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  1. #1
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    Chain tension with a magic gear...is there a 'too tight'?

    I used to get the chain pretty tight on the BMX bikes, but I remember there being a bit of a 'sweet spot' where there wasn't really much resistance backpedaling, but the chain was still snug...I'm assuming that's the 'ideal' that I'm going for.

    I got the new (my first) SS built up and I accidentally found a magic gear. The chain is what I would call "really darn" tight. I think it might be the perfect situation where after I get some stretch out of the chain, it will be in that sweet spot... instead of being in that sweet spot until it stretches, and then having issues. Until then, though, I'm wondering about excessive wear on the BB or the rear hub with a "really darn" tight chain. Am I asking for trouble in these first few miles while it's so tight? My hunch is that my weight on the cranks, and on the rear axle is causing way more wear than a tight chain could cause, but I'm curious about how tight the average magic gear singlespeed chain is.

    The bike has vertical dropouts obviously, and it's a cheap Shimano square taper BB, standard geared hub with a spacer kit/surly 20t cog. The chain is a SRAM PC1.
    Thoughts?
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  2. #2
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    My thought would be to throw a half link on there and see if it is still tight enough without dropping the chain. Then once the chain stretches take the link out.
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  3. #3
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    Not sure if you have a nice frame, or a beater. If you're not too concerned with long term value of the frame, you could dremmel or die grind the dropouts for an extra 0.5mm (or so) of play. I did this on an older C-dale road bike to to get the chain tension just right on a "magic gear" fixed gear bike. I also used a solid axle with nice track nuts and really made sure to crank down on them to ensure no slippage.

    Would this work on a Mt. Bike? I dunno, just throwing it out there.

  4. #4
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    A half link will give too much slack. If you grind the dropout you will never get your wheel back to the original position. Ghetto method has no returns. Either get an eccenric hub, bb, or chain tensioner.
    But if you need a chain tensioner you may as well have a derailleur. Tensioners are fugly. Whatever you do, don't run that chain uber-tight, you will sound like a tard riding around with that dry, stressed chain sound.

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    You are not ansewering the question. CommuterBoy said "I'm wondering about excessive wear on the BB or the rear hub with"

    Is it really bad to have a tight chain?

  6. #6
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    file your axle down to give you more slop in the crop out... Mine is filed down to a half moon shape and it gives enough give or take to account for new or old chains without having to use a half link.

  7. #7
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    Quote Originally Posted by maxforce View Post
    You are not ansewering the question. CommuterBoy said "I'm wondering about excessive wear on the BB or the rear hub with"

    Is it really bad to have a tight chain?
    I said you look like a tard. That means it's really bad.

  8. #8
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    It'll be bad for the chain as well. The extra tension will put more stress on your hub and crank. I think it will cause premature wear. But the chain will wear faster, getting you to that sweet spot faster, I guess, if it doesn't break first. But if it does, you will finally have two brakes on your bike. Keep a couple extra chainlinks in your bag if you decide not to use a tensioning device.

    I kinda hate magic gear myself, due to the small window of it actually being useful. I don't mind tensioners either.

    Quote Originally Posted by atom29 View Post
    I said you look like a tard.
    Uh oh.

  9. #9
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    I thought we already established the fact that I was a tard (?). For the record it's not making that 'dry, stressed chain sound". It could be quieter, but it's quieter than my geared bikes as-is. I'm just curious if anyone has experienced any kind of failure (BB or rear hub related) due to a tight chain. Sounds like no?

    I don't want to alter the dropouts... It's a cheap Taiwan frame, but they don't make it with 135mm rear wheel spacing anymore...the new ones are 130mm, so it's an irreplaceable cheap Taiwan frame.

    I'm thinking I'm going to see if it settles in to that sweet spot in the first hundred miles or so... worth finding out, even if it costs me some wear... Just would rather avoid a catastrophic failure (other than the bike itself umarth, thank you)

    Will a SRAM 8 speed masterlink work on a PC1 chain? I carry a couple links with 8 speed masterlinks.
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  10. #10
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    I am pretty sure that Srams 8 speed would work.

    If the noise is the issue, you have tried giving the chain a wipe and relubing?

  11. #11
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    Quote Originally Posted by CommuterBoy View Post
    I thought we already established the fact that I was a tard (?). For the record it's not making that 'dry, stressed chain sound". It could be quieter, but it's quieter than my geared bikes as-is. I'm just curious if anyone has experienced any kind of failure (BB or rear hub related) due to a tight chain. Sounds like no?
    .
    I 'may' have done I recently trashed a Deore hub, drive side cup pitted, cone disintegrated and whilst I'm not 100% sure of the cause I'm leaning towards running my chain too tight.

