# Uneven chain tension...Thoughts??



## MD Sleep (Apr 6, 2007)

I ride a Ti SS with FCC EBB for tensioning.

I have noticed that the tension in my chain is not perfectly even through the full rotation of my cranks. ie: there are points where the tension is close to too loose, close to too tight and then some parts that are perfect. 

I initially thought it was just an uneven front chainring so I just upgraded from a Surly to a Homebrewed Ti front (which is absolute art by the way). 

The uneven tension is still there so now I am at a loss. Could it be the chain? 

It is not severe to the degree that I would drop a chain or have binding issues, but one of the many beauties of SS for me is having a super efficient and smooth drivetrain. 

Any advice/ thoughts would be appreciated.


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## ISuckAtRiding (Jul 7, 2006)

MD Sleep said:


> I ride a Ti SS with FCC EBB for tensioning.
> 
> I have noticed that the tension in my chain is not perfectly even through the full rotation of my cranks. ie: there are points where the tension is close to too loose, close to too tight and then some parts that are perfect.
> 
> ...


What are you running for a rear cog/freewheel?
What crank? I've seen the bolt holes in the actual crank out of concentricity to the spindle before, but it's uncommon. If it's tight in one spot in the crank rotation, it's likely something in the front, but if it's twice, it's something in the rear. It's unlikely to be the ring, but if it is, i'll take care of it (glad you like it BTW!).
As for being the chain, it is possible to have a bad link that could cause it, but that's unlikely unless you have a new link on a really old chain and/or several sections of chain pieced together.


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## Nonracerrichie (Dec 20, 2005)

*OCD attacks*

It can be the freewheel but there really is not a fix for that, they come assembled and thats that. There is also play within the chainring bolts and the holes in both the crank and chainring. I tend to be a bit OCD with wrenching and have found that loosly assembling the bolts\ring and crank arm and then using say a chopped up business card and adding a sliver or two to the space between the shoulder of the arm and ring to evenly space it all before slowly tightening helps to get it all as round as possible.


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## aka brad (Dec 24, 2003)

From Sheldon Brown

*Centering Chainwheels*

The chain tension on a fixed gear is quite critical, and is regulated by moving the rear axle back and forth in the forkends. If the chain is too tight, the drivetrain will bind, perhaps only at one angle of the pedals (chainwheels are not usually perfectly concentric). It should be tight as it can be without binding. If the chain is too loose, it can fall off, which is quite dangerous on a fixed gear.

Set the rear axle so that the chain pulls taut at the tightest part of the cranks' rotation. One at a time, loosen up each of the stack bolts, and tighten it back just finger tight. Spin the crank slowly and watch for the chain to get to its tightest point. Strike the taut chain lightly with a convenient tool to make the chain ring move a bit on its spider. Then rotate the crank some more, finding the new tightest spot, and repeat as necessary.

This takes a little bit of your hands' learning how hard to hit the chain, and how loose to set the stack bolts, but it is really quite easy to learn.

Tighten up the stack bolts a bit and re-check. Tighten the stack bolts in a regular pattern, like the lug nuts on a car wheel. My standard pattern is to start by tightening the bolt opposite the crank, then move clockwise 2 bolts (144 degrees), tighten that one, clockwise 2 more, and so on. Never tighten two neighboring bolts in a row. You may prefer to go counterclockwise, but try to get in the habit of always starting at the same place and always going the same way. This reduces the chances of accidentally missing a bolt.

Once you have the chainrings centered and secured, adjust the position of the rear axle to make the chain as nearly tight as possible without binding. Notice how freely the drive train turns when the chain is too loose. That is how freely it should turn when you are done, but with as little chain droop as possible.


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## MD Sleep (Apr 6, 2007)

*Thanks guys*

ISAR: It is not your chainring, but thanks for offering to step up and fix it if it was. The thing is perfect as far as I can tell.

In the back: I am running a Hope Pro 2, Surly 19 T Cog and spacers. Normal dropouts as I originally was running gears on my frame.

Up front: I have new XT cranks, FCC EBB, and did my best to visually center up the chainring within the bolt pattern.

When I take the chain off and spin the cranks, I am not seeing a noticeable wobble at the edge of the chainring (I did see a small wobble with my Surly that I just replaced).

So I will re-check the front (I was thinking of holding a straight edge right next to the teeth and spin the cranks to see if it is not spinning true at the level of the teeth.

