# Single speed conversion damaging chain?



## pclay (17 Jun 2014)

I converted my 6 year old Raleigh hybrid a few weeks ago to a single speed bike. I used the DMR single speed conversion kit, and got a new KMC 8 speed chain.

After a few weeks of using the bike, I noticed that the chain looks damaged. It's as if some of the links are getting bent by forces it would not normally see. I kept on the triple crankset, only having the chain around the middle cog.

Is a damaged chain a likely result of the chain line not being perfectly straight? What newbie mistake have I made?

Picture just after conversion:



20140609_183247 by Paul_Clayton, on Flickr

Brand new chain after a few weeks of riding:



20140617_174208 by Paul_Clayton, on Flickr


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## Pennine-Paul (17 Jun 2014)

Your chainline must be way out,
Oh,and get a proper singlespeed 
chain too,I tend to go through a new
chain after about 18 months!


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## raleighnut (17 Jun 2014)

Looks like the cogs too wide for the chain as above get a SS specific chain


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## Smurfy (17 Jun 2014)

In my humble opinion, chain line should be within ~2mm for single-speed, and within ~1mm for fixed.

You only have one gear, so the chain takes a beating every time the road goes upwards. To withstand that level of use, the chainline should be perfectly straight, as that's when the chain is strongest. If it fits, I'd run a proper single-speed/fixed chain, with a three piece link, rather than a regular derailleur chain.


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## Smurfy (17 Jun 2014)

raleighnut said:


> Looks like the cogs too wide for the chain as above get a SS specific chain


Could very well be if every single link is split open the same. @pclay, are you running an 8 speed chain on a 1/8" cog? If yes, it will split the chain open!

You need 3/32" cog for 6,7 and 8 speed chains, and a 1/8" cog for 1/8" chains. However, a 1/8" chain will happily run on a 3/32" cog or chainring.


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## raleighnut (17 Jun 2014)

YellowTim said:


> Could very well be if every single link is split open the same. @pclay, are you running an 8 speed chain on a 1/8" cog? If yes, it will split the chain open!
> 
> You need 3/32" cog for 6,7 and 8 speed chains, and a 1/8" cog for 1/8" chains. However, a 1/8" chain will happily run on a 3/32" cog or chainring.


Could'nt remember the sizes off the top of my head. Thanks


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## GrasB (17 Jun 2014)

First thing I'd do is go swap your chainring for a proper single speed ring. The damage you show can be caused by the chain trying to jump off the short teeth but not quite making it over so the chainring bites into the gap between the links. The fact you look to be running very high chain tension is just going to make this problem worse.


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## pclay (18 Jun 2014)

Thanks for the comments guys. I was running an 8sp chain on the single rear cog that came with the conversion kit. I looked at the chain line and it appeared to be straight when looking at it by eye. One thing I did notice was that there was a lot of creaking/noises when going uphill.

The front cog is 3/32, the chain was 3/32 (8 speed). I do not know the size of the rear cog as it came with the kit. I may have been 1/8. Would this cause the chain to split?

Although I love the idea of single speed, and my thighs feel stronger already (and I regularly do 50 mile rides on a road bike), I am now in the process of converting back to gears.


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## fossyant (18 Jun 2014)

A 1/8th sprocket is a chunky beast, so you should easily tell is it is that.

Can you take a picture of the sprocket from the rear ?


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## pclay (18 Jun 2014)

Hi, I have attached a picture from the rear before I took the damaged chain off. The chain line looked ok to me.



20140617_174030 by Paul_Clayton, on Flickr

Here is a picture of the sprocket and with part of the 8sp chain on it. This looks like a 1/8 cog as the teeth are more chunky that my old 8 speed cassette teeth.



20140618_175149 by Paul_Clayton, on Flickr



20140618_175239 by Paul_Clayton, on Flickr


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## GrasB (18 Jun 2014)

That damage isn't from the rear sprocket. The key is that the badly damaged links are the outer links, running to narrow a chain for a sprocket causes inner link damage. You didn't need those 3 photos to realise that, but it does conform that all is okay with the sprocket & you need to look elsewhere.


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## raleighnut (18 Jun 2014)

pclay said:


> Hi, I have attached a picture from the rear before I took the damaged chain off. The chain line looked ok to me.
> 
> 
> 
> ...


That chain line is awful, to cure it remove the outer sprocket and fit the middle one to the outside of the spider, unless its not possible due to the sprockets being welded together instead of being bolt on.


