# Chain slipping issue



## Ernbar (Feb 28, 2020)

I recently replaced the worn chain in my 1974 Le Tour 10 speed. I went to my LBS and they sold me an SRAM PC830 8 speed chain. I asked about this chain being for 6,7, and 8 speed but they told me it works on the cassettes with 5 sprockets too. I installed the chain and all gears work fine except the smallest one on the cassette that slips under load. I looked at the teeth shape and they all look the same, squared at the top and I can't see any uneven wear. I usually don't ride in that particular gear but the next higher one. It wasn't doing this with the older worn chain and wonder if the chain they sold me is the correct one. TIA for your comments.


----------



## GTs58 (Feb 28, 2020)

That's a 1/2 x 3/32" chain and should work just fine. Sounds like a rear derailleur adjustment is needed.


----------



## rustjunkie (Feb 28, 2020)

chain & cogs wear together and the smallest cog wears the fastest.


----------



## Rambler (Feb 28, 2020)

I worked in a bicycle shop for many years and this is a common problem. The chain and sprockets wear together meshing as a set. Even though it may look OK to the eye, trust me, it's worn to match the chain you removed. On popular higher quality gear clusters you could often purchase individual sprocket. Replace the small gear sprocket with a new one and your problem will be solved. Typically it's only the smallest and sometimes the next smallest sprocket that you will experience this issue with because they have the fewest number of teeth so tend to wear the fastest. The larger sprockets have more teeth in contact with the chain so under load are less likely to slip even if they are worn some. You will need to replace the sprocket or put the old chain back on to eliminate this problem.

There are only a couple other things that can cause a slip or skip as you describe. (1) the chain link is stiff where the chain was joined together so that joint does not flex properly. Each time that stiff link encounters the small sprocket it slips. This can be solved by forcefully flexing the chain side to side to loosen that link. or (2) the derailleur limit screw is not properly adjusted so the chain is either being forced off the sprocket, chain is not riding properly on the sprocket. (3) Lastly alignment between the front crank and rear wheel sprockets is off so much it is not allowing the chain to ride properly on the sprockets possibly due frame alignment but I am ruling this possibility out because your bike worked properly before the chain replacement.

All this being said, I'm still convinced it's the combination of the new chain and old worn sprocket that is your issue.


----------



## GTs58 (Feb 28, 2020)

I really doubt the cog is worn on this beauty. Check the rear wheel alignment, the derailleur alignment and the derailleur adjustment. You have a bike stand?


----------



## Ernbar (Feb 28, 2020)

GTs58 said:


> I really doubt the cog is worn on this beauty. Check the rear wheel alignment, the derailleur alignment and the derailleur adjustment. You have a bike stand?
> 
> View attachment 1147699


----------



## Ernbar (Feb 28, 2020)

Hey thanks for all the comments. Yep that’s my bike Gt and yes I have a stand . I will check things out tomorrow.
One thing that I was looking at was that to my eye, I see a slight cant to the left on the derailleur. I took a picture now and is more visible in person and in daylight.


----------



## Ernbar (Feb 28, 2020)

If in fact the small cog is worn, can I just replace it instead of the entire cassette. I forgot to mention the rear small cog slips while using both large and smaller chainrings up front.


----------



## GTs58 (Feb 28, 2020)

When you say slips, you mean jumping off to the side of the cog? If that's what's happening it's not worn teeth on the 'freewheel', it's the derailleur.
I don't think Schwinn used cassettes during that time.

Do you have a straight on shot of the freewheel? You said the teeth are square at the top but in that picture it doesn't depict that.


----------



## Ernbar (Feb 29, 2020)

GTs58 said:


> When you say slips, you mean jumping off to the side of the cog? If that's what's happening it's not worn teeth on the 'freewheel', it's the derailleur.
> I don't think Schwinn used cassettes during that time.
> 
> Do you have a straight on shot of the freewheel? You said the teeth are square at the top but in that picture it doesn't depict that.




Sorry Gt it's the freewheel. I keep learning stuff from you guys so thanks a bunch for the replies.  The chain stays on the small cog but you can feel a jolt, slip or skip under heavy load. 
I used my calipers to measure the teeth on the small cog and they are pretty consistent in size. Everything looks to be straight and in line so I guess the small cog has worn out as previously mentioned.


