Replace worn chainrings questions

[Copro]

Hi all,

After removing the crank arm for some photos I wanted to replace the worn chainrings with new ones or preferably used ones from another bike. The outer chainring has the sticker "IG chain only" on the outer side - so I am wondering if there are differences in the chainring systems as well.
Having this also awesome video lined up http://bikeride.com/replace-chainrings/ for replacing the chainrings I wanted to get some opinions.

As for the extremely worn middle chainring I am wondering why my own bike (that has almost the same mileage as my brothers's) does not show these extreme signs of damage.

[GeorgeET]

Ye the middle looks bad the large so so. I would replace those. I just replaced the middle one on my.This was the new thicker sprocket and I did not use the spacer washers. Shifts fine.
AS per wear it depends on crank metal composition and maintenance.Also which one you use the most. Not all batches are the same.

Spray all the bolts with penetrant of your choice. I like Liquid wrench. There are better, I posted a list recently.

Here is something I got from Sheldon's Brown site.

"I.G. (Interactive Glide)

The newer Shimano 7-speed cassettes have carried the Hyperglide principle even farther, by adding ramps and contouring to both sides of the sprockets. To do this while maintaining the full thickness of the teeth, the designers had to make the sprockets thicker. Since the sprockets are thicker, the spacers must be thinner to maintain the correct spacing. Also, since the sprockets are thicker, Shimano says you shouldn't use H.G. chains on I.G. cassettes. SRAM chains are compatible with both types.
Shimano says that you shouldn't mix I.G. and non-I.G. sprockets, but if you use one I.G. spacer per I.G. sprocket, you should be all right. Some experimentation may be required for best results with a mixed setup."

Where are you its not in your bio faq?

[Copro]

Thank you for the quick answer.
Just joined this morning and forgot to fill out all the forms. I am from Germany and after visiting Sheldon's site I ended up reading here that if the chainrings already look that bad the chain must have lengthened too much and also needs to be replaced.
http://www.utahmountainbiking.com/fix/chainrng.htm
So I will try and measure the chain wear as well before only getting new parts I was just shocked at the first moment when I saw that some of the tooths were basically gone. But apparently that really can happen during heavy usage judging from the Utah Mountain Biking site ;-]

[trevgbb]

With this amount of wear you will almost certainly need new cassette and chain, and possibly jockey wheels, as they all wear out together and it is a waste of time replacing them individually.

[GeorgeET]

Wear is a strange thing. On my bike the center sprocket was worn but all the others were OK and there was 0 stretch in the chain. With parts coming from Asia mostly quality control varies.

I just replaced the center drive sprocket. In your case both the center and large are worn. Examine the cassette or freewheel carefully, and check the chain. Than decide. While you have it all apart service all the bearings.