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Aluminium rear sprocket...expected life span?

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So I finally got around to changing out my kinked up oem chain. My rear original sprocket has 5K on it but does not look too worn, but I think I'll replace it. A while back I picked up a aluminium rear that was on closeout, just wondering what kind of wear life I can expect?

 

On another note, two of the sprocket bolt nuts would not budge. Could not get a socket on them due to the spokes and the 12mm wrench stripped them...had to cut them off with a dremel. What a pain in the arse....

Edited by Motor7

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So I finally got around to changing out my kinked up oem chain. My rear original sprocket has 5K on it but does not look too worn, but I think I'll replace it. A while back I picked up a aluminium rear that was on closeout, just wondering what kind of wear life I can expect?

On another note, two of the sprocket bolt nuts would not budge. Could not get a socket on them due to the spokes and the 12mm wrench stripped them...had to cut them off with a dremel. What a pain in the arse....

Good choice on replacing. Im no expert but sprocket and chain should also be replaced as a pair. Pretty sure a front sprocket you can swap out every other chain.. But someone can correct me if

Im wrong.

Only input i have for alum sprocket is that it wont last close to what a heavier metal one gets. Much softer metal therefore will wear much faster

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For the sprocket bolts use heat and an impact driver, I barely got mine out last time. Also a trick once they're stripped you can drive a torx bit into the head and spin them out.

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I wouldn't let a front sprocket  go every other chain, it takes a bunch of abuse. Its applying the torque of the motor to the chain with less chain contact than a rear sprocket. Not to mention even a quality front sprocket is only like $15. Not much to spend for cheap insurance.

 

Aluminum sprockets life span will really depend on how you maintain it and the quality of the sprocket. If you keep your chain clean and lubed, 8-10k miles is absolutely possible. Heck I have 10k miles on my aluminum rear sprocket on my R6 and it still has plenty of life in it.

Edited by OhioYJ

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Ok, sounds good...I'll give it a shot and see how long it lasts. I'm not changing the front because it only has about 2K on it...still looks new. 

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Alloy sprockets will cause your chain to wear prematurely.....alloy is better for racing to keep your reciprocating mass low but for general use a good o'l steel sprocket is the go...

Something like a Sunstar or JT brand is good value...

best to change out the front sprocket as obviously this guy turns way more than the rear due to it's small size...

Edited by Craigo 485sm

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All depends on your use.

Riding mainly off-road we generally get through 2 front sprockets to one rear & chain when using alloy rears - that is approx 1,500 to 2,000 miles (depending on how bad the conditions have been). This is based on 400-450cc machines, 250's get longer.

 

Road users seem the wear out the rear rather than the front - this is not something I have ever experienced.

 

I have recently gone to steel rears & also used Supersprox, I can now get 3 or 4 front sprockets to a rear. In fact I'm on my 2nd chain to the same rear Supersprox. The teeth are worn but they are worn uniformly. They are not hooked (like happens with fronts or with alloy rear) and the spacing still matches the new chain well, just has more backlash now as the teeth are slightly thinner.

 

People say to change all three together, and that a worn sprocket will kill a new chain - I say not necessarily.

It is ideal to have new chain & sprockets and swap them all as a set but that would get pretty expensive as sometimes I only get 500 -1,000 miles out of a front. I also change the gearing often which can involved swapping between a 14/15 fronts or 47/49/5 rears.

 

A stretched chain can kill new sprockets - no argument, that happens mainly with non-o'ring chains though, or cheap O-ring chains.

Good quality O'ring chains tend not to stretch, they just wear out. The side to side movement increases (like chain slap) and the O-rings can fail giving you tight spots. They don't seem to literally stretch much though. This is why I'm happy to use a fresh sprocket with a used chain & visa versa.

If the pitch measurement between the chain links hasn't changed then it'll still mess with a new sprocket perfectly, and therefore it also hasn't altered the pitch of the old/used sprockets either so there is no reason why they would harm a new chain.

 

That's my take on it and is how I'm running at the moment.

Edited by DrzDick

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aluminum sprockets = one sprocket per oil change

aluminum sprockets vs chain life = maybe 2 oil changes

steel sprockets = 5-10 oil changes per sprocket change

 

mixing stretched chain or worn sprockets  = makes about as much sense as adding oil instead of ever changing it. 

