brundle_fly

Can you see if my big chainring is worn.It's done 20,000 miles or there abouts

jimc101

Worn yes, worn out, probably not, you can still clearly see the profiled teeth there, the teeth will look much shaper if worn out.

if that was mine, I wouldn't be considering it for replacement yet.

AEO

It's definitely not new, but it still has life left in it.
when it's really worn out, you'll start to feel the poor shifting.

Booger1

It's pretty worn in my book,both sides of the tooth should look about the same,yours has a pretty good hook going.

If your broke,run it....if not,I'd change it,it's not helping chain life much.

KenCarlson

+1

I ride my commuter through northeast winter with salted roads, and after two winters and ~2,000 miles I had a chainring with severely hooked teeth. The teeth were sharp enough that you could cut yourself. But it still shifted just fine.

Since the chain was worn well beyond normal recommendations (1/16"), I replaced the chain and chainring. Didn't need to change the cassette though, it still shifts fine with the old cassette.

DiabloScott

Worn chains wear out chainrings, worn chainrings don't wear out chains. The problem here is only shifting and chain suck.

neurocop

It looks slightly worn to me, but the teeth are not really hooked yet. I may be mistaken, but I believe those 105 chainrings had asymmetric teeth (some higher or lower than their neighbors (was certainly the case for Biopace), which was to make shifting smoother. You may be mis-interpreting this designed tooth variation with wear. Chain wear on CR teeth tends to hook them. This ring therefore looks like it has plenty of life left in it.

hagen2456

That's what I would think, too. Besides, friction increases with those hooked teeth.

Glottis

I'm not that experienced, but it looks fine.
Also, see this post from HillRider:
https://www.bikeforums.net/showthread...1#post11859491

My friend, whose daily commute is around 30 Km, wanted to replace the chainring on his bike 6 months ago. It looked much worse than yours. Based on HillRider's post, I told him it was fine unless the chain is skipping. 5 months later it started skipping, but turned out it was because of a poorly adjusted rear derailleur. The chainring is still good.

Why replace something that doesn't need replacing?

BikeWise1

Looks like we have ourselves a serial cross-chainer! Your small ring shows little, if any wear, which tells me you tend not to use it very much and instead stay in the big ring even when riding up hills in the big ones in back,(unless of course, it is newer). This produces the type of scuffing wear we are seeing on the ring, as the chain enters and exits it at an angle.

Had a guy come through the shop with "shifting issues" who had destroyed a chain, chainring, and lower derailleur pulley on a Dura Ace drivetrain in only 900 miles. His small ring could have been sold for new. When asked he said "big ring's all I ride". And it cost him $300 to fix!

I understand that's not your case, but even at 20K, the wear between rings should be more even, and it doesn't appear to be.

brundle_fly

No I never cross chain.I rarely use the small ring because the roads here are quite flat.I use 11t-25t rear
and am in the big ring and middle or higher on the cassette most of the time.When I go up hills i'm in 39t and in the middle of the cassette.I cycle hard though,so the ring gets some rough old grinding

BikeWise1

Gotcha! I failed to mention that being a masher can result in similar wear pattern. Eventually, as the teeth get shorter, the chain will slip under hard efforts, especially if it is worn. Then you'll likely need to change the chainring, chain, and cassette.

brundle_fly

How many miles do you think I've got left on it- a year maybe ? I do have a new 105 and an ultegra chainring which i'm contemplating putting on.just hate throwing things away when they are still useable

Glottis

Why would he need to change the chain and cassette? I thought a worn chain can mess up a chainring, not the other way around. Unless he continues using it after the chain starts slipping, of course.

DiabloScott

I'd say your chainring is no more than 2/3 to the end of its useful life. Ride it until you get chainsuck or skipping. You'll probably notice the deterioration when your chain is worn out - you put on a new chain and then it won't mate as well and then you'll be dissastisfied with the performance.

Booger1

Worn sprockets accelerate chain wear......and visa versa.Look at any power transmission page on the web,they will tell you the same thing.

The companies that MAKE chains and sprockets say worn sprockets will accelerate chain wear.....I believe them.

DiabloScott

OK, I looked at this one. https://www.renold.com/Support/Worn_Sprocket.asp

It says "probably" and I'm not sure I believe them. What can possibly make a chain elongate other than abrasion of the pins and rollers from the inside? Or maybe they're talking about some other kind of physical damage (not elongation) due to the chain's skipping.

Don't mean to sound arrogant... I'm open to changing my mind based on reasonable explanations.

Booger1

I worn sprocket makes the good chain roll down the backside of the sprocket instead of setting in the pocket,increasing stress and wear on the pins,which in turn makes them wear faster.A worn chain on a new sprocket does the same thing.Whichever one is worn,sprocket or chain,now does not have 1/2 centerline,it's going to accelerate wear,it may be only a couple thousands,but that all it takes.They are going to wear to match the other.

You can get by with more wear on a bigger sprocket because you have more teeth in the chain,meaning it won't skip,but that doesn't mean it's good for the chain.

You can run that sprocket,it will most likely run just fine,and you can run it until you can shave with it,but your not going to have the chain life you should.

fietsbob

Rule of Thumb: 2nd new chain, new cassette and chain time, then when you have
gone thru that 2nd cassette on the 2nd chain, then replace the chainrings too..

that is if you are wanting things to work, best, doing the chain wear gage tests,
to know when.

if you let it go, then the whole drivetrain replacement is more likely.

DiabloScott

A worn sprocket meaning scalloped out like a shark fin, like this one?



I don't see how the chain's position on the teeth changes the amount or type of stress on the rollers and pins.

If the chain is elongated, it will ride up higher on the chainring teeth until the effective pitch of the chainring matches the elongated pitch of the chain - the teeth are thinner there so they erode faster.

If the chainring teeth are worn out but the chain isn't, then the pitch of the chain is smaller than the pitch of the chainring and (if I'm visualizing this correctly) the chain will be more slack in the leading teeth with more of the forces on the last link.

So,
1) I'm not totally convinced that a new chain on a worn chainring actually experiences more stress than on a new chainring, but maybe.
2) I'm not at all convinced that increased stress promotes chain elongation (maybe breakage though).
3) I'm staying with my rec that if a new chain shifts well and doesn't skip or stick on an old chainring... the ring's still good.