'Violent' gear change

tboy823

Hi all

So my new SRAM X9 rear mech arrived today to replace the very bent X7.

Fitted it all, and it went on sweet as a nut - no adjustment necessary, all gears indexing perfect. Brilliant !!

But, in practice, out on the road the gear change is quite 'violent', almost enough to make my feet jump off the pedals. :?

The only thing that has changed (apart from the mech) is the chain, it snapped on my last ride and i had to remove one full link.

Based on this info - anyone got any ideas if the chain length could be the problem - or could there be other issues?

cheers

nicklouse

What gear? What bike? And are you sure the hanger did not get bent st all?

tboy823

From just a quick ride up and down the road, it seemed to be most gears, worse on the small to big shifting on the cassette , but also not good on the big to small shifting. (will do a more in depth check tomorrow).

It's a Boardman Team FS, the hanger is new, i've checked the hanger in relation to the frame and it all looks straight.

:?: :?: :?:

omegas

check jockey wheel distance from the cassette and adjust . Have a look on Park Tools

The Rookie

Seconded, sounds like the upper jockey is too close....

Simon

tboy823

Checked Parktool and now understand what the B screw is for. Will check this tomorrow.

cheers

Dirtydog11

tboy823 wrote:

Hi all


gear change is quite 'violent', almost enough to make my feet jump off the pedals. :?

cheers

Snapped chain, feet "almost jump off the pedals" suggests that your applying pressure to the pedals whilst changing gear?

tboy823

Yes, i'll admit to doing that when the chain snapped - my bad, but not after changing the rear mech, it was just a quick ride up and down the road outside the house.

Gonna take another look at it this morning and check the b screw adjustment.

cheers all

tboy823

Ok, i've set the B screw correctly.

Tried it out up and down the road again and its better but still quite harsh changing from the bigger down to smaller cogs on the cassette.

I'll take it out for a proper test later or tomorrow.

Might still invest in a new chain though?!?!?

cheers all

nicklouse

Get the mech hanger checked.

tboy823

Its new and straight, i've also had a good look and i think its unlikely that the frame is bent.
:!: :?:

tboy823

Well I did about 11 miles today pretty much problem free - took alot of care when changing on the uphills tho'.

But did notice this





As stated above i removed a full link from the chain, so this is now big ring front, big ring rear so maximum chain stretch going round the cogs :shock:

think i'm gonna need to put those links back in, or get a new chain :!:

supersonic

No need to use that gear!

Dirtydog11

Looks tort but fine, in practice you would never use that gear combo(would you?), if it where too short your gears would jam up.

Chainstay growth won't be an issue as they are single pivot.

Russ-Tyson

tboy823 wrote:

Well I did about 11 miles today pretty much problem free - took alot of care when changing on the uphills tho'.

But did notice this





As stated above i removed a full link from the chain, so this is now big ring front, big ring rear so maximum chain stretch going round the cogs :shock:

think i'm gonna need to put those links back in, or get a new chain :!:

No wonder you snapped a chain! dont use those two gears together a big no no :shock:

omegas

wrong use of gears (big to big) this will cause twisting of chain causing premature wear and failure.

supersonic

Chainstay growth won't be an issue as they are single pivo

There is still chain growth.

Dirtydog11

How?

supersonic

The rear axle is still moving away from the bottom bracket. The only way for zero chain growth is a single pivot concentric to the bottom bracket.

This is a four bar anyway!

chez_m356

omegas wrote:

wrong use of gears (big to big) this will cause twisting of chain causing premature wear and failure.

does that still apply on a double though, or does it depend on how many teeth its running?

Dirtydog11

supersonic wrote:

The rear axle is still moving away from the bottom bracket. The only way for zero chain growth is a single pivot concentric to the bottom bracket.

This is a four bar anyway!

In my mind the chainstays are a fixed length and rotate around the point at which they are fixed in an simple arc.

Probably being thick here but I just cannot see how the chain grows, now you know why I bought a five

supersonic

The 5 has a fairly high chain growth! The wheel arcs yes, but around the pivot, not the chainset.

Dirtydog11

Oooh whats that's software ?

Could have some fun with that!

I would probably have a better understanding if I where to have have a play around with it.

tboy823

It's a 2 x 10 set-up so doesn't that mean 20 usable gears? :?:

supersonic

2x10 is less prone to extreme cross over probs than 3x10. But you might get some noise or rub in extreme combos.

Dirtydog, it is called Linkage - is a free download!

Dirtydog11

Cheers!

Downloading the Demo

Quote The wheel arcs yes, but around the pivot, not the chainset.


I think that's the key there ^ and in my case where the misunderstanding/confusion comes in.

386ka

Supersonic, I have just downloaded the demo, great stuff! But where can I find more models?

The Rookie

tboy823 wrote:

It's a 2 x 10 set-up so doesn't that mean 20 usable gears? :?:

Apart from the fact you only have a range of about 13/14 gears (depending on chainwheel sizes) due to replication, as has been said, it's best to avoid extreme chain angles.

Simon

supersonic

Open the web library, should be an online database.

386ka

supersonic wrote:

Open the web library, should be an online database.

Found it, tnx very much!