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Are my Chainring & casette worn?

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Are my Chainring & casette worn?

Old 04-09-17, 04:11 AM
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mpetit
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Are my Chainring & casette worn?

Hi everybody,

Got a 2nd hand MTB and the chain looks a bit stretched (i.e. lifted it off with my fingers at the front chainring).

Now, I don't know if the chainrings and the cassette are worn too. Could you please let me know what do you think? They are Shimano IG which have "exotic" tooth shapes, so it gets me a bit confused.

Thank you!

PS: I'll be replacing the cassette with a 8sp SRAM and the chain for a Connex 8 sp. As I read in other threads there are no serious compatibility issues to mix them with IG chainrings.
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Old 04-09-17, 05:57 AM
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This has been one of my concerns with buying used bikes in the past. Typically I can assess the overall condition of the bike by examining the paint, looking at the screws holding the derailleurs and stem. If they are a little rusty, then its obvious the bike has either been ridden a lot in the rain or simply left outside a lot. Is the chain filthy? Is there a lot of gunk and goo on the chainwheels and cassette? What do the rims look like? Are they beat or clean and smooth?

All this adds up to how many miles has the bike, or how much abuse. This all said, I usually clean the chain, cassette, and chainrings. When they are all super clean, I feel the gear teeth for sharp edges and examine closely for burrs or deformation. If there is a lot of wear between the teeth, you can usually tell under close inspection.

I then check the chain with a Park go-no-go gauge. If I suspect that the chain is the original, and its pretty badly worn, its a safe bet that the chainrings and cassette are worn as well.

I hope this helps. Its my method. I hate IG chain personally, and I am known to swap the whole driveline out for better stuff.
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Old 04-09-17, 06:51 AM
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Thanks for the feedback!

The chain was pretty clean, and so the cassette and the chainrings. The rims are in excellent condition, and so most of the components (all of them original). The bike was certainly not used a lot. The guy who sold it to me recently started riding it (it was his father's bike) but was looking to replace it for a road one since he does mostly that.

As it was in great condition I rode it already for 200-250 km, including a 60 km MTB ride in wet & snowy conditions. Then I checked and found that the chain (original one) was a bit stretched, but not too much (my 0.75 gauge does not go through).
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Old 04-09-17, 07:35 AM
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Sure the teeth are worn, the bike's been used after all. But the real question is how worn and what the condition means for a new chain's wear and for the shifting. IMO (and until a new chain is installed and the bike tested all we have are opinions) the teeth are not very work. Yes there profiles do change due to the designed in shift gates and such. But I will bring your attention to the difference between the top and the bottom shots of the large ring. Note that the large ring's teeth have more wear in the bottom photo. This is where the RH pedal is applying pressure. I see this often as most riders have a strong side that has greater pedal pressures.


As to the IG vs HG aspects- there is really not any adjustment or process differences. In fact at every shop I've worked in we don't even talk about this. We mount the same chains and cogs on either system with no negative results that we or our customers note. Andy
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Old 04-09-17, 09:54 AM
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Originally Posted by NoControl View Post
I usually clean the chain, cassette, and chainrings. When they are all super clean, I feel the gear teeth for sharp edges and examine closely for burrs or deformation. If there is a lot of wear between the teeth, you can usually tell under close inspection.
One cannot tell under close inspection the amount of wear that exists. The best way to determine whether there is functionally significant cassette wear is to mount a new chain. Worn cogs will either skip under pressure or at least be noisier or feel rougher. In the case of chainwheels if they show a shark fin profile I would replace them, or if even a new chain lifts off significantly.

Originally Posted by NoControl View Post
I then check the chain with a Park go-no-go gauge.
Chain gauges in general are a great selling tool for shops, but a steel ruler is much more accurate.

Originally Posted by NoControl View Post
If I suspect that the chain is the original, and its pretty badly worn, its a safe bet that the chainrings and cassette are worn as well.
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Old 04-09-17, 10:55 AM
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Use a ruler to measure the wear (stretch) of your chain. The length of 24 links should be 12 inches, measured center of pin to center of pin. Most people recommend replacing the chain when the length is 1/16" past 12 inches. If it is more than 1/8" , this usually suggests that cogs and chainrings will need to be replaced. For a more detailed discussion, see Sheldon Browns exactly article at Bicycle Chain and Sprocket Engagement and Wear.

Of course, the ultimate arbitrator of whether the cogs or chainrings are worn is to put on a new chain and then see if it skips or the shifting is bad(like the above poster noted).
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Old 04-09-17, 10:59 AM
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Originally Posted by cny-bikeman View Post
One cannot tell under close inspection the amount of wear that exists. The best way to determine whether there is functionally significant cassette wear is to mount a new chain. Worn cogs will either skip under pressure or at least be noisier or feel rougher. In the case of chainwheels if they show a shark fin profile I would replace them, or if even a new chain lifts off significantly.

