Adding new links to old chain
 

Just added a larger sprocket (+3 teeth in rear) and will likely need a longer chain. I just put a new chain on a few months ago (less than 500 miles on it) and hate to buy a new one. I still have the links I removed when I installed it (Dura-Ace 9sp chain).

I know the standard recommendation is to never add new links to an old chain. But I'm skeptical of absolutes. I understand there is a risk of increased tooth wear on the sprockets and rings. I'm planning to upgrade to 10sp in the next year so premature cassette wear is not a concern, but chain ring wear is (just moved from a triple to a new compact). According to my Park chain wear gauge (CC-3) the old chain is OK.

I'm planning to add the links and see if I notice any poor performance or visual gaps before buying a new chain. Is this a really bad idea?

Thanks in advance.

1. You might not need any additional length - three extra cogs doesn't mean three extra half-links.
2. If you do need it, there's hardly any downside so long as you do it right - using the right removable pin etc, or a master link.

You already put the cassette on - if it goes into big big without jamming then you're fine... but stay out of that gear anyway.

+1 to Scott's post. If you use another master link to add the new ones (good thinking saving the leftover links!), the chain should perform fine.

Sure go ahead I keep a bunch of spare links around because I'm always experimenting with gears. Bicycle shops throw spare links away when they install a new chain. Sram 8 and 9 cog chains can be taken apart with a chain tool and put back together. Shimano chains can't do this without the special pin. If you have a shimano they can be joined with Sram powerlinks.

+2 to Scott's post. See if the chain is long enough first, then add links if necessary using a masterlink or the special Shimano pins.

NO Hyperglide (SRAM 8 and 9S chains fall into this category) should EVER be rejoined by pushing the old pins back in. That's why they come with the PowerLinks...

I've done it a couple of times, and so far have never had a problem related to that particular thing. I use master links and therefore have two masterlinks with a couple of chain links in between for the splice.

I will advise to use new masterlinks, as I do feel (based on some experience I've had) that if you ever try to use a master link beyond what would be a normal chain life, they wear out and can actually spontaneously uncouple. I know it sounds strange, but I've had that problem, and it's the only thing I can think of causing it. I think their life span is longer than any chain though, so if you simply never move a master link from chain to chain, you won't have that problem.

a 2nd quick link,+ a inner link on its own falls apart, so rollers fall out.
its a PIA.