Bent mech or hanger?

Trying to figure out why my eldest’s bike’s shifting has gone haywire. It’s 8 speed Box stuff. Gears 8, 7, 6 are perfect. On 5 I can hear it trying to rub against 4. On 4 it’s trying to catch 3 but not jumping up to it when under no load. Shifting to 3 more than half the time it jumps straight past to 2 and doesn’t sound great doing so. And then the next shift gets you 1, when you should still be on 2.

When shifting back down to the smaller sprockets it either jumps past 3 to 4 straight away or after a moment.

I bought some spare mech hangers when CRC closed down but I can’t find them anywhere otherwise I’d just swap it to check.

I have got an XT 11 speed set-up (old mech and shifter, fresh chain and cassette) I can swap in but obviously that’s not a super quick job.

Any ideas what the fault is or how to diagnose it? It’s such a long time since I had problems like this on a bike, I’ve had a run of good luck with gears for a decade odd! Now I’ve written this I feel like it must be the mech but please stop me before I waste a lot of time…

I would recommend buying a hanger alignment tool. Even if they look straight, they can be surprisingly bent. Even a new hanger might not be perfectly straight.

As above, it gives every indication of a bent hanger, no point in swapping stuff over. Stop looking for the spare hangers, they will find you!

Thanks, I will pause for now…

“Stop looking for the spare hangers, they will find you!”

They’re somewhere at work so it’s a much bigger challenge than finding them in the garage!

You can make a hanger alignment tool. IIRC the trick is to use a threaded axle if you have one as it has the correct thread to go in the dropout (????). It’s a long time since I did this though.

Or you can get a cheapy off eBay for less than 20 quid

From the description of box 8 and cheap CRC hangers I’m guessing it’s a vitus nucleus 26? If so the hangers are made of cheese (or the design is weak as I’m sure I tried and after marker cnc one as well). My daughter has bent several in innocuous crashes/knocks.

Yes, it’s a Nucleus 27 VRW! I bought two or three spare hangers when CRC/wiggle died and they’re somewhere in our factory at work…

The last time I had a mech hanger issue was on the first ride on my then brand-new Cotic Soul in 2011!

the hangers are made of cheese

They are meant to be a sacrificial part that bends or breaks in order to avoid damage to the frame.

“They are meant to be a sacrificial part that bends or breaks in order to avoid damage to the frame.”

Although I think they used to be, it feels like most modern mech hangers are much stiffer than older ones so big 12 speed mechs shift properly – and that it’s the mech that gets sacrificed rather than the hanger!

The hangers on my Levo and Moxie (unused as it’s a singlespeed) are chunky!

They are meant to be a sacrificial part that bends or breaks in order to avoid damage to the frame

Yes, I know that but these are particularly cheese like to the point of barely functional. These are supposed to be weaker than the frame not so weak a stiff breath could bend them.