7speed SHORT cage rear derailleur for kids bike

Hoping somebody here has encountered this issue and has a good solution.

My kids 20″ bike is 7 speed. SRAM X-4 rear derailleur. Return spring has gone (couldn’t find new springs online so assume they are not easily replaceable).

It is not marked as such, but looks to be (and should be on such a small wheeled bike) a short cage. However all that I could find online was long cage variants. Decided to buy one of these as cheap and better than nothing.

Looking at the two now I wonder if I can swap the old short cage over on to the new derailleur. Any reason not to do that, is it easy or will I end up with two useless items :-D?

Failing that – anybody know of a source of short-cage 7 speed rear derailleurs??

Thanks

PS – am aware of the SRAM X01 DH rear derailleurs but they are £200 odd. The X-4 is less than £20 🙂

Swapping the cage is possible on many Shimano derailleurs, so hopefully worth a try.

If not then I think you have to buy SRAM.

Tried a road mech? My daughters 29″ came with an SGS Alivio, that got swapped out for a GS SLX sharpish!

Remember 9 speed will work as well, it’s all the same ratio (in SRAMs case, I think)

Isn’t X4 1:1 meaning it’s not compatible with Shimano?

Yes, X4 is SRAM – 1:1 – so any solution needs to be same. Unless I change the shifter of course – which isn’t the plan.

For what it’s worth I tried dismantling the old one without success. As far as I can tell from looking online it’s only the higher end stuff which is designed to be stripped down…

Having a look for road stuff now – thanks squirrelking.

Yes.

I was meaning the respective ratios up to 9 speed are constant whether SRAM or Shimano so the OP isn’t restricted to a specific 7 speed mech. Not sure if SRAM road would be compatible though now I think about it.

EDIT: it is compatible, happy days.

Check out Decathlon. They sell spares specific to the their kids bikes in branded or own (btwin) flavours.

Btwin stuff is generally rebranded Microshift, I’m not sure if it’s just the Advent line or all of it but it would be worth checking compatibility first.

Also, the postage cost is horrendous so unless you are on the strip I wouldn’t bother.