    On the bight side it did me an excuse to buy a new Surly hub, which as it takes a screw on freewheel meant I had to buy a White Industries freewheel
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  12. #12
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    The quick cure for the sound is headphones.

    However, a chain that is too tight will cuase all sorts of issues.... not the least of which is that it could simply snap on you one day.... most likely whilst you are fully out of the saddle, grinding with all your weight, and not prepared at all for the sudden shift in weight.... After you stitch up the gash in your calf left by the chainring, you'll put the tensioner back on, and start to looka t your other options, includ ecc hubs, bbs and progressively less obvious tensioners.

    My opinion is that the magic gear thing is a temporary fix at best. If you have a moderately used chaint hat has already been through its initial wear-in, and you get it magic-geared to proper tension... it will be a longer temporary fix.

  13. #13
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    Do what flipnidaho said - file two flats on the axle, just to the depth of the threads will be enough, and then, when the chain beds in a bit rotate the axle to the unfiled portion.

  14. #14
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    So tight that it is making the bearings sticky is bad.

    Quote Originally Posted by atom29 View Post
    Tensioners are fugly.
    Says the purist.

    Tensioners work.

    "it IS possible that you are faster or slower than anybody else who is having at least as much if not more or less fun"

  15. #15
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    I had a magic gear with PC-1 chain on my SS a while ago. The chain stretches so fast, no need to worry about component wear. Ride it hard for about 50 miles and you should be in the sweet spot you describe. Then 100 miles later you'll need a tensioner.....

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    You will be fine and the parts at risk are cheap. Is the freehub body steel? Does the cog have the fatter base?

    I have been running a magic gear for six years and find that a loose chain is only an issue if your chainline is poor. One way to check your chainline is to remove the spacers from the freewheel and see where the chain moves the cog. The chain wants to be straight and slack so it will naturally move the cog to the best location. Mark this location with a sharpie and mount the spacers accordingly.

    I also like the cog as close to the base of the freewheel so I run the BB spacers on the non drive side and the ring in the middle position.

  17. #17
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    Quote Originally Posted by Adroit Rider View Post
    You will be fine and the parts at risk are cheap. Is the freehub body steel? Does the cog have the fatter base?

    I have been running a magic gear for six years and find that a loose chain is only an issue if your chainline is poor. One way to check your chainline is to remove the spacers from the freewheel and see where the chain moves the cog. The chain wants to be straight and slack so it will naturally move the cog to the best location. Mark this location with a sharpie and mount the spacers accordingly.

    I also like the cog as close to the base of the freewheel so I run the BB spacers on the non drive side and the ring in the middle position.
    Great tip!

    Thanks!
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  18. #18
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    Divernick is right. You will be able to watch that chain wear out right before your eyes.
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  19. #19
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    Sweet. If these chains stretch as fast as you guys are saying, I'm assuming I'll be in the 'sweet spot' before I could do any real damage. I will keep an eye on those rear hub bearings though.

    Anyone ever pre-stretch a chain by hanging it from something with some weight on it? Just a thought.

    great tip on letting the chain center the cog for optimum chainline. I'm pretty sure I've got it dialed in, but I will remember that one.

    Yes, steel freehub body, fatter-base cog.

    Thanks for all the input.
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  20. #20
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    Quote Originally Posted by CommuterBoy View Post
    ...
    Anyone ever pre-stretch a chain by hanging it from something with some weight on it? Just a thought.
    ...
    I presume you're being facetious ... if not... ummm... well that's just not how chain 'stretch' works....

  21. #21
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    ^ No, I was being serious. Haven't tried it, but why wouldn't it work? (use small words, I'm a tard ) Does the chain stretch because of the teeth of the sprocket pulling on each individual link, or does it stretch in between the sprockets becuase of tension? I'm assuming it's due to the overall tension, not the interaction with the sprockets. The part of the chain that's on the sprockets is probably under the least load, since each link is only bearing a small amount of the tension...the part of the chain on top, between the two sprockets, is where I'm thinking that the stretch happens...which you could simulate by hanging the chain with some weight on the bottom.


