Single speed conversion damaging chain?

[pclay]

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

 

[Pennine-Paul]

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!

 

[raleighnut]

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

 

[Smurfy]

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.

 

[Smurfy]

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.

 

[raleighnut]

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

 

[GrasB]

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.

 

[pclay]

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.

 

[fossyant]

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 ?

 

[pclay]

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

 

[GrasB]

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.

 

[raleighnut]

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

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.

 

[RedRider]

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.

 

[Old Plodder]

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

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.)

 

[pclay]

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