with the front derailleur is a Shimano Tiagra, FD-4403 triple.
It has a Shimano, UN53. 68x118mm bottom bracket, I would like to keep this if I can
I like the gearing, but dont feel much need for 48 teeth, but am happy to stick with the same sort of thing.
So my questions:
1) What is a good quality crankset from Shimano that works with MTB indexed shifters giving the same 26t granny, and about the same gearing for the middle and big ring?
2) Do I need to change the front derailleur?
2a) If so, what should I get, of about the same quality?
Unless you really want a new crank, you only need to change the front derailer. A Shimano Deore or a Sram X-7 mountain bike derailer would work marvelously with mountain bike shifters. Don't be fooled into thinking that a more expensive front, like an XT or XTR, will work better either. Shimano's low end front derailers are actually better units then the expensive ones.
If you want a lower high gear, you could get a new outer chainring. Google "46 t 110mm chainring" and about a billion of them will pop up.
Wait a minute, can anyone else confirm if there's a different amount of space between chainrings on a mountain and road crankset? I thought there was simply a different amount of cable pull with mountain and road front derailleurs. I thought you only needed a mountain front derailleur because you have a max. chainring of 48T. Anyway, I know if you look at the Shimano Europe website, yes you can look at the flatbar group to look at the various options you can use. I think you could either use the front derailleur from the flatbar group if you want to use mountain shifters. Or, if you want to use the Tiagra road derailleur, you can use the flatbar group shifters.