----------



## SKPC (Feb 29, 2020)

Hmmmm…...sounds frustrating.  Please take a picture of the cassette up close with the wheel off the bike so we can see the small cog. I am not convinced this is what it is.    What you describe has good answers from everyone but the chain and cog _may _be the wrong players causing your slipping.   Perhaps your freewheel ratchet is dirty or stuck. This will cause the slipping then catching inside the freewheel.  The problem with this is that the other gears do not slip.  More carefully check the alignments of the derailleur hanger, the derailleur cage and make sure it all is squared up front to back and not twisted left or right..  Also fiddle with the "B" screw adjustment on the derailleur if there is one. And lastly, loosen the "*H*igh" gear stop screw to allow the derailleur to move a tad more outboard...it looks pressed into the next cog in your pics which may cause it to jump towards the next bigger cog when applying pedaling force....


----------



## Ernbar (Feb 29, 2020)

Thanks SKPC. I will do that in the morning.


----------



## Rambler (Mar 1, 2020)

@Ernbar after viewing your chain alignment photo above and reading your description above "_I forgot to mention the rear small cog slips while using both large and smaller chainrings up front_" I am even more convinced that your problem is the new chain running on a worn sprocket, not chain alignment. Especially since this issue of chain slip/skip under load only began after replacing the chain. The slight amount your derailleur is pushed to the left is not enough to cause issues with chain alignment to the point of chain slip/skip. The worst that might happen with derailleur  bent to the left might be shifting issues and if bent significantly enough I have seen the derailleur get caught in the rear wheel spokes when derailleur is shifted to the further left position but your's does not look that bad yet. It would be a good idea to straighten and properly adjust the your derailleur but it's not causing your chain slip/skip issue. If I or @rustjunkie have not convinced you that your chain slip/skip is due to meshing of the new chain and worn sprocket maybe you will consider the opinion of _Sheldon Brown_ the often quoted expert in all things bicycle related. Below quote is directly from his website:

https://www.sheldonbrown.com/chain-wear.html

*Worn chain, worn sprocket*

Next let's consider how a chain and sprocket wear together.






The illustration above shows two formerly identical sprockets of a modern, indexed derailer system, viewed from the right side. These sprockets have short teeth so the chain doesn't have to climb very high to disengage for a shift to a smaller sprocket.

As the chain and sprocket wear together, the teeth become sloped at the back, and the rollers ride up on them until the teeth approach a radius that corresponds to the longer pitch of the worn chain. The effective radius (and thus, the effective pitch) of the sprocket has become larger, because the chain is riding higher.

There is excess wear on the rollers. They must roll more and press harder because the surface against which they press is not as nearly at a right angle to the direction of tension on the chain. The downward force from the chain at the top of the sprocket is greater and extends farther back around the sprocket with sloped teeth. Further yet around the back of the sprocket, more teeth must push upward to compensate for this downward force. The sprocket also will wear at the height on the teeth which is taking the load. In extreme cases, the chain may lift entirely off the sprocket and skip forward.

A new chain on a worn sprocket with sloped teeth will sit nearer the bottom of the gaps between teeth at the top of the sprocket but will be tensioned farther back and also may slip up off the teeth and jump forward unless the chain's return run is held under significant tension.


----------



## Ernbar (Mar 1, 2020)

I spoke to the mechanic at my LBS and he told me the 47 year old freewheel is the culprit since we don’t know the service history. He can replace the freewheel and adjust things for $30 to  $40. He said the rule of thumb is to replace the freewheel when the chain is replaced specially being that old. He also said the same thing Rambler mentioned about the old chain and freewheel meshing together as a matched set and not letting the chain properly sit on certain spots specially the smaller cog that wears out faster than the others.  I forgot to mention the old chain wore down to 1.0 according to my wear indicator tool.
I will post results after repairs. Thanks for all your replies.


----------



## hopkintonbike (Mar 1, 2020)

I would check the master link on the chain first, if its not skipping on the larger gears its just because the diameter that the chain has to wrap around is larger, I bet you will find that the master is really tight.


----------



## Ernbar (Mar 1, 2020)

hopkintonbike said:


> I would check the master link on the chain first, if its not skipping on the larger gears its just because the diameter that the chain has to wrap around is larger, I bet you will find that the master is really tight.




The link rotates fine..


----------



## hopkintonbike (Mar 1, 2020)

Then you have a worn gear and as others have stated, straightening out the cage can't hurt


----------



## GTs58 (Mar 1, 2020)

Here's a pic of a Schwinn Passage that's for sale on eBay. Seller says the bike shifts perfectly with out a flaw and everything has been serviced and in excellent working condition. BUT, I see a little problem here. Looks like some of the teeth on the small sprocket and others have rounded off corners, and what's up with that chain?!!   lol  Is his pivot bolt locked up tight?


