Bad Lag

I installed a brand new IZUMI chain yesterday. On today's ride, the chain was skipping over the teeth on the freewheel any time I applied power to the pedals (starting, uphills).

I was unable to discriminate whether it was a particular place on the chain (bad/tight links) or whether it was something else such as insufficient chain wrap. I have never before had this problem with any chain.

Any idea on how to diagnose/fix the problem?

I shortened the chain by about 4 links during installation. My first step is to replace those links.

During cleaning, I noticed no excessive wear on the freewheel cogs.

alcjphil

The problem isn't the new chain. It is a worn out freewheel

oneclick 

I think your value for "excessive" needs re-calibrating.
When the valley is worn 10% wider it's time to replace (or reverse) the sprockets.

SpedFast

Time for new freewheel. See this as an opportunity to change gearing?

redshift1

I've experienced the skipping of a new chain on used sprockets at least a couple of times and as the above posters have said, it's almost certainly caused by worn sprockets. Perhaps you are eye-balling the sprockets to try to see hooked teeth ? You might find this is too crude a method, even with the symmetrical teeth of older style freewheels.

I have been using Shimano hyperglide cassettes lately so eye-balling the sprockets to "see wear'" is pretty much out of the question ( very asymmetric teeth ).

I had the tool below sitting unused in my tool box for a few years until one day I decided to confirm my sprockets were worn and were causing my new chain to skip. Once I learned how to use this tool ( there is a definite technique to be followed, and it's not necessarily intuitive ), I realised how much I had been missing. It's very good.

https://www.amazon.com/Rohloff-HG-Sp.../dp/B00BGDPPIM

P!N20

Too much power

SurferRosa

Bad Lag

I agree, this is most likely the cause. ;-)

I made the adjustments I mentioned above - added links back in and moved wheel farther back in the drop out.

I had the opportunity to look at the freewheel again. It looks just this side of new - both sides of all teeth are square.

So, if that didn't fix it, is it truly viable to just flip the cogs over? I have to tools to do so. Does that really help?

I also have several replacement freewheels but do not want to retire this one prematurely or unnecessarily.

P.S. -
This is an old-style, 5 speed freewheel with symmetric teeth. There is no profile of any type other than flat on both faces.
It is set up as 14-16-18-21-24 with the usual 42-52 up front. As I am always spinning out on the 52X18, I was thinking of going to an old Regina I have which is 13-15-17-19-21. If increasing chain wrap and flipping cogs does not fix this, perhaps it IS time for a new freewheel. It's just that the 42-24 is my bail out gear and sooner or later I'd probably miss it.

P.P.S. - Thanks for the help.

MrGastrognome

Having had this issue not long ago on a bike with a new chain and new cassette (friction shifted but not a freewheel), the cause of my woes ended up being worn out jockey wheels. Too much lateral play made holding a gear impossible and was worse when more torque was applied.
Good luck with the diagnosis!

Bad Lag

Oh, now THAT is a real possibility. These are sealed bearing wheels but they are plastic and old.

Bad Lag scrambles off to order some replacement wheels.

Kontact 

You should be able to tell, and even observe, if the chain is skipping left and right to other cogs, or slipping straight forward because the cog is worn.

Which I would scramble off to check before ordering more stuff.

oneclick 

It's not wear at the sides of the teeth that matters, it's wear of the edge of the tooth where the chain bears.

Freewheel sprockets can sometimes be reversed.
Any screwed on sprockets of course cannot, and larger ones can have shaping to the sides of the teeth to help shifting - reversing them changes help to hurt.
You could - to satisfy your self that a new unit is indeed the answer - flip as many as you can, and see if they skip.

Kabuki12

I only had this happen once . It turned out that the chain was a 10 speed chain which was too narrow for my 6 speed FW. The bike shifted fine on the stand but when I took it out for a ride it skipped when I tried downshifting for a hill.

repechage

Measure the length of the old chain over 12” and observe the stretch.
even way back this was a known thing, an old chain with continued use can spoil a freewheel.

dddd

The problematic cog tooth wear can be up nearer to the tips from using a heavily-stretched chain, or can be at/near the base of the teeth (after perhaps having replaced the chain on schedule a few times), which is more common on well-maintained bikes.

In the latter case, at some point the wear against the driven side of the teeth leaves the un-worn corner up at the tip of the driven side of the tooth protruding in the "reverse" direction, and which then tends to interfere with the chain rollers falling between the teeth (especially under higher levels of chain tension). The result is a failure of the roller to engage between the teeth whereby the next several rollers all fail to engage between the teeth until the chain momentarily advances (skips violently) for an instant until engagement of the rollers between the teeth resumes.