Not sure the best way to check the rear cog but that is a possibility. (Would be a good excuse to get another "Homebrewed"). I could also get a new chain.

My OCD is costing me $$$$ :madman:

Thanks for the input so far.


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## wjphillips (Oct 13, 2008)

aka brad nailed it. That Sheldon Brown article is spot on. You will need to re-adjust your front chain ring. Follow those directions and you'll be good to go.


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## Glide the Clyde (Nov 12, 2009)

Isn't it fairly typical for some varying tension with ss and that this is the case with just about any level of components? Seems to be the case with guys and gals I ride with. I ride cheap stuff and some ride high end CK, Hope or other stuff. We all run tension somewhere in the middle of chain drop loose and binding tight throughout a complete pedal revolution. 

In other words, it's normal and you can't eliminate it entirely?


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## ISuckAtRiding (Jul 7, 2006)

Malibu412 said:


> Isn't it fairly typical for some varying tension with ss and that this is the case with just about any level of components? Seems to be the case with guys and gals I ride with. I ride cheap stuff and some ride high end CK, Hope or other stuff. We all run tension somewhere in the middle of chain drop loose and binding tight throughout a complete pedal revolution.
> 
> In other words, it's normal and you can't eliminate it entirely?


if you're seeing droop in the pedal stroke, it's generally the chainstay flexing.
If you see tight spots and loose spots in the chain when just pedaling backwards in the stand, that usually can be corrected with a decent drivetrain.


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## ISuckAtRiding (Jul 7, 2006)

MD Sleep said:


> ISAR: It is not your chainring, but thanks for offering to step up and fix it if it was. The thing is perfect as far as I can tell.
> 
> In the back: I am running a Hope Pro 2, Surly 19 T Cog and spacers. Normal dropouts as I originally was running gears on my frame.
> 
> ...


i run my bolt holes fairly tight so the ring usually centers itself, but you *might* be able to get a hair of adjustment out of it. If you're seeing a little jump in the cog, that is likely it. It takes very little to give you a tight spot, so if you can see it, it's probably enough. Surly cogs generally run pretty loose on the freehub body, so maybe you can try centering it a little. Loosen your lockring until it's just barely holding the cog, then pedal till you find the tight spot. Then just squeeze the chain together a little and check for a new tight spot and repeat. This usually works if it's the problem.
Hope that helps!


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## Glide the Clyde (Nov 12, 2009)

ISuckAtRiding said:


> If you see tight spots and loose spots in the chain when just pedaling backwards in the stand, that usually can be corrected with a* decent drivetrain*.


Doesn't seem to be helping the OP much. Just saying.


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## ISuckAtRiding (Jul 7, 2006)

Malibu412 said:


> Doesn't seem to be helping the OP much. Just saying.


?
It was in reference to your comment about uneven chain tension, regardless the quality of the components. It is possible to get rid of it. 
If you read my other posts, you'd see that i was attempting to help him.


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## Glide the Clyde (Nov 12, 2009)

ISuckAtRiding said:


> If you read my other posts, you'd see that i was attempting to help him.


I didn't say you weren't and I'm sure he appreciates it as well as the high quality stuff you provide. I might even try some of it myself sometime when I step up to a bike worthy of it.

In my post, I was only trying to say that in most ss instances, regardless of the level of components, there is some varying chain tension within a pedal stroke and it's not fatal. A search will reveal dozens of posts by long time ss'ers who concur. I've tried the loosening the stack bolts/centering the ring and it helps some. That is all.


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## jackspade (Jul 23, 2010)

I still cannot fix my chain tight spot but I still enjoy my SS and since I am using 1/8" cog and chain the tight spot is no longer an issue.


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## MD Sleep (Apr 6, 2007)

*Thanks again*

Everyone has been very helpful. Thanks a ton.

I had to read aka Brad's Sheldon link a couple of times to figure out what the hell he is talking about, but now I get it and think that will be my next move. (Basically using tapping or squeezing the chain with slightly loose front bolts to help even out the front ring....smart.)

Maybe "perfection" in the chain tension is impossible, but I have another SS that I use to ride with my wife and kids and cruise the beach with, and the tension is much more even throughout the pedal stroke. There is definitely room for improvement with this drivetrain.

I will fiddle with it this weekend and give a report back.

