TSDZ2 120mm Axle Broke for the 2nd time on my Fatbike

MaartenL · Jan 23, 2019

Hi all!

I have this issue were my 120mm axle of my Fatbike with TSDZ2 motor broke for the 2nd time. I'm really wondering how this could happen. Here are some pictures for your amusement... =)

Could heat play a role? I did have an issue with the retainer ring which did not fit too well and did not 'lock' the axle so it had some play moving left/right.

Future-Bike mentioned that I replaced the original cranks which came with the set for a set Miranda cranks. It does change the offset but could that brake the axle?

amberwolf · Jan 23, 2019

I don't see any images, but if it is the rear axle in the wheel you're talking about, I don't know how it could break from the motor power/etc.

If instead of axle you mean crankshaft (where the pedals attach) on the TSDZ2 itself, then where exactly is it breaking?

If it's outboard of a circlip groove, then that's where stress risers are more likley to break something anyway.

If it is also outboard of the output sprocket, then pedal torque could be the cause, if you're really cranking hard on them.

If it is inboard of the output sprocket, then that could be motor power doing it.

MaartenL · Jan 23, 2019

I don't know why you can't see any images, I tried on several browsers and it works every time... anyway!

I'm talking about the axle connecting my cranks. It broke exactly were the retainer ring is supposed to sit. Now I'm thinking about what you said.....

Let's say that when I'm standing on the pedals without pedalling (so making a twisting motion on the axle) and for some reason the motor will activate because the torque sensor noticed some pressure it might be possible that this can break the axle.... ?

Bigwheel · Jan 23, 2019

That part is more commonly known, at least here in the US, as the bb spindle.

It looks less like a break to me other than a break down of a manufactured joining of two parts? The spindles are very clean on both parts and there looks like a machined shoulder on the smaller section that it is not clear if there is more inside the longer part of the spindle? Whatever that small shoulder is not at all large enough to support the pressure of a crank arm under power.

It also looks like there is similar joint on the other side of the spindle like they took a stock bb spindle, cut it into two parts and sleeved them into a longer section in order to make it work for the wider bb shell. All in all it looks improperly engineered to me to begin with. That whole spindle should be made from one piece and heat treated properly.

APL · Jan 25, 2019

Circlip's on the BB spindle have been around since the early Gary Fisher days, with no real problems. It's not the
greatest idea, but throughout time, it doesn't have 'all' that bad of a rep.

Like amber wolf says, it's a high stress riser because of the sharp edges in the grove, it really should be a round grove
instead of a square grove. Even better yet, no grove at all,.. and use tube spacers between the crank arms and BB to
center the spindle. But whats done is done, and your stuck with it on that drive.

I would suspect that you have a bad batch of spindles, or perhaps their all bad, or your body weight is a lot, and or
your riding sale is extreme.

One thing you can do is Google 'forums', and then "TSDZ2 spindle braking" and see how many others with these bikes are
having the same problem. That will tell you if yours is uncommon or not.

MaartenL · Jan 25, 2019

Thnx all, it seems that I've been unlucky and should be more lucky with my next spindle. I talked about my problem with Future-bike.it and they send me a whole new set with circlips/retainer rings/washers/cranks and I'll hope to do it right this time.

One questions: there is a set of rubbers you attach. Can anyone again tell me how to install these, pictures would even be better! There is 3 rubber parts I know about.

1. with a metal ring/spring
2. a part which is attached to number 1
3. the rubber part which sits agains the front sprocket

I'm not exactly sure were to put number 1 & 2 and in what order. Well the same goes for the washers etc, but I'm guessing I'll find out in a video.

Pirmoz · Apr 1, 2019

Hello

So i have the same problem.
Bought the extension kit for my fatbike from the same seller and it broke after 150km. Contacted them in january and they were just finding excusses. So i am without my ebike to this day.
Can i ask...how did you contact them..do you maybe know the name of the person? I spoke to a guy on whatsapp and he was really not helpfull.
I must say. So far I am extremely dissapointed with this company.
Hope it works for you now.

MaartenL · Apr 2, 2019

Sorry to hear so! I actually broke two of them which I replaced. I always had contact on Facebook with them. My experiences are mixed as yours. Contact can be difficult / they don't reply very fast.

