The trials and tribulations of fitting an ebay kit

[DynatechFan]

I thought it might be fun (actually probably more therapeutic for me) to share my experiences of installing a kit from ebay on to fairly standard 26" wheel MTB - where the kit is from maybe doesn't matter that much - but I hope by sharing other novices have the chance to plan ahead and/or avoid my mistakes

My mechanical skills are decent, I have built my own bikes/wheels and do some work as a volunteer mechanic for a charity. Got a proper tool kit and bike stand too. Electrically I can rewire a plug but get nervous when warning lights flash or meters are needed

THE BUYING

After much dithering and advice from this very forum the order was placed. The kit arrived in a few days arriving in 2 boxes (wheel et al in one and battery in the other) Alas the battery bracket was bent, contacted the seller, they sent a new one, arrived a week later. So a minor inconvenience and nothing more, quite happy so far

The kit was a cassette rear wheel for 8/9 speed so I needed a cassette spacer for my 7 speed commuter. Trip to LBS seemed to find the right part, but it wasn't in stock, so I had to go back and collect at the weekend. Maybe 3 hours travelling backwards and forwards and £2 in all, only to find the spacer was the wrong one! Tredz sell the correct 4mm spacer, with 3 grooves in it where the cassette rivets are, for £3 delivered - Lesson 1 don't trust your LBS to actually know what they are talking about

Another expense was new tyres. I had been convinced to go to a rear hub conversion and really didn't want any grief with punctures on an ebike commuter. Schwalbe make some excellent puncture resistant tyres - so a pair of very well priced Puncture Guard Land Cruiser Plus were duly ordered from CRC for £27, there were better ones but they were £40+. Didn't need any rim tape or tubes as I have loads - Lesson 2 expect to buy a few other things along the way

My expectations were that "its only a couple of hours" to fit a conversion - how hard can it be . . . so last night I set off to the garage with a couple of hours to spare and a sense of hopeful anticipation

THE BUILDING BEGINS

The battery bracket didnt have any holes that lined up with the bottle mounts on my bike, so I had to drill new one - no drill press but with patience I got it in the right place. That seemed painless - maybe an hour in total. Though I have lost my D lock carrier from the frame so need to find a new way to carry that. Added the controller bag to the frame and put the first wires in. If bolt holes line up this could be a quick, simple job for you

The LCD display came in a few pieces, brackets a bit flimsy but fitted nicely in just a few minutes. Putting in the last nut/bolt and the nut fell on the garage floor and rolled under the Dexion out of reach. Ten minutes to fit the display (plus 20+ minutes scrawming on the floor swearing). Again nice quick job

Fitting the Schwalbe tyre to the wheel was easy enough. Nicely made tyre. All in maybe 5 minutes - be careful to rest the wheel on the axle end without the lead though

Next the back wheel was popped out and lots of checks with calipers confirmed the various diameters should fit - just. The axle was okay but the (frankly huge) wheel nut fouled the rear dérailleur on the lead side, so I had to unscrew it all. That didn't go well because the factory had damaged some of the axle threads when they put in the groove for the power lead. Took probably 45 minutes to get the wheel nut to come off the end of the axle thread . . . grrr Lesson 3 - check all the threads and fittings, have some needle files handy just in case

Anyhow, offer the wheel up again - with the bike in a workshop rack - and it was proving a bit of a nightmare to get in. The wheel is darned heavy so after 15 minutes of not getting it to fit I decided to put the bike on the floor and try again. Still no luck, the wheel just would not go in to the frame. Getting a decent torch and poking around it appeared that the grooved washers that help transfer the torque of the wheel to the frame were upside down - Lesson 4 just because it was put together in a factory doesn't mean they did it correctly.

