vegasrealtor

Hello all,
I have been looking elsewhere and find it hard to determine what the proper course of action is for shopping to replace a worn chain set.
Bike:1992 Trek 930 Single Track with slicks.
Chain ring sizes:5 Bolt 42-32-22

To start off I just bought this bike and have start to basically completely overhaul it so I can put some serious miles on it as part of a daily routine. I just bought a new chain since I checked and confirmed it is worn. The teeth on my current Shimano chainrings are all irregular shaped and some are nearly missing.

If someone has the knowledge I would like to know if I could replace the crank with something like this for what I would consider a cheap price. Shimano Acera Triple Crankset FC M361 175mm 42 x 32 x 22 Black Bike Cranks New | eBay
My crank puller won't be here for a week so if I can order before measuring that would be great.

If something like that won't work, do most people buy each ring separately or where do you find a set of matching chain rings matching your gearing?

Thank you!

Afterthought: I spent more time searching and found all of these that have my chain ring gearing. I just don't know my BB size.
https://www.ebay.com/sch/Bicycle-Comp...&_nkw=42+32+22

FBinNY 

Before spending any dough, take the time to see if you actually have a problem with the existing chainset. Hyperglide or similar cranksets look worn when new, and the cut down or broken teeth might be the shift gates made that way for easier shifting. Then again the rings may be shot.

The best test i whether the chain runs without skipping under load, since that;s what matters. You can also get a sense of the wear by installing the new chain and pulling it away from the sprocket midway of the wrap (3 o'clock). If you can pull it away from the sprocket far enough to see 1/4" of daylight underneath, the ring is well worn, but if not, it's a pass.

As far as replacing the crank goes, odds are you'll need to buy both crank and a bottom bracket because modern cranks take shorter spindles than older ones used to.

Willbird

FB is right on the money :-). I had two Trek 7200's when I started riding mine, one was mine one was my wife's, I put a new cassette on mine and at first look I was thinking "the chain rings are trashed".....well no, they make them that way on purpose :-)....having two bikes, with the wife's having 9 miles on it let me confirm that :-)

nfmisso

IF you decide to change the crank, given that you are running slicks (thus most likely a pavement rider); you may want to consider larger chain rings, like 48-38-28, to give you a bit more speed, at the loss of some really steep hill climbing ability.

Bill Kapaun

IF you actually need to replace the rings, a 22-32-44 or 24-34-42 or similar combinations should work fine with possibly just a slight FDER adjustment. If you stick with the 42T large ring, you likely wouldn't need to.
Going to a 48T large ring would require a new FDER for decent shifting, although you could probably make the old one still shift with a decrease in precision.

I suggest you look at the rings on a NEW bike. You'll see they look well worn to the untrained.
FBinNY gave you good advice for checking them. If they don't skip, they're good.

cale

Doesn't vegasrealator know vegasbikeshopmechanic? You two ought to hook up! Haha

Honestly, it's tough to "tell" from written words. One thing's for sure. The bike is old enough to have been through several drivetrains so don't assume everything is original. Better to examine first, buy second. EVEN using this approach, I've found myself buying third and fourth too!

vegasrealtor

Sorry for the slow reply guys. I have taken some pictures of the crankset to hopefully be able to show the condition better. I do think what I was attributing to bad chain rings, I can now say is most likely a bad front derailleur. The front derailleur will not adjust on the "high" side so it essentially pushed the chain off the ring when shifted into third. When shifted into second it goes on the largest chain ring.
Can anyone help me to find a front derailleur? I found this this one on ebay which I believe might work: New Shimano Altus FD M310 6 28 6 34 9mm 3x7 8 Speed Low Clamp Front Derailleur | eBay
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Bill Kapaun

Sounds like you have the FDER cable too tight.

FBinNY 

Yes, Just like with the rings, which are worn, but still have plenty of life left, I suspect that your FD just needs some basic adjustments.

As Bill K. said, if the FD is goint to the outermost ring, then it's a matter of slackening the cable so 2 puts it onto the middle ring. Also if, it's overshifting and dumping the chain over the outside, that calls for a high limit adjustment.

