1saxman

I'm rebuilding my 1989 bridgestone Comp MB2 that I bought new and basically just rode around the streets. I quit riding and my son had it for a few years, now I have it back. The bike has very low hours on it but it was ridden hard in the dirt a few times when he had it.
A few things were changed, but nothing major - just tires and the chain. When I got it back, the original chain was with it. I want to clean up and re-use the original chain (which is not even dirty). I counted the links - the link pin that was pushed to break it is still in place in the side plate - and it has 106. That seemed low, so I checked the replacement chain, and it had 108. That made me feel better, so now I think the 106 is right. Does this sound right to y'all?
I guess I'll try it when I get to that point. What's the worst that can happen? It won't make the big/big combo, and that is defintely not a problem. But if no links have been removed, and I don't think they have, it should work as well as it did in 1989. The cogs and rings show no sign of wear from a stretched/worn chain. The rear cogs don't even have to be cleaned.

Burton

Chains come in several different lengths and the number of links is usually indicated on the package.

If the chain was or wasn`t cut isn`t as important as if its a good fit. It should be safe to asume you can reuse that original chain, but you`ll need a quick connect link or a reinforced connecting pin specifically for that chain size and make. You can`t reinsert that rivet that was pushed out to break the chain.

If you don`t have the equipment - take it to a shop. It`ll be cheaper than buying the tool.

Al1943

You need to measure the chain for stretch if you haven't.

skilsaw

Here is how to measure Proper Chain Length. The information comes from Sheldon Brown's web page on derailleur adjustment. Scroll down to find Chain Length.

https://www.sheldonbrown.com/derailer-adjustment.html

Chain Length

If you replace your chain or sprockets, you should check your chain length. New chains come longer than they need to be for the vast majority of bicycles. You will almost certainly need to shorten a new chain before installing it on your bicycle. If your large sprocket sizes are anywhere near the maximum your rear derailer can handle, the chain length can be quite critical.
If the chain is too short, it will be at risk for jamming and possibly ruining the rear derailer if you accidentally shift into the large-large combination. Never run with a chain that is too short, except in an emergency.
If the chain is too long, it will hang slack in the small-small combinations. You should never use those combinations anyway, so this is not a serious problem. If you exceed the recommended gear range for a particular rear derailer, you may have to accept droop in these gears.
The best technique for setting chain length is to thread the chain onto the large/large combination, without running it through the rear derailer. Mesh the two ends on to the large chainwheel so that one complete link (one inch, -- one inner and one outer half-link) overlaps. In almost all cases, this will give the optimum length.
Inner and Outer half-links must alternate:


Full-link overlap, correct
with chain on the large chain-
wheel and sprocket but not yet
run through the rear derailer.
Overlaps by a half link.
Already too short
unless it could overlap
by a full link as at left.
Will connect, but
too short except on
a bicycle with a
non-derailer drivetrain. Start with the shortest chain that would permit connection, allowing one extra complete link as shown in the photo at the left above, so the bottom of the chain droops if you align it as in the picture at the right. Then thread the chain through the rear derailer and connect it. Turning the crank by hand, check that the chain will shift to the large-large combination using the front derailer or rear derailer, or both at once, without binding.
Work by shortening the chain, rather than lengthening it. Making the chain too short, then lengthening it is a time-waster. The narrowest chains, used with cassettes that have 10 sprockets -- sometimes 9 -- must be joined using special one-time-use replacement pins or master links. You probably only get one of these with a new chain, so it is important to get the length right on the first try.

1saxman

That's shocker - I put chains back together with the old pin for years when I was riding. I never had one get loose. I'll look into the quick-link.

1saxman

Okay, I see, mine is a 7-spd chain so it doesn't have the special 'one-time use' pin of the 9/10-speed chains. These didn't exist when I was riding before which is why I had no problem putting chains back together.
Thanks Skilsaw for the great post. That's exactly what I needed to know.

Monster Pete

It depends on the type of chain. Older chains, from single speed up to about 5/6 speed can generally be rejoined without problems. I think it's only with 9/10-speed chains that you get problems due to a weak spot.

FBinNY 

I can't speak to all your questions but the chain is too short and it definitely is a problem.

the worst that can happen is you lose track of where you are and accidentally shift to the big/big pair and any or all of the following happen; bent axle, bent chainring, destroyed RD, derailleur hanger tab breaks off, rear dropout/chainstay damage, (need I go on?)

Get a new chain and measure it so it loops the big/big pair with some slack still left for the RD (usually one inch or so minimum).

FBinNY 

This is fine for a chain or bike of the pre-hyperglide era, sually 7 or fewer speeds. It's the advent of Hyperglide that changed the rules. The gated shifting of Hyperglide makes for more positive shifting, but it puts much more side pressure on the plates when shifted under load.

Post hyperglide chains have rivet heads peened over the outer plate to resist plate movement. When those are broken, the lip sheers off so the pin needs to be replaced with a special pin made for the job, or the chain closed with a connecting link.

If you don't go to 8s Hyperglide you're fine continuing your chain closing practice.