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## RedRider (18 Jun 2014)

For what it's worth I run 8 speed chains on a singlespeed without problem. In theory chains designed for derailleurs should be more tolerant of imperfect chainline but it looks quite extreme from your first pic, especially along the bottom run where it leaves the tensioner.


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## Old Plodder (18 Jun 2014)

pclay said:


> Hi, I have attached a picture from the rear before I took the damaged chain off. The chain line looked ok to me.
> 
> 
> 
> ...


On your last photo, it looks like an 1/8th sprocket to me.
Regarding chainline, it's way out! 
Put a straight edge against your chainwheel & see how far out the rear sprocket is. 
(It barely looks as if it will line up with your outer chainring.)


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## pclay (19 Jun 2014)

Thanks for the help guys, I have fitted a new 8sp chain (purchased because I was going to back to gears), and changed the spacers around on the rear. Straight away, there is no longer any creaking noises when going uphill. 

I have taken some measurements as per this link, and I get the following:

Front measurement: 48mm
rear measuremtn 18mm

hub width 135mm/2 = 67.5mm
48+18= 66mm

meaning this is 1.5mm out.

I have a couple of cassette spacers on order and a 1/8 chain.

The chainline now looks like this:



20140619_184109 by Paul_Clayton, on Flickr


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## screenman (19 Jun 2014)

YellowTim said:


> In my humble opinion, chain line should be within ~2mm for single-speed, and within ~1mm for fixed.
> 
> You only have one gear, so the chain takes a beating every time the road goes upwards. To withstand that level of use, the chainline should be perfectly straight, as that's when the chain is strongest. If it fits, I'd run a proper single-speed/fixed chain, with a three piece link, rather than a regular derailleur chain.



Please explain to this thicky how chain tension varies as you go up hill, when compared with multi geared machine. I would see it as the chain taking the same load whatever gear you are in.


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## fossyant (19 Jun 2014)

screenman said:


> Please explain to this thicky how chain tension varies as you go up hill, when compared with multi geared machine. I would see it as the chain taking the same load whatever gear you are in.



Think he means more load as you end up grinding up hills more, than with gears.


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## screenman (19 Jun 2014)

fossyant said:


> Think he means more load as you end up grinding up hills more, than with gears.


Surely the load on the chain does not change, only the load on your legs.


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## fossyant (19 Jun 2014)

Load on legs = load on chain ! You have to pedal much harder than you would if you could drop 3 or 4 gears. Harder pedalling = more drive chain load.

TBH with singlespeed, you can run 3/32 chains. It's when you get to fixed you really need the beefy 1/8 chains. These aren'f flexible like the 3/32 so chain line is important.


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## screenman (19 Jun 2014)

fossyant said:


> Load on legs = load on chain ! You have to pedal much harder than you would if you could drop 3 or 4 gears. Harder pedalling = more drive chain load.
> 
> TBH with singlespeed, you can run 3/32 chains. It's when you get to fixed you really need the beefy 1/8 chains. These aren'f flexible like the 3/32 so chain line is important.



Nope still not clear enough, the gears are the gearbox, the chain the propshaft surely strain is the same to propel the bike forwards and upwards? Say BW is going up hill and 375 watts now that power is going through the chain I believe, if he changes down or up the sprocket but remains at the same power the strain on that chain is surely the same.

Power meters I think used to take the measurement from the chain, some may still do so, these work regardless of the gear you are in for the reason I stated.


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## GrasB (20 Jun 2014)

fossyant said:


> Load on legs = load on chain ! You have to pedal much harder than you would if you could drop 3 or 4 gears. Harder pedalling = more drive chain load.
> 
> TBH with singlespeed, you can run 3/32 chains. It's when you get to fixed you really need the beefy 1/8 chains. These aren'f flexible like the 3/32 so chain line is important.


Doesn't work like that. Chain tension is dictated by the chain speed, given the same power & wheel speed then you need to look at the size of the rear sprocket to work out the chain tension, which is inversely proportional to the sprocket size.






Start with the same power output (thus all 200w). As I know the tyre size (622x28), sprocket teeth & chairing teeth I can work out the gearing in mph/100rpm (not shown here) which gives me the cadence. From there I back work the torque in Nm, it's easy enough to work out the chaining diameter & thus radius from the tooth count & now you have all the information you need convert from Nm to Nforce (eg tension) transmitted via the chain.


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## fossyant (20 Jun 2014)

Geek alert !!