 

i wonder if the 'weight savings' of alu over steel is even comparable to half a banana. 

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whatever anybody tells you or manufactures claim,aluminum sprockets will not last as long as steel,its metalurgically impossible. i've found the biggest thing to wear sprockets and chain(besides not lubing) is using the clutch to wheelie,its a guaranteed chain wrecker,my drz rear sprocket has 19,000klms of road racing and its still going strong, i've changed the chain once and front sprocket once,both at 16,000klms 

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aluminum sprockets = one sprocket per oil change

aluminum sprockets vs chain life = maybe 2 oil changes

steel sprockets = 5-10 oil changes per sprocket change

 

How long are you going between oil changes?

 

Also any weight savings adds up, and since this is rotating weight, it makes an even larger difference.

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aluminum sprockets = one sprocket per oil change

aluminum sprockets vs chain life = maybe 2 oil changes

steel sprockets = 5-10 oil changes per sprocket change

How long are you going between oil changes?

 

Also any weight savings adds up, and since this is rotating weight, it makes an even larger difference.

those figures seem a little off,i change my oil every 5000 klms, theres no way i will be getting 25,000-50,000klms from any sprocket,if your touring you will change the oil less,if your racing you will change the oil more, i don't see how changing oil has any relevance to sprockets

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Anyone look into the new twinring sprockets? Aluminum core with steel teeth. They also have chrome-moly sprockets which are $$$ but don't weight much more than aluminum.

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I hear y'all, but i am trying to understand why a Al sprocket will eat a chain faster then a steel one? Chains are all steel, so I would think that the sprocket would "take the hit" & get worn with no effect to the steel. I have no experience here, just pondering.

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I hear y'all, but i am trying to understand why a Al sprocket will eat a chain faster then a steel one? Chains are all steel, so I would think that the sprocket would "take the hit" & get worn with no effect to the steel. I have no experience here, just pondering.

I'm with you here.

If you read my post I was saying that unless the chain stretches (only cheap arse chains seem to) the pitch distance on the drive edge of the sprocket will be maintained no matter how worn (thin) the sprocket teeth get - therefore the chain will not be worn/harmed by the sprockets wearing out.

 

In my experience the chain is king here!

A good quality chain (that is maintained properly) will look after the sprockets. As the sprockets wear they can be replaced, even alloy ones.

A weak chain will elongate (stretch) which will then drastically wear the sprockets and change the pitch measurement between the teeth - this then renders them useless as they will not marry up with a new/replacement chain.

 

Fit your alloy rear sprocket. When it's done replace it.

 

A better discussion here, now.. would be how to identify when your chain is done, and if it has taken out the sprockets or not...

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I hear y'all, but i am trying to understand why a Al sprocket will eat a chain faster then a steel one? Chains are all steel, so I would think that the sprocket would "take the hit" & get worn with no effect to the steel. I have no experience here, just pondering.

As the alum sprocket wears it slowly forces the chain to adjust itself[wear] to the worn configuration of the sprocket. The spacings between the teeth on the sprocket are greater and it causes the chain to appear to have streatched.

 

The life span of a steel sprocket is greater than that of an alum sprocket. However the life span of an alum sprock dramatically increases with the greater the number of teeth it has.

 

For 38 to 41 teeth a steel sprocket doesn't weight that much more than an alum one. So you might as well stick to steel. As the size increases you find more riders using alum than steel and some really large sized sprockets are only avail in alum.

 

Tony

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I got 7000kms out of my 38 tooth rear sprocket. The sprocket looks good to the untrained eye but it was worn never the less

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As the alum sprocket wears it slowly forces the chain to adjust itself[wear] to the worn configuration of the sprocket. The spacings between the teeth on the sprocket are greater and it causes the chain to appear to have streatched.

I would say yes, the spacing increases but only slightly because each tooth has worn, thus the space between between the teeth increases.

This increase is uniform around the sprocket - same space between each tooth and thus the front (or drive edge) edge of each tooth is still the same distance from the front edge on each tooth either side of it - the pitch of the sprocket has not changed thus the chain is not experiencing addition load because of the uniform tooth wear.

All that has happened is the teeth have got thinner.

The side effect of this is that you get more backlash when transitioning between drive to coast.

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