Pedrito · Apr 14, 2019

Hi, I'm thinking about transforming my fatbike, I already have a tsdz2, do you advise me to buy the adapter to 120mm of future bike or gives problems? Thanks

Pirmoz · Apr 15, 2019

Hello

I had just made a pair of axles at my local guy. He made them from INOX and according to his words the material they use is not able to withstand the forces.
I can sell you one of mine if you wish and can tell you the dimensions for the tube adapter. the extra bearing is dirt cheap.

However the axle that I have doesn't have the inner cut (there are two on one side) because it broke on the inner one same as on the pictures above, and I guess it is used for 100mm BB. for me...it is useless since I have a 120mm BB.

If you are interested let me know and I can help you out so you don't have the problems and wont throw away 90 euros plus shipping, because those guys are.... I won't even say it.

Cheers

Sorry just looked at the picture above...i guess his axle is different than what they've sent me.

Still if interested we will do the mesaures and see if it fits

schibolaus · Oct 31, 2019

Hi Pirmoz, I might be interested in purchasing Inox bottom bracket spindles for the 120mm BB extension for the TSDZ2. How much did those cost? Cheers.

HerskerHans · Apr 12, 2020

Ive broken two now also, starting to get at bit tired of this, im 95 kg and i like to do trailbiking. I guess its not built for trails the tsdz2.

noviceBuilder · Apr 12, 2020

I was considering buying a TSDZ2 to install on a fat bike. But I can't ignore this track record. As I was shopping around, I noticed only three shops sell the fat bike version (eco-ebike, recycles-ebike, and 1 aliexpress merchant). These extensions seem like a hack. I wonder if these 100mm & 120mm spindles come from Tongsheng, or if some third party is making these. Considering the price really takes a jump and most vendors don't offer it, it's probably not Tongsheng who makes them.

Are you guys saving your broken parts to give to a blacksmith, so they can perhaps copy it and improve it? I might be tempted to buy a broken one off one of you to give to a blacksmith to copy.

Would it make sense to buy a smooth spindle like this one, and then have those little gears in the middle of it added?

HerskerHans · Apr 14, 2020

Im gonna attempt to weld mine. ive got two broken ones, the hole for the pedal arm is drilled unneccessary long too which weakens the axle, there is also a groove for a c-lip, so the metal is very thin where it breaks. I cant find the long axle as a spare part either, only the std 68-70mm crank type.

Balmorhea · Apr 14, 2020

The bearings supporting the TSDZ2’s spindle are 15mm inside diameter. Normal pedal bike bottom bracket spindles are 17mm, and this is demonstrated to be just big enough for reliability. The Phil Wood spindle in the link is 17mm.

I note with some horror that the designers— I refuse to call them engineers— of the TSDZ2 have put a snap ring groove In the spindle, right at the point of highest stress. This is a known problem since the 1970s at least, when Viscount/Lambert bikes were equipped with a similarly grooved spindle, and suffered chronic breakages.

I’m sorry to say that the problems with this spindle are by design, and can’t be fixed. Welding a broken spindle will create a heat affected zone and material discontinuities, causing the repair to fail even more quickly. Short of replicating the part in some absurdly strong material like maraging steel, there’s nothing to be done about it.

HerskerHans · Apr 14, 2020

https://www.eco-ebike.com/products/tsdz2-upgrade-bottom-bracket-axle-extension-in-92mm-100mm-120mm?fbclid=IwAR2ouMc3EPvAM8nHe5-67Emn9YM7bu19fI0Em997WnVU438tlTg6u74apCo

HerskerHans · Apr 14, 2020

You have a very good point about bad design, but i think if you grind it down, so you get weld the 5-6mm hole inside where the grooved part is. It should be possible to get it better. since atleast it wont be hollow.

noviceBuilder · Apr 14, 2020

I've been looking into a way to mount a TSDZ2 on a fat bike. I only learned about future-bike.it in this thread, but there are others as you mention HerskerHans. You may find this useful to sort out the supply chains:

It looks like all the vendors are actually the same company apart from future-bike.it. Notice how the email addresses are shared.

Is it strictly future-bike.it spindles that are breaking? The important thing is that we avoid buying more spindles that come from the same factory that's making defective ones. It's important to find out if future-bike.it has any connection to the others w.r.t supply chain - otherwise you're just getting the same defective part.

Would everyone with a TSDZ2 who had a fat bike spindle break please say where they bought it?

Was anyone hurt? Which side is failing, left or drive side?