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## raleighnut (20 Jun 2014)

Surely the highest torque is from a standstill when all of a riders weight is put onto the pedal through the chain. I've seen chains snap (on tv) when riders begin from the starting stands at Velodrome races. (Tech term not known for these stands)


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## JoeyB (20 Jun 2014)

From the two pics of chain line you have posted, I wouldn't be happy with either of them.


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## GrasB (20 Jun 2014)

[QUOTE 3140809, member: 45"]And if the power output is the only variable?[/QUOTE]
All other variables held constant chain tension is directly proportional to power. 



raleighnut said:


> Surely the highest torque is from a standstill when all of a riders weight is put onto the pedal through the chain. I've seen chains snap (on tv) when riders begin from the starting stands at Velodrome races. (Tech term not known for these stands)


Pulling off is an edge case as anything much bellow 40rpm becomes muscle force limited so the chain tension will stay the same no matter the power. If you assume I'm only pushing as hard as my body weight on 165mm cranks my 1-45rpm chain tension on a 42t chainring is 1598.6N, or about 4.5x the chain tension in the lowest example there.



fossyant said:


> Geek alert !!


And?..


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## JoeyB (20 Jun 2014)

This is mine, just took a quick pic...


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## GrasB (20 Jun 2014)

The curve could also be static chain droop. To me he's not taking a photo directly down the chain line.


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## raleighnut (20 Jun 2014)

GrasB said:


> All other variables held constant chain tension is directly proportional to power.
> 
> 
> Pulling off is an edge case as anything much bellow 40rpm becomes muscle force limited so the chain tension will stay the same no matter the power. If you assume I'm only pushing as hard as my body weight on 165mm cranks my 1-45rpm chain tension on a 42t chainring is 1598.6N, or about 4.5x the chain tension in the lowest example there.
> ...


Now increase the crank to 175 and stick 13.5 stone on it ( about average for a 6 footer)


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## GrasB (20 Jun 2014)

About 1750N, anyway track cranks are usually 165, hence why I used that length


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## screenman (20 Jun 2014)

[QUOTE 3140837, member: 45"]Chain tension is affected by (leg) power output and by gearing. On a single speed bike, to apply more power to the back wheel your only option is to pedal harder, and this increases the pulling force on the chain.[/QUOTE]

Which of course would be the same no matter what gear you were in.


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## screenman (20 Jun 2014)

[QUOTE 3141190, member: 45"]No, it would depend on how much power you're putting though your legs.[/QUOTE]
Yes we know that, but 20 mph is putting the same strain on the chain no matter what gear you are in, it is the legs that feel the difference.


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## GrasB (20 Jun 2014)

screenman said:


> Yes we know that, but 20 mph is putting the same strain on the chain no matter what gear you are in, it is the legs that feel the difference.


No, that's covered by the first table - 29/11 is 345N, 52/20 is 190N both at 200w @ 20mph

Basically a smaller rear sprocket means a slower chain so more force is applies per 1/2" of chain pulled.


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## screenman (20 Jun 2014)

GrasB said:


> No, that's covered by the first table - 29/11 is 345N, 52/20 is 190N both at 200w @ 20mph
> 
> Basically a smaller rear sprocket means a slower chain so more force is applies per 1/2" of chain pulled.



So please explain how the power meter that uses the chain tension Polar I think works.


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## GrasB (20 Jun 2014)

screenman said:


> So please explain how the power meter that uses the chain tension Polar I think works.


Power is force multiplied by time. You measure the chain tension & you can work out the force being exerted, you measure the chain speed & you work how quickly that force is being exerted. You now can work out how much work is actually being done by that force, aka power.

200w == 345.4N @ 579mm/s == 237.5N @ 842mm/s == 190.1N @ 1052mm/s

A chain tension measurement device by necessity also is a chain speed measurement device as the same techniques apply for the raw signal, it's just the way you process the data that defines what you measure. You simply & run different analysis on the chain data at the same time and you have speed & tension, or power


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## screenman (20 Jun 2014)

[QUOTE 3141228, member: 45"]I think, though I'm open to persuasion, that your mistake is saying that the chain is the equivalent of the property shaft on a car. That's not correct as the chain is in the middle of the "gearbox" and not the final drive. The propshaft rotation of a car is always at the same ratio to the rotation of the wheels. On a bike the force on a chain is lower in a lower gear and requires more chain distance travelled to keep the same speed.[/QUOTE]

That is the bit I am having trouble getting my head around. So if I stand on the pedals with my back wheel locked the chain between ring and sprocket will be x if it is on say the 13t but y if it is on the 21t.


