Acera 8spd RD and compatibility

[Sittingduck]

Sup team

I have a 'worn' Acera 8 spd RD. I have done my best to strip clean lube where needed and removed jockey wheels and re greased the sleeve bearing things. I have a new chain and cassette but the chain is not sitting comfortable on the bottom jockey wheel. It is slipping off to the side a bit - mainly in lower gears. I suspect the wheel teeth are worn and have a few road RD's lying around but nothing of hybrid heritage

Is there any particular reason I can't substitute the Acera 8 speed RD for say a 10 spd road RD? To my mind the RD unit is 'dumb' and the intelligence is in the shifters - matched to the cassette spacing? Perhaps crucially, I am thinking of using a Tiagra RD and happen to know the pull ratio on the shifters / cassette spacing is different to other RD's, e.g. 105/Ultegra, but in this instance that wouldn't matter or would it?

I could potentially just put in a new jockey wheel from one of the spare RD's but this would be of typical sizing not like the humongous bad boy that the Acera RD is fitted with - I am guessing that wouldn't work very well...

TIA,
SD

 

[DCBassman]

I'd just source the correct jockey wheels and carry on with the Acera, it will probably outlive you!

 

[Sittingduck]

Yebbut, it's on a shoe-string budget innit. The bike cost me ten english pounds and looking to keep costs down! Maybe you're right though, should probably cough up for a second hand 8spd rear mech...

 

[C R]

Yebbut, it's on a shoe-string budget innit. The bike cost me ten english pounds and looking to keep costs down! Maybe you're right though, should probably cough up for a second hand 8spd rear mech...

The pull ratio of a 10 speed derailleur will be wrong for an 8 speed indexed shifter. Your best bet would be trying to see if you can use the jokey wheel of the 10 speed in the 8 speed.

 

[T4tomo]

I think, but happy to be corrected, that as 10spd Tiagra has same pull ratios as 11 speed road, the RD is expecting a different pull ratio, so it wont work.

8 & 9 speed shimano road and MTB kit is all interchangeable but you've waggled over the edge of compatibility with 10 spd Tiagra, as it has 11 speed pull ratio's.

 

[Ming the Merciless]

Just replace the jockey wheels. They are meant to be replaced as they get worn out.

 

[Sittingduck]

Well... this is all very inconvenient, I must say. Back to ordering bits online again... thought this project would have been done by now

Thanks for the guidance.

edit: BTW I got it wrong it's an Altus RD and I have found one on eBay might as well just get a new unit as the current one is pretty shabby.

 

[presta]

My bike came with an 8 speed Acera, but it didn't last long, within 11,000 miles the parallelogram was so worn it was self-changing. Since 8&9 speed are the same pull ratio, I replaced it with a 9 speed Deore.

 

[DCBassman]

Well... this is all very inconvenient, I must say. Back to ordering bits online again... thought this project would have been done by now

Thanks for the guidance.

edit: BTW I got it wrong it's an Altus RD and I have found one on eBay might as well just get a new unit as the current one is pretty shabby.

Better yet, Altus RDs sre nukeproof. A new one now (RD-M310 or 410) will both do 8 and 9 speed.