The good news is that this is usually fixable, allowing at least one more chain's service life to be gotten from the old, often precious or rare freewheel or cassette.

Trimming away any reverse-protruding sharp corners is all that it takes, and which can be done without even removing the wheel from the bike.
I use a roughly 3/8" diameter grinding stone in a Dremel for this purpose, usually having to only address the teeth on one or two of the cogs which are troublesome.
I start with a larger diameter wheel/stone that has been used for a while and thus worn down below 1/2" diameter. Part numbers 8215 (gray) and 85422 (green) both work well for this and many other uses, and are easily found online.

I don't worry about the grinding dust getting on my chain since I am saving so much time and money versus sourcing and installing any new cogs or complete cassettes/freewheels. I can fix a typical 13-17t cog on the bike in 2-3 minutes, and have done this many dozens of times now. It doesn't always work or work on the first try because I start with the removal of perhaps just a 1mm bevel or because the cog teeth are too heavily worn to be fixed using my procedure.

Taking off too much metal will ruin a cog. The cut bevel surface should be near 45-degrees, actually a little closer to a radial line is better (so 35-40-degrees).

Repeating for clarity, since a worn cog allows the chain to run in a more-advanced position on the cog, the original location of the driven side corner up at the tip of each tooth becomes too ********-ed (my spelling dodging this site's idiotic censor here, why don't they also ban "idiotic" I don't know) such that the rollers (especially under higher chain tension) will make forceful contact there, preventing roller engagement between the teeth. Each subsequent roller then rides further away from the valleys between teeth as the chain now follows a much bigger radius than at the base of the teeth. Gross slippage follows as the disengaged chain rollers rotate up toward the most heavily-loaded teeth up near the 12-O'clock position where the rollers normally disengage the cog under maximum chain tension.
A used chain usually can/does work fine on such worn cogs because it's greater pitch between rollers still offers clearance at the protruding sharp tips of the teeth, allowing the rollers to drop in between adjacent teeth.

repechage

I had one DNF race in 1975.
chain was about two months old, “new” stainless steel one from Japan, I forget the brand.
as I was riding up a category, new 14-18 freewheel.
one short steep hill.
the skipping was so bad I had to drop out.

worked fine just riding along but not under power.

Bad Lag

I understand and thanks for the help.

We are just mis-communicating. What I called the "side" is what you are calling the "edge of the tooth". I called it the side because I was viewing the freewheel face-on to the cogs (viewed parallel to the axle).

Each tooth has a sharp corner fore and aft. Wouldn't a picture be worth a thousand words here?

I will get a chance to test the changes I made during today's ride.

Bad Lag

Could it be the derailleur?

I have a Nuovo Record derailleur. The spring is still strong but could slop (wear) in the top pivot cause chain slippage?

Bad Lag

Is there a "spec" for too much chain stretch? I have all sorts of measurement tools and related gizmos. For instance, I could measure the chain length under compression and tension.

repechage

the old way before Park devised a tool was 3/32” over what should be 12” was way too much.
there was no real definition of limp or stretched but obviously straight.

side by side comparison of new to old usually answers the question without tools

Bad Lag

So, 24 links should be nominally 12" center to center and 12.09" is way too much. I can also use a new chain as a reference point (I have an unused SRAM).

Thank you.

Bianchi84

In my experience, chains wear out with freewheels when together for a long time. I'd just change to new freewheel that's appropriate to chain and drive train.

Bad Lag

I may just clean the old chain, relube it, measure it and reinstall it first, just to see if it works.

Yep, exactly that - a new freewheel will be installed later today.

This has never happened to me before. Because I want to learn more about this, I'm still going to make some measurements (comparative anatomy, as it were) and take some pictures for posting.

I may remove the cogs from the body, too, for closer inspection, flipping over and possible replacement.

It's a hobby, right, and you've given me lots of great ideas.

bboy314

My method of troubleshooting this situation is to install a new (or known unworn) freewheel and see if it still skips. My guess is your freewheel is worn - it can be pretty hard to tell from a visual inspection.

plonz 

I’ve also had a more “duh” cause of this issue when changing link count. Check to be sure one of the links is not binding from putting the pin back in. I’m the proverbial bull-in-a-china-shop with a chain tool so have gone almost exclusively to quick link set ups.