Broken teeth on chainring
04-23-09, 06:09 PM
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Broken teeth on chainring
First off, I apologize in advance for any incorrect terminology. I'm still learning.
1997 Trek 820 Mountain Track. Specs HERE
New to me for a few weeks now.
Third front gear (outer chainring) has 2 broken teeth, next to each other. They appear to be well worn, indicating that they have been broken for a while. There appear to be more worn teeth on the 2nd gear also.
When standing on the petals in 3rd gear, the chain would occasionally skip.
The rear cassette has a few shiny spots, but I don't know enough about the geometry of the teeth to know if they are supposed to be like that or not.
The chain is not worn out, per the 12" measurement test.
I am tight on money, and I can turn a wrench pretty well, so my questions are:
1. What all needs to be replaced? Cassette, chain, chainrings, complete crankset, etc.???
2. What special tools do I need?
3. Where and how much are the parts?
4. Should I find a good LBS to do it for me, and how much am I looking at there? (the Bicycles, Inc. by the house charged me $15 to tighten a loose hub, which I later found out was very expensive.)
Thanks in advance,
FIN
1997 Trek 820 Mountain Track. Specs HERE
New to me for a few weeks now.
Third front gear (outer chainring) has 2 broken teeth, next to each other. They appear to be well worn, indicating that they have been broken for a while. There appear to be more worn teeth on the 2nd gear also.
When standing on the petals in 3rd gear, the chain would occasionally skip.
The rear cassette has a few shiny spots, but I don't know enough about the geometry of the teeth to know if they are supposed to be like that or not.
The chain is not worn out, per the 12" measurement test.
I am tight on money, and I can turn a wrench pretty well, so my questions are:
1. What all needs to be replaced? Cassette, chain, chainrings, complete crankset, etc.???
2. What special tools do I need?
3. Where and how much are the parts?
4. Should I find a good LBS to do it for me, and how much am I looking at there? (the Bicycles, Inc. by the house charged me $15 to tighten a loose hub, which I later found out was very expensive.)
Thanks in advance,
FIN
04-23-09, 06:17 PM
#2
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First off, I apologize in advance for any incorrect terminology. I'm still learning.
1997 Trek 820 Mountain Track. Specs HERE
New to me for a few weeks now.
Third front gear (outer chainring) has 2 broken teeth, next to each other. They appear to be well worn, indicating that they have been broken for a while. There appear to be more worn teeth on the 2nd gear also.
When standing on the petals in 3rd gear, the chain would occasionally skip.
The rear cassette has a few shiny spots, but I don't know enough about the geometry of the teeth to know if they are supposed to be like that or not.
The chain is not worn out, per the 12" measurement test.
I am tight on money, and I can turn a wrench pretty well, so my questions are:
1. What all needs to be replaced? Cassette, chain, chainrings, complete crankset, etc.???
2. What special tools do I need?
Chain whip and correct size tool to remove the cassette. A chain break. A 5mm allen wrench to remove the chain rings.
3. Where and how much are the parts?
Your LBS can get the parts for you.
4. Should I find a good LBS to do it for me, and how much am I looking at there? (the Bicycles, Inc. by the house charged me $15 to tighten a loose hub, which I later found out was very expensive.)
Find another LBS and get an estimate BEFORE you give them the bike to repair.
Thanks in advance,
FIN
1997 Trek 820 Mountain Track. Specs HERE
New to me for a few weeks now.
Third front gear (outer chainring) has 2 broken teeth, next to each other. They appear to be well worn, indicating that they have been broken for a while. There appear to be more worn teeth on the 2nd gear also.
When standing on the petals in 3rd gear, the chain would occasionally skip.
The rear cassette has a few shiny spots, but I don't know enough about the geometry of the teeth to know if they are supposed to be like that or not.
The chain is not worn out, per the 12" measurement test.
I am tight on money, and I can turn a wrench pretty well, so my questions are:
1. What all needs to be replaced? Cassette, chain, chainrings, complete crankset, etc.???
2. What special tools do I need?
Chain whip and correct size tool to remove the cassette. A chain break. A 5mm allen wrench to remove the chain rings.
3. Where and how much are the parts?
Your LBS can get the parts for you.
4. Should I find a good LBS to do it for me, and how much am I looking at there? (the Bicycles, Inc. by the house charged me $15 to tighten a loose hub, which I later found out was very expensive.)
Find another LBS and get an estimate BEFORE you give them the bike to repair.
Thanks in advance,
FIN
Chain whip and correct size tool to remove the cassette. A chain break. A 5mm allen wrench to remove the chain rings.
Your LBS can get the parts for you.
Find another LBS and get an estimate BEFORE you give them the bike to repair.
04-23-09, 08:43 PM
#3
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I think what you're seeing is actually part of the design of the chainring. As part of their strategy toward smoother shifting, Shimano designed some of the teeth to be considerably shorter in key areas to aid chain deraillment and pick-up. Shimano has a marketing term for it, I can't recall what it's called right now. I had a friend who bought a new Cannondale MTB a while back and was sure he had a defective crankset when he first noticed the shorter teeth. It would be very difficult to have a couple broken teeth in a certain spot without some other noticeable damage. Bashing about on rocks might be about the only way. Likely there's nothing wrong with your chainrings at all. I agree they look odd, but it seems to work. Shimano's been doing it for years. Any chain slipping is more than likely an adjustment issue.