Quickly turned the washers over and it *nearly* fitted but was still not willing to go in to the frame. It looked like the brakes were fouling the wheel somehow, so I spent 15 minutes removing them - still no better. So I decided to turn the bike over. Put some bits of 2x2 on the floor so the LCD didnt get damaged and over we went. It was obvious now that the wheel wouldn't fit the frame because the drop out spacing was too narrow. Measured the frame - spot on at 135mm. Measured the axle, 139mm!? And, other than the changing grooved washers nothing can be done to make it smaller. Spent maybe another 30 minutes trying to get the wheel in but it wont go. Leave out the washer on the cassette side and it jams the cassette. Leave out the washer on the non drive side and it might fit but no way is that okay for torque transfer. Basically the frame / chainstays wont flex enough - its a CrMo MTB, nothing special - but strong.

And that was it, roughly 3 hours in the garage, two brackets fitted and the bike now upside down in pieces with a wheel that wont fit

Right now I am regretting the whole rear hub thing - I know it makes sense for lots of practical usage reasons. Not even sure what to do next, but I will return tonight for another go . . .

 

[Nealh]

Spreading the rear D/O's 4mm shouldn't be an issue a bit of your 4 x 2 and a decent wedge should be enough to open the drops, allowing for a bit of spring back open the D/O's a bit wider.
Once the motor is in situ you will probably find the D/O's need a bit of fettling with a file or dremmel, often 3 or 4 mm is required for the axle to sit deep enough to allow the tab of the A/R washer to fit.

 

[tommie]

Lesson 5 - Should have purchased a mid-drive

Honestly, this forum is littered with endless pages of fitting issues with hub drives.

you can easily have a mid-drive conversion fitted in three quarters of an hour and off you go.

 

[Deleted member 4366]

Cro-mo frames are normally dead easy to stretch. It's aluminium ones that are the hardest, especially frames for 20" wheels with the massive chain-stays that you get on some of them. I've gone as wide as 150mm on some frames and never had any problems.

Without the anti-rotation washer on the left, the disc normally rubs on the frame or caliper mount. In fact you normally need to add an extra single 12 mm washer behind the AR one to get that right.

You can often gain a bit of space on the cassette side if there's any space between the top gear and the frame by putting the AR outboard and using one or two thinner normal 12mm washers inboard.

The AR washers might not have been installed upside down by the factory. Don't forget that the wire has to exit downwards.

Don't waste your time trying to install a wheel in a stand. It's almost impossible. With any new kit, the first step should be to turn the bike upside down and sort out the motor spacing, starting from the disc side.

When you go back tonight, just give the frame a big heave-ho and the motor will drop in.

 

[Nealh]

Unless you have the tools both hub and CD have issues.
CD's also can have fitting issues with Bottom bracket and chain line.
BB shell can have welds that need filing down.

 

[anotherkiwi]

Hub motor I had to buy a file for the dropouts (steel)
Mid-drive I had to get the lock ring thinned down to fit.

50/50

 

[DynatechFan]

thanks folks - I have pulled together a car jack and pile of 4x2

The two torque washers were definitely upside down and it took me ages to notice

As a former metallurgist I would be very wary of converting an aluminium frame to ebike this way without an external torque arm (wouldn't fancy bending chain stays in aluminium much either) thankfully steel doesn't have the same fatigue limit issues so I'm good with that

As a total newb to all things ebike I *still* think a hub conversion is a good place to start

 

[DynatechFan]

Time for an update - bit of a family crisis meant I had to pull all the e-bike bits off the bike and use it unassisted for a while - Lesson 5 life goes on and this stuff always takes longer than you hope. Today I finally got some garage time and went back for another go . . .

One thing I had done in the mean time was get a car jack in the frame and pushed it out to 155mm. Taking out the jack and the frame was exactly where I started - wow how springy is that! But I had managed to bend the dérailleur hanger and mess the gear indexing, so had to fix that as best I could - by eye its ok and the indexing seems ok. If needs be, later on, I will take the bike down to the workshop of the bike charity I help out with and get a proper dérailleur straighter on it - Lesson 6 if you are going to bodge make sure you know how to fix it when it goes wrong

Anyhow, returning to the wheel that would not go in. Two weeks ago I had been offering the wheel up without having swapped over the cassette. When it proved so troublesome I had left the original wheel usable so the bike wasn't off the road - today I decided to "go for it" and swap the cassette, come what may the bike was running with the hub motor wheel even if I couldn't get the ancillaries / electrics sorted.

