Update: - mid motor install

[kernow60]

Hi all
Well I have been enjoying my Bafang 8-Fun installation it's going well, I have a few mods to see too so I can get a better chain line and a better range of gears. I have ordered a Corona 36t chain wheel to fit in place of the 44t, a couple of reasons to go for the 36t initially, instead of the 42t, firstly I need to get my fitness levels up and the 36t will give me that extra bit better assistance on the hills etc, also a higher cadence, with the view to maybe increase to 42t at a later time if I feel the need.
Also I have purchased a Shimano HG41 - 11-34 - 8 speed cassette to replace my 12-32 again to give a better range, also the fact that it seems to be recommended on this site quite a lot, so once it's all arrived I will install and update.

One question if someone could advise please, I have gone into my settings changed from kph to mph, I now have 9-levels of assistance instead of the default three, and increased the speed up to 40kph although I'm not sure it's made that much noticeable difference ?
My query is the wheel size setting it has several choices in the menu but not sure which I should use I am using the 700c size at present but am wondering if I should be using 28"? I have 27.5" (650b) and wheels and tyres, the trouble is there is nothing in the settings menu to accommodate my size wheels, the tyres are marked 2.1 which I assume to be the width.
Cheers.

P.S. one other thing I have noticed I seem to be able to change gears up or down really smoothly, on the ones that I can use at the moment, without any problem whatsoever, no noises nothing, so is it really necessary to momentarily kill the power to make gear changes as suggested one should.?

 

[trex]

select 28". The speedo is not entirely accurate anyway.

 

[Fordulike]

I have ordered a Corona 36t chain wheel to fit in place of the 44t

I think the lowest you can go down in chainring size to get the improved chainline is 42T. This is because the chainring has to wrap around the final drive housing inwards. A 36T chainring will need an adapter and actually push the chainline further out.

I could be wrong and I think Trex can clarify this.

P.S. one other thing I have noticed I seem to be able to change gears up or down really smoothly, on the ones that I can use at the moment, without any problem whatsoever, no noises nothing, so is it really necessary to momentarily kill the power to make gear changes as suggested one should.?

As you have the 250w, then probably not neccessary, as you say it's changing smoothly. If you ever move up to a 750w, then you would need to do this to help prevent destroying the drivetrain.

 

[Kinninvie]

I bought an adapter and 32T chainring for mine but the chainline was so bad it would only allow me to use the 2 top gears so completely useless.
Changing gear with 250W is usually ok but if you are on a steep hill I would still stop pedalling momentarily,although really you should be in the correct gear for the hill BEFORE you start going up it.
Altering the speed limit to 40Kph wont make a difference as you dont really have enough power to get past that sort of speed unless its flat and the wind is blowing the right way.
My bike pulls a maximum of 1360 watts and can only reach 50Kph and thats with a 42T-11T gearing and on the flat.
28" is the nearest wheelsize for you although you could use a gps for comparison and try different settings.

 

[Fordulike]

Kinninvie is on the ball when he's says to be in the correct gear when climbing a slope. What I find works for me if I'm in the wrong gear and need to change down, is squeeze the brake cut-off slightly and change gear at exactly the same time. That way you can still keep momentum by continuing to pedal.

The Bafang still takes an annoyingly long time to re-engage the motor, but I find it reduces loss of power to a minimum.

 

[kernow60]

select 28". The speedo is not entirely accurate anyway.

O.K. thanks trex, yeah I assumed the speedo's on these kits probably are not the most accurate, but would like to get it as close as possible, so will go for the 28" setting.

 

[kernow60]

I think the lowest you can go down in chainring size to get the improved chainline is 42T. This is because the chainring has to wrap around the final drive housing inwards. A 36T chainring will need an adapter and actually push the chainline further out.

I could be wrong and I think Trex can clarify this.


As you have the 250w, then probably not neccessary, as you say it's changing smoothly. If you ever move up to a 750w, then you would need to do this to help prevent destroying the drivetrain.

