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Old 11-06-08, 10:30 PM   #1
NextRightThing
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chain replacement woes

I have a 1983 Raleigh Super Course 12spd. I've put about 150 miles on it since I bought it and decided to check the chain stretch. It was between 1/16" and 1/8" 10 links out, which means the chain is stretched but the crank and cassette should be okay. So I go and order the SRAM pc-870 chain (3/32" x 1/2"), which is what Sheldon Brown recommends for bikes of this vintage.

I installed it, and didn't adjust the length at first, as the old chain was just as long as the new one. The chain skipped repeatedly under power on the two smallest cogs in the rear, the smaller of the two being MUCH worse than the larger.

Took two links out, same result.

two more links out, same result.

two more links out, way too tight.

put two back in, and just didn't use those gears for the ride.

I get home after a 45 mile ride and compare the old chain to the new; the new one seems to not fill the 'valleys' between the teeth quite as completely as the old chain does. I am left to believe that either the original chain was a 1/8" x 1/2", or the teeth are worn, but they certainly do not look 'ramped' by how it has been described to me and what I saw on Sheldon's site.

What do you guys think? If I do need a 1/8" x 1/2" chain, what might you recommend that is comparable to the SRAM pc-870? I will be doing collegiate races this spring, and the bike will usually see 100+ miles of hard riding a week.

Thanks!
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Old 11-06-08, 10:39 PM   #2
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If you are getting skipping in the two smallest cogs in the rear, your cassette is worn and needs to be replaced.

A couple of other comments though...

1. How did you rejoin the two links you previously removed? SRAM 8 speed chains use rivetted pins which are not designed to be removed and reinstalled.

2. To size your chain properly, wrap it around the largest front chainring and the largest rear cog. Figure out where the chain would be joined to just fit this combination then add two links (1" of chain). That is the proper chain length and will never need to be adjusted.

3. I use whatever is the cheapest 8 speed chain that I can find. I think the last SRAM PC-830 chain I bought was under $10.
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Old 11-06-08, 11:18 PM   #3
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I have the SRAM 870 on my vintage bike, and I've taken it apart at the links and put it together again. No problems at all.

The issue I see is not having a chain that was absolutely the right length before, so you had nothing to go buy. I'd suggest seeing where it's at by shifting it into it's 12th gear - large front chainring to small rear cog. Then look at the position of the rear derailleur. What you should see is the two pulley wheels at 12:00 and 6:00 - straight up and down relative to each other, like the numeral 8. If this is where it is, then we can rule out chain length as posing a problem. From there I'd put my attention on the rear. Are we looking at a freewheel or a cassette here?
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Old 11-07-08, 05:44 AM   #4
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I have the SRAM 870 on my vintage bike, and I've taken it apart at the links and put it together again. No problems at all.
How hard do you ride that vintage bike? It would make me quite nervous to stand on the pedals and grind up a big hill using a chain that I knew was compromised. With the rivetted pins, there's no way the refitted pin will be as strong as the original.

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The issue I see is not having a chain that was absolutely the right length before, so you had nothing to go buy. I'd suggest seeing where it's at by shifting it into it's 12th gear - large front chainring to small rear cog. Then look at the position of the rear derailleur. What you should see is the two pulley wheels at 12:00 and 6:00 - straight up and down relative to each other, like the numeral 8. If this is where it is, then we can rule out chain length as posing a problem.
He absolutely has something to go by for chain length: big/big combo plus an inch. That's the standard method (and only guaranteed method) for sizing a chain aside from doing some math.
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Old 11-07-08, 08:11 AM   #5
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I have the SRAM 870 on my vintage bike, and I've taken it apart at the links and put it together again. No problems at all.
This is a dangerous practice.

Derailleur chains like the SRAM were NEVER meant to have their pins pushed partially out and rejoined without a quicklink. Other chains, like Shimano use a special pin.