Hang on to your dough, and search for a tutorial on adjusting the front derailleur, or find a bike co-op where you can get some hands on guidance.

Check out the Fremont Bicycle Clinic downtown.

vegasrealtor

Thanks for the quick responses. The high side set screw wasn't moving the derailleur at all so thats what made me assume the derailleur needed changed. I was watching tutorials but no one really mentioned how to determine if the cable was too tight.

Does everyone think the chainrings are fine? I tried to show the damage as well as I could.

FBinNY 

I can't stress enough the need to UNDERSTAND what you're working on. Just viewing a tutorial isn't necessarily enough. To make the one point that might help set you onto the right path. The limit screws are line the concrete barriers along the length of the bridge. They define the width of the roadway, and prevent you from driving off and into the drink. But they don't affect your actual lane placement, you do that.

Likewise with the derailleur. The limits are just that the limits, but the position of the derailleur with each shift is controlled by you via the cable.

Watch or read a few tutorials until you have a good sense of what to do, or visit the co-op where the hands-on guidance is a much better learning environment.

Or, spend dough that you don't need to.

vegasrealtor

That makes a lot of sense. I'll explore adjusting the cable and do that tomorrow to see where I end up.
Thank you.

SkyDog75

I've found the tutorials on Park Tool's web site to be particularly good. Here's their guide for adjusting front derailleurs:
Park Tool Co. » ParkTool Blog » Front Derailleur Adjustments

vegasrealtor

Who can help with this? The second chain ring and the largest seem to be so close together that I can never utilize my 2nd gear. This is I'm sure what I thought the issue was in the beginning.
The picture shows what it looks like when shifted into second.
The second picture shows it in greater detail.

FBinNY 

If you assembled the crank set with both the middle and out rings with the brand label out, and on opposite sides of the crank spider mounting tab, then they are correctly spaced. In fact they cannot be too close to each other.

I think you keep looking for problems tat aren't there, and there a limit to how much people can help you via the internet, which is why I steered you toward the co-op, where someone can look at the bike, tell you what's right, and what's wrong.

Maybe you can try this. Shift to the smallest chainring, if you cannot, disconnect the cable and let the spring do it for you. Then attach the cable, and try shifting by pulling it away from the downtube like a bow string. If you can shift this way, it confirms that stuff is basically OK, except that you don't know how to adjust a front derailleur.

AnkleWork

Maybe recheck for correct assembly.

vegasrealtor

Turns out I am just an idiot. Since I thought I would be replacing the chain rings I didn't pay attention during removal. I somehow thought it was best to put the largest chain ring behind the crank spider mount. It seems to all be working now. I'm just tweaking the barrel adjustment to get crisp shifts.
One last question on this, will the wore down chain rings ruin my chain faster than normal? At one point should I be going for new chain rings?
Thanks!

FBinNY 

So, what else is new?

There's a lot of debate on that point, even among very knowledgeable people. I'm of the school that chain wear happens within the chain itself, so sprocket condition has little, if any, effect. In my belief system, chains wear sprockets, but sprockets don't wear chains.

But as I said, there's debate on this. So consider the relative cost of chains and sprockets, and figure that extending sprocket life even at the expense of chain life is a decent trade off.

ThermionicScott 

Believe it or not, there's no damage to those chainrings. The ugly teeth with cutaway sides or the ones that are only half as tall as their neighbors were stamped that way at the factory to aid shifting.

Some wear can be seen here and there, but don't buy new rings until a new chain skips on them.

md11mx

I'm a firm believer in taking care of my chains by keeping them clean and lubed and writing off any required replacement of parts investments as money well spent for the enjoyment received wearing them out. Roughly speaking a chain cost about the same as one movie with your significant other. Cheap entertainment.
Cheers,
David in Alaska

vegasrealtor

That makes sense. It looks like I paid about double for my chain but certainly next time it looks like I could spend $10 and be ready to go.
Now I just need to get the parts to rebuild my front hub and I'm ready to finally ride this thing.
Thanks again everyone.