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Thread: Magic Gear

  1. #1
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    Magic Gear

    I run magic gear on my alfine bike with standard dropouts. I get quite a bit of chain stretch which I handle by using a couple of different sized cogs and half links, but it seems like I'm dealing with it every every few weeks. I'm no hammerhead so it seems to me like I'm dealing with it more often than I should.

    Which 3/32 chain is the most resistant to stretching?

  2. #2
    dru
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    An 8 speed should be more durable than a 9. You should be fastidious about cleanliness and lube if you want to offset premature wear, or stretch as you call it.

    Drew
    occasional cyclist

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    Quote Originally Posted by Corporal Punishment View Post
    I run magic gear on my alfine bike with standard dropouts. I get quite a bit of chain stretch which I handle by using a couple of different sized cogs and half links, but it seems like I'm dealing with it every every few weeks. I'm no hammerhead so it seems to me like I'm dealing with it more often than I should.

    Which 3/32 chain is the most resistant to stretching?
    1- chains don't stretch
    2- that much 'stretch' (full half inch??) says that something else is going on
    3- There are no 'standard' drop-outs
    Honestly... ahh I give up

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    Quote Originally Posted by highdelll View Post
    1- chains don't stretch
    2- that much 'stretch' (full half inch??) says that something else is going on
    3- There are no 'standard' drop-outs
    1) My chains stretch. I didn't think that was special or magical to me.

    2) My last chain stretched far more than a single half link. Hell, it stretched more than a full link. I only threw it out when it stretched out to the point where it was binding up on chainring/cog teeth. The fact that it stretches never bothered me - only the frequency of having to mess with it, hence my question about the most stretch resistant chain. I clean and lube it every couple of weeks.

    3) I'm guessing you understood what I meant. If I had track dropouts or sliders, I wouldn't need to run a magic gear.

    If you know of a 3/32" chain of a superior non-stretchiness quality, or if you believe my chain is stretching prematurely and you have some possible solutions, I'd greatly appreciate your passing that information along. Cheers!

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    Quote Originally Posted by Corporal Punishment View Post
    1) My chains stretch. I didn't think that was special or magical to me.

    2) My last chain stretched far more than a single half link. Hell, it stretched more than a full link. I only threw it out when it stretched out to the point where it was binding up on chainring/cog teeth. The fact that it stretches never bothered me - only the frequency of having to mess with it, hence my question about the most stretch resistant chain. I clean and lube it every couple of weeks.

    3) I'm guessing you understood what I meant. If I had track dropouts or sliders, I wouldn't need to run a magic gear.

    If you know of a 3/32" chain of a superior non-stretchiness quality, or if you believe my chain is stretching prematurely and you have some possible solutions, I'd greatly appreciate your passing that information along. Cheers!
    You are both right, kind of. Chains do not stretch as most people use the word (incorrectly), they WEAR. However, as they wear they become longer or extended, which is a/the definition of "stretch".

    Most people incorrectly misuse the meaning of stretch as an adjective in a way that insinuates something is elastic, which is simply wrong. If you were to say you have a "stretch chain" you'd be saying you have a chain that is elastic whereas if you have a stretched chain you have a chain that has become extended. Grammar lesson over...

    As for cleaning/lubing, every few weeks may be fine if you ride very little or generally ride in conditions that leave your chain fairly clean. If you put in 300 miles/wk in muddy conditions that would be far too infrequent. I completely clean and lube my chain every ~5 rides to keep the wear on chain/cog/chainring to a minimum. My rides average about 30 miles so I guess I use 150 miles as a general rule (about 20x a year).

    And as for a chain that would stretch less, look for a bushingless chain as the rollers will not wear as quickly. KMC makes many many different versions. Perhaps you are putting your chain in a goofy chainline too frequently which would cause the bushings to wear into the rollers more quickly than if you had a straiter chainline??

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    Quote Originally Posted by Corporal Punishment View Post
    1) My chains stretch. I didn't think that was special or magical to me.

    2) My last chain stretched far more than a single half link. Hell, it stretched more than a full link. I only threw it out when it stretched out to the point where it was binding up on chainring/cog teeth. The fact that it stretches never bothered me - only the frequency of having to mess with it, hence my question about the most stretch resistant chain. I clean and lube it every couple of weeks.

    3) I'm guessing you understood what I meant. If I had track dropouts or sliders, I wouldn't need to run a magic gear.

    If you know of a 3/32" chain of a superior non-stretchiness quality, or if you believe my chain is stretching prematurely and you have some possible solutions, I'd greatly appreciate your passing that information along. Cheers!
    OK - they do not 'stretch' /wear a half an inch - if they did, your pitch would be so far off that you would either; throw chains from the CR/Cog) teeth catching or your DT would just skip like crazy - and then throw the chain. - no matter the tension.