04-23-09, 08:44 PM
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Pwnerer
04-23-09, 08:59 PM
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But in any event, a picture would help to see if we're talking about the usual shaped teeth, or actual damage to the chainring
04-23-09, 11:51 PM
#6
Pwnerer
I screwed up and ran over a curb once, and it shaved off about 4 teeth off the large chainring. Oddly enough, there was little other damage to the bike that was visibly evident. My shoulder, that was a different story.
But in any event, a picture would help to see if we're talking about the usual shaped teeth, or actual damage to the chainring
But in any event, a picture would help to see if we're talking about the usual shaped teeth, or actual damage to the chainring
This question is asked about once a week.
04-24-09, 12:11 AM
#7
Bicycle Repair Man !!!
If you were to overhaul the drive train you could probably get by with $100.00 in new parts...there are decent mtb triples out there for $50.00 (it's cheaper than buying chain rings), cassette should be $30.00, and a nice chain about $15.00.
If a crank is especially nice then it is worth buying new chain rings although these will cost a fair bit more... the Raceface on my MTB ran $400.00 new and a new set of high performance rings would be well over 100.00 at retail.
If you are going to overhaul an older / worn drive train then it is best to replace all the worn parts.
If a crank is especially nice then it is worth buying new chain rings although these will cost a fair bit more... the Raceface on my MTB ran $400.00 new and a new set of high performance rings would be well over 100.00 at retail.
If you are going to overhaul an older / worn drive train then it is best to replace all the worn parts.
04-24-09, 03:48 AM
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Just to clarify, I said the middle ring's teeth were worn, not missing.
The outer chainring's worn teeth appear to be bigger than the middle, and I can't seem to find any on the inner ring.
If they're supposed to be like that, then I'm VERY happy.
I found a stiff link this morning, so I think that is what was causing the skipping.
Thanks for the advice,
FIN
The outer chainring's worn teeth appear to be bigger than the middle, and I can't seem to find any on the inner ring.
If they're supposed to be like that, then I'm VERY happy.
I found a stiff link this morning, so I think that is what was causing the skipping.
Thanks for the advice,
FIN
04-24-09, 03:53 AM
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If you are low on cash, Nashbar has a Shimano crank on sale for $9.99 with free shipping (today only).
I have used them and they are acceptable - well worth the money.
https://www.nashbar.com/bikes/Product..._200276_200374
I have used them and they are acceptable - well worth the money.
https://www.nashbar.com/bikes/Product..._200276_200374
04-24-09, 04:12 AM
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If you are low on cash, Nashbar has a Shimano crank on sale for $9.99 with free shipping (today only).
I have used them and they are acceptable - well worth the money.
https://www.nashbar.com/bikes/Product..._200276_200374
I have used them and they are acceptable - well worth the money.
https://www.nashbar.com/bikes/Product..._200276_200374
160mm cranks are short, but if the fit is close ok.
04-24-09, 07:58 AM
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Just to clarify, I said the middle ring's teeth were worn, not missing.
The outer chainring's worn teeth appear to be bigger than the middle, and I can't seem to find any on the inner ring.
If they're supposed to be like that, then I'm VERY happy.
I found a stiff link this morning, so I think that is what was causing the skipping.
Thanks for the advice,
FIN
The outer chainring's worn teeth appear to be bigger than the middle, and I can't seem to find any on the inner ring.
If they're supposed to be like that, then I'm VERY happy.
I found a stiff link this morning, so I think that is what was causing the skipping.
Thanks for the advice,
FIN
04-24-09, 08:49 AM
#12
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Thanks. I feel kinda stupid, but at least its not broken.FIN
04-24-09, 09:33 AM
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If you're getting skips, did you put the chainring on yourself? I recently had a similar problem and it turned out that I did not align the ring properly with the crank (was 90 degrees off) and that was all it needed to skip sometimes.
04-24-09, 11:25 AM
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If the chain is well worn (quantify, please), then you'll almost certainly need to change the cassette along with the chain. However, (and the reason I asked you to quantify) your best approach may be to not change either. Just ride the drivetrain until something breaks, or you save up enough to replace the parts that you know need it.
Meanwhile, strip the bike down to the bones and start to get acquainted. Clean everything. Rebuild the hubs and bottom bracket (essentially, replace worn bearings and re-pack). Check and re-tension/true the wheels. Replace brake pads. Soak the chain and cassette cogs (not the freehub). Re-wrap the handlebars. Then ride the heck out of it.
Meanwhile, strip the bike down to the bones and start to get acquainted. Clean everything. Rebuild the hubs and bottom bracket (essentially, replace worn bearings and re-pack). Check and re-tension/true the wheels. Replace brake pads. Soak the chain and cassette cogs (not the freehub). Re-wrap the handlebars. Then ride the heck out of it.
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