Quantify sprocket wear ?

How much wear is too much on the gearbox sprocket ?

The chain will not move back and forth when laid over a new sprocket. When laid over the old sprocket it moves 1/16-3/32". Is there a quantitative to decide when it is time to change the front sprocket ?

Greg

Eyeball symmetry of teeth. My acceptance criteria for worn cycle consumables has made a significant upward swing since I was 16yo. :mrgreen:

+1 Concours

Your chain will have a dimension that spans 20+ links (pin to pin) depending on the pitch. Too long and you wear out the sprockets prematurely. As mentioned earlier, the teeth of the sprockets have a flat at the apex of the teeth, about 2mm wide, when that becomes a sharp edge get a new set of sprockets and a new chain.

Concours and museums staff on this forum all always say to replace and/or re-manifacture to ideal or face facts you are too slip shod to own a Commando w/o constantly injuring it. So replace small sprockets with each new chain or ignore the best advice. Wrap chain over sprocket and try to lift links out of valleys to see where teeth are taking the loads with spun up. I get shopping for chain and hold down power and speeds when teeth get about 1/3rd out of valley as way easier to change than sprockets which can function pretty good till the nubbins allow chain to just slip over make noise not motion. Worn teeth spacing shortens chain link tightness life as pointed out already, so another philosophical decision to balance time and cost vs benefit like oil and oil filters. Thin teeth tend to fan over some before breaking off and rubbing down to nubbins.

Well if you have to post such a question then replace. But you are supposed to replace all 3 items involved as a set. That's a lot of money ,remembering that one of the 3 worn out will drastically affect wear on the other 2.

Well there ya go best to replace everything every time including the rear brake sprocket-teeth too or just wasting out time time asking stupid questions - now we know you are destroying another Commando in slip shod ignorance. So again what is there to discuss as best proper path is when ever some chain slack appears to always spend ~ $300 every 6-8000 miles or remain ashamed.

Relax... not so wasteful... repurposing is alive

Hmmm... very attractive yet functional. :?

Hi,

the only reason why you don't want to change the front sprocket is removing the primary train. Once removed it is advisable to change it. If you change the chain earlier (e.g. every 5000-6000mls), you must not change the sprockets everytime. After 5000mls my rear sprocket looks like new. Using good chains can prolong sprockets life considerably. I can ride 3 chains with on sprocket set. But if you wait until the chain is worn out, you must change everything. This strategy may not be cheaper, but you must not remove primary train such often.

Ralf

ludwig said:

Better is to alternate between 2 chains :
when de 1st shows some slack , (or every 1000 mls ), instead of tensioning it , replace it with the 2nd .
You will always have a clean , lubed chain ready .
Both chains and sprockets will last longer .

Click to expand...

Yes, that is the most efficient approach.

Seem to be mixing sealed oil bath primary with exposed final drive chains but most efficient is making the teeth and links counts all odd numbers especially prime's and cryogenic tempering on top of never letting chain get so dry it can't flush its self generated metal dust out of interfaces. unless in gritty conditons then best to run dry unless a sealed chain. I've tested this on chain saws as well as Commandos to find it suits my lazy ways.

I've had chains come off sprockets from wearing slackness in sport bikes heats that also eat up tranny bushes. Had
come apart a number of times from master links coming apart from stuff getting under them while holding steady throttle-speed to be surprised by a wiggley snake passing me, but no damage. This has occurred on both my Combats and my SuVee with plain and sealed chain. Slack in links and sprocket teeth are not the only thing to watch for extending chain use beyond reasonable, which is a sliding scale for everyone. Some folks wear out tires on long trips and chains too because they did not carry extra chain and sprockets and tires with them so going by the advice left here implies they are too slack to own a motorcycle w/o injuring its parts, sheeze. Most efficient down/dirty assessment is link lift amount out of valleys which at some point of wear - chain tension has no effect on helping.

https://www.youtube.com/watch?v=HsiEBXd_g9c

hobot said:

I've had chains come off sprockets from wearing slackness in sport bikes heats that also eat up tranny bushes. Had
come apart a number of times from master links coming apart from stuff getting under them while holding steady throttle-speed to be surprised by a wiggley snake passing me, but no damage. This has occurred on both my Combats and my SuVee with plain and sealed chain. Slack in links and sprocket teeth are not the only thing to watch for extending chain use beyond reasonable, which is a sliding scale for everyone. Some folks wear out tires on long trips and chains too because they did not carry extra chain and sprockets and tires with them so going by the advice left here implies they are too slack to own a motorcycle w/o injuring its parts, sheeze. Most efficient down/dirty assessment is link lift amount out of valleys which at some point of wear - chain tension has no effect on helping.

https://www.youtube.com/watch?v=HsiEBXd_g9c

Click to expand...

To have chain and sprockets in good condition is one of the most important requirements for bike security - thats no question. If the rear sprocket teeth look clearly uneven it is time to change. It is also important to check the master link and lube the chain regularly. But it is hard to say how long a sprocket will last. That depends on the ride conditions. I myself had never wore out chain and sprocket after 5000mls. O-ring chains last much longer than standard chains, but I am suprised how long reinforced chains can last nowadays.

