Bicycle Mechanics - chain won't fit cog

Brand new chain, brand new cog supplied stock with Shimano Nexus 8 hub. Supposedly both are 3/32" and yet I'm getting this:
150718

What gives? It looks like the pitch is mismatched, but how could that be when every standard bike chain uses the same pitch?

That's crazy. The cog came stock with a Shimano hub? What about the chain, where did it come from?

Did some research. Quoth St. Sheldon:

Pitch



Chain/Sprocket Pitch

The pitch of a chain is the distance between adjacent drive rollers. All modern bicycles use 1/2" pitch. Some older chains, especially those used on track (http://sheldonbrown.com/gloss_tp-z.html#track) bicycles used 1" pitch chain (see skip link (http://sheldonbrown.com/gloss_sa-o.html#skiplink) and block chain (http://sheldonbrown.com/gloss_ba-n.html#blockchain).) For a while, Shimano (http://sheldonbrown.com/gloss_sa-o.html#shimano) experimented with a 10 mm pitch for track use, but it never caught on. Sometimes people mistakenly refer to "track pitch" vs. "road pitch" when they are really referring to the wider (1/8") sprockets used on single-speed bicycles, instead of the 3/32" thick sprockets used on derailer (http://sheldonbrown.com/gloss_da-o.html#derailer)-equipped bicycles.

Could be you got a hold of a different pitch chain or cog? Looking more closely, looks like it could be a 10mm pitch chain.

According to Sheldon, Single speeds, and Internal Gear Hub bikes, use 1/8"

According to Sheldon, Single speeds, and Internal Gear Hub bikes, use 1/8"

That's referring to chain width, a different issue. This is distance between the rollers, measured lengthwise along the chain.

Get a chain checker on that chain. I would be willing to bet it is 10mm pitch.

I would be willing to bet that you have a 3/32 chain on a 1/8 cog.

What about the chain, where did it come from?

Chain is IRD Black Lightning
http://www.interlocracing.com/chains.html


According to Sheldon, Single speeds, and Internal Gear Hub bikes, use 1/8"

According to Sheldon Shimano IGH cogs are 3/32"
http://www.sheldonbrown.com/harris/shimano-nexus.html

Ok guys so I looked up some specs and took some measurements:
-A 3/32" cog is supposed to be about 2.1mm wide, but Shimano's measures 2.3mm.
-A 3/32" chain is supposed to be 2.3mm wide, but IRD's measures 2.27mm.

So there you have it, Shimano's stuff is a little too big and IRD's stuff is a little to small and as a result they won't fit.

Does anyone know where to get a real 3/32" cog for an IGH unlike this fako from Shimano?

The chain you're using looks like an IRD derailleur chain. You need a single speed chain. A 1/8" chain, to be precise (according to Shimano).

http://www.petracycles.co.uk/product_info.php?language=en&currency=USD&products_id=9355&source=googleus

Ok guys so I looked up some specs and took some measurements:
-A 3/32" cog is supposed to be about 2.1mm wide, but Shimano's measures 2.3mm.
-A 3/32" chain is supposed to be 2.3mm wide, but IRD's measures 2.27mm.

So there you have it, Shimano's stuff is a little too big and IRD's stuff is a little to small.

BTW the pitch is on the money.

You can't use a 10 speed chain on a single cog hub.

Ok guys so I looked up some specs and took some measurements:
-A 3/32" cog is supposed to be about 2.1mm wide, but Shimano's measures 2.3mm.
-A 3/32" chain is supposed to be 2.3mm wide, but IRD's measures 2.27mm.

So there you have it, Shimano's stuff is a little too big and IRD's stuff is a little to small and as a result they won't fit.

Does anyone know where to get a real 3/32" cog for an IGH unlike this fako from Shimano?

Ahhh, ok. Re-re-re-RE-looking at the picture I see now that it's not pitch.

Brand new chain, brand new cog supplied stock with Shimano Nexus 8 hub. Supposedly both are 3/32" and yet I'm getting this:
150718

What gives? It looks like the pitch is mismatched, but how could that be when every standard bike chain uses the same pitch?
It sure looks like a 3/32" chain on a 1/8" cog. How does it look with a 1/8" chain? I'd just run 1/8" chain and be done with it because 1/8" chain runs fine on both 1/8" and 3/32" cogs and chainrings.

It sure looks like a 3/32" chain on a 1/8" cog. How does it look with a 1/8" chain? I'd just run 1/8" chain and be done with it because 1/8" chain runs fine on both 1/8" and 3/32" cogs and chainrings.