This is a safety critical failure. The bottom bracket spindle is most likely to snap while you're standing up on the peddles - then imagine that happening going down hill or at a high speed (which is usually the case when you're standing up).

HerskerHans said:
https://www.eco-ebike.com/products/tsdz2-upgrade-bottom-bracket-axle-extension-in-92mm-100mm-120mm?fbclid=IwAR2ouMc3EPvAM8nHe5-67Emn9YM7bu19fI0Em997WnVU438tlTg6u74apCo

The pics don't show whether that spindle is the same, but when you view this video of it, it looks like it has the same cotter pin groove that the future-bike.it one has, so it apparently has the same weak point.

If they're going to use grooves for cotter pins, shouldn't they be using titanium?

Malitsuikka · Apr 16, 2020

Hi!
I have TSDZ2 BB100mm (500W, 48V) on my Fatbike and got my shaft broken yesterday (after 560 km use). I have sent message to Ebird Store and waiting their comments. Anyhow... shaft was broken from circlip groove, chainwheel side. Motor is still mounted to the bike. ==> Is there instructions somewhere how to remove this broken shaft.... can motor be mounted to the bike.... do I need to remove also torque sensor or is it possible just to pull out the shaft??

noviceBuilder · Apr 16, 2020

Malitsuikka said:
Hi!
I have TSDZ2 BB100mm (500W, 48V) on my Fatbike and got my shaft broken yesterday (after 560 km use). I have sent message to Ebird Store and waiting their comments. Anyhow... shaft was broken from circlip groove, chainwheel side. Motor is still mounted to the bike. ==> Is there instructions somewhere how to remove this broken shaft.... can motor be mounted to the bike.... do I need to remove also torque sensor or is it possible just to pull out the shaft??

You've been a great help. So we know that it's not just 120mm spindles that are breaking.. it's also the 100mm ones. You've also confirmed that the defect is not just in future-bike.it, but also in the other shop chain.. so all supply chains are likely shipping bad spindles.

This installation video and this spindle installation video might help answer your question on how to disassemble.

Malitsuikka · Apr 16, 2020

Hole for crank mounting bolt is way too deep.... it could be almost 10 mm shorter and then shaft wouldn’t be shallow at the circlip groove area ..... bad design I think.

Balmorhea · Apr 16, 2020

Malitsuikka said:
Hole for crank mounting bolt is way too deep.... it could be almost 10 mm shorter and then shaft wouldn’t be shallow at the circlip groove area ..... bad design I think.

If the hole ends near the location of the groove, the stress riser of the change in section could have more effect than a deeper hole. The snap ring groove is the biggest problem, followed by the insufficient outer diameter of the part. These spindles would be breaking just about as often even if they were solid.

Holes along the axis of a shaft don’t have much effect on structural integrity, because stresses are highest in the skin and negligible near the center.

casainho · Apr 17, 2020

noviceBuilder said:
You've been a great help. So we know that it's not just 120mm spindles that are breaking.. it's also the 100mm ones. You've also confirmed that the defect is not just in future-bike.it, but also in the other shop chain.. so all supply chains are likely shipping bad spindles.

I installed at least 6 TSDZ2 motors bought on PSWPower and I never had any issue of that (100mm ones). I weight 105kgs and I always put my full weight on the pedals, I even calibrate the torque sensor for my full weight on each pedal.

Malitsuikka · Apr 17, 2020

Interesting.... I just wonder could gear ratios play some role ( I have (1st gear ) 34T at front and 34T at back ==> rather hard to get up really steep slopes)... even with 500W help ??
What about tightening torque of crank bolt.... I do not have torque wrench and spec is asking 40 Nm for that bolt??

noviceBuilder · Apr 17, 2020

casainho said:
I installed at least 6 TSDZ2 motors bought on PSWPower and I never had any issue of that (100mm ones). I weight 105kgs and I always put my full weight on the pedals, I even calibrate the torque sensor for my full weight on each pedal.

Are you sure you got 100mm TSDZ2 spindles from pswpower.com? Their website is a mess. I've picked through it and every TSDZ2 listing (like this) states: "The Mid Drive Kits are designed to fit bikes with a 68mm (2.68 in.) or 73mm (2.87 in.) wide bottom bracket shell and 35mm inside diameter. " with no option to go bigger. I only find their Bafang BBSHD for 100mm. Do you have a direct link?

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