Originally Posted by
carpediemracing
Find a rider that uses the small-small set up. Find another rider with the same large chainring and large cog that uses the big-big method.
Put it in the big-big. Lift the rear wheel off the ground. Turn the pedals. There's a lot of friction in the big-big when using the shorter chain setup.
My current setup was done that way (big-big). Never noticed any extra friction but then I guess I don't have anything to compare too. However, using big-big resulted in the exact same length as the stock chain. I just checked though and in small-small the two pulleys are "nearly" horizontal with just a bit of tension. Pretty much what I would have expected had I used the small-small method. Probably because with a 28 the chain will be close to max length for the derailleur as that's the biggest recommended cog.
psimet also makes a good point. It's one of those safety habit things. You always wear a helmet or seatbelt when you ride or drive. You don't plan on crashing either vehicle when you start off (unless you're committing suicide, murder, or you are a stunt person), but you still do it. Using the small-small method is very safe and eliminates accidental wheel popping out (or worse) when you inadvertently use a wheel with a larger large cog (heck, the second cog may be bigger than your current big cog).
I currently have an 11-28 on the bike. Moving to 11-23 would result in a shorter chain using the big-big method but probably the same length using the small-small since both use an 11. Obviously the big-bib method won't work if I size it for the 23 when I try to put in a wheel with a 28. However, I wasn't planning to do that. Sounds like I'm going to end up with the same length chain again.