He's using a 10 speed chain on a single speed cog. That's the problem.

I checked the Shimano tech site, and they have both 3/32" and 1/8" cogs for Nexus. Both the chain and the cog are 3/32" from the looks of them, but his chain is way too narrow. He needs a 3/32" fixie/track/BMX chain.

He's using a 10 speed chain on a single speed cog. That's the problem.

I checked the Shimano tech site, and they have both 3/32" and 1/8" cogs for Nexus. Both the chain and the cog are 3/32" from the looks of them, but his chain is way too narrow. He needs a 3/32" fixie/track/BMX chain.

3/32" refers to the inner width.
You can pop on any 3/32" chain and get the same results where the chain won't fit because it's too narrow. The only thing that changes between track/bmx 3/32" and derailer 3/32" chains is the outer width.
What's needed is a 1/2" pitch x 1/8" width chain.

3/32" refers to the inner width.
You can pop on any 3/32" chain and get the same results where the chain won't fit because it's too narrow. The only thing that changes between track/bmx 3/32" and derailer 3/32" chains is the outer width.
What's needed is a 1/2" pitch x 1/8" width chain.

Technically they are all 3/32", yes. However - as the OP has found - not all 3/32" are the same. It is only tenths of a millimeter, but it's enough to cause problems. That's why I always use singlespeed or, at the most, a 5/6/7 speed chain on an IGH; those millimeters count.

I haven't decided on his cog. He says it's a 3/32" It's hard to tell in the picture, since it's so small (I run 1600x1200 resolution on my monitor), but it does look like a 3/32". Of course, if it IS a 1/8" cog, then all the debate about 3/32" chain widths is moot.

Shimano cogs work fine with 8 speed derailleur chain as do 3/32" width SRAM IGH cogs. I have run several bikes that way. Depending on the maker some 9 speed and 10 speed chains are about .008" narrower internally between inner plates and such a chain could have a problem. Rohloff specifically recommends 8 speed derailleur chain with their hub sprockets as otherwise there can be clearance problems between chain and hub body with some sprocket and chain combinations.

The statement that IGHs use 1/8" chain is not necessarily true as the only IGH maker I know of who routinely sells 1/8" IGH cogs in the USA any more is Sturmey Archer. When SA dominated the IGH market in the USA the 1/8" chain statement was true but that was 20+ years ago.

Technically they are all 3/32", yes. However - as the OP has found - not all 3/32" are the same. It is only tenths of a millimeter, but it's enough to cause problems. That's why I always use singlespeed or, at the most, a 5/6/7 speed chain on an IGH; those millimeters count.

I haven't decided on his cog. He says it's a 3/32" It's hard to tell in the picture, since it's so small (I run 1600x1200 resolution on my monitor), but it does look like a 3/32". Of course, if it IS a 1/8" cog, then all the debate about 3/32" chain widths is moot.

Shimano 8-speed hubs come standard with two 3/32" cogs, a 19 and a 21 I believe. I have a new 19 t cog that measures 2.2 mm wide.
You can use SA 1/8" cogs with these hubs. I use a 1/8" Isumi chain, figuring a wider chain lasts longer. As soon as the stock cog wears out (hopefully before the entire hub fails) I'll throw on a 1/8" SA cog.

You can't use a 10 speed chain on a single cog hub.

But the chain is an order of magnitude closer to spec than the cog. So the problem is really more that the Shimano cogs are out of spec.


Shimano cogs work fine with 8 speed derailleur chain as do 3/32" width SRAM IGH cogs. I have run several bikes that way.

Do you have any idea if the 3/32" SRAM sprockets are more true to size?


Ahhh, ok. Re-re-re-RE-looking at the picture I see now that it's not pitch.

I think the reason it appears like a pitch problem is because the outer chain plates are much wider han the inner chain plates. So it takes a full link (two rollers) before you start to get a mismatch and 2-3 full links for the mismatches to add up.


Shimano 8-speed hubs come standard with two 3/32" cogs, a 19 and a 21 I believe. I have a new 19 t cog that measures 2.2 mm wide.
You can use SA 1/8" cogs with these hubs. I use a 1/8" Isumi chain, figuring a wider chain lasts longer. As soon as the stock cog wears out (hopefully before the entire hub fails) I'll throw on a 1/8" SA cog.

Yup that's what I have here, but according to my digital calipers they're not even close to 2.2mm; definitely 2.3mm if not 2.35mm.

