I have a 28X39X52 Specialized road crankset that I want to use on a newer Serrota Colorado with a braze-on front derailleur clamp-on)mount. That's a 24 tooth difference. I haven't been able to locate anything that can handle this spread in a braze-on (my current is Shimano bottom pull clamp-on. So, is there anyone that knows if there is a current or older front braze-on that can handle this? I use a 12-28 7 speed freewheel in back too.