Old wheel out and 7 speed cassette was off in a few minutes, just as it should be. Gave it a good clean while I was there. Then the "fun" began. Using the 4.5mm spacer behind the 7 speed cassette instantly looked wrong, the cassette tightening nut would barely tighten and everything was well proud of the torque washer - even if it went in the frame it wasn't going to rotate. Thankfully I had a 1.8mm spacer that my LBS sold me (and I thought was wrong). Pulled everything apart and tried again - this time the cassette would tighten properly BUT it still obscured the torque washer. Took it all apart again to see what could be done with the axle. A cup and cone axle would give me some way out but not a chance, sealed bearings and no adjustments in sight. In the end I put extra washers *behind" the torque washer so it was sufficiently proud of the cassette. Offered up the wheel and there was about 7 mm of frame flex needed - with a hefty tug it went in. Wow! A few checks/tweaks of the dérailleur and it seemed to be there for good. Three hours this morning and the darn thing is actually in. I was so pleased I went for a spin just to check the gears were ok. Didn't really feel the extra weight or any extra resistance, the mug of tea afterwards was particularly satisfying - Lesson 7 persistence and staying calm in the face of endless calamity will get you there in the end

Moving now to the crank sensor / pedal assist system. This had looked dodgy from the start, at least 2mm of metal removal was needed to make space between the back of the crank and the bottom bracket / PAS. The kit came with a dinky PAS bracket that slots in the the splines of the BB on the left hand side, so my first task was to get the crank off and clean the splines. Again both quick and easy. Offered up the sensor and it wouldn't bed in to the crank splines properly, so a good half an hour was needed with tooth brush and cocktail sticks to extract every tiny bit of dirt. Still not perfect but good enough. I decided to file back the crank by hand rather than use power tools. It took a while but once reshaped and finished with a bit of medium wet and dry looked like it had been made that way. All tolled maybe 1 hour of effort to get the crank sensor on. The clearance between the crank and sensor is tiny so I am hoping the sensor doesn't come to any harm, we shall see.

And then, suddenly it was nearly there. Put the modified battery bracket back on. Made all the connections - that was nerve wracking, all those little pins. Again this kit was a little different to other ebay ones in that it only had 4 connections. Very delicate looking connections. Lots of cable ties here and there. Added the battery and turned the battery on. Nothing

Then I remembered there was an on/off switch on the handlebars too. Pressed it and it fired up . Went straight out of the garage and went for a spin, came back with a big smile - it worked

In total I had probably put 2 (shortish) days in to the build. All the cables etc are workable but things aren't as neat as I want. The battery bullets are also outside the controller bag so my plan is to waterproof heat shrink those. Tomorrow is a proper shake down ride, if all goes well the next task is some tinkering and tidying. The throttle and brake sensors are not yet fitted so I will look at them too - from a brief test ride I don't see a need for them just yet. The controller bag is naff though, so will look at getting a decent waterproof fox fitted to the frame somewhere.

Would I do it again? - probably. Was it satisfying to do? - probably. Do I trust it to be reliable? - probably. Off to put the kettle on (again!)

 

[Deleted member 4366]

Why did it need a spacer behind the cassette? I've fitted loads of cassette motors, but I never needed a spacer.

 

[DynatechFan]

Well a couple of days of road testing and (fingers crossed) it all works - even in pouring rain and near zero temperatures. Plan to get some heat shrink on the exposed cable bullets from the battery.

WRT the cassette my donor bike is a retro MTB running NOS 7 speed STX SE, the cassette is too narrow to tighten properly on an 8/9 speed hub. Usually its a 4mm spacer, but for some reason the conversion kit wheel needed a 1.85mm