----------



## Ernbar (Mar 2, 2020)

Something’s  going on  possibly the chain came off the derailleur’s top wheel and jamming it causing the slack?


----------



## Autocycleplane (Mar 2, 2020)

All of the standard advice given here is good stuff, your small cog on the freewheel may in fact be too far worn for a new chain.

But... Given what you describe - only the smallest cog slips in either ring - I would also look at the rear derailleur one more time before throwing cash at the problem. You put a new SRAM chain on the bike that I am gonna guess is more narrow than the one you pulled off. The more narrow the chain the more particular the upper and lower limit screw adjustments need to be on the rear derailleur, as well as it's overall alignment in relationship to the cogs. Regardless of whether you swap the freewheel this likely needs addressing anyway, so I would start there first and see if you can get the small cog back.


----------



## Mr. Monkeyarms (Mar 2, 2020)

After all of these great suggestions that I was thinking all of the same things, I went back to post #7 to look again. The pic and your description lead me back to my original thought. The derailleur and hangar could probably use some fine tuning. Both pulleys should be in line with the gear. Your bottom pulley looks inward a touch. Had my road bike get knocked over on the drive side a number of years ago that tweaked it just a bit so the smallest cog spit and sputtered. A couple minutes with the proper size, tight fitting hex wrench and limit screw tuning had it running smooth as butter.


----------



## Ernbar (Mar 5, 2020)

Long story short, none of the bike shops in my area have the Park Tool FR4  part to remove the Style J  freewheel I have so i ordered one online and will be doing this myself. Prior to ordering I contacted Park Tools and spoke with Calvin who verified the FR4 is what I need.


----------



## Ernbar (Mar 9, 2020)

Rambler, you sir are 120% correct. I finally got my Park Tools FR4 remover and removed the freewheel and replaced it with a new Shimano one, problem solved! No more slipping or skipping. The problem was as Rambler said a worn small cog. Thanks for ALL of your suggestions and comments, you are a great bunch of cool dudes.


----------



## Sven (Mar 11, 2020)

Ernbar said:


> Long story short, none of the bike shops in my area have the Park Tool FR4  part to remove the Style J  freewheel I have so i ordered one online and will be doing this myself. Prior to ordering I contacted Park Tools and spoke with Calvin who verified the FR4 is what I need.



What kind of bike shop doesn't have one of the most common freewheel removal tools?


----------



## Ernbar (Mar 11, 2020)

Unfortunately nowadays it’s hard to find places that work on older bicycles and cars. Back in the mid 90s  I had a 55 Chevy 210 and none of the multiple repair shops I went to asking knew how to rebuild a simple 2 barrel Rochester carb. I learned how to do it my self.


----------



## Two Wheeler (Mar 28, 2020)

rustjunkie said:


> chain & cogs wear together and the smallest cog wears the fastest.





Ernbar said:


> I recently replaced the worn chain in my 1974 Le Tour 10 speed. I went to my LBS and they sold me an SRAM PC830 8 speed chain. I asked about this chain being for 6,7, and 8 speed but they told me it works on the cassettes with 5 sprockets too. I installed the chain and all gears work fine except the smallest one on the cassette that slips under load. I looked at the teeth shape and they all look the same, squared at the top and I can't see any uneven wear. I usually don't ride in that particular gear but the next higher one. It wasn't doing this with the older worn chain and wonder if the chain they sold me is the correct one. TIA for your comments.





 I too had the same problem on my 74 Le Tour. I replaced the chain and had the same problem. I then replaced the cluster and the problem went away.


----------



## Sven (Mar 28, 2020)

Dan Shabel said:


> I too had the same problem on my 74 Le Tour. I replaced the chain and had the same problem. I then replaced the cluster and the problem went away.
> 
> View attachment 1163153
> 
> ...



That is one super clean machine..wow!!!


----------



## Two Wheeler (Mar 28, 2020)

Sven said:


> That is one super clean machine..wow!!!




Thanks, it was a one owner that spent most of its life in a spare bedroom. It now has its original stem, NOS handle bar wrap and a correct seat. I put about 2,500 miles on it before retiring it and buying a new road bike. It now sees about one ride a year with the Gateway Coasters.


----------



## Ernbar (Mar 29, 2020)

Too bad you retired it. That bike can ride for ever and it looks brand new. I rotate my daily rides mostly between my 74  Le Tour, my 73 Continental or my new 700C hybrid. My other older Schwinns get a turn too.


----------

