Good morning and thanks for allowing me to join.

I would really appreciate your help, please.

Last year I took my MB to a company local to me so they could check whether it was suitable for a rear-hub conversion. It was wheeled off to the workshop and 5 minutes later the answer was “yes, no problem “. I brought the bike home to give it a thorough clean and remove various accessories and before I got chance to return we went into the first lockdown.

Fast-forward to last week. I prepped my bike, paid for the conversion and dropped it off to be done. The same mechanic took a look at my bike and said “oh, I am not sure if I can do this “. He then went on to explain that because I had a Hollowtech bottom bracket the normal way to fit the pedal assist sensor wouldn't work and that he would look at removing the smallest chainwheel and modifying the magnet disc to fit. I agreed.

But the following day he rang me to say that it couldn't be done. For the reason previously explained plus I have hydraulic brakes and “there is no way to fit a brake sensor”. Dejected, I brought the bike home yet again. And began reading... and reading......... and reading. (I know what some of you are already thinking).

I decided that I was going to attempt the conversion myself. I am reasonably adept with tools and repairs (the main reason I was going to have the conversion done for me is because a different company had told me that the setup “had to be programmed and calibrated” to stuff such as wheel size, gearing and my weight etc (naively I accepted this).

But the more I read the more confused I get.

My bike is a Boardman Pro FS (2009), not the absolute highest spec but certainly decent and in remarkably good condition because it has hardly been used (because of injuries sustained at work) and I am determined that it won't collect any more dust. When I was originally thinking of the conversion, front or rear hub were the most affordable. Plus, I like the idea of keeping the bike fairly “stock” as my intention is to actually pedal as much as possible and only use the drive when absolutely necessary. My other consideration was that I could (if there was ever a problem with the electrics etc) just swap out the rear wheel, remove the battery pack and still use the bike without too much faff.

But I now need to find a way to fit the pedal assist sensor and also which one/where from? Another question for a rear hub setup is this... let's say that I am half way up a long hill and my legs are knackered, can I just use the throttle and (without the pedals turning) continue on electric only (hope that makes sense)?

If the answer to the last question is no, I may well go mid-drive, that throttle question becomes moot because obviously the pedals will turn if a throttle is fitted and used (which is, I now realise, the reason most oem bikes with MD have no throttle) . But, although in some ways the MD system is more straightforward, swapping back out (if needed) is more work.

I have spent hours and hours now and my head is about to explode. As much as I would like to save a few quid by ordering direct from China, I am convinced that buying from a UK supplier will be preferable because not only will I have the benefit of a warranty but most importantly, we all need to start supporting UK shops/companies more because if we don't, they are doomed.

What system do you recommend and why?

Which UK based companies do suggest?

 

I am mid 50’s, about 13 stone (82.5kg) which is a bit over my preferred 11 stone, but my stamina has dropped off a cliff. My days of proper off-road mountain biking are way behind me so most of my riding will be roads and canal/river paths but I do want to be able to explore a bit too as I have a little holiday shack on the outskirts of the Wyre Forest.

 

Thank you in anticipation.

There are loads of ways to fit pedal sensors. You don't need anything special. Choose a kit so that I can see which pedal sensor they supply, and I'll tell you how to fit it.

SST, for the pedal sensor one needs a BZ10C pedal sensor cost about £10 - £18. It is designed for use with Hollowtech or Sram type ext bearing BB's, can be bought with both types of connector commonly used. Normal sensors supplied can be modified if one is good at diy.

For brakes one has to be a bit inventive and either use sugru or some two part epoxy glue like Araldite or Gorilla to epxoy the sensor to the brake body. Depending on which type of sensor is use two types decides how it will befitted.

If you fit a brake sensor only one is needed and it is often best to fit one to the rear brake lever.

 

We can tell you how to go about doing both if you supply pics of the items you have.

Two places now have said that there is no possibility of fitting on the chainring side because there isn't enough space?

