Author Topic: Chain length?  (Read 2337 times)

djd828

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Chain length?
« on: November 02, 2015, 11:43:52 PM »
I am in the process of building a Thorn Raven and have started ordering many of the parts.  I plan to order the frame in early 2016.  I bought a KMC X1 chain yesterday but realized that I purchased the 96 link version of the chain.  I discovered later that there is also a 110 link version of this chain.  I will most likely get the size 565L version of the Raven and plan to run a 38 x 17 setup.  Does anyone know if the 96 link chain will be long enough for this setup?  I would use the formula on the Rohloff website but I don't know the length of the  Raven chainstay.

Thanks,

Dave

RonS

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Re: Chain length?
« Reply #1 on: November 03, 2015, 12:42:41 AM »
Hi, Dave

I think you're going to have to swap that chain for the longer one. I have a size 565 Raven with 38X16 gears and my chain is 98 links.

Chain stays on 565L are 445mm

Ron
« Last Edit: November 03, 2015, 12:58:52 AM by RonS »

djd828

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Re: Chain length?
« Reply #2 on: November 03, 2015, 02:38:28 AM »
Thanks Ron, that's what I suspected.  Seems like the  longer ones are sold out everywhere.  Any other model recommendations?

Dave

John Saxby

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Re: Chain length?
« Reply #3 on: November 03, 2015, 02:46:10 AM »
KMC 8.93 works for me, Dave, with the shiny silver quick-link.

SRAM PC-850 chains also work. They use an SRAM quick-link

Both of these are 8-speed chains, and both are well-made & not expensive.

djd828

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Re: Chain length?
« Reply #4 on: November 03, 2015, 02:56:48 AM »
Great, thanks again John.  Everything is coming along as planned I and hope to be riding the new Raven in a couple months.

mickeg

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Re: Chain length?
« Reply #5 on: November 03, 2015, 03:27:38 AM »
If you get any extra quick links, make sure you get the right ones.  KMC makes two different ones for 8 speed chains.

http://kmcchain.us/connectortype/8-speed-below-ml/

I have never cut a chain before I had the wheel and crank on the bike.  I put the chain on the cog and chainring, then I cut the chain to the correct length.

djd828

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Re: Chain length?
« Reply #6 on: November 03, 2015, 03:47:11 PM »
If you get any extra quick links, make sure you get the right ones.  KMC makes two different ones for 8 speed chains.

http://kmcchain.us/connectortype/8-speed-below-ml/

I have never cut a chain before I had the wheel and crank on the bike.  I put the chain on the cog and chainring, then I cut the chain to the correct length.

Thanks Mickeg, you were reading my mind a bit.  I wont do anything with the chain until I get the frame but this does spawn additional questions.  When I get the frame and cut the chain to length, do I do anything with the EBB afterwards?  Meaning, do I fit the chain and leave the EBB alone or do I have to fit the chain as best as possible then make a slight adjustment to the EBB to set the chain tension properly?  As you can probably guess, I never dealt with a single speed setup or an EBB but I would like to try to do this myself....without having to buy another chain as a "do over." 

Thanks again,

Dave

Andre Jute

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Re: Chain length?
« Reply #7 on: November 03, 2015, 06:41:40 PM »
You'll get specific instructions and hints on setting the EBB from the helpful chaps here. But you should fix it in your mind permanently that a Rohloff hub gearbox operates by preference on a pretty slack chain, so you should leave yourself a bit of leeway.

You can get a Rohloff manual in English free off the net. It makes good reading.

mickeg

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Re: Chain length?
« Reply #8 on: November 03, 2015, 06:52:23 PM »
The chain will get longer, not shorter.  So, with the wheel and crank on, I think it is best to set the eccentric so that the bottom bracket is pretty far back (towards the rear wheel).  Then wrap the chain around the crank and cog on the wheel to see where to split the chain.  Split it.  If you are unsure exactly where, making the chain too long instead of too short is better at this stage.  You might have to remove the wheel to put in the quick link that comes with the chain to make it a whole loop because the quick link starts out a bit short when you first assemble it.  Then put the wheel back in with the chain on.  That loop will likely be quite droopy at this point, so tighten the chain using the eccentric.  If you split the chain too long, not a problem, easy to take out another link and redo it.  An 8 speed chain can be very forgiving, so if you accidentally make it too short, you can reinstall the link again if the link was not driven all the way out of the side plate.  But it is easier to make a chain shorter instead of longer, so if unsure exactly where to split it, make it too long instead of too short.