Chain gauges in general are a great selling tool for shops, but a steel ruler is much more accurate.
Sweet Quivering Carp Lips, there's always someone to put their spin on whatever you say in here. Makes it awful hard to be a participating member of this forum. Hey I just told you how I did it on my own bikes. I didn't say it was the only way. A go-no-go gauge is a good tool for determining wear. Use a ruler if you wish to quantify the wear, but in my book if a chain is worn it needs to be replaced. If I suspect the other drivetrain components are worn, they get replaced. Also, for what its worth, I CAN tell if a chainring is worn just by looking at it.
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Old 04-09-17, 01:49 PM
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For an 8-speed chain anything under 0.75% is OK. Even when new the chain is abut 0.25%. Replace when you are at 0.75%
Your cogs looked OK, but you will notice skipping or noise if they are not.
Lubricate well. The chain lasts maybe 1000 km and the cassette 3-4000 km. All depends on lubrication, water, dirt....

I have the CC-2 chainchecker just because the other tools don't tell me how close I get to the limit. But any method gets the job done.
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Old 04-09-17, 02:16 PM
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If you wait until the wear is visible, then you've ruined everything, and you need to replace it all....
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Old 04-09-17, 02:37 PM
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Thank you all for your replies. I installed a new chain, kept the old cassette, and went for a spin, about 36 km on road, double and single track. The bicycle spins smoothly, I've experienced no chain skipping at all and applied quite some power a lot of times, since I rode on rolling terrain. So I guess it is OK for the time being!

Now that we're on, I do feel some skipping on the third highest cog (so third smallest one) on my road bike (9 sp) after I changed the old chain (rode ~ 4000 km with it, kept it clean and it was replaced before it hit the 0.75 in the chain gauge). After 400 km on the new chain, skipping still happens under power, especially when starting from standstill. Could it be that my cassette is gone?

Thanks a lot again!
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Old 04-09-17, 02:39 PM
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Did the previous owner only have one gear, HIGH? Are you living in a flat part of Florida?

I think I can see a little wear on your outer chainring, but it appears too be minmal.

The cassette appears to be good, but one might need closer examination of the 3 smallest sprockets.

MEASURE the chain for stretch. Then if it is stretched more than 1/16" per foot, replace. Once you get the new chain on, you'll know pretty quickly if the cassette is worn, and then choose what to do about it.
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Old 04-09-17, 02:45 PM
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Both show some wear, but seem OK to me. If the size is the same, I'd leave the cassette in place and try with the new chain. If it skips, then replace it, but there's an excellent chance it'll be fine.

BTW - minor occasional skipping often resolves on it's own, so if the skipping is occasional enough that you can live with it, then you might give it a while and see if the problem goes away.
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Old 04-09-17, 02:57 PM
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The whole thing looks toast to me. You'll just ruin the new chain.
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Old 04-09-17, 04:19 PM
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Folks, the .75 is not a percentage of chain wear it is .75mm of chain wear. Other than a ruler there is only one chain gauge that is accurate. It's the $60 shimano gauge.
Your chain is ok for now. Periodically measure it for wear (1/16" in 12') then replace it. After you replace it carefully ride the bike and see if the chain skips on the cassette. If it does replace it.
From your pictures the rings look good.
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Old 04-09-17, 04:58 PM
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Originally Posted by cny-bikeman View Post
One cannot tell under close inspection the amount of wear that exists. The best way to determine whether there is functionally significant cassette wear is to mount a new chain. Worn cogs will either skip under pressure or at least be noisier or feel rougher.
Rohloff sells a cassette gauge. It is a short length of chain attached to some kind of lever. You engage the lever and if you cannot insert the fifth link between the teeth of a sprocket, it means that the sprocket is toast.

The idea is that a worn chain has a longer pitch and will progressively wear the cassette such that the cassette will match the chain. When you put a new chain on a worn cassette, the chain will wear faster, and may skip because it cannot fully engage the sprocket.

It also makes perfect sense when the OP writes that skipping occurs on the third smallest sprocket. This sprocket is generally used more often than the smallest. And larger sprockets (19 and above) generally don't suffer as much because more cogs engage with the chain, reducing wear.

If you read on this, you'll come across various advices, some suggesting that a worn sprocket can be "restored" by running a fresh chain... Others would advise to replace the sprocket/cassette to reduce chain wear.
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