ive just replaced my rear jockey wheel with tacx shimano 9pd jockey wheel and the chain just comes off the jockey wheel and into the derailleur cage.the teeth on the tacx wheels are more shallow.as anyone else had the same experience? what jockey wheels are best to use?

I’ve only used Tacx for years, have you got the right spacers on?

Tacx here on an XT. No probs at all

Chain completely worn out and not matching their teeth, perhaps?

brand new sram pc971 chain ,new cassette,new chain ring ,correct spacers,but the chain is not matching the lower jockey wheel teeth well.

Check the jockey rotates freely without the chain to drive it….you may have the wrong spacers or just clamped it too much.
Check it has grease inside the bearing.

If all else fails, just buy a pair of BBB ones from Dotbike for £10, fill them with grease and the job is done.

PaulD

Spend a little more and get them lovely KCNC jockey, been using them for some time and no issues

Just use Shimano jockey wheels, its not like Deore ones are dear.

i am using the £5 a pair shimano ones off CRC in mine