Roger M

Before I post over on the Mechanical forum..

I just finished building up this bike. During the shakedown ride, I noticed the chain not settling in to the teeth during shifting. It only slides in completely when it wraps all the way around to 6 o'clock on the ring.

EDIT: The chain is a new KMC X8 8 speed (less than 30 miles now). The dirt/grease is from the 7 speed cassette that I didn't bother to clean.

It does the same on big and small rings. Are the rings not installed correctly(in sync)? Other suggestions?

Any help is appreciated.

noobinsf 

Have you checked the chain for wear?

niliraga 

I also get this briefly, with the middle ring of a triple on one bike. using 80s era chainrings (in good shape) with a modern - and new - 7/8 speed chain. once settled in everything is totally fine, just not sure why the surfing happens - keen to learn from your thread here.

base2 

I vote for chain wear. In your description the chain is the common denominator. Plus you can see in the photograph that it is old, a bit gritty KMC x8 speed & also the links don't line up on the teeth the same from link 1 to the last.

You are attempting to use/reuse an old chain that is too worn to be servicable.

Are your rings a matched set? The clocking of some sets of some rings is different from other sets of rings. This is done so that as the chain lifts off one ring the teeth in the other ring are in an appropriate place to have the chain settle in nicely. You didn't change rings did you?

Modern rings have ramps/pins/cutouts to allow chains to settle in better. Your rings appear to be flat. Not that it should matter much here.

Roger M

The chain is new(less than 30 miles).

I will edit the post. Thanks for pointing that out.

79pmooney

How old are the chainrings? Tooth wear can be very hard to judge but new chains will not run well on worn rings and cogs. Also, are these old 5-6 speed chainrings? They may need to be 7-8 speed rings to be narrow enough for the chain.

tyrion

Then I think it's worn chainrings.

jdawginsc 

Wouldn't worn rings make it easier to seat though (sharp teeth)...?

randyjawa 

Looks like improper derailleur set-up, to me.

tyrion

Maybe. Looking at the picture above I thought the chainlinks looked too short for the teeth spacing, but on second thought that's because it's not seated and is bending around a bigger radius than if it was seated.

Maybe the almost new chain doesn't flex enough laterally until it breaks in a bit.

Choke 

All chains from 5 speed to 12 speed (and 13sp I'm sure) are the same width on the inside, i.e. between the sideplates. The width of the outside is what varies and that is done by changing the thickness of the sideplates.

I normally run 9sp chains on my 5-8sp systems because I find that they shift just a bit better and being thinner they seem to be less inclined to rub the big ring when the chain is on the small ring and the smaller end of the freewheel.

clubman 

Chainline?

ridelikeaturtle

This thread intriques me, as I just changed the BB on a bike and I suspect the chainline, and wow it shifts a ton better (btwn 1 and 2 on the front) than it ever did before. What changed? I went from a square-taper BB to an external cup and ultra-torque crankset/chainrings. This was on a 1997 Colnago steel frame. However, now the crankset matches the F&R ders (would that make any difference?). It all worked fine before, but even a quarter turn off of my limit screw on the front derailleur might overshift. Not anymore.

As a result, I'm now a fan of everything matching to get the best performance.

If you've got a mismatch of stuff... to me, that's where I'd start. Get the right chain, get the right chainrings... basically, get the right stuff that was designed to work together, and it'll make your life easier (give you more margin for error).

repechage

Not necessarily.
I read it correctly, fresh chain, ok on cassette (or freewheel) but look at those chainring teeth, "catch a wave" profile to me.
if you have a known good chainset, exchange it, I think the rings.

You could alternately, remove the rear wheel to release any tension and with gloved hands as you will get greasy, "walk' the chain onto the big ring starting at 6 o'clock and to the right, counterclockwise.
I bet it will resist meshing uniformly.

Ferrouscious 

chainrings from the vintage era are not matched. this is the reason why you have to buy sets of chainrings these days; the teeth and shift gates have to line up. if you're not dropping chains, don't worry about it. I personally like the sound of the chain shinking into place.

jdawginsc 

Big ring, absolutely now that I am looking at it on the computer rather than the phone. The small ring looks pretty decent and the OP says it happens on that one too...if it was tension it would likely do better on the big ring.

