New longer derailleur or more links?

[mdvineng]

It does look a bit tight. Is the chain under a lot of tension? Then you are putting force on the chain and it might break. Otherwise using big chainring with big cog will work, if not ideal.

Not as much tension as pedalling though.

 

[hamster]

Have I been doing mine wrong all these years? I always set mine up on the longest I can get away with on small/small without the chain rubbing on the cage. I figure that then if it doesn’t work in large/large it was never meant to be!

Helps using a bit of bent old spoke to hold it all together while measuring.

It's called 'read the manual'!

Shimano is pretty clear. If big-big is unavailable it's very easy for pedalling action to haul the whole lot into the rear wheel. If you do it properly you will not only trash the rear mech but also rip off a few spokes, hub flange and even perhaps the derailleur hanger.

 

[My_Teenage_Self]

your chain isn't even sat properly on the large cassette ring in the pics either. I'd ride that as it is all day long.

 

[Guinessisgoodforyou]

It's called 'read the manual'!

Shimano is pretty clear. If big-big is unavailable it's very easy for pedalling action to haul the whole lot into the rear wheel. If you do it properly you will not only trash the rear mech but also rip off a few spokes, hub flange and even perhaps the derailleur hanger.

If the limit stops are set properly, how does this happen?

 

[Mod-Master]

I would comment, but I can’t stop admiring the sock-slider combo… sales pitch incoming…

 

[grantoury]

Not as much tension as pedalling though.

I think it will add up and can get too high

 

[Gtpulse]

It's called 'read the manual'!

Shimano is pretty clear. If big-big is unavailable it's very easy for pedalling action to haul the whole lot into the rear wheel. If you do it properly you will not only trash the rear mech but also rip off a few spokes, hub flange and even perhaps the derailleur hanger.

I’ve never really questioned it until just now!

I get why you’d do that to make sure there is enough capacity to shift to large/large but what if having done that you shift to small/small the chain is too long and the cage isn’t under tension? It would be for the same reason i.e. the rear mech/chainring/chainstay combo is incompatible.

Fear not I have fitted many many chains over the years and haven’t trashed anything so far. *actually I did once wrap a rear mech around the wheel shifting uphill, ended up single speed to get home again. Right or wrong I set up the limit screws on the mechs by eye before there is a chain on there and fine tune afterwards. I very carefully shift through the range while the bike is still on the stand before I’m happy nothing is going to snap or self destruct around the rear wheel.

 

[Guinessisgoodforyou]

Right or wrong I set up the limit screws on the mechs by eye before there is a chain on there and fine tune afterwards. I very carefully shift through the range while the bike is still on the stand before I’m happy nothing is going to snap or self destruct around the rear wheel.

Spot on.

 

[hamster]

I get why you’d do that to make sure there is enough capacity to shift to large/large but what if having done that you shift to small/small the chain is too long and the cage isn’t under tension? It would be for the same reason i.e. the rear mech/chainring/chainstay combo is incompatible.

Put simply, you need a longer cage mech. But Shimano errs on the safe side on compatibility, there is often enough to add an extra tooth or two.

On my tourer I do run a medium cage mech and it does get a bit slack on the top three gears on the small ring. I use it to get a super low crawler gear with 20T granny. The difference is that the chain flops around and it's all safe if nasty, unlike the big-big combo which if unreachable has catastrophic results - not least becasue you would be going faster and the force on the rear wheel is larger.

 

[Guinessisgoodforyou]

Mech can't go into spokes if the limit stop is set correctly.