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Chain "stretched"?

Old 08-16-03, 09:36 PM
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Chain "stretched"?

According to conventional wisdom, a chain should have links that are exactly 1" long. 12 links should measure exactly 12". Well, the chain on my roadie fits these criteria, but I can still see alittle bit of light between the links and the chainrings at the "top" and "bottom" areas (i.e. when the chain begins and ends contact with the ring). I can't see any light in the "middle". I also can't see any light between the chain and the sprockets.

I've just ordered a 39T chainring to replace my 42T and I ordered a chain for my mtb about 2 months ago that's only seen about 50 miles of use. Is the chain on my roadie OK or should I swap it with the mtb chain? I'd like to do this when I put the 39 on since I'll be removing the chain anyway...

Thanks for your help. If you need any more info, let me know and I'll send it along...

PS Is there a decent guideline for how often the chain should be replaced (i.e. # of miles) to prevent ring wear?
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Old 08-16-03, 09:50 PM
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Originally posted by CarlJStoneham
Is there a decent guideline for how often the chain should be replaced (i.e. # of miles) to prevent ring wear?
Chain wear varies widely from rider to rider due to a variety of factors:
1. How attentive a rider is to cleaning and lubrication;
2. what type of weather and road conditions a rider encounters;
3. rider style, e.g., grinders vs spinners; and
4. other factors that are unique to each rider.

Therefore, your best bet is to regularly check for chain wear (aka., stretch) using either a 12" rule or a Park Tools chain checker. You may find that you wear through chains on a regular basis if you tend to ride the same routes, in the same conditions at the same physical exertion levels.
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Old 08-16-03, 11:44 PM
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Sounds like your road chain is ok. Chain wear occurs in areas not visible: the hole inside the rollers and the pin through the roller. Measurement is the only
practical way to evaluate. Cassettes wear at 1/2 to 1/3 the rate of chains and chainrings at 1/4 the rate of chains. Mileage on a chain will run 2k to 10kmi
per chain, most get less than 5kmiles. In my experience 9spd chains wear out
faster than 8spd. Steve
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Old 08-17-03, 02:29 AM
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Sch, I probably wait too long to change my chain, cos by the time I go to replace it, the new chain does not want to mesh with the cassette (slipping and jumping) and the rings are pretty far gone too. So I replace the lot....very expensive!!!

If I simply change the chain well before it "appears" worn, like at 2kmi, will it still mesh with everything and save me money in the long run? Do you know the specified "chain stretch" measurement for a 9spd chain to tell exactly when to do this?

And finally, do you think those more expensive aftermarket chains are better value than a Durace chain? I'm about a 72kg rider who is a slowly reforming 'grinder', wannabe 'spinner'...and I ride in some rain.
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Old 08-17-03, 08:33 AM
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It's not chain stretch ... it's chain wear. All chains have the same link length so the 12-inch rule method applies to all speed chains. The only difference between them is their width.
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Old 08-17-03, 10:13 AM
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No one I am aware of has gone to the trouble of comparing chains for longevity
and the price differences of 2-4x between chains are difficult to understand.
From a consumer point of view, there is little evidence that a $50 stainless
steel chain will last significantly longer that a $15 chain. True it won't rust but
rust is not going to be a failure mechanism. If it is, the whole bike, not just the chain is at risk: preteen bikes, abandoned bikes, Canadian winter bikes.
There will be little functional and longevity differences between DuraAce and the bottom end Shimano chains, between SRAM PC59 and PC99 chains. There are subtle shifting improvements, a few grams difference in weight minor alloy changes but it does not add upto 2-3x cost difference. All chains need cleaning and lubing, even stainless and titanium chains. Steve
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Old 08-17-03, 12:27 PM
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sch, I'm going to politely disagree on the longevity of chains. Chains higher up in Shimanos, Campys, and other manufacturers lines do in fact last longer when used under the same conditions.

Jim,
a mechanic for to many years now in the medical field
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Old 08-17-03, 04:57 PM
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I've found the Durace 9spd chain to be significantly better than the Ultegra chain, to the extent I am much more confident it will not break on me. I am not a 'Durace snob' either...I use Ultegra rings & cassette with the Durace chain.

I haven't tried a more expensive chain, but am thinking a stainless steel (Wiperman?) model would have a very hard surface which may better resist the grinding effect of road grit, especially in the rain. Even if the chain costs 25% more and lasts like only 20% longer, that also represents extra life for your cassette and rings.

Talking of chains...you can't effectively lube the main load carrying rollers of the chain can you? I mean most of the chain lube must simply be lubricating the side plates, which is not where the wear takes place that results in the links becoming 'longer'? Motorcycle O-ring chains have this worked out....anything similar available for a training/sport bicycle chain?
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Old 08-17-03, 07:29 PM
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Originally posted by chainreka

Talking of chains...you can't effectively lube the main load carrying rollers of the chain can you? I mean most of the chain lube must simply be lubricating the side plates, which is not where the wear takes place that results in the links becoming 'longer'?
I'm not sure how you lube your chain but I put a drop on the rollers themselves while turning the cranks backwards. Once each roller has received a dollip of lube, I wipe the excess off. I don't lube the sideplates and I'm fairly confident that the lube has worked its way into the roller.
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Old 08-17-03, 09:19 PM
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I dribble it on while turning cranks backwards, with the end of the bottle resting at either side of the roller, which ends up near the sideplates. My question was how can you be confident that lubing the outside of the roller will result in lube getting inside the roller, where it really needs to be?

O-ring m/cycle chains have grease sealed in there from the factory with o-rings to hold it in, for life of the chain hopefully. I think m/cycle chains are lubed as much to keep the o-rings in good condition as much as any other benefit.

BTW: What is the limit for chain wear by length, before you've wrecked the rings and cogs too?

I just measured my chain...I'm in metric land, so 12''=300mm (near enough?) I got 304mm for 12 links, that's measuring from absolute end of outside links. So I have 4mm of wear (about 1/6 of an inch?). Is it too far gone to even think of getting a new chain to use with the old cassette? The little chain ring is already on it's second chain (turned backwards)...I can grab the frontmost part of the chain and pull it mostly clear of 1-2 teeth on the small chainring at that point. Big one was new, but is also looking a little used...might just last another chain.
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