Thanks SS guru's. Your "understanding" of my drivetrain OCD has been much appreciated. I was worried that this would turn into an online intervention and direct admission to rehab :eekster:


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## gearwhine (Aug 20, 2009)

I actually have the same exact problem with 2 of 3 of my shimano cranks...I use HBC rings as well. The only one that doesn't give me this problem is the M952 with his spiderless ring. My M960, and M970 with HBC rings give me tight spots. I have tried the sheldon brown method (all the way to the point of hitting the chain so hard I've bruised my hand), I have flipped, spun, etc. the chainring in every position possible, and it's always a tight spot in the same spot of crank rotation every time.

This occurs while using an HBC 2 piece cog, surly cogs of all sizes, WTB cogs...doesn't change where the tight spot occurs.

I have just given up trying to alleviate it. It's the cranks and it's not causing any problems other than mental problems.


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## ISuckAtRiding (Jul 7, 2006)

gearwhine said:


> I actually have the same exact problem with 2 of 3 of my shimano cranks...I use HBC rings as well. The only one that doesn't give me this problem is the M952 with his spiderless ring. My M960, and M970 with HBC rings give me tight spots. I have tried the sheldon brown method (all the way to the point of hitting the chain so hard I've bruised my hand), I have flipped, spun, etc. the chainring in every position possible, and it's always a tight spot in the same spot of crank rotation every time.
> 
> This occurs while using an HBC 2 piece cog, surly cogs of all sizes, WTB cogs...doesn't change where the tight spot occurs.
> 
> I have just given up trying to alleviate it. It's the cranks and it's not causing any problems other than mental problems.


That's a bummer. If you tried flipping the rings, orienting them differently, etc, and it's all still in the same spot in the crank, then it's the bolt hole location of the crank. Sometimes it happens, unfortunately. If you want, mail them to me and i can open up the holes to give you a little more float.


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## umarth (Dec 5, 2007)

I believe aka brad posted the relevant stuff. Instead of using your hand, try the handle of a hammer or something. It'll work better. Also, make sure the chain is appropriately lubed. 

On the off chance that people are trying to get perfect tension all the way around- don't. You have a good chainline, SS specific chainring and cog and you should be ok. I like to have things a little on the loose side because things tighten up here on rides because the mud and muck and I'd rather not be fighting more chain resistance than I ought.


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## gearwhine (Aug 20, 2009)

ISuckAtRiding said:


> That's a bummer. If you tried flipping the rings, orienting them differently, etc, and it's all still in the same spot in the crank, then it's the bolt hole location of the crank. Sometimes it happens, unfortunately. If you want, mail them to me and i can open up the holes to give you a little more float.


You're talking about sending you the cranks, correct? I'd be up for that. It's been frustrating enough to get it fixed up. I'll shoot you an e-mail or call (I believe I have your number from previous dealings) about it next week.


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## perttime (Aug 26, 2005)

Do you get the tight spot once in a crank rotation, once in rear cog rotation, or something else?

A few different cogs have done well on my Hope hubs but trying to center the cog, as ISAR suggested in post 9, or changing to a different cog could be worth a try too if centering the chainring doesn't help.


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## wjphillips (Oct 13, 2008)

One other thing I would suggest is make sure you are not using aluminum chain ring bolts. Use steel or Ti instead. They are less likely to need re-adjusting.


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## dblspeed (Jan 31, 2006)

I've seen that no matter what, chainrings and cogs are never perfectly round and/or centered, hence uneven chain tension; so I learned to live with it and now I look for the best compromise, if the cranks can spin freely backwards (ie loose enough) and I don't loose the chain in the rough (ie tight enough) then it's fine.


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## MD Sleep (Apr 6, 2007)

*Update*

So I messed around with the drivetrain again this am.

First I checked the front again without the chain and the ring visually was running true with no visible wobbles.

Next, put on the chain and just for the heck of it tried the sheldon method. First by tapping, but then I did it with hand pressure. I could actually feel that the play was in the back not the front.

Took off the rear wheel and low and behold I had a fairly loose lockring and some play in the rear cog. The amount of play was maybe a millimeter but had a big impact on the tension. Tightened the rear up. Re-adjusted the EBB and it is 80% better.

The remaining 20% is probably what I will have to live with as some of you have stated.

Thanks for the help. Problem solved! If you are motivated, I love how problems lead to learning and further understanding. :thumbsup:


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## perttime (Aug 26, 2005)

MD Sleep said:


> The amount of play was maybe a millimeter but had a big impact on the tension.


For chain tension, one millimeter is quite enough to make a big difference.


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