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How to understand a Worn Freewheel or Cassette

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How to understand a Worn Freewheel or Cassette

Old 12-22-22, 03:08 PM
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ser_gio
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How to understand a Worn Freewheel or Cassette

Hello all,
I have a vintage MTB with Suntour groupset from 1992. I really like this bike but the chain skips at the 6th cog. I replaced the chain and still the same issue. This happens under heavy load. Given that the freewheel is 30+ years old, I am assuming that is the culprit. Now, I found the same freewheel on sale for $30. This is manufactured in late 1990. Do you think this is in good condition and has many more miles left? I am having difficulty understanding the wear condition. Any help would be appreciated. Please see the photos of the freewheel which I am considering buying.


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Old 12-22-22, 03:16 PM
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You can buy a brand new 7 speed freewheel for the price of that old one. If I could get it for $5 with free shipping I might buy it to try out. You can't assess how worn a freewheel is from a picture. You don't have to buy a Suntour freewheel for your bike
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Old 12-22-22, 03:23 PM
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Doesn't look particularly worn to me. When you refer to the 6th cog, do you mean the second smallest, which looks somewhat more worn than the rest? And when you indicate 'skips' do you mean that the chain jumps clear over this cog under high load, or the chain clatters away as if it is in-between gears?

Finally, 'replaced the chain'... did you replace your old chain with another old chain? Or did you replace the chain with a 11-speed chain a local shop carelessly shoved you out the door with?

Sorry to sound fussy, but I volunteer at a bike Co-op, and every statement made our clientele regarding their bikes has to be very carefully considered. For example, when someone says that they "broke their rim", without seeing it in person, it could mean:
  • Flat tire
  • Busted spokes
  • Dented rim
  • Bad hub (multiple reasons)
  • Bad freewheel/cassette
  • Etc.
BTW: Suntour 7-speed cog spacing is somewhat different than Shimano and all other brands. IIRC, the Sunour spacing between the smallest cogs is wider, and it gets narrower in the big cogs. Nevertheless, I've been able to make Shimano (and clone) freewheels and cassettes work very well with Suntour indexing, such as Suntour's excellent XC-Pro thumbies.
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Old 12-22-22, 03:28 PM
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ser_gio
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Originally Posted by alcjphil
You can buy a brand new 7 speed freewheel for the price of that old one. If I could get it for $5 with free shipping I might buy it to try out. You can't assess how worn a freewheel is from a picture. You don't have to buy a Suntour freewheel for your bike
Thank you for your feedback. I agree with you and I have another vintage bike with all changed-out parts. But this one has only original parts and I try not to start replacing.
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Old 12-22-22, 03:35 PM
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Originally Posted by Dave Mayer
Doesn't look particularly worn to me. When you refer to the 6th cog, do you mean the second smallest, which looks somewhat more worn than the rest? And when you indicate 'skips' do you mean that the chain jumps clear over this cog under high load, or the chain clatters away as if it is in-between gears?

Finally, 'replaced the chain'... did you replace your old chain with another old chain? Or did you replace the chain with a 11-speed chain a local shop carelessly shoved you out the door with?

Sorry to sound fussy, but I volunteer at a bike Co-op, and every statement made our clientele regarding their bikes has to be very carefully considered. For example, when someone says that they "broke their rim", without seeing it in person, it could mean:
  • Flat tire
  • Busted spokes
  • Dented rim
  • Bad hub (multiple reasons)
  • Bad freewheel/cassette
  • Etc.
BTW: Suntour 7-speed cog spacing is somewhat different than Shimano and all other brands. IIRC, the Sunour spacing between the smallest cogs is wider, and it gets narrower in the big cogs. Nevertheless, I've been able to make Shimano (and clone) freewheels and cassettes work very well with Suntour indexing, such as Suntour's excellent XC-Pro thumbies.
Thank you for detailed comments. This has 3 x 7 gearing. When I say 6th cog, I mean the second smallest one. I replaced the chain with KMC Z8.3 which was taken out of my other bike and had 0.4% elongation as per Park Tools chain gauge. Since the recommended discard-the-chain elongation is 0.75%, I used this chain. I can buy and use a brand-new chain if you think this is the culprit.

Chain skips in gear 20th under heavy load in high speed. Hard to describe, but it feels like it moves to the adjacent cog (5th one, or gear 19th). When I use the bike in Gear 19 or 21, I don't have any skipping regardless how hard I push the bike. This made me think that the 6th cog (which has been my favorite and used a lot) is to blame.
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Old 12-22-22, 03:37 PM
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Originally Posted by ser_gio
Hello all,
I have a vintage MTB with Suntour groupset from 1992. I really like this bike but the chain skips at the 6th cog. I replaced the chain and still the same issue. This happens under heavy load. Given that the freewheel is 30+ years old, I am assuming that is the culprit. Now, I found the same freewheel on sale for $30. This is manufactured in late 1990. Do you think this is in good condition and has many more miles left? I am having difficulty understanding the wear condition. Any help would be appreciated. Please see the photos of the freewheel which I am considering buying.
If you're wanting to keep it all original, it could be a job for Pastor Bob's freewheel Spa
Pastor Bob is a forum member here, And he fractures, fixes and fine tunes freewheels.
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Old 12-22-22, 06:05 PM
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Skips only in #6? It's been ridden by someone with one favorite gear. Very common. Now SunTour made lots of spare cogs and unscrewing them and screwing on a new wasn't hard (before 30 years of sitting there) but you had to have the new cogs. They are still around but not common and maybe not cheap.