Is the front derailleur up too high and the bottom brace is clipping the chain?

dddd

It is often the case that on any mixed-component vintage build that the chain will not fall into engagement with sprocket teeth, instead surfing (good word description by niliraga) or "skate" to one side or the other without the teeth engaging the chain.

So this can be a front or rear sprocket, whatever, but is easily tuned away by slightly beveling the tips of the sprocket teeth, thus relocating the sharp tip some fraction of a millimeter in the needed direction.

Holding a file against a rotating chainring or applying a grinding tool to a steel freewheel sprocket is what I often to to solve a number of shifting issues, from indexing incompatibility to having the chain drop inwards of the small chainring (needed correction shown below!) to failure of the chain to move from the second-smallest freewheel cog to the smallest freewheel cog (usually because of vintage derailer limitations WRT rear axle spacing).
And this is just a few of the many sort of instances where I've solved a shifting problem this way.

For the pictured malady, you will have to simply observe which side that the chain needs to move towards in order to engage the teeth on center, and then apply some slight beveling to that side of the sprocket's teeth.

Pictured below is one of my techniques in action, in this case applying a needed bevel to assist engagement onto the small chainring's teeth during downshifts.
The trick here is to position both the file and your hand so that the crankarm's rotation isn't impeded, and not to grind off a lot of metal, which depends on how sharp and aggressive that your file's surface is.

Johno59

Is it possible you have a old 1/8" chainring and your new 3/32" chain doesn't engage. I can see neither are badly worn but whilst a 1/8 chain will fit a 3/32 chainring it doesn't work the other way round.

SJX426 

The first pin at the 3:00 position looks off with the third pin right over the center between the teeth. Then the offset gets progressively worse towards the FD. Part of it is the difference between the radius from the crank center to the bottom of the valley between the teeth and the radius of the chain. BUT, it shouldn't result in a misalignment shown.

Have you tried to settle the chain by hand for a full 180* of the ring?

I do agree that the FD is too close to the chain but I don't think this is the root cause.

Worn chain ring is the suspect root cause, IMHO.

Do you still have the old chain and how does it measure and fit on the chain ring?

Roger M

The front derailleur is pretty close to the big ring, and aligned(as far as my blind eye can tell).The chainline looks OK to me. If I decide to make it a triple, this bottom bracket won't work.

I found another old 110bcd chainset with good condition 48/38/28 rings. I'll try the 48t today and go from there.

Thanks for all of the input. Much appreciated.

repechage

possible a chainring width thing too, pictures only go so far. There was a reduction in width between 5-6 speed and 8, most of the time not an issue. Most.

repechage

[QUOTE=Roger M;21971436]The front derailleur is pretty close to the big ring, and aligned(as far as my blind eye can tell).The chainline looks OK to me. If I decide to make it a triple, this bottom bracket won't work.

I found another old 110bcd chainset with good condition 48/38/28 rings. I'll try the 48t today and go from there.

Thanks for all of the input. Much appreciated.


/QUOTE]
When the Shark bites... half past 6 babe...

niliraga 

suspected this might be the case - am having a similar issue. Short of buying more modern front rings I think I'll just live with the "settling" delay up front, and enjoy the much crisper frequent shifting in the rear (where modern slim chain moves across the modern slim cogs of an HG-type freewheel)

RiddleOfSteel

[QUOTE=repechage;21972227]I believe you are right. Upon another look, the top edges of the big ring's teeth (where the chain rollers would touch/engage) are worn and a little mangled (flaring visible). The tooth profile along that edge also has two different edges/angles. The chain's rollers are now "thinking" that the upper edge/angle is the right one and settling there in that very small "pocket" rather than continuing down to the other edge/angle, into the trough between the teeth. Hope the newer ring solves it.

thook

are you sure the chainring bolts are nice and tight? seems i had the same surfing problem a long time ago and discovered a few bolts were loose so the ring was flexing under simultaneously shifting and pedaling