Back in 1970, after coming off the ferry from England and off through Belgium in cold foggy weather, a fellow biker we met was riding his Triumph. He was a free roaming hippie of the era and knew nothing about mechanics. His bike was merely a means of getting from A to B. Well, his drive chain had about 6 inches of slack in it and would undulate like a snake as he went down the road. Well, we had not gone very far when his bike came to a stop. The chain was not the cause of the stoppage but I have never forgotten being on the side of the road troubleshooting this Triumph in the darkness. Double trailer trucks would roar by and literally shake the ground. When the driver saw us on the road apron he would hit the flame thrower lights. You could actually feel the heat coming off the light beam as they thundered by. We got the Triumph going by resetting the points using a match book cover. I would imagine he got an abrupt stoppage via a snapped chain before he made it to the Oktoberfest in Germany.

I've thrown enough chains on saws and bicycles, motorcycles and chain couplings to know its rather rare to get an abrupt disruptive shock or snag just coast down on mc or stop throwing chips or driving a pump. Occassionally chain can pile up and blast through shields or cases or its whiplashing end snags something on the way out. But so rare is like worrying about flat tire coming off rim, usually just a be of thrill pulling over to deal with tire. Its is good or bad memories feeling hi beams on back of neck and ground trembling before the air blast turbulence rocks and rolls ya.

Roller chain drives have many little factors that multiply going round and round, like chain teeth phasing.
http://www.sheldonbrown.com/chain-life.html

My 1st no name Combat had hi hard mileage on it drum teeth when I got it and oiled it a lot so never dry but constant oil grime dispersing that wore teeth down enough when re-built I set chain on loose side to creep up on tension but on first hwy break in use it'd slip off if I gave WOT or tried to climb Mt steep much and barely got me home by careful smooth throttle use and eventually used worn drum to experiment with replacing ring of teeth that worked but would foul on swing arm. But ole no - name had rump rod then so was the day I yelled out to big gathering of bikers for some pecking order testers - clunker vs moderns and since didn't have to slow much for turns could still lay down as much or more power leaned and into straight at they could. Surprised Pleased me no end Ms Peel was whipsered in my ear the next day reflecting on all the antics pulled off for first times. With new drum on didn't have to hold back form unbelievable better G glees. Tranny spockets pointing and fanning over became next wear weakness.

I'm glad that hoboT is willing take on the curmudgeon role and save me the grief. To bring this back to the original question, it sounds like it is time to replace the sprocket when the teeth are worn to a point (!).

In my experience chains last 6-8000 miles (lubed every other tankful of gas). Rear sprockets last for 2-3 chains. The front sprocket must go forever. My current one must have 40,000 miles on it ( bought it when we were living in CT) and most of the flat on the tip of the tooth is intact. Changing the front sprocket with every chain is probably a good idea if you don't have to work for a living and like to remove the primary just for fun.

Running a saw chain dry is just plain nuts, IMHO.

Greg

Greg the industrial standard to replace roller link chain is 2% increase in stretch. Pluch up links after each ride to feel for yourself when the wear factor is accelerating beyond your learned tolerance and always steer clear of grit.

hobot said:

Greg the industrial standard to replace roller link chain is 2% increase in stretch. Pluck up links after each ride to feel for yourself when the wear factor is accelerating beyond your learned tolerance and always steer clear of grit.

Click to expand...

Hi Steve,

The chain wear I get. I actually remove it occasionally and push all the links together and pull them apart. When the extended chain is 2 links longer, it is a goner. The question was about the front sprocket wear since I had not changed it since I went up from 19 teeth. The pulling face is worn and like I said the chain is loose in the gullets, but most of the flat at the apex of the tooth is still there. As far as grit, we live on a dirt road and sometimes paved roads don't go where I'm headed. I'll take my chances with chain lube and the scorn of the museum staff.

Greg

I think this is an useful explanation:

https://www.youtube.com/watch?v=sFDXB_KH4vs

Until teeth fan over or chain slips over them or just breaks its purely a person/philosophical choice. The only way to know it your sprocket is wearing chain faster than expected is to start with all new and monitor link lift out valleys at back of sprockets. Or off the bike method, which I'll have to calibrate with the valley lift scale so no need to remove to monitor. Thanks for the clinical gem of 2% stretch in ~99-100 link chain is ~two link lengths worth. Occasional intervals of grity dust is not same test as routine miles of it both ways. I get 8-10,000 miles before 1/3+ lift out of valleys by running bone clean and dry. So if disciplined lubing lets someone's hi end unsealed chain wear 2 links loose under 8,000 then I'm even more pleased with myself with more free time spent on rational productive activities. So someone's idea of well lubed may not be, but Know the Norton factory oiler is more than adequate to get closer to double chain life by constant drip>sling which is what the poor brits did depending on economy in era oil was cheap as dirt. With a new sprocket you can compare how they differ for sense of wear but that ain't the same as knowing how much sprocket wear begins eating to fast into chain time/money. When chain is fairly new its tension will pull links tighter into valleys but at some point it doesn't and then begins the blurry threshold to replace a thing or 3. My SuVee has more online ads for package deals for 2 sprockets + chain than hunting down single items in case that gives sense of Norton normal vs rest of the world.

Btw I ran out of 520 chain on Peel's poor decision conversion so tried 530 X-ring chain and it worked just fine and didn't wear out before I decided to bury 1st Peel.