    And I like the axle-shaving idea... if it doesn't stretch right out I will look into that. Seems like the least permanent way to gain a tiny bit of slack... at least in terms of cost.
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    Sorry, didn't mean to sound condescending...
    Chain 'stretch' is a bit of a misnomer. It doesn't actually stretch, it wears, and the wear causes the linkages to develop spaces and the overall length of the chain increases. Since it is wearing, not stretching, hanging weight from it won't do anything but... Well, make you look a little like a ****tard. :P

  23. #23
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    Hanging weights from a chain is a 'tard of an idea.

    How about using the chain on your geared bike for a bit before putting it on your SS?

    I'm runnin magic gear on my 26" rigid. Chain is way stretched now, but no issues with drops. I also don't have a problem with running a tensioner if I have problems.

    Last thing-RE: half-link. User "bad mechanic" has good info on which half link to run. Although I haven't had problems with SRAM powerlinks, his seems to be a stouter method.

  24. #24
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    ^ I actually had the idea of using an older, worn 8 speed chain. I have a couple of them hanging around. But then I thought that maybe I could get this one on there, so I gave it a shot, and it fit. If it becomes an issue I could just start using the old 8 speed chain off of my commuter when I replace it.

    so what actually causes the 'stretch' in a chain? is it the pins wallowing out the holes in the links due to repeated movement? If that's it, hanging weights from it would be a 'tard of an idea. If it's simply the result of the force exerted on it, then the weights would work.

    I honestly didn't know half-links existed until last week when I first visited this forum and found out that I am a 'tard. I will do some searches on them...but I think a half-link would create too much slack. Since I already have a few SRAM powerlinks, I'll probably go that route until I break something (not brake something, obviously)
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    It is the pins and links wearing and creating looseness in the chain...

  26. #26
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    ^^ Another fact I didn't need to know until I built a SS. This "simple" thing is, like, complicated.
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    Quote Originally Posted by CommuterBoy View Post
    ^^ Another fact I didn't need to know until I built a SS. This "simple" thing is, like, complicated.
    Actually chain wear (or 'stretch') is very much a concern for geared riders as well. It affects how the chain interacts with the cassette, and a chain that is kept on too far past its lifespan will prematurely wear out your cassette... Depending on how much you invest in your cassettes this can get expensive quick.

  28. #28
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    Quote Originally Posted by CommuterBoy View Post
    Will a SRAM 8 speed masterlink work on a PC1 chain? I carry a couple links with 8 speed masterlinks.
    I don't think it will work. You should test it out but when I went to 1/8" chains none of my old master links would work. They are too skinny. But I also don't remember which master links I tried, so test it out. Either it will fit or it won't, pretty simple test. But better to find out at home instead of on the trail when you need it.

  29. #29
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    ^ I will check and report back for future 'tards. "better at home than on the trail" is good advice. "Better at home than on the way to work in the dark when it's 2 degrees out" is more what I'm thinking...

    And I'm well aware of chain stretch and how it can wear cassettes. But I never had to know 'how' it stretched...just that when it did, it was time for a new one. I get about 2500 miles out of a chain, and have gone through at least 3 chains on a cassette...so 7500 miles at least. You can easily get more than that out of a cassette if you're more careful than I am about replacing the chain.
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  30. #30
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    Quote Originally Posted by CommuterBoy View Post
    ^ I will check and report back for future 'tards. "better at home than on the trail" is good advice. "Better at home than on the way to work in the dark when it's 2 degrees out" is more what I'm thinking...

    And I'm well aware of chain stretch and how it can wear cassettes. But I never had to know 'how' it stretched...just that when it did, it was time for a new one. I get about 2500 miles out of a chain, and have gone through at least 3 chains on a cassette...so 7500 miles at least. You can easily get more than that out of a cassette if you're more careful than I am about replacing the chain.
    Sorry, but if the SRAM is a 1/8th width chain, no way the 8 speed works. I didn't think that the PC1 was a wide chain, so boners on my part.

    I mean really, you shouldn't be riding without a powerlink and extra chain as well.

  31. #31
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    I've been riding since the mid 80's and I've broken exactly zero chains. So it's hard to get in that mindset. I do carry a couple masterlinks, but they're both 8 speed because that's what the commuter is (and they will work on a 9 speed in a pinch, which is what the MTB is. I wouldn't think the SS would run more of a risk of breaking, especially with a beefy chain, but maybe I'm pushing that envelope by running it tight.... Guess I'll get a couple powerlinks.
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  32. #32
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    Quote Originally Posted by CommuterBoy View Post
    I've been riding since the mid 80's and I've broken exactly zero chains. So it's hard to get in that mindset. I do carry a couple masterlinks, but they're both 8 speed because that's what the commuter is (and they will work on a 9 speed in a pinch, which is what the MTB is. I wouldn't think the SS would run more of a risk of breaking, especially with a beefy chain, but maybe I'm pushing that envelope by running it tight.... Guess I'll get a couple powerlinks.
    I've ridden for a much shorter time, but I've broken three or four. One of the breaks was my fault, and two of them were with 1/8th chains. I think they suck and don't use them for that reason. Still, really sucks to walk several miles when it is so easy to have a back up...

