If you look at industrial production: bosch / yamaha / shimano motors they are 350w max and use 36v battery so it s not that much...

Reading here and elsewhere this is what I'm leaning towards (good source: https://www.electricbike.com/mid-drive-kits/)
A. Bafang (500-1000w): seems that it s the best value, reliable easy to install etc...
B. GNG 1000w: seems to be better with climbs that bafang. Worried about the size of the bottom braket as it mentions 68 only? How hard is it to install this one (controller not integrated)
C. Cyclone: One of the most powerfull one but reliability issues? Hard to install (controller not integrated)?
D. Tongsheng TSDZ2: bafang with a pedaling power sensor? reliability issues?
QUESTION 2: feedback on motor for my needs?

2. Battery:
- I m ok with backpack or frame attached. However those bikes usually have small space within the bike triangle so it will have to be attached to the bottom bar hanging style.
- Capacity: I m thinking several hours outings so doesn't need something crazy but hill climbing usually needs capacity.
QUESTION 3: feedback on battery for my needs?
Would 36v be ok to keep the cost down? I see good bootle kits for £200.

QUESTION 4: What is your advice to source all this? Used would be nice but quite hard to find? China or local?

Any feedback and this project is well appreciated!
Here is an industrial production of what I m trying to achieve: https://www.lift-mtb.com/

 

[Nealh]

Unless you already have the bike them probably better to get a ready made e- mtb, coverting a normal bike with a decent kit isn't always cheap.

Bafang BBSHD appear to be the most reliable but will need a very good battery to get the best out of it. For several hrs riding you will probably require at least 30 ah of battery most likely as to packs.

 

[Trevormonty]

When comes to quality FS eMTB, the motor integration and excellent power delivery from factory middrives can't be matched by kit. If you already owned a quality bike I say kit is worth try but new bike plus kit won't be much cheaper than factory eMTB and will leave you disappointed.

You need to test ride factory middrive to understand how good their power delivery is, then a cadence sensing bike. Try edging both bikes around steep hairpin corner and you will soon see the difference.

 

[sefunlekite]

Hi Neal, thanks for your help. I though about it, this one crossed my mind: http://www.chainreactioncycles.com/lapierre-overvolt-am-400-e-bike-2017/rp-prod148739

With some luck it s possible to find a capable full suspension used bike around £500. I ve budgeted £300 motor + £200 battery. £1000 total is far away the minimum £2000 required for a full susp quality bike. But I am dreaming here?

The bbshd is more around the £500 mark. So was hoping the standard bbshd would do. What do you think? The cyclone and gng are less than 300. They are harder to install.

Standard production shimano / yamaha / bosch come with 500wh which is around 14A right?

 

[sefunlekite]

Hi Trevor, I ve never tried any of them. So it s definitely a good point. However, going downhill I m planning on not using the motor so it would be for steep technical climbing that it would be an issue. Doesn t the Tongsheng TSDZ2 have a better pedealing sensor that brings it close to factory motors?

 

[Trevormonty]

I'm not sure of that motor, only tried BBS01.

 

[Nealh]

The battery is the main element of the bike not being rude but £200 on battery for a crank drive for several hrs riding will be pants.
tsdz2 appears to have an Achilles heel with blue drive gear, it doesn't like to be stressed with too much power in high gear ok once you get going but for climbing and starting definitely sounds like a low gear at all times.
Tsdz2 is a torque sensor drive it only delivers power proportionally to the effort you put in, on each start up/switch on you have to not touch anything to allow the system to calibrate before use.

 

[Nealh]

GNG and Cyclone aren't that popular as have in the main been surpassed by the Bafang BBS and its copies.

 

[Deleted member 4366]

Don't think about using a back-pack for the battery. it will really spoil your ride. If you want to do a conversion, get a bike that has the possibility to fit the battery in the triangle.

 

[sefunlekite]

Thanks guys for the helpful replies
@Nealh: I get your point. As I want to use my legs (with assistance) and not the throttle I believe I got get away with 500 to 750w. This would make me save money for a better battery. Would recommend the bbs02 over the tsdz2? I believe there are reliability issues from both no?
https://electricbike-blog.com/2016/02/08/3-months-of-singletrack-abuse-on-a-bbshd-this-masochistic-mid-drive-still-begs-for-more/amp/

@everybody: what is your take on 26 Vs 27.5 wheels. I read all kind of conflicting opinions. In the end it s 1inch difference on the rims... problem is it s hard to find good used enduro bike with 27.5 as it s quite recent.

