Chain Not Seating on Chainring Properly, Wrong Pitch?
 

Hello folks, I've recently encountered an interesting problem. In trying to replace the chain on my neighbor's singlespeed, I've found that the chain I put on will not properly mesh with the teeth of the chainring. The chain is a standard singlespeed chain with internal width of 1/8". Rather than an issue of being the wrong width however, I think this is an issue with the pitch of the chain. It's as if the chain has too short a distance between rollers for this chainring. I thought all bicycle chains were always 1/2" between rollers, but with this one, it seems as if they need to be further apart to allow it to actually seat on the chainring correctly. What are people's thoughts on this? Any ideas what the problem may be? From what I've read online, people seem to diagnose this as a worn chainring, but I'm not entirely sure that makes sense to me. Wouldn't a worn chainring have wear on the teeth such that there is excess space both in front of and behind each tooth and still be able to let the chain on, just loosely? I've attached a picture, sorry for the low quality. Thanks for any help you can offer.

https://cimg1.ibsrv.net/gimg/bikefor...ceead99812.jpg

Measure across as many links as you can, and divide it by the number of links. See if it is a standard sized chain.

Another option would be to hold another chain against it, and see if the links are the same length.

I'm betting worn chainring. Look to see if the teeth in line with the cranks are the same shape and width as the teeth at right angles. If they are not identical, the difference is wear. A chain fitting loosely is a worn out ("stretched" chain on a newer chainring.)

Do you still have the old chain? Pull it tight (nothing radical needed; just need to pull out all the play) and measure the distance between pins 12 pairs of links apart with a steel tape measure or ruler. If the length is 12 3/32" or more, there's your answer. A new chain won't run on a cog/chainring that's worn to match a chain that stretched. (Well it might but it will be a poor experience.)

"The chain is a standard singlespeed chain ..."

Is it? Looks like a chain from a moped or go cart.

3/32" (geared, but most singlespeed MTBs use it) chain on 1/8" (bmx) chainring would be my 1st guess. Just asking for a singlespeed chain can be a crapshoot, and if you get the wrong one, it no workee. Getting it wrong in the opposite direction also doesn't work, but if memory serves, fails the other way... the chain won't stay on the ring, whereas yours won't go on in the first place.

As already suggested, it could be a worn chainring, but it doesn't look bad enough to do that. It looks like a steel ring?

--Shannon

Yes, it looks like he needs a 1/8 chain.

Agreed, worn chainring, the slots that the chain links would fit into have elongated (larger) so pitch is effectively > 1". If you have another chainring around, try it or compare the two. I would also check the gear on the rear wheel, it most likely is also very worn.

That's not a new chain, is it? It looks like the chain has elongated at least a half link (1/2") in the 32-tooth (16") circumference of the ring, or about 3%. Acceptable wear is about 0.5%.

It's a new chain that was in an unopened SRAM box that said "single speed" on it, so I'm pretty sure it's for a bike. It's definitely wider than a 6/7/8 chain though.

It came in a sealed SRAM box that said "single speed" so I'd be surprised if it wasn't for a bike. It is definitely wider than a 6/7/8 speed chain

That's a clever way to check the wear. Thank you

Thanks for all the suggestions. I'll have a look at it again tonight after work. Hopefully it won't be too hard to get ahold of a new crank if it needs it.

Weird. Looks like the pitch is too short for the chain wheel and it also doesnt look like a SRAM chain. Get a better picture for identification.

All bicycles for a very long time have been made with the exact same pitch. 1/2 inch.

So the issue is not pitch. In fact chain comes in pitches that are exactly 1/8" apart from each other. That chain doesn't have a 25% difference in pitch.

So you issue is likely a worn chain ring. Unless a roller for some reason is not in the right position or some of the side plates are tight not letting the link swing fully into position. Which on chains from days long gone has been an issue. But they fix themselves after the chain is used a little.

How about checking to see if the chain fits the rear cog. If it fits the cog then your problem is with the chainring.

The thing with single speeds, especially less expensive ones, is the chain tension is not consistent throughout the entire revolution of the crank.

If it was originally setup with the chain too tight at one point, I’m guessing it will not only stretch the chain, it will probably wear (bend?) the teeth more at that point. And Lord knows, the rider will make that crank turn.

John

On a freewheel bike, a worn chainring usually has a "shark fin" pattern, or teeth are ground down to points. Look online for examples. If this is a fixed gear bike, with no brakes, and a very tight chain, perhaps that could explain the worn chainring without the usual wear.

You need an "Exotic" 5/32 bike chain.


Perhaps "BMX" & not "single speed" would get you the results you want? Maybe call it a "415" chain...

Definitely a possibility, this is not a nice bike.

Yeah, the rear sprocket doesn't have the typical shark teeth wear, but what you're saying, along with what I quoted above, all makes sense.

Is it a SRAM PC-1? The PC-1 on SRAM's website definitely does not look like this chain. What do the markings on the actual chain say? Is there anything that confirms a manufacturer or a model number? I'm nearly certain that's not a SRAM chain...at least not a current production one.

The ring just doesn't look that worn to me. It appears to be a very heavy steel ring and it doesn't show the typical wean patterns associated with a ring that's severely worn. A worn ring should still have a 1/2" pitch between the tops of the teeth, right? Sure, they'll be ramped and it'll be easier to skip a chain, but I think the pitch would be maintained. The pitch of the ring and pitch of the chain appear to be unsynchronized by about half of a link around half the circumference. That seems awfully strange.

I'm looking forwarding to hearing back on the identity of this chain and if it appears like it really does have a true 1/2" pitch.

Agreed. Even if the chain ring was worn the pitch wouldn't change and the correct chain would still fit the teeth.

I say correct chain because a 3/32 chain on a 1/8 inch ring will look like what you got going on here because it will not fully seat on the teeth.

Wow, I'm shocked. I got a pair of calipers to measure the chain. As expected, the pitch is 1/2". The width however, was not 1/8". It was in fact 3/32". And further, having looked at the markings on the chain, it is very much not a SRAM chain, which is really odd, because I bought it new from my bike shop and it was in a SRAM box and everything. I'll put pics of the box, a section of excess chain, and the caliper measurement below. Sorry to have troubled you all with this. I really thought I had a 1/8" chain, after all, that is what the box said. I guess the lesson here is to always double check and make sure you're actually dealing with what you think you are.

https://cimg2.ibsrv.net/gimg/bikefor...f2633a869c.jpg
The box it came in, labelled SRAM PC-1, what I thought I had.
https://cimg3.ibsrv.net/gimg/bikefor...ba7cfa0f81.jpg
An excess piece of chain, the markings say TAYA, not SRAM.
https://cimg8.ibsrv.net/gimg/bikefor...639cc1ef0c.jpg
The measurement of the internal width of the chain, it's definitely 3/32", not 1/8"

Mystery solved! I wonder if the bike shop got out two chains at once to install, and accidentally put this one back in the wrong box.

^^^^^^ Back in 2015, quite possibly.....

I think you found the problem a few days ago with the 3/32 chain causing the chain to right slightly high. Hopefully it is now fixed.

I thought I'd post this Wippermann chart from a couple of years ago. Ignoring the wear (they have done quite a few more tests since this time).

http://1.bp.blogspot.com/_urSQl6wUA5...chain+wear.bmp

What I found unique was that the initial length of all the chains were slightly different. And, the Campagnolo Record chain measured slightly short.

Very interesting, thanks for sharing.