Chain replacement with new sprocket question

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burkbuilds
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Location: Rome, Georgia

Chain replacement with new sprocket question

Postby burkbuilds » Thu Feb 18, 2010 9:12 pm

I'm planning to change my rear sprocket to 40 tooth from stock 42. I've already changed the front from 16 to 17 right after I bought the bike new. I have only had to adjust this chain up one time and only about a quarter turn then to get it back in specs. I'd prefer to keep using this chain instead of paying out the money for a new chain, but I know that typically you have to get a new chain for new sprockets when they are worn or it may cause the chain to fail if it's already worn. Is there any way to check and know for sure if I can keep using this chain or do I run a big risk by not replacing it with the new sprockets? What about just comparing the teeth on the new sprocket to the old sprocket and checking for significant wear on the old sprocket. If it's not worn down or "pointed" teeth or anything and it has the same relative size and shape of the new sprocket teeth would that be a good indicator of compatibility of my new sprocket with the old chain or should I just bite the bullet and buy a new chain? I've got over 11,000 miles on the existing chain, but like I noted, it hasn't changed much yet and seems to be in excellent shape.

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Triangles
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Re: Chain replacement with new sprocket question

Postby Triangles » Fri Feb 19, 2010 7:27 am

check your chain for "stretch" I don't know what the spec for pitch of our chain is, but I think it might be in the manual. Let me know if you can't find it and I'll look it up. I found the following below. I don't know if I believe the 100K number. I'd believe 25K and maybe 40K if religiously maintained.

http://www.sheldonbrown.com/brandt/chain-care.html wrote:Chain wear depends almost entirely on cleanliness and lubrication rather than being a load problem. For bicycles the effect of load variations is insignificant compared to the lubricant and grit effects. For example, motorcycle primary chains, operated under oil in clean conditions, last as much as 100,000 miles while exposed rear chains must be replaced often.
The best way to determine whether a chain is worn is by measuring its length. A new half inch pitch chain will have a pin at exactly every half inch. As the pins and sleeves wear, this spacing increases, concentrating more load on the last tooth of engagement as the chain rolls off the sprocket, thus changing the tooth profile. When chain pitch grows over one half percent, it is time for a new chain. At one percent, sprocket wear progresses rapidly because this length change occurs only between pin and sleeve so that it is concentrated on every second pitch; the pitch of the inner link containing the rollers remaining constant. By holding a ruler along the chain on the bicycle, align an inch mark with a pin and see how far off the mark the pin is at twelve inches. An eighth of an inch (0.125) is one percent, twice the sixteenth limit that is a prudent time for a new chain.
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burkbuilds
Posts: 350
Joined: Thu Jan 14, 2010 9:29 pm
Location: Rome, Georgia

Re: Chain replacement with new sprocket question

Postby burkbuilds » Fri Feb 19, 2010 11:42 am

Thanks for that information, I will check the "stretch" and see how much it is.

kawboyCAFE
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Re: Chain replacement with new sprocket question

Postby kawboyCAFE » Tue Apr 20, 2010 12:08 am

i clean my chains once a year, but i lube them about every 500 miles. i can usually get about 25,000 - 30,000 miles out of my chains. todays o-ring chains are built alot better than they use to be. i usually only have to even think about adjusting my chains at oil change time. and usually i dont have to adjust much, if any. at 11,000 miles, you should be okay putting the new sprocket on the same chain as long as you keep it lubed like you are suppose to.

burkbuilds
Posts: 350
Joined: Thu Jan 14, 2010 9:29 pm
Location: Rome, Georgia

Re: Chain replacement with new sprocket question

Postby burkbuilds » Tue Apr 20, 2010 8:07 pm

My chain and front sprocket were in great shape. I even took pictures on here somewhere of the new rear sprocket lying on top of the old sprocket and there's no discernible wear on the rear sprocket either, so I just replaced the rear sprocket and it seems to be fine.

Thanks for everybody's input. :)


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