Damage to chainring

[david7591]

When cleaning my bike today, I noticed the damage shown in the photo to the middle chainring. Does anyone know how this might have happened without me noticing? And would you ride the bike until such time as a repair can be effected?

[NATURAL ANKLING]

Hi,
Beyond repair.
Before you spotted it did the selection play up?
Even if it did not then there is a possibility that the chain might snag and do more damage / jam.
Needs replacing.
Inspect the rings when its cleaned up for further damage to the teeth, you are looking for cracks.
Even badly worn chain wheels don't go like this often.
Make and model cranks / rings may help with an explanation.

My guess wold be jammed chain when changing gear.

[landsurfer]

+1
Scrap and replace .... what quantity teeth and BCD ?
I have a stock of new but unwanted chainrings .... If i have one that will fit you can have it for the postage.

[Brucey]

you didn't notice before, right? I'm betting that is because the 'damage' didn't really make any difference....

So if it works OK, run it like that. If it starts to misbehave, change it for a new one. If you go with a new one, check that the rest of the transmission (chain, sprockets, other chainrings etc) is OK; running a worn chain on a new chainring can wear a new chainring PDQ.

As to how it got like that.... well changing under full pressure can do that sort of thing. If you had Scotty (from Star Trek) as your bike mechanic, he'd be saying "she cannae tek it..."

BTW if you are still not convinced about carrying on regardless, there is only one tooth missing; heck, they even make 'em like that 'cause they shift better....

cheers

[david7591]

To be honest I was shocked to find the damage. I do recall a noisey change a few days ago when standing on the pedals, and I do wonder if that was the cause, however at the time I noticed no difference in performance of the bike. My question about riding it in this state was asked because it will take a few days to get a spare part and replace.

[david7591]

+1
Scrap and replace .... what quantity teeth and BCD ?
I have a stock of new but unwanted chainrings .... If i have one that will fit you can have it for the postage.

Thank you landsurfer, that is very generous of you. It's a Shimano 105 10spd triple with a 39T middle ring. However, when it comes to mechanics, I'm afraid I have a low level of competence, nor do I have the tools, facilities or confidence to undertake replacing a chainring. Therefore it will have to a trip to the LBS, and they be a bit sniffy about fitting a part supplied by the customer.

[NATURAL ANKLING]

Hi,

+1
Scrap and replace .... what quantity teeth and BCD ?
I have a stock of new but unwanted chainrings .... If i have one that will fit you can have it for the postage.

Thank you landsurfer, that is very generous of you. It's a Shimano 105 10spd triple with a 39T middle ring. However, when it comes to mechanics, I'm afraid I have a low level of competence, nor do I have the tools, facilities or confidence to undertake replacing a chainring. Therefore it will have to a trip to the LBS, and they be a bit sniffy about fitting a part supplied by the customer.

Business is business, why would they send you elsewhere.....................

[Brucey]

To be honest I was shocked to find the damage. I do recall a noisey change a few days ago when standing on the pedals, and I do wonder if that was the cause.....

er, yeah, best if you don't do that.... it tends to break stuff....

....however at the time I noticed no difference in performance of the bike. My question about riding it in this state was asked because it will take a few days to get a spare part and replace.

honestly, if the rest of the transmission is already a bit worn, you may as well carry on as you are and only bother to fit a new chainring when you replace the rest of it. I'd be far more worried about the chain TBH (see below). If you do replace the chainring, it is a very good idea to get the exact right one that is meant to fit your chainset; others might appear to 'fit' but once installed you may find that you have degraded shifting performance.

BTW if you are in the habit of making shifts under full load

a) I'd advise you to get out of that habit if you want your transmission to be reliable and

b) it is quite likely that your chain is also now damaged.

On the latter point, the chain can be variously twisted, sideplates can be cracked/gouged, and rivets can be pulled halfway out by full-load shifting, even if it doesn't actually break teeth off chainrings. Sometimes this chain damage is obvious; the chain will 'look weird' at one point. However other times it isn't obvious at all that the chain is damaged, and it will then just break in use later on, nearly always at the least convenient time. Needless to say this can cause a nasty accident.

