old's'cool

No pics at the moment, but trust me, nothing unusual to look at. [edit - so I thought. On investigation, the problem cogs are visibly hooked - see below for photos]
The freewheel appears to be in like new condition. I doubt it is a question of alignment or trim of the derailleur, I've inspected and tested these possibilities pretty thoroughly.
The issue is, when riding on either of the two smallest cogs, the chain skips intermittently, with frequency increasing with pedal force.
Here is the history:

• starting configuration 13-15-17-19-21 Suntour freewheel, Shimano Crane RD - no issues whatsoever
• Configuration 2 13-15-18-21-24 Suntour freewheel, Shimano Crane RD, skipping issue first appeared
• Configuration 3 13-15-18-21-24 Suntour freewheel, Shimano 600 Arabesque RD
• Configuration 4 13-15-18-21-24 Suntour Freewheel, Suntour Honor RD

The skipping issue is present in configurations 2, 3 & 4, possibly a little worse in configuration 3. The chain is a 5/6 speed chain and has been a constant in all configurations. The skipping occurs when on both the middle and large chainrings, and only occurs on the 13 and 15T sprockets. The 13-24 (skipping) freewheel is a Winner Pro. The 13-21 freewheel is marked NWN.
Next weekend I'll go back to the starting configuration just to verify the issue is isolated to the 13-24 freewheel.
Has anyone seen this before, where a freewheel with no visible defects causes a skipping issue?

SteveSGP

If it's a used freewheel that's where I'd look first.

auchencrow

Used freewheels get to "know" their chain and no other.
- even when there is no visual clue that a cog is worn.

The same is true of new FW's - They want to know a new chain, and will skip on an old one.

mazdaspeed

sounds like the cogs are worn, might want to check the chain for wear too.

repechage

As it's the smaller cogs, they are most suspect. That advised, chains stretch faster than cogs wear. Could be your chain has stretched and worn into the old freewheel. Keep those as a set at this point, and you might be shopping for a new freewheel and chain.

I had only one mechanical cause for dropping out of a race, fresh freewheel and old chain.

wrk101

Appears to be like new = used. I have rehabbed hundreds of bikes, and I have yet to have been able to visually tell the difference between a good FW and a worn out one, unless it is totally trashed. +1 They seem to get chain memory, when I need to keep an older FW, I make sure I save the chain (unless it is worn out of course). Just did that on a Helicomatic FW. Worked like a charm.

I have a handful of Suntour indexed FWs, unfortunately, I do not have the old chains. Every single one of them skips with a new chain.

look171

Get a new chain and problem solved.

old's'cool

Excellent points about the chain and freewheel wearing in together. That's a definite possibility with the starting configuration. Why didn't I think of that! When I get my hands dirty on the weekend I'll measure and check.
Thanks everyone!

old's'cool

You guys pointing to cog wear are right on. On close inspection, the 15T especially, and the 13T cogs are visibly hooked. Other than that, the freewheel looks pretty minty. It's a great relief, knowing a logical explanation for the problem. Short term fix, I'll go back to the non-skipping freewheel. Longer term, I'll see if I can mix & match some cogs to resurrect the 13-24 freewheel, as the range and ratios are more favourable overall. I knew I could count on BF C&V to help me figure this out.

pastorbobnlnh 

What version Suntour FW are you running? I have lots of cogs, many are new. Maybe we could just replace the couple of problematic cogs.

old's'cool

The freewheel is a Winner Pro. Here's some photos of one just like it: https://s1193.photobucket.com/albums/aa359/PulaoRey/Suntour%20Winner%205%20Speed%20Freewheel%20Smooth%2013%20thru%2024/?action=view¤t=IMG_3339.jpg&
The problem cogs are 13T & 15T. The rest look pretty fresh. Must have been ridden by a real masher!
I got curious and checked the chain just now, and it's about at the limit, 12-1/8" over 12 link-pairs. I would say the 15T cog is worse than the chain, I wouldn't have used it if I'd noticed how hooked it was before.
I'll add some relevant pics to this thread on the weekend; I do appreciate everyone's help!

auchencrow

old's cool - The cogs looking worn was a sure sign, but be advised that a FW cog does not have to look worn to BE worn. Sometimes it is indiscernible to the naked eye but the skipping problem will follow it with any bike you put it on.

Road Fan

But it should be worthwhile to replace the bad cogs, even though it's not guaranteed to be a solution.

2manybikes

If the amount of wear on the chain and the freewheel are not about the same, skipping would be typical.

Amesja

The little cogs tend to wear faster even if they are all used evenly. more force on fewer teeth and the chain is really bending around them I guess.

A worn cog will thrash a new chain in no time.

This pops up a lot on bicycle forums but even more often on motorcycle ones. When it comes to motorcycle chains we (people who know better) always replace chain & sprockets together. Sprockets are cheap and chains are really darn expensive. It's a poor economy to re-use old sprockets with a new chain. The wear is really hard to see or even measure but sure as heck it'll be pantographed into the new chain in short order. When you are spending upwards of $150-200 on chain not buying $40-50 worth of sprockets is dumb in the long run unless you are one of those folks who just ride down to the hangout and back once or twice a month and put <1000 miles a year on your bike.

At least with bike chains they are pretty cheap for the most part unless you go super-high end. I have yet to see a $200 bicycle chain though -not uncommon for a decent mid-level motorcycle chain.

Captain Blight

Yeah, hooked teeth and a stretchy chain are a surefire way to get skipping. DAMHIKT.

old's'cool

Thanks for all the advice; well noted. I went back to the original configuration for now. I'm also working on getting a 13-24 FW with good cogs, as that is my preferred setup, which allows favorable half-step gearing with 48 & 52T chainrings. The 13-21 is configured as single step with 46 & 52T chainrings. I could do half-step with a 49T chainring, but 49T 110BCD chainrings are hen's teeth. Niagara Cycle has the Surly stainless one for $60 shipped, but this is supposed to be my beater bike.
Anyway, in appreciation for all the tips, here are photos of the bits.



Suntour NWN 13-21 freewheel from original configuration.




Suntour Winner Pro 13-24 freewheel with hooked 13T & 15T sprockets




Shimano Crane RD from original configuration




Shimano 600 RD




Suntour Honor RD




Suntour Honor & 13-24 FW installed.

Amesja

Niagara is my one-stop shop for most of my stuff for project bikes and restorations when I have lots of time. They have great prices (but double-check Amazon Prime items as some things are even better there than through Niagara even without the shipping.)

Just don't expect for stuff to come quickly from them. It usually takes them a week to get an order together and shipped off. Not as bad as it used to be, but not quick. If I want it quick I go to the LB$ and pay retail for it and the privilege of getting it right away.

old's'cool

Yep, I'm never in a hurry. I have 4 bikes in service right now, and enough spare parts to deal with most situations.