Replacement parts

[Andy Bluenoes]

I reported in my ongoing Oxygen MTB thread that I think the rear derailleur is out of alignment with the rear cassette causing a massive grinding sound on the chain when in lower gear.

The oxygen has a Shimano Acera rear derailleur so Im trying to find a replacement part to fit, but getting confused as usual....there appear to be subtle differences between the ones I have found.

Would someone be kind enough to drop a link to a suitable replacement part please? Im also going to replace the chain and cassette, so those would be great too.

Here is a pic off the current one:

 

[Nealh]

It doesn't have to be exactly the same you can upgrade to Deore or XT range as long as it is for 9 gears.

Is the grinding due to derailleur / chain rub and just needs adjustment or may be worn small jockey wheels on the derailleur. Remove the chain and see if they rotate freely.

 

[Nealh]

Have you tried backing off the backs top screws and tried resetting the adjustments.
Start in high gear (9) and adjust (H screw) until it doesn't' jump to 8 then flick straight to low gear (1) and adjust (L screw) so that id doesn't jump to 2 or the spokes. then flick up and down thru the gears making fine adjustment using said backstop screws. Also check cable tension whilst in top and low gear.

 

[Andy Bluenoes]

Thanks Nealh
The noise sounds like the chain isnt sitting on the cassette properly, or clipping the adjacent sprocket even though its not jumping off. If i rotate the pedals backwards, the derailleur is pushing back with the chain movement, and dropping down the gears before jamming.

Ive found some replacements now, will order them for the weekend. Will take everything apart and try out what youve suggested before I fit them though. I can always return the items if unopened, or keep them for when they are needed.

 

[KTM Bike Industries UK]

That picture shows the mech in a horrible position, so its no wonder its making a horrible noise.

The top jockey wheel should be about an inch lower with the cage with the logo on it being pretty much horizontal.

It looks like the mech spring is probably rusted up so its not spring back like it should.

There are a host of replacements available, all the will work. If you're not comfortable with doing it, you'll need to split the chain and set the new mech up. Just take it to a bike shop.

 

[Andy Bluenoes]

Is it that much out? Could that be due to bad adjustment of anything, or is it just past its sell by date?

Ive oredered the parts for delivery tomorrow, and watched a few vids on how to do it, so hopefully will be okay to do myself

 

[Deleted member 4366]

You adjust the top jockey wheel position with the B screw, which is sticking out the back of your derailleur.

I doubt that there's anything wrong with your derailleur or cassette. Get it properly adjusted and lubricated first before buying anything. There's loads of vids on Youtube how to do it, but they don't all include the B screw adjustment.

 

[Andy Bluenoes]

You adjust the top jockey wheel position with the B screw, which is sticking out the back of your derailleur.

I doubt that there's anything wrong with your derailleur or cassette. Get it properly adjusted and lubricated first before buying anything. There's loads of vids on Youtube how to do it, but they don't all include the B screw adjustment.

I just watched this one:

So looking at the B screw on my derailleur, it looks like its screwed out a long way judging by the blue thread lock....which would indicate the jockey wheel is too close to the cassette?

 

[Deleted member 4366]

You need to adjust the A-screws (H&L) as well.

Also, any dry chain makes grinding noises. Lubricate it with 90 grade gear oil.

 

[Andy Bluenoes]

You need to adjust the A-screws (H&L) as well.

Also, any dry chain makes grinding noises. Lubricate it with 90 grade gear oil.

Will do, thanks D8veh. Ive been using that wetlube stuff up until now.

 

[Deleted member 4366]

Will do, thanks D8veh. Ive been using that wetlube stuff up until now.

90 grade gear oil is much cheaper and is probably better.

 

[argoose]

Gear oil will hold dirt/grit and turn into grinding paste.
I used to use purple extreme on no assist bike, best I came across, but seemed a bit thin for assist bike. Changed to MX motorcycle chain wax thinned with xylene to carry it into links. Sheds water and won't hold dirt/grit.

 

[Deleted member 4366]

My last £9 chain, which is the only chain I've ever changed in 15000 ebike miles, lasted 4000 miles with one squirt of gear oil every 1000 miles. I changed it because the chainwheel was worn. I bought that chainwheel as a used crankset, so it was probably worn when I fitted it 4000 miles previously. The cassette still looked like new.

My new chain is now up to 600 miles and has had one squirt of gear oil in that time, only because I was doing another bike, so while I had the oil out, I did mine.

I've only ever cleaned a chain once. That was after I tried white lightning lubricant that gummed up my rear derailleur completely.

Nobody will convince me that I'd be better off using any other means of lubrication than gear oil. It's also perfect for motorcycle chains. I used that for most of the half a million miles that I did on motorbikes. Prior to that I used to boil the chains in that Link-life wax stuff, but after a lot of experiments, I realised that it did nothing to prolong the life of the chains. That was before O-ring chains for which the gear oil also works very well.

 

[argoose]

Tried gear oil on motor bike, fling off went all over rear wheel and tyre.
I suppose if you find something that works for you then best to stick with it.
I found wax type lube is the only thing that works in the acidic red dirt of the Brecon Beacons. A lot of standing water on the MTB trails round here.
When using oil based lubes I can smell metal when driving home in the van. Twisting the chain is like a crunchy bag of crisps.
Nothing works for more than one ride, but with wax based, crap can be rinsed off before reapplying, no need to de grease or deep clean with chain cleaner tool.

 

[AardvarkFrogg]

Tried gear oil on motor bike, fling off went all over rear wheel and tyre.
I suppose if you find something that works for you then best to stick with it.
I found wax type lube is the only thing that works in the acidic red dirt of the Brecon Beacons. A lot of standing water on the MTB trails round here.
When using oil based lubes I can smell metal when driving home in the van. Twisting the chain is like a crunchy bag of crisps.
Nothing works for more than one ride, but with wax based, crap can be rinsed off before reapplying, no need to de grease or deep clean with chain cleaner tool.

Hi I'm new here been reading for a while, havent actually got out on my ebike yet but was hoping to try Brechfa at some point in the future, does the red dirt come that far over ?

 

[argoose]

Hi I'm new here been reading for a while, havent actually got out on my ebike yet but was hoping to try Brechfa at some point in the future, does the red dirt come that far over ?

No mate, careful how you hydrate, I picked up a UTI from getting bite valve sprayed with puddle water.
Gorlech trail is the best over there. Just normal black dirt and rock