TSDZ2 Crank fell off - what spec for replacement nut?

terravoir1

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I literally had the same problem this morning! Huge pain and left me stranded to take the dreaded tube and had to ditch my bike.
 

saneagle

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Oct 10, 2010
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People don't seem to understand how crank-arms work. theye're meant to be soft aluminium and the crank shaft is meant to be hardened steel. When you tighten the bolt, the aluminium squishes to take the exact form of the shaft. As it squishes, the aluminium work-hardens as well so will keep the correct shape and not squish any further. When you tighten the bolt it must be enough to squish the aluminium, otherwise the aluminium will stay soft and start to wobble after some miles. It's not the bolt that comes loose, it's the aluminium. The solution is to tighten the bolt to 40Nm, which is a lot - not something you can do with a multi-tool.

If your arm comes loose, the wobbling will change its work-hardened shape, so it will no longer fit correctly. The best solution is to heat it right up to anneal the aluminium, which takes it back to its start condition.
 

Bikes4two

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Feb 21, 2020
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Unless you are an experience mechanic of some sort used to tightening things, I very much doubt that without a torque wrench you'll be able to 'guess' the 40nm torque required for the crank bolts.

I've cycled in excess of 6,000 miles on my main TSDZ2 bike and after some intial loosening of my cranks, I bought a torque wrench and was suprised how far short of the required torque I'd been tightening to.

Now I no longer have problems but even so and out of good practice, I periodically (as in every few months maybe?) check for tightness on all fixings on the bike, not just the cranks and yes, the cranks nearly always need a bit of a 'torque top-up' but never by much and certainly not enough that I've 'felt' any crank arm movement when cycling.
 
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Nealh

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When I fitted my tsdz2 to the Ute I didn't use a torque wrench, but simply tightened them to spanner tight then gave them a good 1/4 turn and helping hand with a small clubby . Not come lose yet in a couple years of riding.
 

guerney

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Sep 7, 2021
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What is it about these TSDZ2s? Not only do owners have to contend with screw anxiety, shaft snap anxiety, moisture ingress, pedal high-q factor, overheat and melty blue gear anxieties (among others), now they've got crank anxiety... An aluminium crank arm has never fallen off my Bafang BBS01B, and I didn't even tighten them all that much - about half a moderate oik's worth, if that, no taps with a mallet or anything else. I haven't tightened the cranks since installation. Over 4,000km and nothing has fallen off.

Hope the TSDZ8 is a better manufactured motor! It looks like a Bafang, so that's a step in the right direction.
 
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Nealh

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The same applies to BBS cranks s it does TSDZ, if not tightened enough they will loosen or come off. My old BBS01 came off after the bolt came out.
 

guerney

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The same applies to BBS cranks s it does TSDZ, if not tightened enough they will loosen or come off. My old BBS01 came off after the bolt came out.
I was going to write "Maybe I'm like, really strong or something", but suddenly remembered that those bolts, like nearly all the others in the BBS01B kit, arrived tipped with a bit of blue threadlocker, which might help prevent crank arms falling off? Or perhaps I really am stronger than I think I am, or TSDZ2s are very inconsistently manufactured, or manufactured consisently badly.

Forumites who don't appear to experience too many problems with TSDZ2s, use theirs at low power. Some like yourself, after making a few modifications.
 
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Nealh

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That's because maybe the TSdz doesn't need the same effort as the BBS.
 

guerney

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That's because maybe the TSdz doesn't need the same effort as the BBS.
On my 20" wheeled folding bike at least, once the BBS01B's cadence sensing is activated (it can be set to fast activation in firmware), it shoots off and continues with laughably minimal effort.
 
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Bikes4two

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Feb 21, 2020
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What is it about these TSDZ2s? .........
I like the TDSZ2 because the torque sensing ride feel is what I wanted, it's a simple as that (along with the mid mounting position which I prefer to a hub).

The motor is made to a low price point and I suspect designed for a 'use case' more akin to urban riding that carrying some 120Kg giant across mountainous desert and yes, the TSDZ2 does seem to have a list of generic problems, not all of which effect all riders and all motors and non of them for me have been more than mild irritants and all simply resolved.

6,000+ miles on and no sign of my Blue Gear wearing nor anything else that I'm aware of and my particular motor is quieter than my fellow riders on Bosch Active Line, Shimano Steps, Mahle X35 and Fazua, (but I know that not all TSDZ2 are that quiet).
 

guerney

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I like the TDSZ2 because the torque sensing ride feel is what I wanted, it's a simple as that (along with the mid mounting position which I prefer to a hub).

The motor is made to a low price point and I suspect designed for a 'use case' more akin to urban riding that carrying some 120Kg giant across mountainous desert and yes, the TSDZ2 does seem to have a list of generic problems, not all of which effect all riders and all motors and non of them for me have been more than mild irritants and all simply resolved.

6,000+ miles on and no sign of my Blue Gear wearing nor anything else that I'm aware of and my particular motor is quieter than my fellow riders on Bosch Active Line, Shimano Steps, Mahle X35 and Fazua, (but I know that not all TSDZ2 are that quiet).
You and @Nealh use very little assistance, IIRC @Nealh gets something like 70km range from a 8Ah battery. @Bogmonster666 drives his the hardest, but with original firmware not OSF, also experienced few problems, apart from recently discovered rising damp or something. @peter.c gaveup using his, saying they're ok until used at high power. Initial TSDZ2 price (before modifications) is beguilingly attractive, but they're not for me - I prefer a robust well made cadence sensing motor nothing falls off from, which provides as much power as feasible while remaining legal, enabling my arrival at work unsweaty, and the dragging of heavy 90kg trailers up steep hills with ease, while still providing speed on flat roads. Weight and efficiency, I don't care about. Each to their own use case.
 
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Nealh

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Towing I get 24miles/38km with my 8ah battery or there abouts , with my roadrat I get 30 miles/48km from a 6ah battery (that's not towing). Both are flat terrain usage though.
 
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guerney

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Towing I get 24miles/38km with my 8ah battery or there abouts , with my roadrat I get 30 miles/48km from a 6ah battery. Both are flat terrain usage though.
I get 43 miles from my 19.2Ah battery with the controller limited to 15A, over mixed terrain. Goodness knows how many miles I could tow a 90kg trailer over hilly terrain, I'm fearful of attempting finding out, because of course I'd end up stuck at some point with a heavy unmovable trailer. TBH I don't imagine towing range will be massively less, not half anyway, because I've set "Keep current" to 100% in firmware... but I'm not at all sure about this hypothesis. I'd need to buy a spare battery to discover towing range.
 
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