Front Derailleur Rub
I have a 52-42-32 front crank and a 12-26 cassette. I had a 28 chainring laying around and I was thinking about lower gears so I put it on. The chain now rubs on the bottom of the front derailleur with the three smallest cogs on the cassette because the derailleur lacks the needed capacity. Will this cause any problems?
Will the derailleur go any lower? Generally the front derailleur should clear the big ring by only the thickness of a penny.
Could you shorten the chain? It needs to be long enough that the derailleur does not reach its forward limit when the chain is on the big chainring and largest cassette cog.
There's really no reason to use the smallest chainring with the 3 smallest cogs.
Most road triples are equipped with a 30 granny ring.
I recently added a 28 FCR to a 30/42/53 10spd and found the same issue. Also, you tend to get chain rub on the middle CR when you cross chain from the small to small sprockets. However, when riding I only use the small FCR with the 5 largest rear cassette sprockets. You are well into the gearing over lap with the center CR and it makes no sense to do otherwise. I ride my triple like a double on the flats and rolling hills and just keep the very low gearing for time of need.
Originally Posted by rmac
I have a 30/40/50 triple where I changed the 30 for a 26 FCR on my Cross Bike. The issue is the same. This is all on Campagnolo gruppos. It was the only way to get the gearing I wanted. I find that I only use the lowest gearing when climbing very long mt roads where I need a breather and don't want to stop. Also, I am able to climb very steep hills. I used this method because I didn't have the option of using the XT derailluer and a MTB cassette as with Shimano. I suggested this route to my neighbor who went on the BAGBARI in Iowa last summer and she came back eternally grateful for the low gearing in the headwinds.
I like to go on rides like the BTC or RTR in Colorado and find after a week of high mountain passes I need all the help I can get. Adapt your riding to the equipment you use. If you need the lower gearing then optimize the use. At 64 I need all the help I can get and still ride in the mountains.