(Was typing while you were posting)

I had been thinking that a sensor on the rear brake only would be sufficient and, from looking at the various types, I was thinking of drilling the lever and fixing the magnet with both adhesive and a small self tapper? (once I have ascertained the correct position of course).

Two places now have said that there is no possibility of fitting on the chainring side because there isn't enough space?

(Was typing while you were posting)

 

There isn't much space true.

The BZ10C sensor is like most it uses an offset bracket to sit behind the BB Black spacer, the magnet disc has the center removed so it can freely clear the ext bearing. One may have to sacrifice the small chain ring and affix the disc with the bolts direct to the chain ring tapping's or epoxy it direct to said tapping's.

 

Can you show us the sensor you have ?

If sacrificing the small chain ring means you may miss the low gears then think about the rear cassette and fitting one with a bigger/lower gears like a 42t low gear.

 

Alternately one could experiment on keeping the small chain ring by placing extra spacers to move the chain rings out a few mm, it may or may not affect the chain line but shouldn't do if the gears are used correctly by not cross chaining, the derailleur may have enough adjustment for a few mm extra reach.

I had been thinking that a sensor on the rear brake only would be sufficient and, from looking at the various types, I was thinking of drilling the lever and fixing the magnet with both adhesive and a small self tapper? (once I have ascertained the correct position of course).

 

Rear brake cut off is all that is needed, mainly for on road use it free's one up to signal right across traffic and brake as well.

The sensor depends if it is a plunger type sensor or a magnet sensing one.

Nealh, I haven't purchased a kit yet because I still deciphering what I need to order.

Two places now have said that there is no possibility of fitting on the chainring side because there isn't enough space?

(Was typing while you were posting)

Fit it on the other side then, like mine. Don't panic. There are 100 solutions. These bike shops know nothing. they can't even be bothered to read forums to improve their knowledge.

 

Did you not read my previous post.? Am I wasting my time writing all this?

 

Edited May 18, 20214 yr by vfr400

Fit it on the other side then, like mine.

 

That is the other option.

Here a link to the sensor, if you want julet water proof connector they are available.

The disc used is thinned down one of 3.5mm.

1pc Assistant Sensor Pedal Electric bicycle Bz-10c Supplies Accessories | eBay

 

Most LBS or fitters are lacking in knowledge of what is available or can be achieved out of the ordinary. Kits sometimes needs a bit of imagination and thinking outside of the box as to speak.

Nealh, fitting on the other side was exactly what I thought (and asked the question when I collected the bike) and he said impossible.

Any chance of pics of yours please?

And his explanation was that the sensor would only work if pedalling backwards. I didn't say anything to him but my immediate thinking was surely just reverse the two wires?

And his explanation was that the sensor would only work if pedalling backwards. I didn't say anything to him but my immediate thinking was surely just reverse the two wires?

Because he's too thick to think about flipping the magnet to make it work in the other direction!

Sorry all of mine are fitted behind the chain ring, but fitting on the LHS just means one may have to orientate/reverse the sensor or disc for correct signal and direct of travel.

And his explanation was that the sensor would only work if pedalling backwards. I didn't say anything to him but my immediate thinking was surely just reverse the two wires?

 

Wiring remains the same just orientation of one component part is required.

I will take a pic of RHS hollowtech fitting for you later or tomorrow one with small chain ring removed and one with all three in situ.

Hi, I've converted a bike similar to yours (hollowtech crank, hydraulic brakes), some info in my thread https://www.pedelecs.co.uk/forum/threads/yose-350-rear-hub-kit-transplanted-onto-scott.40186/

 

Hollowtech. To test things I adjusted my gearchanged (easy job) so the smallest front gear cog was never used, removed my crank (easy, no tools needed), attached the magnetic disc to the smallest gear then cable-tied the sensor in place. I used a normal disk so had to enlarge the centre to fit over the bottom bracket. I've a ordered a hollowtech removal tool so I can soon fit a proper bracket for the sensor.

