Originally Posted by
10 Wheels
I real life that is Not True.
My Felt has a 11/34 cassette that works. Shimano says 28 T is the limit.
In real life on
your bike this works. Longer derailleur cages do NOT mean a derailleur will work w/ larger than spec'd cogs. The ONLY thing a long cage does is wrap more chain. Period. It does not do anything else. All Shimano road derailleurs like yours have the same max cog size rating, the ONLY difference is the capacity to wrap chain on a triple. Whether or not the derailleur works is more a function of how long the derailleur hanger is than anything else. Shimano says 27 on that derailleur, not 28, is the max cog because that is what they can be certain will work on any bike.
In real life 28 will work every time because it's only 1 tooth over. But that is all you can say with certainty...any other combination needs to be tested to confirm it will work, and my money says anything over 30 is not working very well (B screw buried or reversed is known as "not doing it right").