Do I need to replace chain for mid-drive?

[Bob65377]

Converting a bike with front:
48t
38t
28t

to a TSDZ2 with front:
42t

Rear cassette 8.

Do I need to replace the chain?

 

[sjpt]

Should be OK. You could shorten it a little but not necessary.

Depending on chainline you may need to fit something to keep the chain on on the front; you can even keep the old front derailleur for that.

If the chain and chainrings have worn bit you may find the old chain is fine with the old chainrings but skips on the new. Skipping is more often a problem with new chain and old cassette; if you are unlucky a new chain could force you into getting a new cassette.

 

[Bob65377]

Thanks for tips of keeping front deraullier! I guess I keep it in a fixed position and detach the wire.
Ok. If I need to replace the chain I will take the bike to a bike shop and replace cassette at the same time. Maybe might be a good idea anyway because its quite worn before I start mounting the motor.
Thanks for advice!

 

[Nealh]

The chain will be slack and likely two - four links too long, gear changes and slipping may well occur in the high gears, chain slap on the stay may occur. Simply warp the chaIn around the 42t and and lowest (#1) cassette gear and allow two links extra.
Measure the chain over 12 links in two or three places and as long as the center to center pin length is no longer then 12 & 1/16th reading it will be fine. If one is a metric buff then 15 links should be 381mm - 383mm max.
The tolerance is 1/16th or max 2mm stretch over the perscribed length's.

 

[Bob65377]

The chain will be slack and likely two - four links too long, gear changes and slipping may well occur in the high gears, chain slap on the stay may occur. Simply warp the chaIn around the 42t and and lowest (#1) cassette gear and allow two links extra.
Measure the chain over 12 links in two or three places and as long as the center to center pin length is no longer then 12 & 1/16th reading it will be fine. If one is a metric buff then 15 links should be 381mm - 383mm max.
The tolerance is 1/16th or max 2mm stretch over the perscribed length's.

I am not quite sure if I understand. I will give it a try and see if I figure it out. Thanks!

 

[Nealh]

Quite easy remove the chain from the derailleur and run it only over the two largest gears front and back, pull the two ends taut and they should over lap by two - four links max. . If more then then remove the excess links allowing for a quick link to rejoin the two ends.
Two links is 1" so is two seperate links, some folks call them half links but in fact is incorrect. Each link has a seperate pivot point.

 

[Bikes4two]

Purists like to use a steel rule to determine chain wear - I used to do it that way too then I got a wear guage as per the pic below. Purists poo po them but I find them entirely accurate enough and a damn sight easier to use than a steel rule and thus one is more inclined to measure more frequently.

Loads of vids on youtube about using these guages - here's an example (link).

I put a new chain on when I fitted my TSDZ2 and that was 3,000km ago and the guage is not even near the lowest level of wear (a standard 9 speed chain from Decathlon which is in fact a KMC chain)- I'm not a brutal rider though - ECO mostly but I do really push the pedals, so unless your chain is already 'stretched' I'd stick with what you've got (but reduce by a few links if needed. Personally, I didn't need to do that as my long cage deraileur dealt with the existing chain length).