I think you have a choice - fit the disk to the smallest cog and lose use of that cog, or fit it on the opposite side (gears all work but I but I don't like the way it looks - not neat).

 

Brakes - I've not connected the sensors yet and the bike works fine (but sensors are highly recommended), you can glue a magnet & sensor to the lever, or you can buy new parts with built in sensors.

 

Keep us updated

i've also converted a Hollowtech crank bike using a rear hub kit from Woosh.

(kit from Woosh)

I'm mid forties, weigh about 14 stone, pretty unfit at the moment and the DWG22C kit from Woosh is a great fit for me.

 

The most tricky part was the PAS sensor installation.

 

I removed the smallest cog and fitted the magnetic disc in place of it. I used a seat tube mounted sensor, did some fiddling and got the sensor as close to the magnet disc as i could.

 

Another question for a rear hub setup is this... let's say that I am half way up a long hill and my legs are knackered, can I just use the throttle and (without the pedals turning) continue on electric only (hope that makes sense)?

yes you can but you also need to factor in how steep the hill is, your weight and what motor you buy. I've found that with the assistance from the hub motor im never too tired to stop pedaling for hills.

 

Mo

vfr400.... No, you aren't wasting your time at all. I am a carer so I am up and down stairs frequently, in between typing replies and reading, so there is inevitably some cross posting. But I appreciate everyone who is replying and I am reading everything (sometimes in catchup).

vfr400.... No, you aren't wasting your time at all. I am a carer so I am up and down stairs frequently, in between typing replies and reading, so there is inevitably some cross posting. But I appreciate everyone who is replying and I am reading everything (sometimes in catchup).

make it simple. Just tell us which kit you want to buy, then we can tell you how to fit the sensor. There will be absolutely no problem, I promise.

Looking at your photo vfr400, is there something (spacer?) between the magnet disc and the bearing? I have zoomed in but cannot tell.

I have a scrap pas to experiment with (as per photo).

Would I be right in thinking that I could Dremel out some of the centre so that the disc fits onto the splines, use a spacer to keep the disc away from the bb case and then tighten everything up (meaning that the left pedal is now offset by a few mm)?

For that type, you do it like this, assumimg that you have a 68mm BB tube. Check it first:

1. Thin down the magnet disc in where that extra thickness until it's flush with the rest of the disc is using a file or a Dremmel

2. Drill or Dremmel out the centre to 25mm so that the crank spindle can pass through it. Slightly chamfer the inner edges to keep them off the edge of the bearing seal.

3. Remove the cranks and both bearing holders and remove any spacers behind them.

4. Remove the sensor from its bracket and refit it the other side.

5. Reassemble the bearing holders with the sensor bracket behind the left side one.

6. Reassemble the crank with the magnet disc between the bearing holder and the pedal arm.

7. Use the plastic threaded cap to pull the left crank on. There should be just enough thread to get it started. you only have to pull it to. Don't worry if the left crank isn't on as far as it was before as long as you can insert and do up the clamp screws. You need that cap to pull it on far enough to get the screws in.

 

If you removed a spacer from the right side, you'll have to re-adjust your derailleur the equivalent amount.

Couple of questions.

Is the number of magnets significant?

If four would be enough, is it feasible to attach four neodymium magnets directly (using their own magnetic ability) to the bolts on the smallest chainwheel and then position the sensor accordingly? Or, in order for them to be attracted to the bolts would this mean that they would be incorrectly polarised for the sensor?

This isn't as easy as I had hoped.

I can't find anyone with UK stock and looking on the likes of AliExpress etc it seems that very few of the stores will ship from EU to the UK (good old Brexit).

But I am just getting more and more confused.

I am settled on a rear hub configuration and the Mxus Xf08c looks like a good contender, using a downtube battery with built in controller. All of the kits are shown as including a separate (silver box) controller but no battery. Are there two types of downtube battery, one with built in controller and one without? Or do I just order a kit and a battery and then not use the separate controller?