The bolts that are used to hold the eccentric in place have pointy ends that create little divots in the Aluminum of the eccentric.  When you pedal, you are pushing down on the pedals, which also pushes down on the bottom bracket and on the eccentric.  So, you are actually pushing that soft Aluminum eccentric into the pointy ends of the bolts.  One problem I have had is not tightening the bolts enough, they got loose over time I think because the little divots got a little deeper as I pedaled.  I posted another link on my rubber band methods of making sure that the bolts do not fall out from vibration.

http://thorncyclesforum.co.uk/index.php?topic=11125.0

Instructions from Thorn say you have to be careful that you do not make minor changes in the chain tension that is too small of an adjustment.  If the little divots that you push into the eccentric are too close to each other, they can result in a long groove in the eccentric instead of a series of divots.

I carry a spare quick link and some of my left over chain in case I have a chain break on me while touring.  Never needed it yet, but the extra links are cheap. 

Around home I use a 44T chainring, but for a tour where I am doing a lot of hill climbing, I use 36T chainring.  Thus, I use a second quick link and regular chain link to lengthen my chain for when I use the 44T.  When I built up my Nomad, I bought a bunch of spare quick links.

The eccentric is installed in the shell so that the thick part is in the bottom - that is so that the screws that hold it in place push against a thick piece of metal, not a thin piece that could be deformed.  That does not answer your question, but I wanted to make sure you knew that.  See photo, the thickest part of the eccentric is under the bottom bracket, not above.
« Last Edit: November 03, 2015, 06:57:25 PM by mickeg »

djd828

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Re: Chain length?
« Reply #9 on: November 03, 2015, 07:26:15 PM »
Thanks again Mickeg,

I believe the frame will arrive with the thickest part of the EBB in the 3 o'clock position so that I have the optimal amount of adjustability.  I'd like to cut the chain to length and leave the EBB in the 3 o'clock position if that is possible. 

By the way, is there a preferred way to keep track of where the adjustment holes are on the EBB so that you can avoid the potential long tracks running along the EBB?  I have read that some use permanent marker to mark lines on the EBB and shell and others look through the screw holes to see where the indentations are. 

By the way, the more I see those yellow Nomads, the more I want one....I haven't bought the Raven frame yet ;)

Dave

mickeg

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Re: Chain length?
« Reply #10 on: November 03, 2015, 08:06:11 PM »
I am not really sure what the Raven is, but I think it is basically  the same as a Thorn Sherpa, but with a Rohloff instead of derailleurs.  I have a Sherpa, the Nomad and the Sherpa are very different bikes.  Nomad is much heavier.  If you are not planning to carry a lot of gear, the Nomad is not the best bike for you.  The Nomad looks nice, but it really is built for heavy duty use.  My Nomad is much heavier than you would likely want unless you plan to really load it down.  I have also used my Sherpa with a pretty big load, it worked very well for that.

Someone else on this forum had a good idea, when he adjusts his eccentric, he puts his bike upside down.  Takes one bolt completely out.  Then he can look in the hole and see where that little divot is before he loosens the other bolt to make any adjustments. 

To the best of my knowledge, there is no specified minimum distance between those little divots, but what I am doing is trying to make sure I do not put them closer that about 4mm from each other.  I am guessing 4mm because the bolt is (I think) an M8 bolt, so if I can just barely see the center of a divot at the edge of the hole, that would be about 4mm.

I am using the word divots to represent the little depressions that the pointy bolts put in the eccentric.  I hope my usage of that word is not confusing.

These are the bolts they use.
http://www.sjscycles.co.uk/thorn-m8-extra-fine-cone-pointed-screw-for-eccentric-bottom-bracket-shell-prod12630/?geoc=us

Photo of my Sherpa with a full camping load, it handled the load quite well.