Edit: To the new freewheel - as others said above, try it. Visuals tell you nothing unless it's way beyond worn.

SunTour is good stuff and I applaud trying to stay original and proper, but ... freewheels are consumables like sneakers for basketball players. If you gotta go out on that court and play, good sneakers are worth far more than trying to keep your favorite Nikes going. Shimano, SunRace and others make good freewheels that work. (And once its dirty, they all look the same.)

Now, an older chain might run fine over that #6 and will in time wear down its sisters to match. I have two newish freewheels with the same (my preferred) gearing. Better one had one worn cog that rode OK if I didn't push it and skipped every time I did on my best 7-speed. I took the other off my city bike, put it on the good one and ran the older city bike chain over the freewheel with the skipping cog. Runs like a dream. They both do.

Last edited by 79pmooney; 12-22-22 at 06:13 PM.
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Old 12-22-22, 06:44 PM
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Two points

1- the pictured freewheel is close to new condition as far as wear goes.

2- it's rare, but not unheard of, for wear to cause skipping on any of the larger freewheel sprockets. So, I'd do dome more diagnostics before replacing the freewheel.
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Old 12-22-22, 11:48 PM
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As the years have gone by after the non SR SunTour ended I find it less and less worthwhile to invest much in an indexed SunTour system. The cog to cog spacing and lever cable pull amounts were different across the range of travel. I was told that it was based on cable tension goals. Whatever it clearly lost in the real world market place.

This from someone who first had SunTour on his first sew upped bike, a 1972 Fuji Finest. Ran BarCons and then ST's indexed ones till mid 1990s. I have disliked the Shimano 500 lb. gorilla for years. But at some point one must get with the future if they want to continue to wear out parts by using them. That and the preference to not bend axles on FW hubs that handle 7 cogs. Andy
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Old 12-23-22, 07:53 AM
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Spot on Andrew R. Stewart! Suntour is/was a somewhat sad case: perhaps David and Goliath with Goliath winning. Time to move on at this point.
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Old 12-23-22, 08:15 AM
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Originally Posted by alcjphil
You can buy a brand new 7 speed freewheel for the price of that old one. If I could get it for $5 with free shipping I might buy it to try out. You can't assess how worn a freewheel is from a picture. You don't have to buy a Suntour freewheel for your bike
Depends on friction or index
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Old 12-23-22, 01:11 PM
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Check your derailleur alignment before you start replacing parts.
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Old 12-23-22, 01:36 PM
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Shimano MF-TZ30Tourney Freewheel (14-34T 6 Speed)

Three of this particular Freewheel I have used emitted a Cluck/Click after moderate wear. All the teeth looked like they were still usable but the Cluck would intermittently start in the 3rd gear. Man I had more than a bugger of a time chasing those dam Clucks checking everything and then I switched out a wheel set that had a different Freewheel and the Cluck disappeared. I have not figured out why this happens but these Freewheels are very economical so I just replace them when they Cluck...


Image From:https://www.redringtones.com/chicken-clucking/
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Old 12-25-22, 01:29 PM
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Originally Posted by zandoval

Shimano MF-TZ30Tourney Freewheel (14-34T 6 Speed)

Three of this particular Freewheel I have used emitted a Cluck/Click after moderate wear. All the teeth looked like they were still usable but the Cluck would intermittently start in the 3rd gear.
I have a theory, one of the more knowledgeable members here can verify or shoot it down (probably both!)
Wear on a cog doesn't start with the teeth, but the transition between the teeth. the teeth will look fine but when the chain pulls further into the transition it wears the chain into that cog wearing the roller pivot in the chain, then the wear on the cog teeth begins. The chain skips in other gears before the teeth wear is evident because the chain and that one cog are mated. Worn in. if the gears had been changed more and the wear spread across the cogs more, there might not be a problem now.
So I'm saying the cog wears first in the transition and that wears the chain next.
Anyway, my theory.

Last edited by Schweinhund; 12-25-22 at 01:33 PM.
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Old 12-27-22, 08:47 AM
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I'd replace it with the all-chromed Sunrace 7-speed. (Under $25 shipped.) The all-chromed models are their best quality product. The cogs are ramped, so shifting will improve.

https://www.ebay.com/itm/17524944499...Bk9SR_D92sCqYQ
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Old 12-27-22, 10:01 AM
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Thank you for the advice. This looks great. I am also a fan of chrome-color parts
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Old 12-27-22, 07:08 PM
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Originally Posted by SurferRosa
I'd replace it with the all-chromed Sunrace 7-speed. (Under $25 shipped.) The all-chromed models are their best quality product. The cogs are ramped, so shifting will improve.

https://www.ebay.com/itm/175249444991?
Not attacking or anything, sunrace freewheels appear to be pretty decent stuff.
You're aware that zinc isn't chrome, right? it's more of a rust preventative than anything else.
Plus it's shiny
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