Bicycle Mechanics - Gear Adjustment

My wife was complaining about her gears not shifting right after a 53 miler last Saturday. I looked at it and sure enough. It won't shift to the biggest rear cog (25) when it's in big ring up front.

She has a tripple and it will shift into the 25 from the middle and small ring, but will not shift into the 25 from the big ring.

Was wondering what type of adjustments I can make to remedy this problem. I'm familiar with how to adjust the derailleurs and cables when I hear the chain rubbing against the derailleurs, but I've never run into this before.

With a triple,there is absolutely NO reason to be in the big/ big. Besides being poor form,it increasees drevetrain wear.It may not shift to that combination because the chain is too short.If that is the case,be glad it doesnt.It it shifts when in the middle and samll,it really is not derailer adjustment.

Did you try to adjust the limit screw on the rear derailleur? It could be a short chain, which can easily be seen because the rear derailleur pulleys will be pulled almost horizontal at that point. If it's not rubbing the front derailleur than those are the only 2 things I can think of.

If it shifts in the other rings,it ain't the limit screw.

It's not the limit screw because it shifts fine in the middle and small ring. The the chain look a little short. I agree with Pokey, you shouldn't be in big and big. I made some adjustments to the front derailleur and it shift great in all gears except big and big. I'll tell the wife not to try to shift in big and big.

good plan.