Chainring wear

[Eugene]

My drive train has some serious mileage on it. My chain checker shows between 0.75 and 1 wear. 

My plan was to replace the cassette, chain and chainrings. I already have a new cassette and chain and was going to get new chainrings too. 

I was watching an episode of Bikeapeeds. The bike on the show had similar chain  wear to mine and the mechanic said it wasn't necessary to change the chainrings. 

That got me thinking.... How do you tell if the chainrings are worn? 

I hate wasting money, but if I'm putting on a new cassette and chain, I still want to replace the rings. 

[The Ouzo]

My bike has 35 000km on it, been through around 5 or 6 chains, on my second cassette, chain rings are still going strong, although starting to make some noise. 
 

Your chain is your consumable, if you replace that before it gets to far gone then your cassette and chain rings will last a fair while. 

Edited Saturday at 06:48 AM by The Ouzo

[Dexter-morgan]

Try cjain waxing, your chain will last 5 times longer. The investment is worth it.

[Mamil]

2 hours ago, Eugene said:

My drive train has some serious mileage on it. My chain checker shows between 0.75 and 1 wear. 

My plan was to replace the cassette, chain and chainrings. I already have a new cassette and chain and was going to get new chainrings too. 

I was watching an episode of Bikeapeeds. The bike on the show had similar chain  wear to mine and the mechanic said it wasn't necessary to change the chainrings. 

That got me thinking.... How do you tell if the chainrings are worn? 

I hate wasting money, but if I'm putting on a new cassette and chain, I still want to replace the rings. 

Replace chain and cassette. Take the bike for a ride and see if new chain slips off chainring when putting down the power.

If your luck is anything like mine, it does.

[David Marshall]

The theory of drive train wear (the way I understand it) is not too difficult to comprehend. What does cloud the issue is the wide range of designs available - which leads to very different experiences.

Basically what happens is that the chain enters the cassette through the rear derailleur at a low tension (the RD spring tension) and leaves the cassette at a much higher tension (you pushing the pedals).

As the chain pins wear the chain effectively becomes longer and wears the front edges of the gear teeth as the chain is pulled through the cassette with increasing tension.  The effect of this is widening of the gap between the points of the teeth.  This is why when you put a new (shorter) chain on a worn cassette the chain rides on top of the points when entering the cassette (low tension) and then engages with a mighty clunk at some point when the tension increases. Probably only on one or two gears on the cassette will do this.

At the other end the chain enters the chainring under high pressure.  Within the first couple of teeth the chain is forced into the trough between the teeth and even if it is elongated the wearing effect is much less than on the cassette.  This is the reason that chainrings don't need to be changed as often as cassettes. 

So when do you need new chainrings?   

On a 1X set up worn teeth will look more hook like than when they were new. The real indicator is when the new chain is very noisy. You may be able to see the chain hooking up on the ring for a moment before dropping off.  The start of chain suck.

On the 3 X cranks this was usually first noticeable on the middle ring.

On 2 X cranks chainring wear is relatively slow.  Road 53/39 rings lasted "a lifetime" - not so the cassettes. 50/34 compacts tend to wear the 50 ring while cassette wear is less because people tend to ride 1 X on that ring over the full cassette range.  A sure sign that it needs replacement is the occasional unintentional chain drop when riding big - big.

No hard and fast rule.  Too many variables.  Size, materials, service intervals, riding conditions and so on but I think this covers the basics.

 

[Eugene]

So, I guess I'll change the cassette and chain and see if there is any slippage. If all is well, I save some bucks

I didn't mention, it is a road bike

[DieselnDust]

10 hours ago, David Marshall said:

The theory of drive train wear (the way I understand it) is not too difficult to comprehend. What does cloud the issue is the wide range of designs available - which leads to very different experiences.

Basically what happens is that the chain enters the cassette through the rear derailleur at a low tension (the RD spring tension) and leaves the cassette at a much higher tension (you pushing the pedals).

As the chain pins wear the chain effectively becomes longer and wears the front edges of the gear teeth as the chain is pulled through the cassette with increasing tension.  The effect of this is widening of the gap between the points of the teeth.  This is why when you put a new (shorter) chain on a worn cassette the chain rides on top of the points when entering the cassette (low tension) and then engages with a mighty clunk at some point when the tension increases. Probably only on one or two gears on the cassette will do this.

At the other end the chain enters the chainring under high pressure.  Within the first couple of teeth the chain is forced into the trough between the teeth and even if it is elongated the wearing effect is much less than on the cassette.  This is the reason that chainrings don't need to be changed as often as cassettes. 

So when do you need new chainrings?   

On a 1X set up worn teeth will look more hook like than when they were new. The real indicator is when the new chain is very noisy. You may be able to see the chain hooking up on the ring for a moment before dropping off.  The start of chain suck.

On the 3 X cranks this was usually first noticeable on the middle ring.

On 2 X cranks chainring wear is relatively slow.  Road 53/39 rings lasted "a lifetime" - not so the cassettes. 50/34 compacts tend to wear the 50 ring while cassette wear is less because people tend to ride 1 X on that ring over the full cassette range.  A sure sign that it needs replacement is the occasional unintentional chain drop when riding big - big.

No hard and fast rule.  Too many variables.  Size, materials, service intervals, riding conditions and so on but I think this covers the basics.

 

What Dave said ^^^

 

In addition, if the chain is worn beyond 0.75%, I'm very confident your chainrings are going to be worn too. The teeth  that are at 45 degrees to 135% behind your crank arm are the ones most likely to be worn as they are the sector of the chainring in the power zone

9 hours ago, Eugene said:

So, I guess I'll change the cassette and chain and see if there is any slippage. If all is well, I save some bucks

I didn't mention, it is a road bike

the chainrings might be worn horribly but usable. Your will however experience accelerated drivetrain wear