I will see how things are once the 36t arrives and I can see how it lines up. I have quite a few shims I can use to move the motor in or out of the b/b so I can play with it, in fact I have a 3.5mm one in at the moment so the 44t chainwheel doesn't come into contact the bottom fork, if the 36t looks like it's not going to work I always have the option to return it and change for a 42t.
At my age I'm not really interested in speed, just a leisurely ride where I can enjoy it and maintain a reasonable level of fitness.

 

[kernow60]

I bought an adapter and 32T chainring for mine but the chainline was so bad it would only allow me to use the 2 top gears so completely useless.
Changing gear with 250W is usually ok but if you are on a steep hill I would still stop pedalling momentarily,although really you should be in the correct gear for the hill BEFORE you start going up it.
Altering the speed limit to 40Kph wont make a difference as you dont really have enough power to get past that sort of speed unless its flat and the wind is blowing the right way.
My bike pulls a maximum of 1360 watts and can only reach 50Kph and thats with a 42T-11T gearing and on the flat.
28" is the nearest wheelsize for you although you could use a gps for comparison and try different settings.

Thanks Kinninvie
Point taken, but I will see how things pan out once my 36t ring arrives, at the moment I also can't use the top two (lowest gear) rings, but the rest are fine.

 

[Kinninvie]

Kinninvie is on the ball when he's says to be in the correct gear when climbing a slope. What I find works for me if I'm in the wrong gear and need to change down, is squeeze the brake cut-off slightly and change gear at exactly the same time. That way you can still keep momentum by continuing to pedal.

The Bafang still takes an annoyingly long time to re-engage the motor, but I find it reduces loss of power to a minimum.

If you momentarily stop pedalling that immediately cuts motor power off and the delay in powering up is negligible.
I have a brake disconnect connected to a button and it takes almost 2 seconds to reconnect which is a long time going up a hill so is just there as an emergency kill switch in case the throttle sticks open (which it has once !!).

 

[kernow60]

O.k. both the Shimano HG41 - 11-34 - 8 speed cassette and the 36t Corona chain-ring arrived toward the end of last week. So yesterday I decided to fit the items to see how things were going to pan out, first off I measured the distance from the seat tube to the edge of one of the teeth on the standard 44t c/r to give me some idea of the difference once the smaller 36t c/r is fitted.

The Corona 36t c/r is flat no offset or dish to throw it inward, so after I removed the standard c/r plastic guard and the 44t c/r, I then offered the 36t c/r in place of the 44t c/r, and then decided to remove the motor assembly along with the previously installed spacer which was to prevent the teeth of the c/r coming into contact with the bottom fork and with the smaller diameter 36t c/r there was plenty of clearance as the fork tubes taper in toward the bottom of the seat tube at this point.

Once installed I remeasured the distance from the seat tube to the edge of the teeth on the 36t c/r and it was pretty much the same as the the 44t c/r with the spacer installed, no more 1mm difference.
Next job was to remove the rear wheel and fit the replacement 34t ~ 11t 8-speed cassette. Re-installed the rear wheel made some fine adjustment to the rear mech and I now have 7-useable gears, the only one which was not going to work was the 34t gear, the chain line stretching things a bit.
So I set the next one down the 26t gear as the lowest gear and it now changes really smoothly all the way up the the top 11t gear and back again the 36t x 28t giving me 38.1inch gearing which should be more than low enough for me.

Went out to give it a try earlier and although top gear 36t x 11t is now obviously lower that the previous 44t x 12t it's still o.k. especially seeing I want to get my level of fitness up, and I may consider at some stage upgrading to a 42t c/r

 

[chris_n]

If you upgrade to a proper dished 42 you will be able to use all of the gears and have a lower bottom gear and a higher top gear.

 

[kernow60]

If you upgrade to a proper dished 42 you will be able to use all of the gears and have a lower bottom gear and a higher top gear.

Well probably not, unlikely the 42 will be much different than the 44 in that I would have to space the motor off the b/b to avoid the c/r contacting with the bottom fork, obviously at this stage I can't be certain, but my current set-up works well for me personally in that I'm now able to use more gears that with the 44, and like I said getting my fitness levels improved is first and foremost at the moment.

