Hi.

 

New to the forum but have reading lots of interesting posts about the various types of electric motors. I have settled in my mind to get the bbs02 mid drive kit as this offers alot of torque for getting up hills. I pretty much want to rely on throttle most of the time where i can, and hear only good things for being able to do so with mid drive systems.

 

I would like to purchase a bike that would be suitable for such kit, especially allowing space for the battery in the down tube and have disc brakes. Can anyone recommend any specific mountain bikes that are fairly cheap to buy that would be compatible.

 

Thanks

Practically any mtb will do, HT or FS with a decent triangle. Probably 18" frame or more.

For used look on ebay or freeads etc or for new something from Halfrauds will do the job. How about Apollo Evade from them £120 cheap and cheerful will do the job.

Make sure bottom bracket is 68 or 73mm and has disc brakes, if mech disc brakes just swap over for HDB's which can be had for about 50/60 quid.

Edited February 8, 20179 yr by Nealh

I pretty much want to rely on throttle most of the time where i can, and hear only good things for being able to do so with mid drive systems.

I think that you've misunderstood what you've read or read inaccurate information. If you're going to use an illegal motor, a hub-motor will do the job much better, assuming that you want to ride on the road. Mid motors are arguably better for proper off-road stuff, but on the road, you'll get a much better ride with a hub-motor. You just have to choose the right one.

 

A Bafang BPM at 48v and 25 amps will give you all the power you need. If you have very long steep hills, like in the Alps, you should choose a lower speed wind, something like 201 RPM, otherwise anything up to about 260 RPM would be good. That's in a 26" or 700C wheel. You need higher RPM for small wheels.

 

There's plenty of other good climbing hub-motors. the BPM is one of the cheapest.

 

I built this bike using a 48v BPM at 23 amps for a guy that was at least 110kg and had only one working leg (note the crank reducer on the side you can see). It was his only means of transport. It had no problem dragging my 100kg up Lincoln Hill in Ironbridge Gorge, which reaches 31.5%:

 

http://i451.photobucket.com/albums/qq236/d8veh/Allens%20bike/20141111_141623_zpse79266ed.jpg

 

If you want to stick with a BBSxx motor, the HD would me my choice for throttle-only, Regarding the bike choice, I would look for a bike with a 68mm bottom bracket with the downtube going straight up from the BB like the one in the photo. The latest trend is for the downtube to leave the BB horizontally before going up to the steering head. That tilts the motor downwards, closer to the ground. You also need a triangle frame to mount the battery.

If you get a BBSHD dont worry about wether the BB is 68mm or 73mm as the 68mm BBSHD will fit both unlike the BBS02 which you have to leave the locknut off on the 73mm BB.

Also,dont get a 73mm BBSHD as that will NOT fit a 68mm BB.

I can recommend the Specialized Rockhopper Sport (2017 model) - I have one and the BBSxx works perfectly - I chose the mid drive conversion because of its torque, weight distribution and aesthetics. I use the bike as a daily commuter and as a 'weekend warrior' mountain bike - it does both jobs brilliantly. You will definitely benefit from the bike's hydraulic disc brakes and possibly consider the optional hydraulic brake sensors that are available for the kit. However, to make a neat job of those, you'll need different brake levers than those supplied either on the bike, or in the kit.

 

The bottom bracket size states 73mm on the Rockhopper spec sheet, which I thought would mean that I wouldn't be able to use the locking nut. Whilst the bottom bracket itself is, indeed, 73mm wide, the bottom bracket 'shell' is only around 70mm and therefore accommodates the locking nut easily.

 

The locking nut fits! Note that you will need the longer hex bolts and extra washers to use as spacers.

Eclipse Bikes

supplied these for me...

 

Also (another happy accident)! with this bike; the supplied Bafang chain ring sits at exactly the right space from the chain stay, so there is no need to worry about having to purchase another ring, or spacers.

 

Perfect!

 

The chain hasn't come off once...

 

For the battery, talk to Jimmy at INSAT International - he makes the best quality and value e-bike batteries on planet Earth, and will give you sound advice regarding the best options for your use. Think about whether you want it mounted on the frame, (I eventually chose not to, although it fits fine), a rear carrier, or in a back-pack. Jimmy can even make a more compact battery to fit within a saddle mounted bag, if you supply the dimensions - Just put aside 1/2 hour, or so, he's very thorough!

 

Remember, a 500w, 750w, or 1000w motor is illegal to use on anything but private land, with the land owners expressed permission. If I were a retailer, I would refuse to give you any advice other than to fit a 250w motor. However, having taken a cursory look on the internet, I can find no examples of cases brought to court in the UK, nor examples of any prosecutions...Nevertheless, the potential risk is all yours.

 

If you want any advice with regard to installation, just ask - I'd be happy to help!

 

This should help with some of your installation questions:

Edited February 13, 20179 yr by JohnnyBBadd