Bicycle Mechanics - Front derailleur for modfied Cannondale V800

I "hybridized" a Cannondale V800 I bought recently. Besides changing to pavement tires, I wanted more top end/downhill gear. So the manager of a local bike shop gave me a take-off crankset with a 52 tooth chainring. Now the indexed front shifting is a little flaky. Yes,I DO understand how the adjustment and limit screws work. I bought another derailleur from the LBS and it hardly worked at all -- I think it was made to be compatible with a 3x9 speed chain. To get the best out of the existing derailleur I had to mount it so close to the chainrings that it almost touches, I had to bend the bottom rail to make it more aggressive in forcing a shift. I can set the 2-1 and 2-3 shifts with the limit screws but when I set cable tension to shift 3-2 reliably, it doesn't shift 1-2 reliably and vice versa. I have to overshoot the shifts. I feel like the derailleur has a problem because it was not made for the larger chainring. Its a personal challenge to me make this work and keep the indexed shifting. I think I can do it with the right derailleur but I am having a problem finding out what that is. Most front derailleurs now seem to be made for 9 and 10 speed chains.

I might post a picture later if that will help.

Don in Austin

What shifters and fd are you using? Shimano MTB shifters pull a different cable amount then their road shifters so road and MTB front derailleurs don't index properly with each other's shifters.

If you are still using the MTB shifters, you will have a problem finding an MTB front derailleur that's usable with a 52T big ring since they are typically made for a 44T big ring. If you are using a road front derailleur it's not going to index well with the MTB shifter.

What shifters and fd are you using? Shimano MTB shifters pull a different cable amount then their road shifters so road and MTB front derailleurs don't index properly with each other's shifters.

If you are still using the MTB shifters, you will have a problem finding an MTB front derailleur that's usable with a 52T big ring since they are typically made for a 44T big ring. If you are using a road front derailleur it's not going to index well with the MTB shifter.

The shifters are Shimano Alivio. The problem is exclusively with the second chain ring. There is excess travel such that I can dial in the shifts into 1 and 3 with the limit screws. The problem is that a cable adjustment that gives me a reliable shift from 3-2 does not give me a reliable shift from 1-2 and vice versa. This seems to me to be a problem with the fit between the derailleur and the chain rings as there should be central adjustment that works for both these shifts.

I could see a problem with travel if I lost my shifts into 1 or 3 when dialing in the shifts into 2 but that is not happening. But maybe it would with a derailleur dialed in for the bigger rings.

Isn't there also an issue with chain width? I understood the front derailleur was different for a chain used with 9 or 10 rear speeds.

Don in Austin