Just got back from Bikeshop, the guy they've got there should be a mechanic for one of the tour teams, he's really great.
Besides the problem with the chain rubbing on the inside of the largest chainring, it was also suffering from shifting problems up and down on the rear cassette.
I had the outer and inner gear cables replaced around the rear mech about a year ago.
The guy today initially attempted to adjust the gears, this didn't work, he said they are all over the place, so he stripped the inner cables out, replaced, then removed the outer cable near the rear mech, measured it, i asked why he's measureing it, he said he finds best results when the outer cable is trimmed at 14", and this one is only 12", so he replaced the outer cable, did some more tweaking, and some more limit adjusting, and bingo, every gear on the rear perfect first time every time.
Then came the front chainring, he removed the bottom bracket, and replaced it with a new bottom bracket which was 2-3mm longer on the axel, asked me to take it for a spin.
I couldn't believe the difference, the only way i can explain it is each gear change is 'punchy'. It seems to snap/punch into position really sharply on the rear, and the rubbing has dissapeared completely on the front largest chain ring, the only drawback is there is a 'very slight' longer shift required to get the chain over from the middle chain ring to the largest chain ring, but when i say slightly longer, its not difficult to do, and it doesn't jam or anything like that, its a really quick change still but you can tell that the chain is travelling just that little bit further than it was.....but i can live with that, as every gear is working brilliantly on the middle chain ring, however i've lost the top two gears on the largest chain ring due to chain rub on the front derailer due to the longer bottom bracket...
