Uneven chain wear. Why?

[elus1ve]

I did more than 10,000km on my bike since i got it and never touched the chain before (the PO changed it right before selling it to me). So my buddy showed me how to check for chain slack other than visually looking at it.

So first thing I learned is that the chain has different wear at different part and that the slack will vary from one point to another with the bike on the center stand, gear in neutral and the rear wheel rolling freely.

I can understand that the chain can wear unevenly but I just couldn't understand why the slack would feel any different at different points since pushing up or down on the chain should distribute the force over the whole chain and across the sprockets (remember it's in neutral and the rear wheel is moving freely). I couldn't wrap my head around this and my buddy couldn't tell me more either. Was hoping someone here could enlighten me.

 

[FinalImpact]

That's happening due to links being bound. As in, some sections of the chain move *think straighten out* easier than the others. Likely a lack of lube in some sections.

I'd drench it in cleaner + grunge brush, wipe it thoroughly and repeat. Ride it shortly, wipe and lube it real good. Test again. I also spin EVERY roller to confirm none are bound.

 

[tejkowskit]

10,000km and no chain maintenance, yikes! Time for some TLC on that chain and sprockets. Clean it well and lube it up. You'll notice a smoother and quieter ride with a clean and lubed chain with proper slack. It's also a good idea to take the front sprocket cover off and clean in there. I even go as far as removing and cleaning the rear tire hugger and chain guide on the swingarm and cleaning those once in a while.

Chains stretch unevenly giving you some tighter spots. When adjusting slack make sure to measure from the tightest spot in your chain.

 

[major tom]

Sprockets are not always perfectly round especially after market. This will cause uneven tension and slack. As others have said chains do not wear evenly, especially with a lack of lube. Remember, those links wrapped around sprocket teeth will not allow to be tensioned the same as links hanging freely.

 

[Water Bear]

I would guess that it's nothing more than the chain stretching in some spots more than others. Put a tight length of chain between the sprockets and press down, it will be less slack than when you put a loose length through and try again.

I dare not hazard a guess why the chain wears unevenly; I'm not sure I actually slept last night and the ideas coming to mind are setting off warnings in the self-monitoring centers of my brain.

 

[elus1ve]

Bound links and sprocket not being round would explain uneven tightness and uneven wear.

I should clarify that when I say I did not touch the chain, I meant I never had to tighten it or change it before. I clean it with a brush and wd40 without removing it every year + the regular lubing applications. I also clean and grease the front sprocket and the area around once a year as well. It is far from being sparklingly clean as FinalImpact's but I believe I do a decent job at taking care of my bike. And after more than 10,000kms, the chain slack is still within specs.

As soon as the slack measurement of the tightest area of the chain is out of specs, I am going to do a thorough cleaning of the chain and check each link before tightening the chain.

 

[FinalImpact]

Bound links and sprocket not being round would explain uneven tightness and uneven wear.

I should clarify that when I say I did not touch the chain, I meant I never had to tighten it or change it before. I clean it with a brush and wd40 without removing it every year + the regular lubing applications. I also clean and grease the front sprocket and the area around once a year as well. It is far from being sparklingly clean as FinalImpact's but I believe I do a decent job at taking care of my bike. And after more than 10,000kms, the chain slack is still within specs.

As soon as the slack measurement of the tightest area of the chain is out of specs, I am going to do a thorough cleaning of the chain and check each link before tightening the chain.

^^ I see what you slipped in there.... Blah

I'm not shy with the throttle but do rev match as the norm. She's only up to 18,4XX miles and the chain slack is just starting to show after 4 sets of tires and never having to remove slack/make slack adjustments.
My point is this; if ever there were chain that should stretch from being pulled on, I think this it (12k shifts are plentiful). That said the addition of slack from wear is being reduced by regular maintenance. If our trend continues I should get some miles from the chain. :thumbup: Also, its pretty uniform in its slack no matter where I check it.

 

[Carlos840]

I did more than 10,000km on my bike since i got it and never touched the chain before (the PO changed it right before selling it to me). So my buddy showed me how to check for chain slack other than visually looking at it.

So first thing I learned is that the chain has different wear at different part and that the slack will vary from one point to another with the bike on the center stand, gear in neutral and the rear wheel rolling freely.

I can understand that the chain can wear unevenly but I just couldn't understand why the slack would feel any different at different points since pushing up or down on the chain should distribute the force over the whole chain and across the sprockets (remember it's in neutral and the rear wheel is moving freely). I couldn't wrap my head around this and my buddy couldn't tell me more either. Was hoping someone here could enlighten me.

I think there are a few different things going on here:

First, the different wear at different parts of the chain. The simplest explanation is probably just grease and dirt. Your chain is never greased with a perfect coverage, and dust and sand is not picked up uniformly, so your chain will wear faster in spots that have less grease and more dust and slower in spots that have more grease and less crap.

Now, regarding the slack feeling different, it is pretty normal, i don't know the physics explanation of it, but a string is always tighter the closer you get to the anchor points, and looser the closer you get to the center.
If you have ever played a stringed instrument it is extremely obvious. The strings barely move up or down close to the bridge or the nut, but can be moved a lot if pulled in the middle.

Same thing applies to the chain, which is why you should measure slack in the center of the chain, between the two anchor points.

 

[elus1ve]

^^ I see what you slipped in there.... Blah

I was taught to use benchmarking to help visualize and compare so I'm using you as a benchmark :thumbup:

I'm not shy with the throttle but do rev match as the norm. She's only up to 18,4XX miles and the chain slack is just starting to show after 4 sets of tires and never having to remove slack/make slack adjustments.
My point is this; if ever there were chain that should stretch from being pulled on, I think this it (12k shifts are plentiful). That said the addition of slack from wear is being reduced by regular maintenance. If our trend continues I should get some miles from the chain. :thumbup: Also, its pretty uniform in its slack no matter where I check it.

And here you go about setting benchmarks again. 18,xxx miles with no slack adjustments. Based on that, I now know that it's ok that I haven't done any slack adjustment after 6000 miles

 

[elus1ve]

I think there are a few different things going on here:

First, the different wear at different parts of the chain. The simplest explanation is probably just grease and dirt. Your chain is never greased with a perfect coverage, and dust and sand is not picked up uniformly, so your chain will wear faster in spots that have less grease and more dust and slower in spots that have more grease and less crap.

Now, regarding the slack feeling different, it is pretty normal, i don't know the physics explanation of it, but a string is always tighter the closer you get to the anchor points, and looser the closer you get to the center.
If you have ever played a stringed instrument it is extremely obvious. The strings barely move up or down close to the bridge or the nut, but can be moved a lot if pulled in the middle.

Same thing applies to the chain, which is why you should measure slack in the center of the chain, between the two anchor points.

My question wasn't clear in my first post, sorry. By different slack at different point, I mean that measurement is always taken at the middle point between the front and rear sprockets, and you would rotate the rear wheel to get to a different point on the chain. It is apparently normal that slack measurements differ.