TSDZ chain drop fix

[EMGX]

I know I'm not alone with aggravating and gear limiting chain drop with TSDZ2 and probably other DIY mid drives that place the chainring outward resulting in poor chainline. I need large cogs on the cassette for everyday hill climbing and on this Dahon Jack 8 speed the chain drops inboard whenever attempting the inner two. It doesn't adjust outward enough to use as designed but installed upside down and only using the outer surface has prevented drops and only very slightly rubs when on the largest cog.
Just a thought if others are plagued by this shortcomming.

 

[PedalUma]

I know I'm not alone with aggravating and gear limiting chain drop with TSDZ2 and probably other DIY mid drives that place the chainring outward resulting in poor chainline. I need large cogs on the cassette for everyday hill climbing and on this Dahon Jack 8 speed the chain drops inboard whenever attempting the inner two. It doesn't adjust outward enough to use as designed but installed upside down and only using the outer surface has prevented drops and only very slightly rubs when on the largest cog.
Just a thought if others are plagued by this shortcomming.
View attachment 216275

I am with you. The rear end just shifts it off the chainring. It looks like the aluminum 32-t narrow/wide chainring was set at one link off. It is badly worn. The 'wide' teeth are badly sharpened and the 'C' gaps way too large. The chain and gears must also be replaced. I have made those or similar chain guides work but it takes some reconfiguring, such as a little spacer. ToSeven has a small ring that is steel , five bolt at 110 BCD and holds up really well. Small rings just cannot be offset. For most bikes it is fine, but for MTBs with a wide dropout it is a very real problem. Why did you go for a four ringbolt spider? It is not that I want to be a PITA, it is because I am observing and want to be helpful if I can. I have been through this same frustration. When you replace the chainring open the plastic cover behind it and lube the main gear and little step-down gear, this will quiet the motor. Do not over lube just a touch will do.

 

[EMGX]

Pictures can be deceiving. The chain is properly set in the chainring, not a link off. The chainring is like new, it's a wolf tooth product and it's made that way with tooth shape. Chain isn't worn at all and neither is the cassette. The spider is aftermarket made for TSDZ2 and allows smaller chainring than the stock spider (which can accomodate a 34t chainring I have another one with a 30t chainring on another bike also equipped with a TSDZ2. I do have a flat steel 34t chainring that the TSDZ2 seller (years ago) provided along with the stock 42t steel chainring. The aftermarket spiders were very inexpensive. This motor probably could use some lube as it's gotten noisier over the years, thanks for the reminder.

PS
In order to get a lowest gearing possible I used a 12-42 cassette which provides 20 gear inches but of course the stock SRAM X4 can't handle 42t without an extender. Wolf tooth roadlink didn't work with the derailleur hanger but one that I think came for free with a cassette does work well with the B screw removed. I also use a friction shifter which shifts smooth and fast across multiple cogs, same couldn't be said about the stock shifter. I really like the Dahon Jack, it's a great 26" folding bike.

 

[PedalUma]

Could an extender screw with a spacer work on the guide?

Under what conditions is it dropping? Underload while shifting to a lower or the lowest gear. Or in a higher gear while not pedaling and coasting on a bumpy surface.

 

[EMGX]

Without the chainguide it always drops when shifted to the inner two (largest) cogs, even on a bike stand. I'm happy with the chainguide as it is but it couldn't be easily modified anyway, the screw visible on the outside of the guide fastens to a rod that is clamped into the seat tube bracket part. The length of the rod limits how far it can reach out, not the screw itself. I think the shorter chainstay of folding bikes is the main cause (besides the poor chainline) even though the Dahon chainstay is only less than an inch shorter than my Schwinn hybrid currently mounted with my other TSDZ2 with 30t chainring and 11-40 8 speed cassette. No chain drop on the Schwinn. I also have a 20" folding bike that had same chain drop issue when a TSDZ2 was installed - I made my own chainguide for that bike but I like the one on my Dahon much better. It is high quality for what it is IMO. I see that someone else posted an Amazon review using same way upside down/backward to correct chain drop on their Bafang mid drive.

 

[PedalUma]

Just asking: What if you took a two inch long section of hose put it around the chain and strapped it to the existing chain guide?

 

[EMGX]

No idea, the current chain guide is working out fine so no need for anything further in this regard. Raining today so I'll head out into the garage and lube the TSDZ2 gears. I have a tub of Super Lube so that's what I'll use and have used the same on my other motor in the past.

Edit:
While lubing the gears I saw that there is a weep hole cast in the housing which would be normally in the most dependent/lowest position if the motor was oriented they way Tongsheng intended but the way I have installed it points forward where water flying off the front wheel would be directed so I plugged it with silicone sealant. There is still drainage available where the wires exit the motor which are now oriented downward instead toward the back of the housing.
Also PedalUma, as you indicated, it does look like the chain guide could be extended outboard more with a longer compatible screw and a spacer between the guide slide bracket and the rod that is captured by the seatpost clamp. Not necessary for my use because I just need to stop the chain from dropping inboard which the guard accomplishes as I installed it.