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Chain comming off chain ring under load / power (pictures)

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Chain comming off chain ring under load / power (pictures)

Old 06-01-17, 01:54 PM
  #1  
LukeD1uk
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Chain comming off chain ring under load / power (pictures)

So I have had this issues for the last few rides and mainly on my last right which was a 3hour 85k ride. I couldn't figure out what was going on so I spent a few hours lasting night cleaning everything and re indexing all my gears to see if that was the issue was and I found it.

When cycling along as soon as I am putting out some sudden power (our the saddle, pulling away from a stop, sprinitng) the chain will pop off the big chain ring and back on again. This even happens a little bit when cycling along fast and hitting a bump in the road.

It happens so fast it comes off and on again almost instantly. I think its either the chain itself or the chain ring is really worn down. but I don't know if the chain ring teeth are worn enough to cause this (picture below) or if its the chain.

The bike is a Schwinn 754 from around 1990, It was a friends and I don't know how old any of the components are.


Could you guys please take a look at the pictures and let me know what you think of the condition of the chain ring please?


Chain Ring 1 (top)
i.imgur.com/hsSNiXp.jpg

Chain Ride 2 (bottom)
i.imgur.com/i5EbAPy.jpg

The Bike:
i.imgur.com/S6nHWlT.jpg



Thanks
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Old 06-01-17, 01:59 PM
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Pic assist


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Old 06-01-17, 03:11 PM
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From the way the chain is engaging the teeth of the ring it looks pretty worn, best bet would be to measure the chain. The chain dropping off a chainring is usually a sign that the chain ring is badly worn I suspect your up for a new cassette,chain and chainring
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Old 06-01-17, 03:21 PM
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Originally Posted by headasunder View Post
...... new cassette,chain and chainring(s)
agree 100%; maybe less expensive to replace the crankset than just the chainrings.
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Old 06-01-17, 03:22 PM
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That chain is badly worn. Get new one. You will also need a new cassette.

If you're interested, here's the explanation. The pins and rollers on a bike chain wear out. The pins get smaller on the outside, and the rollers get bigger on the inside and smaller on the outside. The net effect is the chain gets longer. You can see that in your photos where your chain links are not lining up with the cog teeth.

The elongated chain then rides on the sides of the teeth of the cogs, causing the u-shaped valley between teeth to get longer. This happens to the rear cogs faster because they're smaller. When you install a new chain on a worn out cassette, it will skip.

Generally, if you replace chains at the first sign of elongation, usually after 1500-3000 miles, depending on your riding style and chain hygiene habits, you can get a cassette to last about 2-4 chains, and the front cogs will last several tens of thousands of miles. But this chain is long past due.

Your chainrings still look OK.
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Old 06-01-17, 03:46 PM
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That is a nasty looking brake track on your rear wheel.
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Old 06-01-17, 05:54 PM
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Thanks for the Pic assist @corrado33 and for your detailed information @oldbobcat.

Its pretty much what I thought, I guess I will look to get a new chain and Big Chain Ring, the Rear cassette looks good to me, maybe I should post a pic. This bike is from 1989 and I dont know if the Chain, Cassette or Rings have ever been changed. I ride pretty hard and far so I will get this fixed.

Thanks all
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Old 06-01-17, 06:01 PM
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Don't be too surprised if the new chain starts to skip on the old cassette. I'd go ahead and take stock of your current one and order a replacement in advance. No offense to Nigel, but it kind of strikes me as wasteful to throw away the whole crankset if one ring is worn, even if that is cheaper than getting a replacement ring.
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Old 06-02-17, 09:32 PM
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Thanks for the information.

Would taking out 1 chain link help? I'm thinking it might just tighten it all up a bit and keep it on the ring a bit better?

I have a race (on a friend bike) in 1 week and I need to train on my bike. Parts will take time to arrive specially seeing as it's such old components.
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Old 06-02-17, 09:48 PM
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Originally Posted by LukeD1uk View Post
Would taking out 1 chain link help? I'm thinking it might just tighten it all up a bit and keep it on the ring a bit better?
no.
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Old 06-02-17, 10:01 PM
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BUT THAT CHAIN THO

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Old 06-02-17, 10:06 PM
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From the top and bottom images, it seems that the chain's pitch is too long for the sprocket, causing the phase shift and poor engagement. That can cause the chain to climb up onto the tips of the teeth, then drop back when the phase is matched again.

This is classic when the chain is "stretched" and can be confirmed with a 12" ruler.

So far I agree with some of the others that a chain measurement is called for, likely resulting in a chain replacement.

However, I don't believe your chainring is showing much wear, so I'd hold off for the moment. OTOH - I'll bet two beers to one that a new chain will skip on your cassette, so it'll be a new chain and cassette for now, and possibly, but not necessarily a new chainring.
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Old 06-02-17, 10:32 PM
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Old 06-03-17, 12:24 AM
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Originally Posted by LukeD1uk View Post
Thanks for the Pic assist @corrado33 and for your detailed information @oldbobcat.

Its pretty much what I thought, I guess I will look to get a new chain and Big Chain Ring, the Rear cassette looks good to me, maybe I should post a pic. This bike is from 1989 and I dont know if the Chain, Cassette or Rings have ever been changed. I ride pretty hard and far so I will get this fixed.

Thanks all
I will suggest looking over the pulley wheels as well. Often they are in bad shape on older bikes. They are not that expensive if need be. You may experience chain-skipping pairing a new chain with an older cassette.
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Old 06-03-17, 10:06 AM
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@FBinNY

can I buy any chain? from say Canadain Tire?

canadiantire.ca/en/pdp/supercycle-bike-chain-1-2-x-3-32-in-0737435p.html#srp

Says its for:
"Most derailleur bikes, Dimensions: 1/2 x 3/32"
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Old 06-03-17, 12:47 PM
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The chain has to match the number of speeds on the cassette, is 8s chain for 8s cassette, 9s for 9s etc,

There's some latitude, so you'll sometimes see chains marked for 7s or 8s, which would be OK for either.
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Old 06-03-17, 06:30 PM
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Originally Posted by FBinNY View Post
The chain has to match the number of speeds on the cassette, is 8s chain for 8s cassette, 9s for 9s etc,

There's some latitude, so you'll sometimes see chains marked for 7s or 8s, which would be OK for either.

I'm not sure what you means 7s, 8s, 9s... You mean how many rings are on the rear cassette?
Sorry, never changed a chain before. Ill go watch a GCN video

Add:
Ohhh you mean 7 speed, 8 speed, 9 speed. So I need a thinner chain depending on the amount of gears on the cassette. Got it

Add 2:
My cassette has 7 gears.

Last edited by LukeD1uk; 06-03-17 at 06:48 PM.
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Old 06-03-17, 08:12 PM
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Chain rings look OK. You have a little bit of wear on the big one but it will work fine, once you put on a new chain.

You need a chain and cassette. Although I haven't seen the cassette, the condition of the chain tells me the cassette is badly worn.
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