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## GrasB (20 Jun 2014)

screenman said:


> That is the bit I am having trouble getting my head around. So if I stand on the pedals with my back wheel locked the chain between ring and sprocket will be x if it is on say the 13t but y if it is on the 21t.


No, because in both cases there is no time difference so no work is being done.

Once time is involved things get a little different. Assuming the same chainring at the front, if the rear wheel is turning at 10rpm then you'll fall at different rates. The closer you get to falling at an accelerating rate of 9.81m/s/s the lower the force being applied will be less. A bigger sprocket means more chain travel, that means you'll be falling faster & thus exerting less force on the chain.


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## raleighnut (20 Jun 2014)

GrasB said:


> No, because in both cases there is no time difference so no work is being done.
> 
> Once time is involved things get a little different. Assuming the same chainring at the front, if the rear wheel is turning at 10rpm then you'll fall at different rates. The closer you get to falling at an accelerating rate of 9.81m/s/s the lower the force being applied will be less. A bigger sprocket means more chain travel, that means you'll be falling faster & thus exerting less force on the chain.


But the static chain is experiencing load and if the load increases it will eventually fail, if load is applied to the lever of the crank arm and the other end is stationary


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## GrasB (20 Jun 2014)

raleighnut said:


> But the static chain is experiencing load and if the load increases it will eventually fail, if load is applied to the lever of the crank arm and the other end is stationary


But the load isn't increasing. It's staying at the same level as the same constant force is being applied. Slowly, very, very slowly, this will stretch the chain & if there are any flaws in the metal it may cause them to expand & thus the chain will break.


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## GrasB (20 Jun 2014)

[QUOTE 3141264, member: 45"]If you're in first gear it's really easy to pedal. It's easier for the chain to pull on the big ring at the back, but it has to travel further for the same output at the road. To travel at the same speed in say 6th gear you have to push harder with your foot but for less distance travelled of the chain. The pull on the chain is stronger to get the wheel to turn, so the chain is exposed to more force.[/QUOTE]
But the load on the pedal isn't increasing & the rear wheel isn't turning so the chain tension, for the same chain ring size, will stay the same.


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## raleighnut (20 Jun 2014)

The OP still managed to knacker a chain though


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## pclay (20 Jun 2014)

raleighnut said:


> The OP still managed to knacker a chain though



Yes i did, Now going back to gears. Going to sell the Raleigh for about £50 if i can. considering a £200 fixie from ebay.


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## GrasB (20 Jun 2014)

pclay said:


> Yes i did, Now going back to gears. Going to sell the Raleigh for about £50 if i can. considering a £200 fixie from ebay.


On that subject, I think part of the chain damage problem is that you're using a non-toothed tensioner with a multi-gear chain & chainring setup. This will allow the chain to move much more than it would normally. I'm still of the opinion that the chain damage was caused by it trying to change chainrings but not quite being able to so the chainring trying to lever the side plates off.

Personally I'd go buy a 1/8" sprocket, chain, chainring & chainring shims then try again if I was to run that bike but getting an already setup single speed may well be the best option for you.


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## GrasB (21 Jun 2014)

[QUOTE 3141301, member: 45"]I'm not talking about a static wheel am I? This discussion stemmed from a claim that there will be more force on a fixed chain going up a hill, than on a bike with the option of easier gears. And that's correct. Introducing static wheels is just confusing things.[/QUOTE]
But this doesn't answer the question that screenman asked.


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## GrumpyGregry (21 Jun 2014)

I saw damage like that when using a pined and ramped chainwheel off an mtb chainset on my first ss mtb which didn't have a chainguide in place. Basically under pressure, far higher and more sustained that it would ever be on a geared biike, thanks to the ramps, the chain was trying to move to another chainwheel that wasn't there. Mashtastic, horrid noises, much swearing. This is exacerbated if the chainline isn't good imo.

On the next bike, now sold, I used a plain, non-ramped, all teeth same size, no pins, Salsa chainwheel. No problem.


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## GrasB (21 Jun 2014)

[QUOTE 3141955, member: 45"]He asked how chain tension varies when going up a hill on a fixie. It addresses that question. As I said, the business of chain tension when the wheels aren't moving is irrelevant and is confusing the issue.[/QUOTE]
Then quote the CORRECT post then. Also static tension is never irrelevant & writing it off as being confusing/irrelevant means you're making sure he can never understand what's actually going on.


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