Thank you very much

 

[Doomanic]

Ive got a good used enduro bike with 27.5” wheels for sale. It’s not going to be anywhere near 500 quid though. Fitting a motor would ruin it too.
I’ve just bought a Trek Powerfly LT and it’s a revelation; handles like a dream and goes like stink.

Do you really need more than 250w? I’m not sure you do and more power = less run time, meaning a bigger, heavier, more expensive, battery is required.

 

[sefunlekite]

@doomaniac: yep I agree a smaller power engine is better.
I know that industrial productions are better but it s way out of my budget.

So i pull the trigger and got lucky: 2015 KTM LYCAN, it has:
- 27,5 tire 2,5 width. Strong alex rims
- Upgraded high quality fox performance 34 front 150mm back 130mm (got the orignial rockshox with it to sell)
- 200mm Slx brake in the front 180 at the back
- Modern and beefed Geometry with Plenty of space for battery (it s an XL 21 inch) and the motor has no kinky down tube.
Now the bad: Shimano pressfit BB92 to deal with. Yep super annoying as far as I know I can only fit a BBSHD with an adaptor: https://lunacycle.com/bbshd-locking-bb-adapter-for-pressfit-pf41-bb86-bb92-86-5mm-bbs/
OR do you think this one will work (way cheaper): https://m.ebay.com/itm/J-L-BB92-BB86-BSA-Bottom-Bracket-Conversion-Adapter-Convertor/301825746922?_mwBanner=1

As the BB is 92mm how can i fit a bbso2 or tsdz2 which are limited to 73mm? Sanding the BB musn t be a good idea?

Thanks again for your help!

 

[Deleted member 4366]

You have to buy the 100mm version of the motor. You might need to put a spacer on the shaft too.

It's not just the adaptors you need. You have to stop the motor from rotating around the BB, so you need to fabricate a tie-bar somehow.

 

[sefunlekite]

You have to buy the 100mm version of the motor. You might need to put a spacer on the shaft too.

It's not just the adaptors you need. You have to stop the motor from rotating around the BB, so you need to fabricate a tie-bar somehow.

You are right that s why Luna cycle sell it with a triangle to attach it to the mounts.

 

[sefunlekite]

Hey so back with more decision: a friend of a friend is a bike guru and doctor. He has:
1) told me the extra 1.9cm on the BB are not necessary to maintain frame integrity. It was design this way to be able to fit a bb92.
2) he can grind it no problem. He makes his own frames so it s nothing for him!

So back in the game of choosing the right motor. I believe I don t need tons of power just the right help (torque) at the right moment. I m now leaning towards the tsdz2 because compared to the bbso2:
- it s said to be more pedalling feeling because of the torque sensor than the Pas from the bbso2.
- lighter
- reliability issues have been sorted a bit it seems. Metal gear replacement has solved the blue gear issue. I plan of using my gears to rest the engine. Still bafang is the proven solution...
My question s are
1) Do you agree with this choice?
2)What version do you recommend: it seems that you can get anything 36- 52v and 250-750w.
The 36v 500w would save me on cost of batteries. But would it be Powerful enought? What is the weight link to batteries v and amps?
3) what are your recommended sellers: I m looking for a good compromise of price customer service and warranty. UK? Europe?

For now I have nurtured the bike a bit with a brake bleeding and some tweaking.
Thanks again!

 

[sefunlekite]

Another thing: by reducing the BB size and thus the chainstay position versus the bike will I get a misaligned chain? Is it fixable?

 

[wheeliepete]

Your friends friend is right that removing 19mm from the bottom bracket will not weaken the frame, BUT it will not reduce the width of the chain stays/pivot to allow fitting of a 73mm bbs02. Have a look at this Giant f/s fitted with a 100mm bbshd.

https://www.empoweredcycles.com/blogs/news/bafang-bbshd-bottom-bracket-adaptor-for-shimano-press-fit-41-89-5mm

 

[sefunlekite]

So potential problems:
1) the chain might touch the frame and suspension pivot?
2) the chain might be misaligned?
3) the motor might not fit and touch the frame?
That s quite a bit.
I read on an Amazon review that the tsdz2 fits into 80 mm max (is that true?) so that s 12mm to clear 6mm each side... I ll have a look tonight

 

[sefunlekite]

 

[wheeliepete]

The width of the bottom bracket is not the only thing to focus on. The secondary drive casing(big round bit) on the motor has to spaced far enough out to clear the chain stay/pivot. Then you can start worrying about chain alignment. F/S bikes are about as hard as it gets to convert and end up with a bike you want to ride and is fit for purpose.