Originally Posted by
mike455555
i recently bent my front crank on the large cog...
If you bent the chainring, and that chainring is bolted on instead of riveted, you can replace just the ring.
Originally Posted by
mike455555
its a 7 speed bike with this <Shimano M151> crank set, is there an upgrade to it without blowing the budget...
If that's your current crankset, you can replace it with the same model. (Contrary to one person's opinion above, those steel-ringed inexpensive Shimano cranksets are really durable. Heavy, but durable.) If you replace your crankset with the same model, you know it'll work with your existing bottom bracket's spindle length. Shimano's great at marking their parts, so you can confirm the model and crank arm length by looking on the back side of the crank arm.
Originally Posted by
mike455555
the guy at the LBS said off set was important but as its my first time replacing a crank i was curious as to the difference in them
Square taper cranksets are made with a particular bottom bracket spindle length in mind, and there have been lots of spindle lengths used by different manufacturers at different times. If your bottom bracket spindle is too long, your chainrings will be too far outboard. Your derailleur may not be able to reach the big ring. If your spindle is too short, the chainrings could be too far inboard. The derailleur might not be able to reach the small ring.