There are measuring points that the manufactures have for their machines. For my Case dozer, the book shows me where to measure from and what the wear is. I've never figured it out on mine, I can feel the bushings and see that they are still round, but my sprocket is getting ready to be replaced.
On the sprocket, you want allot of flat metal at the end of each tooth. The more they wear, the more of a point the develop. This is what touches the bushings, and the more the sprocket wears the greater the opening and the less contact that you have with the bushings. The bushings are in the chain and are the big money items to replace. You can have them turned in most machines, but it takes a special press to do this. To have it done, you either have to remove the track and bring it to a shop, or bring the machine there and have them do it. Big money either way. The more wear you have, the faster other parts start to wear. At 80%, you are still good and have a long ways to go. Of course, a track loader is doing allot of driving, so wear is going to be an ongoing issue. Different machines also wear faser then others. And rubber tracks are totally alien to me, so I couldn't guess what goes on there.
Just feel the bushing in the sprocket with your hand to see if it's round or flattened out. If you can feel the wear on the side that's touching the sprocket, you know that it's getting ready to be replaced or turned. Check the other side to see if it's new or has already been turned. At 80%, there should be minimal wear on the bushings, and you shouldn't be able to feel very much be touch.
The rails are the part of the tracks that ride on the rollers. They are the flat metal parts that also wear out, but it's pretty slow and not really a concern until they are gone. If you see flat metal on the sides of the rails, then it's not something to worry about.
The idler can develop a groove in it from the rails, especially if the tracks are too tight. It's a pricey replacement, but not one of those things that wears out very quickly either.
Same thing with the rollers. If one stops turning, then it will create a groove in it and cause excessive wear on the rails. If they are flat and you don't see any grooves in them, then they are fine. Some have oil in them and might be leaking. If this happens, you might have to replace it before it seizes up.
If you posted close up pictures of the tracks and started a new thread on the machine that you are interested in over in the Construction Equipment forum, you'll get allot of feedback on the condition of the undercairrage and probably some insite on that particular machine that you are looking at.
Heavy Equipment Forums - Powered by vBulletin is a good site for Construction Equipment, but it's not like TBN. They are friendly enough, but sometimes you get a helpful response, other times you get arrogance and smart mouth replies. It's worth a try, and doing a search on a specific machine over there can give you some insites from time to time.
Eddie