    And no...you are so wrong about a chain 'stretching' that far, that I have to assume you use half-links so solve a prob. for a magic-gear

    A CHAIN WILL NOT 'STRETCH' SO FAR AS A HALF-INCH AND NOT GIVE YOU MAJOR TROUBLE BEFOREHAND - NOT POSSIBLE. <~~~ that's a period.
    Honestly... ahh I give up

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    After wearing out a lot of chain, and getting only 1200-1500 miles/chain I think I've found the one. The KMC 510hx (1/8"), for 3/32 use the 610hx. It is no feather weight, but on my Nuvinci I have already put 50% more mileage on it, and I still have plenty of wear left in it. At this rate I expect to double my best mileage from last year.

    Now the fun part. If you have run your chain as worn as you say without experiencing bad chain karma it is likely that your chainring/cog is seriously worn as well. In many cases that I have seen a new chain will work alright in worn out gears, but it wears at a much faster rate than it would in a system that is in sync.

    One thing I added that gave me a few hundred miles more was mudflaps on my fenders. The front mudflap keeps road spray off of my chain, and after installing it I went from 1200 miles to 1500 on the next chain. So, keeping your chain clean can also mean adapting your rig to the elements a bit on top of regular maintenance.

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    I'm having good results with a SRAM PC-890 with Gusset S-Links and KMC master links.

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    Quote Originally Posted by jtrops View Post
    After wearing out a lot of chain, and getting only 1200-1500 miles/chain I think I've found the one. The KMC 510hx (1/8"), for 3/32 use the 610hx. It is no feather weight, but on my Nuvinci I have already put 50% more mileage on it, and I still have plenty of wear left in it. At this rate I expect to double my best mileage from last year.
    Thanks. I'll look into those chains next time I buy a new one. I avoid the 1/8" chains because I run a bashgard which tends to make a little noise with 1/8" chains. Maybe I can try to find some spacers or something to sort that out.

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    Quote Originally Posted by highdelll View Post
    A CHAIN WILL NOT 'STRETCH' SO FAR AS A HALF-INCH AND NOT GIVE YOU MAJOR TROUBLE BEFOREHAND - NOT POSSIBLE. <~~~ that's a period.
    YES, POSSIBLE. <~~~ that's a period.

    My total chain length is about 40" give or take. That's 40 full links - 80 pins/bushings. Each bushing only needs to wear, elongate, stretch or however you want to semantically describe it 1/80" to stretch the entire chain by 1 full inch. That's so small its practically imperceptible to the human eye, except yours perhaps.

    And as I said in my OP, its not long after that time when I toss the chain because it starts to bind on the chainring/cog teeth. NOT BEFORE. <~~~ that's a period.

    The cog/chainring teeth look fine to me and the only time the chain jumps is when it WEARS/stretches to the point that there is so little tension it jumps off the cog during rough riding. That's how I know its time to change the cog size or take out the half link or both to get proper tension back. Otherwise, I'll ride that sucker until it a) breaks or b) starts binding on the cog/chainring teeth. I'd be spending a lot of money on chains if I changed it every time it stretched a little. Maybe I'm stronger than I thought, or maybe I'm buying the wrong chains. Or maybe both.

  11. #11
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    Overtensioning would cause premature wear but you'd notice a tight chain. What chains are buying? I'm not the stronest guy out there but at 230 and SS only, I don't even put that much stress on my chains.

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    Quote Originally Posted by Corporal Punishment View Post
    Thanks. I'll look into those chains next time I buy a new one. I avoid the 1/8" chains because I run a bashgard which tends to make a little noise with 1/8" chains. Maybe I can try to find some spacers or something to sort that out.
    I'm running the 510hx on my commuter because I need a 1/8" chain for the cog on my Nuvinci. The 610hx is a 3/32" chain of the same construction, just narrower. When my chain on my SS 29er goes I'll be switching to a 610.

    I should also point out that I replace my chains when I get to the standard wear point (.75-1.0% elongation). So I expect to get close to 3k on my current chain before it gets to that point. It sounds like you are running your chains a little longer, 40" x 1.25%=.5". So given all of that it seems to me that you are probably running your chains a little longer than recommended. If that works for you I'm not going to argue. I have seen chains wear out faster on rings that had very little perceptible wear. And so it may be another part of the puzzle at least.

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    I just measured my chain. I was guessing before. I was way off - its about 47". Currently running 32/21 CR/cog on my H/T 26er. 1% stretch would equal 1/2 link. I'm sure overtensioning plays a part because, well, its magic gear after all so when it stretches a bit and I move up to the next size cog, sometimes its a little tight but as long as the crank turns well, I just live with it because I know it will stretch soon anyway.

    My last chain was a SRAM PC850 (I think). The one I replaced it with is a PC 890.