Also I wouldn't hold your breath waiting for ther cog or chain to wear out on an IGH. That's why I went for a lighter 10 speed chain cause 1/8" chains and cogs are way overbuilt for the gentle demands of a straight chainline.

Possible solutions if the SRAM cogs aren't any narrower:
1. Brompton derailleur cog
http://www.brompton.co.uk/page.asp?p=3070
2. File extra tabs off Shimano freehub sprocket
http://www.hubgear.net/sprockets.html

-A 3/32" cog is supposed to be about 2.1mm wide, but Shimano's measures 2.3mm.


Not sure where you got that info, most 3/32" single speed cogs measure 2.3mm. The exceptions, at least among the cogs we carry, are Surly and Rockwerks which measure about 2.0mm, but those are threaded cogs anyway. We usually use 8 speed chains here in the shop, but I prefer single speed 3/32 chains myself, like the Wippermann 708.

Brompton derailleur cogs measure 2.1mm, I don't have a SRAM cog to measure for you.

I just measured both an 18 and a 23 toth new Shimano sprockets as 2.16 to 2.25mm thick and a 24 tooth Sachs cog as 2.10 to 2.12mm thick. The Sachs cog does seem to be a bit thinner and more consistent in thickness. It looks to me like the SRAM cog has the teeth area more polished to remove stamping related burrs and high spots before final finishing. The Shimano cog is chrome plated while the Sachs one appears to be Parkerized like many military guns. The 19T SRAM cog that came with my P5 hub is 2.0mm thick nominally.

Good luck in finding the SRAM cogs in the USA. Mine, except for the P5 one, were bought from Sachs, pre SRAM buyout.

Not sure where you got that info, most 3/32" single speed cogs measure 2.3mm. The exceptions, at least among the cogs we carry, are Surly and Rockwerks which measure about 2.0mm, but those are threaded cogs anyway. We usually use 8 speed chains here in the shop, but I prefer single speed 3/32 chains myself, like the Wippermann 708.

Brompton derailleur cogs measure 2.1mm, I don't have a SRAM cog to measure for you.

First let me say thanks for the measurements to which I'll add that the surly cogs for shimano freehub splines are about 2.0mm wide.

Second, according to your website (http://www.sheldonbrown.com/gloss_ch.html) (Sheldon/Harris) 3/32" refers to chain with an internal width of 2.3mm (though actually 3/32"=2.38mm). Common sense dictates that unless you plan on just jamming the sprocket into place it needs to be 10-15% smaller (or around 2.1mm) in order for the teeth to move freely between chain links as noted here:
http://www.gizmology.net/sprockets.htm

Lastly, if I go the filed-off-freehub-sprocket route does anyone have advice on whether to use a "1st sprocket" w/ built in spacer or a regular one? The reason I'm asking is because the first sprockets are essentially offset and I need some offset for the nexus hub, but I'm concerned the built in spacer will render them too wide to fit under the snapring and stuff on the hub. Thanks again for your input everyone.

Chain is IRD Black Lightning
http://www.interlocracing.com/chains.html



According to Sheldon Shimano IGH cogs are 3/32"
http://www.sheldonbrown.com/harris/shimano-nexus.html

The IRD chain is listed as a 10 speed chain. Per information from two sites I checked in the past 10 speed chains are NOT 3/32" internal width. They are listed as 11/128" or .008" (.2mm) narrower internally than a 3/32" chain. This WILL cause problems with some 3/32" sprockets. Check bicycle chain widths on the KMC chains web site.

http://www.kmcchain.com/file/en/chain_choice_chart.pdf

Page 7 on the KMC PDF shows the width of Shimano 9 speed chains as 11/128" too.

The same for Wippermann chains on their web site.

http://www.connexchain.com/Bicycle-chains/9-Speed/1_327.html

and

http://www.connexchain.com/Bicycle-chains/10-Speed/1_326.html

I have seen repeated way too often on BF that all current derailleur chains are 3/32" Once you get to 9, 10 and 11 speed chains THIS IS NOT TRUE and I wish people would stop posting so. They are narrower for both inside and outside widths than 5 through 8 speed derailleur chains all of which are 3/32" internal width.

IMO you are having the problem due to trying to use a 11/128" internal width 10 speed derailleur chain rather than a 3/32" 8 or fewer speeds chain on a nominal 3/32" cog. Incompatible parts.