So if you had to do just one thing, it would be to inspect the chain very carefully. Lots of good bike shops would insist that you change the chain (and therefore the cassette) for the sake of your own safety, following damage of this sort.

cheers

[NATURAL ANKLING]

Hi,
TBH I completely forgot about the chain

With that damage as said, the chain needs a careful eye.
You are going to need someone experienced to look at your whole gear system, shop will err on safety so will cost, have you a mate who's good with bikes
Your not a sportive rider are you

[mercalia]

you didn't notice before, right? I'm betting that is because the 'damage' didn't really make any difference....

So if it works OK, run it like that. If it starts to misbehave, change it for a new one. If you go with a new one, check that the rest of the transmission (chain, sprockets, other chainrings etc) is OK; running a worn chain on a new chainring can wear a new chainring PDQ.

As to how it got like that.... well changing under full pressure can do that sort of thing. If you had Scotty (from Star Trek) as your bike mechanic, he'd be saying "she cannae tek it..."

BTW if you are still not convinced about carrying on regardless, there is only one tooth missing; heck, they even make 'em like that 'cause they shift better.... :lol:

cheers

You should see the original RSX chain rings talk about irregular one is almost denuded just a small runt of a tooth left with others strange cut outs - we are talking NEW chainrings here

any one looking at this after using normally would think the inner ring is seriously worn/damaged as few of the teeth have a normal regular shape? some even have disconcerting troughs with weird cuts outs

strange teeth

If your chain is very gritty I suppose it could fail to engage properly and bite a tooth off

[tykeboy2003]

To be honest I was shocked to find the damage. I do recall a noisey change a few days ago when standing on the pedals, and I do wonder if that was the cause, however at the time I noticed no difference in performance of the bike. My question about riding it in this state was asked because it will take a few days to get a spare part and replace.

I would NEVER change gear while standing on the pedals.

Still surprised that the chain ring broke rather than the chain though.

[Mattyfez]

It's odd, I've seen mountain bike ones bent before, from hitting inconveniently placed rocks but that looks like it's snapped off, which is odd as there's not much lateral force on a ring..

[david7591]

Thanks for comments. I've never changed chainrings under full pressure (whilst standing) just cogs. Thinking about it, when I mentioned above about a noisey gear change it was changing cogs not chains, and I'm wondering whether that was symptom rather than cause, with damage already done. The transmission had been a little noisey for a couple of days, however I just put down to fact I'd been a bit lazy and hadn't cleaned it thoroughly for a while. I have ridden bike since finding damage on short runs up to twenty miles, and despite being clean, it's definitely more rattley. I haven't had any issues changing gear though. However I'm nervous in taking it too far from home, whilst I organise repair. At the moment it's my only bike, and I need it for commuting (shortest route 10 mile round trip, though sometimes I take longer route). Would it be ok carrying on riding in this way for a couple of weeks, whilst I sort repair?

[foxyrider]

you didn't notice before, right? I'm betting that is because the 'damage' didn't really make any difference....

So if it works OK, run it like that. If it starts to misbehave, change it for a new one. If you go with a new one, check that the rest of the transmission (chain, sprockets, other chainrings etc) is OK; running a worn chain on a new chainring can wear a new chainring PDQ.

As to how it got like that.... well changing under full pressure can do that sort of thing. If you had Scotty (from Star Trek) as your bike mechanic, he'd be saying "she cannae tek it..."

BTW if you are still not convinced about carrying on regardless, there is only one tooth missing; heck, they even make 'em like that 'cause they shift better.... :lol:

cheers

You should see the original RSX chain rings talk about irregular one is almost denuded just a small runt of a tooth left with others strange cut outs - we are talking NEW chainrings here

any one looking at this after using normally would think the inner ring is seriously worn/damaged as few of the teeth have a normal regular shape? some even have disconcerting troughs with weird cuts outs

RSX.JPG

At one time we used to get a punter almost daily claiming these ramped teeth were faulty and demanding replacements. Some of them wouldn't even accept it after we'd shown them all the other bikes with the same ramps and pins!

[NATURAL ANKLING]

Hi,
If you look at the pic posted by "mercalia" in the rectangular box, this coincides with max torque, though not all that goes through that individual tooth.
Its just where its deemed common to shift / part way through upshift?