Do you think these chain rings need replacing?

[Phil21]

Ultegra 6703 triple with about 15,000km, all weathers. I've never replaced chain rings before so I'm not sure what to look for, all the little ramps and things are confusing. Bike was recently into the LBS for servicing and they said they were 'a little worn' but 'good luck getting parts at the moment'.

[rafletcher]

I’d say the middle ring is getting worn, others are ok.

https://www.sjscycles.co.uk/chainrings/shimano-ultegra-fc6703-130mm-bcd-5-arm-middle-chainring-d-type-silver-39t/

[LittleWheelsandBig]

I’d agree with that.

[Phil21]

Because of the 'shark's tooth' profile right? Thanks for the link - yes I currently have that in my basket It would definitely be good if I could avoid replacing the big ring at 95 GBP each

[LittleWheelsandBig]

You have worn your chain past 1% and spent a lot of time in the middle ring. You can see the middle ring is worn high on the teeth and where the teeth have plastically deformed (squashed wider at the roller contact point). Both of these characteristics are visible in two opposing regions of the circumference corresponding with the top of ring when your pedal pressure is highest (horizontal cranks or thereabouts). Nothing much happens to the chainring teeth when your cranks are vertical.

The small ring shows similar wear but to a much reduced extent. You don’t do many miles in the small ring but the chain tension can be higher.

The big ring has low chain tension and wear is always slow.

The middle and big rings get hacked up by gear changing, particularly if you are a bit brutal, but that is different to wear.

[Phil21]

Thanks both. I have ordered a new middle (both the chain and cassette are recently new too).

[Asterix, the former Gaul.]

I've a worn steel inner in front of me* that I had to replace.  It looks a lot worse than yours.

* it's the perfect size for a mug coaster

[Bianchi Boy]

I normally replace all the rings at the same time. Yes it's expensive, and you may find a new chainset is cheaper, but the partially worn rings will wear the chain quickly.

I assume you are doing cassette and chain at the same time?

Maybe leave the inner ring. But the other two would need replacing.
Sent from my H8216 using Tapatalk

[LittleWheelsandBig]

Your middle chainring isn’t aligned correctly, though the granny ring is. There are bumps or arrows that should line up with the crankarm. That ensures the pickup pins and shifting ramps move the chain under the least chain tension. Shifting at other times tends to be tough on the chain and chainring teeth. The only reason you would orientate the rings differently was if the cranks were on a recumbent.

[Phil21]

Your middle chainring isn’t aligned correctly, though the granny ring is. There are bumps or arrows that should line up with the crankarm. That ensures the pickup pins and shifting ramps move the chain under the least chain tension. Shifting at other times tends to be tough on the chain and chainring teeth. The only reason you would ofientate the rings differently was if the cranks were on a recumbent.

Thanks, following your post I downloaded the Shimano manual. I see it now, I will fix it when I install the new one.

[Phil21]

Was out at the weekend...boy, having the rings aligned correctly makes a HUGE difference to the big/middle shifts! They are so slick now. I wonder how long I rode like that for...I can't remember removing the chain rings before but I can't imagine they came like that from the manufacturer.