 

[anotherkiwi]

Sounds like a case of wrong frame for the BBS to me. The advantage of having a BBS is that you can chose another frame which works better and mount your kit to that instead. Then you would have the correct chainline and the gears you need.

 

[kernow60]

Sounds like a case of wrong frame for the BBS to me. The advantage of having a BBS is that you can chose another frame which works better and mount your kit to that instead. Then you would have the correct chainline and the gears you need.

How can it possibly be a case of the wrong frame, different manufactures use different designs so it's unlikely that you would find any two frames alike.
In any case when you add a mid motor kit to a standard road bike, mountain bike or whatever, if it wasn't originally designed to be an e-bike then how are you going to guarantee it's going to be a perfect fit in every case.
I am more than delighted with my choice of bike and also the outcome that as transpired with it.
Someone mentioned in one of my previous threads that most people who fit these kits can't always use all the available gears and therefore have to compromise by selecting the best set-up that suits them, which is just what I have done, I have more or less a near perfect chain-line for seven out of the eight gears which is pretty good in my book, I have also read on here that some people actually drop a gear altogether and use a 7-speed set-up, another option for me if I wish.

 

[anotherkiwi]

1. Don't be so touchy! We are all in this together

2. I wasn't aware you had an 8 speed

My personal opinion is that if you have clearance issues the frame isn't ideal. There are factory built 11 speed mid-drive pedelecs so you really should be able to have 8 gears.

Personally I couldn't ride up some hills around here with a 26 bottom gear on the back. I am looking at a 32 or 34.

Constructive criticism OK?

 

[kernow60]

1. Don't be so touchy! We are all in this together

2. I wasn't aware you had an 8 speed

My personal opinion is that if you have clearance issues the frame isn't ideal. There are factory built 11 speed mid-drive pedelecs so you really should be able to have 8 gears.

Personally I couldn't ride up some hills around here with a 26 bottom gear on the back. I am looking at a 32 or 34.

Constructive criticism OK?

O.K. point taken apologies if I seemed a bit critical.

In fact I can actually get all 8 gears with the 36t on but the 36t x 34t isn't an ideal chain line so I stopped it at 26t which still gives me a lower ratio than the 44 x 28 which is the best I could get with the 44 c/r, again couldn't get near the 44 x 32 ratio without the c/r coming into contact with the frame.

Ideally if the 36 c/r was slightly dished it would be fine but it's flat and fixed directly in place of the 44 with the motor fully inserted against the b/b.
I would say that if I played around with a spider with say a a 38t or 40t c/r I think I could easily accomplish the perfect chain-line for all 8-gears, which for now will be a future project.

So at the moment I'm happy with my current set-up, and will look into a larger c/r once I'm fit enough to do so.
I'm currently using level 6 everywhere I ride with the option of 3x higher levels if I really feel the need, whereas I was on level 9 all the time before changing to the 36t c/r

 

[cyberdyne_systems]

More importantly, where are the pictures of your work?

 

[kernow60]

More importantly, where are the pictures of your work?

O.K. give me a couple of days and I will sort some pics

 

[kernow60]

O.K. here we go will try to post some pic's....................

Disregard the date stamp, forgot to re-set the date after re-formatting the camera's memory card

My Diamondback e-bike Bafang 8-Fun 250w


36T Corona Chain-ring



34t ~ 11t Shimano Cassette


27.5" (650b) Wheels Hydraulic Disc brakes

 

[cycling weakly]

Hi. I have a GSM which seems to be the same as the Bafang on the outside. I found the 46 tooth chain ring & 11-28 cassette too high geared. I could have fitted an 11-34 cassette but with 8 speed the last step up to the 34 is massive. I bought a Precialpe?? 36 tooth chain ring with "narrow- wide" teeth. Came from France in 3 days & cost £ 35.00 including delivery. It has less dish than the original but it doesn't really matter because I now rarely need to use the 3 lowest gears, but it does give me the peace of mind that riding in the Pendle hills. I can still get home if the motor fails.