Somebody mentioned the problem what it is so complicated? clearly the OP have a 1/8 cog hub and with the picture it is super clear the guy is trying to put a road chain, doesnt matter if the darn chain is for 6, 7, 9 or 11 speeds... it wont fit. Or the guy change the cog or change the chain. No other options and clearly the best thing to do is to change the darn chain for a regular 1/8 chain.

The IRD chain is listed as a 10 speed chain. Per information from two sites I checked in the past 10 speed chains are NOT 3/32" internal width. They are listed as 11/128" or .008" (.2mm) narrower internally than a 3/8" chain. This WILL cause problems with some 3/32" sprockets. Check bicycle chain widths on the KMC chains web site.

http://www.kmcchain.com/file/en/chain_choice_chart.pdf

Page 7 on the KMC PDF shows the width of Shimano 9 speed chains as 11/128" too.

The same for Wippermann chains on their web site.

http://www.connexchain.com/Bicycle-chains/9-Speed/1_327.html

and

http://www.connexchain.com/Bicycle-chains/10-Speed/1_326.html

I have seen repeated way too often on BF that all current derailleur chains are 3/32" Once you get to 9, 10 and 11 speed chains THIS IS NOT TRUE and I wish people would stop posting so. They are narrower for both inside and outside widths than 5 through 8 speed derailleur chains all of which are 3/32" internal width.

IMO you are having the problem due to trying to use a 11/128" internal width 10 speed derailleur chain rather than a 3/32" 8 or fewer speeds chain on a nominal 3/32" cog. Incompatible parts.

Excellent points and well said.

So I guess if I want to keep the same chain I should proceed with modifying a freehub cog as clearly 9 or 10 speed cogs don't exist in the 3 spline format. And I do want to keep the same chain because:
1. This is for a recumbent and I'm looking to save chain weight to somewhat offset the weight of the IGH.
2. I'm hoping to possibly use a sub 16T cog for extra chain clearance and higher gearing...something which clearly isn't possible on the Nexus 8 with a 1/8" or externally wide 3/32" chain, but should be possible with a 10 speed chain according to my measurements.
3. The old cog cost me nothing and a new one will be $3-$10 whereas I've already committed $60 to the chain and would probably require over $20 to replace it with even a bottom of the barrel 1-8 speed chain.

P.S. Here's another reference to filing the extra tabs off 9 spline cassette cogs:
http://stein.dommel.be/brompton/chapters/Sprocket.html#257


Somebody mentioned the problem what it is so complicated? clearly the OP have a 1/8 cog hub and with the picture it is super clear the guy is trying to put a road chain, doesnt matter if the darn chain is for 6, 7, 9 or 11 speeds... it wont fit.

Except the fact is it isn't a 1/8 cog. Shimano supplies 3/32" cogs with the Nexus 8 hubs and measurement confirms that mine weren't mispackaged. Tatfiend has the real problem figured out. It's that 9 and 10 speed chains are 11/128", not 3/32". This issue probably isn't usually noticed because unlike 3/32" singlespeed cogs, 3/32" cassette cogs seem to run narrow to facilitate derailling.

Chucky;

You got it. I personally would lightly file or stone the IGH cog till the chain fit rather than modifying a standard derailleur cassette cog as the IGH cog is not designed to let the chain come off of the sprocket easily while a cassette cog is.

Also the cassette sprocket is thin enough at the splined area that some sort of spacer will be required I believe to have the cog retaining snap ring on the Shimano hub keep the sprocket from wobbling a bit. I personally would try one of the Surly SS conversion cogs shown at the below link as the cog to modify if you do not do so to the original Shimano cog. It is thicker in the splined area than a normal cassette cog so may not require a spacer.

http://sheldonbrown.com/harris/singlespeed.html#surlycog

OK, I must be missing something here. Why in the world would you want to go and file/modify the cog, when you are clearly using the WRONG CHAIN??!! Get the right size chain! Either 1/8" or 3/32" (6-7-8 spd)

Chucky;

You got it. I personally would lightly file or stone the IGH cog till the chain fit rather than modifying a standard derailleur cassette cog as the IGH cog is not designed to let the chain come off of the sprocket easily while a cassette cog is.

