Following my first mid motor bike conversion I thought I would give some feedback, via a number of posts, which hopefully will be useful to those thinking of doing something similar.
Some donor bike advice as follows:
1. Think ahead about how you want to use the bike. I had originally planned to do the conversion using my existing aluminium framed road bike and purchased the Tongsheng TSDZ2 mid motor kit and Hailong 48v 22.5Ah downtube battery with this in mind. Less than 24 hours after placing the order I changed my mind after talking to someone at the supplier (see my point in part 1 about buying from someone in the UK) who had his own TSDZ2 conversion. He pointed out that the weight concerns in selecting a road bike are largely irrelevant on an ebike with a large battery. This got me thinking of all the off-road routes I could tackle on an MTB/gravel type ebike that I would never even consider on my road bike. I eventually went for a Giant Roam 3, an aluminium frame “sports hybrid” in industry jargon, with front suspension and hardtail which was in my price range. I would describe the choice as a qualified success.
2. Most importantly chose a bike with adequate space for the motor. I know this sounds obvious but it is actually quite difficult to establish in advance. Buying a bike online/unseen will always be a gamble. Much better to be able to examine the bike and be able to TURN THE BIKE UPSIDE DOWN and look carefully at how the chainstays leave the bottom bracket (see photo below). There are two important factors:
A) The geometry or “sweep” of the chainstays as the leave the BB shell. Although spacers can be used to move the motor outwards to potentially avoid clashes with the frame (I have no experience of this) that will mess with the chainline which I wanted to avoid. When I was looking for a suitable donor bike those with a single chainring at the cranks looked problematic to me. One frameset I looked at actually stated that a 38T chainring was the largest they would advise using to avoid clashes with the frame. Bikes with a double or triple chainring setup I believe will necessarily have more swept back chainstays to accommodate them.
B) The location of any cable lugs or other protrusions on the chainstays close to the BB shell (ideally any of these should be aft of the chainstay bridge). I was unaware of this issue when selecting my bike and hence had to take a hacksaw to a cable mounting lug that clashed with the TSDZ2 stabilising plate. This was perfectly do-able but not ideal on an otherwise pristine bike.
Out of interest having finally got the motor to fit, somewhere on day 3 of the build, I removed it and stuck some pound shop plasticine on the drive side chainstay and replaced the motor to make an impression that I could then measure. The results in the photos below show the clearances between the BB shell (41.5mm OD) and the chainstay measured flush with end face of the BB shell (25mm) and 4mm beyond but parallel to the end face of the BB shell (45mm). I offer this as a guide only, do not rely on these measurements as amongst other things BB shell thicknesses vary as do the motor manufacturer’s specification.
3. If possible chose a bike with all external cable routing. The fashion for concealing cabling in the down tube works against an ebike conversion. Because of the restricted space between the motor casing and the bottom bracket shell there will be at most room for an unsheathed “inner” cable. All hydraulic hoses and cables with an outer casing will have to be pulled out of the down tube and routed outside of the frame where there are no longer any lugs to hold them.
4. If fitting a down tube battery, chose a bike with a straight down tube and take a straight edge to check it. I made the schoolboy error of thinking that because the down tube on the Giant Roam looked straight it was straight. The slight downward curve on the down tube, combined with the slight upward curve of the battery mounting plate gave me a real headache when it came to mounting the battery (see photo).
Most of the above issues can be overcome with some compromises if/when they are encountered but it will always be better to avoid them in the first place.
Part 3 will cover motor installation.
Some donor bike advice as follows:
1. Think ahead about how you want to use the bike. I had originally planned to do the conversion using my existing aluminium framed road bike and purchased the Tongsheng TSDZ2 mid motor kit and Hailong 48v 22.5Ah downtube battery with this in mind. Less than 24 hours after placing the order I changed my mind after talking to someone at the supplier (see my point in part 1 about buying from someone in the UK) who had his own TSDZ2 conversion. He pointed out that the weight concerns in selecting a road bike are largely irrelevant on an ebike with a large battery. This got me thinking of all the off-road routes I could tackle on an MTB/gravel type ebike that I would never even consider on my road bike. I eventually went for a Giant Roam 3, an aluminium frame “sports hybrid” in industry jargon, with front suspension and hardtail which was in my price range. I would describe the choice as a qualified success.
2. Most importantly chose a bike with adequate space for the motor. I know this sounds obvious but it is actually quite difficult to establish in advance. Buying a bike online/unseen will always be a gamble. Much better to be able to examine the bike and be able to TURN THE BIKE UPSIDE DOWN and look carefully at how the chainstays leave the bottom bracket (see photo below). There are two important factors:
A) The geometry or “sweep” of the chainstays as the leave the BB shell. Although spacers can be used to move the motor outwards to potentially avoid clashes with the frame (I have no experience of this) that will mess with the chainline which I wanted to avoid. When I was looking for a suitable donor bike those with a single chainring at the cranks looked problematic to me. One frameset I looked at actually stated that a 38T chainring was the largest they would advise using to avoid clashes with the frame. Bikes with a double or triple chainring setup I believe will necessarily have more swept back chainstays to accommodate them.
B) The location of any cable lugs or other protrusions on the chainstays close to the BB shell (ideally any of these should be aft of the chainstay bridge). I was unaware of this issue when selecting my bike and hence had to take a hacksaw to a cable mounting lug that clashed with the TSDZ2 stabilising plate. This was perfectly do-able but not ideal on an otherwise pristine bike.
Out of interest having finally got the motor to fit, somewhere on day 3 of the build, I removed it and stuck some pound shop plasticine on the drive side chainstay and replaced the motor to make an impression that I could then measure. The results in the photos below show the clearances between the BB shell (41.5mm OD) and the chainstay measured flush with end face of the BB shell (25mm) and 4mm beyond but parallel to the end face of the BB shell (45mm). I offer this as a guide only, do not rely on these measurements as amongst other things BB shell thicknesses vary as do the motor manufacturer’s specification.
3. If possible chose a bike with all external cable routing. The fashion for concealing cabling in the down tube works against an ebike conversion. Because of the restricted space between the motor casing and the bottom bracket shell there will be at most room for an unsheathed “inner” cable. All hydraulic hoses and cables with an outer casing will have to be pulled out of the down tube and routed outside of the frame where there are no longer any lugs to hold them.
4. If fitting a down tube battery, chose a bike with a straight down tube and take a straight edge to check it. I made the schoolboy error of thinking that because the down tube on the Giant Roam looked straight it was straight. The slight downward curve on the down tube, combined with the slight upward curve of the battery mounting plate gave me a real headache when it came to mounting the battery (see photo).
Most of the above issues can be overcome with some compromises if/when they are encountered but it will always be better to avoid them in the first place.
Part 3 will cover motor installation.