  33. #33
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    I don't think you have anything to worry about, CB. I run my chain on my fixed mountain bike tighter than Lorena Bobbit's snatch, and it has worked fine that way for months.

    It's stretched beyond the ability of a tool to measure and didn't like interacting with a smaller chainring (which I discovered the day before a race when it sounded like Satan popping bubblewrap), but even that problem went away after a few rides (which I think gave it and the smaller ring some time to get to know each other). If I can spin the cranks forward with the bike in a stand and the weight of the rear wheel doesn't cause the cranks to spin back when they've come to a stop, I've dialed in the right amount of tension for me.
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  34. #34
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    Quote Originally Posted by CommuterBoy View Post
    ^^ Another fact I didn't need to know until I built a SS. This "simple" thing is, like, complicated.
    It's only as complicated as you make it.

    If the frame has a derailleur hanger then put in more links and add a tensioner.

    If the frame does not have a derailleur hanger then custom make some simple little bent up doohicky that attaches to the axle. Go grab a spoon and drill like that one cool guy did a few years back.

    If you're worried about looks then you are the one complicating the simplicity behind the divinity of it all. Or is it 'the divinity behind the simplicity'? Whatever .....


    As for the magic gear thingy - been there, done that, don't care for it. It doesn't always last so long and i've found it winds up being more work in a season that other solutions. Worse yet, once I found out the hard way that the chain stretched beyond the "handling" of the teeth it was riding on. Thought I broke the chain until I picked myself up off the ground and saw what happened. Nursed it home and dropped that "magic" into the "g" file. I choose safety over magic now.
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  35. #35
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    Quote Originally Posted by AndrewTO View Post
    It's only as complicated as you make it.

    If the frame has a derailleur hanger then put in more links and add a tensioner.

    If the frame does not have a derailleur hanger then custom make some simple little bent up doohicky that attaches to the axle. Go grab a spoon and drill like that one cool guy did a few years back.

    If you're worried about looks then you are the one complicating the simplicity behind the divinity of it all. Or is it 'the divinity behind the simplicity'? Whatever .....


    As for the magic gear thingy - been there, done that, don't care for it. It doesn't always last so long and i've found it winds up being more work in a season that other solutions. Worse yet, once I found out the hard way that the chain stretched beyond the "handling" of the teeth it was riding on. Thought I broke the chain until I picked myself up off the ground and saw what happened. Nursed it home and dropped that "magic" into the "g" file. I choose safety over magic now.


    Word.

  36. #36
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    There is a dude in the "SS Swap" thread with a Forward Components EBB for trade. If your crank is compatible with it, I'd go for that.

    As for chain stretch:
    Chain Maintenance

  37. #37
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    Quote Originally Posted by flipnidaho View Post
    file your axle down to give you more slop in the crop out... Mine is filed down to a half moon shape and it gives enough give or take to account for new or old chains without having to use a half link.
    Anyone making an eccentric axle for Shimano rear hubs? I looked at mine and there is room for this to work. Might not be enough room with large qr/breezer dropouts though.

    Maybe someone can talk Homebrew into making some...
    lean forward

  38. #38
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    Quote Originally Posted by umarth View Post
    I kinda hate magic gear myself, due to the small window of it actually being useful. I don't mind tensioners either.
    "make your own majic"




    Both running strong for many years

    Top ran 30x15 for 7-8 years, finally broke a cog tooth last year after loosening up how many chains; now 34x19 with a (very) little extra filing after consulting the FixMeUp! calculator. New cog and chainring at the same time as new chain = little longer break-in, ie noise in the stand, but feels perfect on the trails



    Bottom running 45x18




    +++1 SRAM PC8

    Always carry a small length of chain and a spare SRAM-whatever EZ-link thingy - but haved only used them for friends bikes
    Last edited by struggleT; 01-19-2012 at 09:01 AM. Reason: Oops said the wrong gear its 34x19 not 36x19

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