Just because you haven't experienced chain failure doesn't mean it's safe to do. Try it on a cusomters bike and wait for the lawsuits to roll in.
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Old 11-07-08, 08:14 AM   #6
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Originally Posted by NextRightThing View Post
I have a 1983 Raleigh Super Course 12spd. I've put about 150 miles on it since I bought it and decided to check the chain stretch. It was between 1/16" and 1/8" 10 links out, which means the chain is stretched but the crank and cassette should be okay. So I go and order the SRAM pc-870 chain (3/32" x 1/2"), which is what Sheldon Brown recommends for bikes of this vintage.

I installed it, and didn't adjust the length at first, as the old chain was just as long as the new one. The chain skipped repeatedly under power on the two smallest cogs in the rear, the smaller of the two being MUCH worse than the larger.

Took two links out, same result.

two more links out, same result.

two more links out, way too tight.

put two back in, and just didn't use those gears for the ride.

I get home after a 45 mile ride and compare the old chain to the new; the new one seems to not fill the 'valleys' between the teeth quite as completely as the old chain does. I am left to believe that either the original chain was a 1/8" x 1/2", or the teeth are worn, but they certainly do not look 'ramped' by how it has been described to me and what I saw on Sheldon's site.

What do you guys think? If I do need a 1/8" x 1/2" chain, what might you recommend that is comparable to the SRAM pc-870? I will be doing collegiate races this spring, and the bike will usually see 100+ miles of hard riding a week.

Thanks!
You need a 3/32 chain. Any chain will do. The $10 Sram PC-48's will be perfectly fine. Please learn how to properly size chain length here:

http://www.parktool.com/repair/readhowto.asp?id=26

It's not guess work. There's a precise procedure that needs to be followed (big/big +1). You almost always have to change rear cogs when you change the chain - they wear together.
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Old 11-07-08, 08:27 AM   #7
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It is my understanding that stretch between 1/16" and 1/8" over 10 links means you cogs are probably pooched. The reccomendation I have always heard is replace before 1/16" over 12 links. You probably need a new freewheel.

Having too long a chain (by one or two links) is not usually a cause for skipping. Usually a too-long chain just sags or rubs or causes the derailleur to rub on the cogs, not skip.
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Old 11-07-08, 09:58 AM   #8
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So it's likely the cassette, damn. I'll size it properly today and see how it rides.

Even though the old chain fills the 'valley' between the teeth more completely, it's the same size chain????

Yeah, I do ride the bike hard. So I'm lucky I ordered an extra chain.

are cassettes still easy to come by? (it's not a free-hub)
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Old 11-07-08, 10:50 AM   #9
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Shimano 7 speed freewheels are readily available and relatively inexpensive. I had the same issue where I failed to replace my chain before the chainrings and cassette were worn. When I did put a new chain on, I had the same problems you describe. At some point, I will replace the whole drive, but I decided to put the old chain back on and just run everything until it's completely shot.
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Old 11-07-08, 11:19 AM   #10
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will I need a narrow chain for a 7 speed cassette?
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Old 11-07-08, 01:18 PM   #11
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I've never had a chain break on me, but I am a perfectionist - 'tis true. I check everything twice before going on a long ride. And I make certain the chain goes back together exactly as was. Others may have had breakage from this, but I haven't. Now, with that said, I'll go break a chain now for sure! LOL.
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Old 11-07-08, 01:29 PM   #12
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I've never had a chain break on me, but I am a perfectionist - 'tis true. I check everything twice before going on a long ride. And I make certain the chain goes back together exactly as was. Others may have had breakage from this, but I haven't. Now, with that said, I'll go break a chain now for sure! LOL.
Shimano chains are vsry likely to break if a new pin is not used during installaton.

Sram chains are based on Sachs chains and I always thought it was OK to reattach them - just much easier with a quicklink.