Also the cassette sprocket is thin enough at the splined area that some sort of spacer will be required I believe to have the cog retaining snap ring on the Shimano hub keep the sprocket from wobbling a bit. I personally would try one of the Surly SS conversion cogs shown at the below link as the cog to modify if you do not do so to the original Shimano cog. It is thicker in the splined area than a normal cassette cog so may not require a spacer.

http://sheldonbrown.com/harris/singlespeed.html#surlycog

I actually just picked up the surly cog fom the LBS (notice I gave the width a few posts back). However, the thing that concerns me is the splined area is a lot thicker than the stock nexus cogs (~4.5mm vs ~2.5mm) which I don't think will leave room for the snap ring. It's also expensive, so I'd be pissing away a lot of money if I screw it up or if I decide I want/need a different tooth count. So I think I'm going to take it back.

As far as modifying the stock nexus cog there are two issues:
1. It's much easier to file off some tabs than to evenly file a flat surface.
2. I need a new cog anyway because both the 19T and 21T stock nexus cogs result in chain/frame interference.

Since cassette cogs are cheaper than any other choice, I figure they'll be good to experiment with; For example to see if I can squeeze a 14T or even 13T cog onto the Nexus 8 hub or just to find out if the more ubiquitous casette cogs make a good substitute for the 3 spline variety. Besides I found two recommendations for the spline modification on the web...one from a bike manufacturer, so how bad could it be? If I have chain derailment problems then at least I know what's causing it and how to fix it, unlike the sprocket thickness and chainline issues which I'm still unsure of.

Ideally I guess the 13T Bromption derailleur cog would be best, but I'm not sure if the hub can accommodate such a small cog nor am I sure it's narrow enough for the chain (Sheldon brown has a table of sprocket widths (http://www.sheldonbrown.com/speeds.html) and they're almost all 2.0mm or less, even for 6 speed cassettes). Most importantly it costs 3x as much as the cassette cogs and I can't get it locally.

Decisions decisions...

Chucky;

Sorry I did not notice the Surly cog thickness in the splined area.

I keep forgetting that not everyone has access to a lathe like I do. I would mount the Shimano IGH cog in the chuck and with the cog spinning lay a file or stone on the sides of the teeth area on both sides to narrow the cog in the required area. It would remove the chrome but chain oil should keep it from rusting.

With access to machine tools I have made a number of bike accessories and modified parts on occasion.

Even working the cog against sandpaper on a hard flat surface, with the cupped side down, could narrow it enough to work with the chain. It might take some time though.

With the typical long chain line of a recumbent chain line is less critical for an IGH. Rohloff lists +- 5mm as the accuracy needed for a modern derailleur chain.

I'm with dperreno. Stop wasting time and just go buy the right chain! ha ha

After some further measurement I'm almost certain the Brompton 13T derailleur sprocket will work, but I think the master links of the chain might rub the dust cap (and they don't make the sprocket in 14T). My chain is also about 3 links short so I'm thinking maybe I should forget about filing and just buy the Brompton sprocket along with an even narrower chain (newer 10 speed chains are 5.9mm whereas the pre2006 campy 10 speed chain I'm using is 6.1mm) in order to guarantee clearance. I hate buying more expensive parts, but I figure it's beter to have some room for error then to be pulling my hair out over microscopic tolerances.


I'm with dperreno. Stop wasting time and just go buy the right chain! ha ha

If I use a thicker chain then I have to use a larger tooth count sprocket or else the chain will interfere with the dust caps and shift mechanism of the hub and if I use a larger tooth count sprocket then the chain interferes with the frame. So the only way to avoid chain interference is to use a low tooth count sprocket and a narrow chain.

Somebody mentioned the problem what it is so complicated? clearly the OP have a 1/8 cog hub and with the picture it is super clear the guy is trying to put a road chain, doesnt matter if the darn chain is for 6, 7, 9 or 11 speeds... it wont fit. Or the guy change the cog or change the chain. No other options and clearly the best thing to do is to change the darn chain for a regular 1/8 chain.

Great post Ultraman6970, way to keep up with the conversation. It's only like the 50th fricken time in this thread the OP has confirmed it's not a fricken 1/8" cog.

Great post Ultraman6970, way to keep up with the conversation. It's only like the 50th fricken time in this thread the OP has confirmed it's not a fricken 1/8" cog.

You're right, sorta. It's a 3/32" cog but he's trying to use an 11/128" chain. Same problem. Chain is too narrow for the cog. Get the right size chain. End of problem. Sheesh!

Ok so I got the 2.2mm wide brompton sprocket, but it's still not narrow enough for the chain to fit comfortably (11/128" = 2.18mm) and I don't want to file it because that would ruin the case hardening.

Also, those of you who don't understand why I can't use a wider chain need to take a look at this picture:
153389