A co-worker needs a need chain for his bike. Unfortunately he had a problem a couple of months ago on the way to work and someone helped him with the problem but this required them to remove some links in his chain. He doesn't know how many links they took out, but he indicated that he has the odd problem with the bike that he believes is caused by the chain being too short.

By now his chain is worn enough that it should be preventively replaced. He asked me to assist him, but I'm not sure how long to make the new chain. Normally one just matches up the new with the old and makes it the same size. In this case we know that won't work. Should I simply match them and make the new one about 2 or 3 links longer?