I lost a chain so bought a sram 991 as a replacement.

Its a standard Carrera banshee X so sram x5 rear mech and standard 9 speed cassette which I believe to be 11-32

I installed the chain and it was too long so removed a link then repeated, repeated then once more.

Suddenly the chain is too short and with the rear mech fully loosened it gets into the top cogs but grind badly.

I put a link back in and now its too long on the bottom cogs and the chain hits itself on the rear mech

I then tensioned the rear mech and it doesn’t make a blind bit of difference. Just seems to move itself a little

Please Help!!

Oh to add Ive already ordered a 11-34 which I suspect will only make things worse I think?
thanks
Christian

How are you defining the correct chain length?
When you say ‘I put a link back in’ how did you do this?

Big/Big (suspension at full compression) and add 2 links is pretty reliable.
Chain being ‘too long’ when Small/Small is of little consequence (and is a combo you should be unlikely to ever use).The alternative is usually having set so short it ends up destroying it self when you try to use big/big.

I used a chain tool and added back one I had split

Most (all that I know) chains of 9speed+ either need to use a special joining pin or a ‘split link’ to join them.The heads of the pins are peaned over.When you push them through they enlarge the hole in the side plates.If you re-use an old pin it ends up like a dick in a bucket.

Give me chainsaw length, biggest front ring and biggest rear ring sizes…there is an app that recommends best chain length in links. Links seems to be an inner play and outer plate…

What’s happened in that photo? That’s more than one added link from too short.. You need to rejoin it with quick links not reuse a pin once it’s been pushed out

Does it allow for chain growth and cage length?

First up, ensure the indexing & cable tension is right.

cookci – Member
Suddenly the chain is too short and with the rear mech fully loosened it gets into the top cogs but grind badly.

Possibly it’s the right length but the B screw needs adjusting if the jockey is too close cog, which will making grinding sounds. By top cog, I assume you mean biggest cog (which is actually lowest gear).

When it’s in the biggest cog and biggest chainring, the mech should be stretched forwards almost fully, but should still have a bit of play in it, i.e. you should be able to pull the cage forward/up an inch or two more. That allows for the suspension. Or, with suspension fully compressed (air out of shock), the mech will be as far as it can go.

Big/Big is a combo that’s fine on a 2x set up. 3x it’s not something you’d normally use due to cross chaining issues.

I have been using the quick release joining thingy.

Obviously because of this when i remove something i need to remove effectively 2 links in length worth because the quick link needs to connect to 2 of the inner parts of the chain

Also, Big/Big chain sizing should be done without routing through the mech.

And see:

http://www.parktool.com/blog/repair-help/chain-length-sizing
http://sheldonbrown.com/derailer-adjustment.html

If it’s an fs bike you need to try it with the suspension compressed to get chain length right.

I’ve removed the same link again now so the chain is “too short” as I said it earlier but actually it probably isn’t now I know a little more.

it grinds on big big on the rear but like it was said earlier I probably won’t use it anyway… as long as it doesn’t pull the mech off if I change by mistake I guess

Does this look ok? Do you think I will get away with 11-34T?

Looks ok.Try it with the suspension fully compressed.
I don’t reckon it’ll work with the 34.

Does this look ok? Do you think I will get away with 11-34T?

Yes.

No.

You’ll never use that gear it doesn’t matter.

Your maximum adjustment is 1 link so I’d just go 1 link up from too short.

Stretch aside (which might be 1% or about 1 link and a tiny bit), the links in your new chain are the same length in your old chain.

Once you get this right, next time just use the same number of links.

In the first pic the chain looks way too long 4 or 5 links?

Your on the big chain ring and the 32 on the cassette !

Tom are you saying I shouldn’t even try to do this?

The difference between the 2 chain lengths is just this:

I’d be inclined to go on the longer end of the two. Although you’ll probably get away with it like you have it in the most recent pic, and you shouldn’t use that gear anyway, it only takes a bit of a mishap and you could have a problem.

Whereas in the earlier (small-small) pic, if you did use that combo (which you are even less likely to IMHO) it’ll be shit but won’t **** your mech up.

That looks a link too short…if that is a full bounce bike then if you are in that gear and the suspension is moving, it’s going to be too tight somewhere along the travel…

is it possibly a medium cage mech?

If it is, You will never get it spot on in both little an little or big and big because the mech hasn’t got enough capacity. You shouldn’t be using these gears anyway so as long as your chain is just long enough for Big and big then you should be ok.

You will have some slack when in little and little. This is fine.

It’s not supposed to be rideable in that big/big combination. There just needs to be enough chain so that it doesn’t get jammed if you shift into it accidentally because then you can’t even get the wheel out and you end up a bit buggered.

If it’s too short and gets jammed you can the wheel out, I assure you. It’s just that everything gets strained and buggered.

I run my chains two links to short, because I only have a medium cage mech. It really damages things though, I’d avoid it if you can.

Suspension compression would make it worse.

In your first picture it’s too long, so you have to go with the next pair of links shorter. In the second picture it looks right, but that’s just what happens in that combo. You should be fine, but check the effect of suspension compression.

Looks like it might be a medium cage as the distance between the 2 cogs is about 78mm ish.

I fully compressed the suspension and it still pedals on big big and shifts.

I think I might leave it at that.

The reason I bought the new rear cassette which I won’t be installing is because the current cassette wobbles a little when the bike is freewheeling. There is no play… something is bent!

Cheap/crap freehub body?

What’s the hub?

Its a specialized stout hub. Could this be causing my random gear changes on the rear? It only wobbles very slightly and noticed due me buying a repair stand for xmas.

Could be, maybe… Hard to tell from here. Seeing as you’ve ordered the other cassette, try tightening the lockring on the existing one, and if that makes no difference, try fitting the new one to it and have a look with that.

If it’s better, but you don’t want to buy a new Mech to use it, send it back for an exchange for one you can use.

MTB’s are becoming nightmare to maintain especially with all the rock gardens near me!

I’m bidding on a road bike at the moment so hopefully I can split the load a bit across the 2 bikes!

Thanks for all your help everyone 🙂

If the cassette is wobbling, then could be the lock ring isn’t done up tight enough, you need spacers maybe, or the freehub is loose / needs servicing.

I had a wobbly cassette on a Formula hub and turned out the freehub was wobbling and I just needed to tighten the freehub bolt inside. However for that kind of hub I needed a daft size allen key that isn’t normally found in standard allen key kits.

Its a specialized stout hub. Could this be causing my random gear changes on the rear?

If you’re based in hampshire (or can be bothered tp drive to southampton) I’ve got a stout hub you can have for free. Needs a good service but you can probably canibalise the two into one good hub?

Free to a good home if cookci isn’t interested

that’s a nice offer thankyou. I might pull it all to bits when my new cassette arrives.. hopefully i’ll figure out exactly whats faulty