That being said, this summer I rode in a 24 hour race without problems, then the next time I used my MTB, going for a short ride around town a few weeks later, my chain broke in two places simultaneously - a short section actually fell out onto the ground!!! The next ride after I reassembled, a link in my chain somehow got badly twisted and I had to limp home - I may have a damaged cassette or something.
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Old 11-07-08, 02:47 PM   #13
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Shimano chains I would never re-attach. In fact - I would never let one on my bike. I had nothing but trouble with Shimano chains before. Once burned, twice shy.

Friends Don't Let Friends Ride With Shimano Chains.
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Old 11-07-08, 03:25 PM   #14
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Shimano chains I would never re-attach. In fact - I would never let one on my bike. I had nothing but trouble with Shimano chains before. Once burned, twice shy.

Friends Don't Let Friends Ride With Shimano Chains.
I am the opposite - I have only ever had problems with Sram/Sachs chains. One summer I must have broken my chain five times - a Sachs chain I had installed in the spring.

I cannot remember ever breaking a Shimano chain (that I installed properly using a new pin).
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Old 11-07-08, 04:21 PM   #15
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I am the opposite - I have only ever had problems with Sram/Sachs chains. One summer I must have broken my chain five times - a Sachs chain I had installed in the spring.

I cannot remember ever breaking a Shimano chain (that I installed properly using a new pin).
You are honestly the first person I've ever heard say this in over ten years! Every broken chain that comes into the shop is Shimano. Every Shimano chain I've had broke. Goes to show that there are exceptions to most pieces of advice..
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Old 11-07-08, 04:53 PM   #16
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You are honestly the first person I've ever heard say this in over ten years! Every broken chain that comes into the shop is Shimano. Every Shimano chain I've had broke. Goes to show that there are exceptions to most pieces of advice..

I worked in bike shops for ~ half my life and I have also seen more Shimano chains broken, but I have always had better luck with them. I have seen many non-shimano chains break too, though.
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Old 11-07-08, 04:55 PM   #17
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will I need a narrow chain for a 7 speed cassette?
You can still purchase chains intended for 6/7 speed systems which have protruding pins but in my opinion that would be silly when you can get very cheap chains that are designed to work with 6/7/8 speed systems that are lighter, probably stronger, and come with the very convenient quick link.

Cheap chain: http://www.niagaracycle.com/product_...ducts_id=20751

Cheap freewheel: http://www.niagaracycle.com/product_...oducts_id=6178

Disclaimer: Niagara has quite cheap prices and shipping but they don't seem to stock anything and it will likely take a week before your order ships out. If you are closer to the west coast, give www.universalcycles.com a try (almost as cheap plus offers a discount on $100+ orders). For me, I get stuff in about the same amount of time from either as one is only 2 days by FedEx and the other is 6-7 days by UPS but the former takes 5 days to ship and the latter only 2.
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Old 11-07-08, 10:25 PM   #18
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what are the chances that my chainrings are shot? Is there any good way to measure something like this?
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Old 11-08-08, 09:11 AM   #19
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what are the chances that my chainrings are shot? Is there any good way to measure something like this?
At 1/16" -1/8" I doubt your chainrings are shot. One way to tell how much wear they have is to look at the points of the teeth that would be pointing up at you with the cranks parallel with the ground (when your leg would pushing straight down on the cranks). If these teeth look quite sharp, your chainrings have excessive wear. If they still have flat sections left at the top, just go ahead and reuse them.
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Old 11-08-08, 07:58 PM   #20
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It is my understanding that stretch between 1/16" and 1/8" over 10 links means you cogs are probably pooched. The reccomendation I have always heard is replace before 1/16" over 12 links. You probably need a new freewheel.

Having too long a chain (by one or two links) is not usually a cause for skipping. Usually a too-long chain just sags or rubs or causes the derailleur to rub on the cogs, not skip.

I agree. Chain length issues usually won't cause skipping. Also, if this was a used bike, you don't know who did what to it, ie the previous owner may have run a chain to the point of extreme wear and toasted the freewheel and maybe the chainwheels, too.

Despite the problem, it will be nice when it is fixed!
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