    I have 3 cogs - 20T, 21T and 22T. There's a half link difference in chain length between the 20T and 22T. A new chain fits perfectly using a half link and the 21T. When it starts to stretch, I'll change the cog to 22T and when it stretches further, I take out the half link and change the cog to 20T. Then later move up in size as the chain stretches further. And so on and so on. I'm pretty sure I went through that process 3 times before the links elongated to the point that i started getting binding. Even then, as long as the chain doesn't break, I could care less but the noise drives me crazy. ;-)

    My goal here is to ride more often and mess around with changing the cog/half-link less often.

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    610hx is half the price of the PC890. Even better! Great reviews too. Thanks again for the tip!

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    Quote Originally Posted by jtrops View Post
    I'm running the 510hx on my commuter because I need a 1/8" chain for the cog on my Nuvinci. The 610hx is a 3/32" chain of the same construction, just narrower. When my chain on my SS 29er goes I'll be switching to a 610.
    Fallbrook specifies a 3/32" chain for the Nuvinci N360. Supposed to use 3/32" cogs, not enough clearance for a 1/8" on mine.

    I picked up my SRAM PC-890 for $20 from Universal Cycles a while back. It has approx 500 miles of use, no noticeable chain stretch whatsoever. Still is exactly at the 12" mark when using a straight edge.

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    Quote Originally Posted by crazylemurboy View Post
    Fallbrook specifies a 3/32" chain for the Nuvinci N360. Supposed to use 3/32" cogs, not enough clearance for a 1/8" on mine.

    I picked up my SRAM PC-890 for $20 from Universal Cycles a while back. It has approx 500 miles of use, no noticeable chain stretch whatsoever. Still is exactly at the 12" mark when using a straight edge.
    I have a Nuvinci N171B w/ a Suntour (a nice old one, not one of the new garbage versions) 1/8" 16t BMX freewheel. It's good to hear that you are getting such good mileage from your PC-890. I think my last SRAM chain I had on that bike was a PC830, which is supposedly the same strength just a bit heavier, and it lasted 1200 miles before I got to .8% elongation. To be fair, that was through the winter, and it was before I put the mudflaps on. So, I could have had better mileage, but still nothing like what I'm seeing with the KMC. I also understand that cargo bikes tend to go through chains a bit quicker than other bikes. I guess when I'm carrying two kids with four bags of groceries it is a bit stressful on a chain.

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    Quote Originally Posted by jtrops View Post
    I have a Nuvinci N171B w/ a Suntour (a nice old one, not one of the new garbage versions) 1/8" 16t BMX freewheel. It's good to hear that you are getting such good mileage from your PC-890. I think my last SRAM chain I had on that bike was a PC830, which is supposedly the same strength just a bit heavier, and it lasted 1200 miles before I got to .8% elongation. To be fair, that was through the winter, and it was before I put the mudflaps on. So, I could have had better mileage, but still nothing like what I'm seeing with the KMC. I also understand that cargo bikes tend to go through chains a bit quicker than other bikes. I guess when I'm carrying two kids with four bags of groceries it is a bit stressful on a chain.
    Ah, I did not know the 171B used a 1/8" chain. My N360 has the shifter interface inside the dropouts, and a 49 mm chainline. Can you say tight clearances? I am using P50 SKS fenders without mudflaps. I keep my chain reasonably clean. I found one of the biggest components in chain wear is... chain lube! I've been using Prolink for ages. Recently switched to Rock N Roll lube. Wow is all I can say. I can go weeks without cleaning the chain, not mere days. Prolink gathered dirt and grit at an alarming rate. I'm installing mudflaps and a SKS chainguard this week to improve pant usability and chain wear. I'm a nut when it comes to making parts last. One thing to note: when I switched to from PC-850 (wore out in about 1800 miles) to PC-890, I went from aluminum gears to Surly stainless steel cog and chainring. I also increased the overall gear size considerably. I was using 38/20, went to 42/22 and now running 48/22. Hard to say any one factor has improved chain wear, but the results are astounding and measurable.

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    Just a quick update. It's been a couple of months now on the PC-890 and no magic gear cog adjustments have been necessary so far. Its holding up very well. I guess the nickel plating is doing its job after all.

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    Nice! I'm glad to hear the PC-890 is working for you. I am also using the same chain from before. I'm at the 1900 mile mark and the chain has just begun to stretch. Measuring under tension, the pin at the 12th link is JUST past the 12" mark by about 1/16" so it's probably halfway or just over to the replacement point. So far much better durability than any Shimano chain I've tried or any other 8 speed SRAM offering.

    Due to chain stretch, even this minimal amount, my magic gear is just a bit too slack for my comfort so the Surly tensioner is back on, but with minimal tension just so it snugs up against the cogs. That tensioner can apply way more pressure than necessary. I have begun to consider a bottom bracket tensioner such as the YESS ETR/B, but for the time being this is working fine. There is definitely a point where the 'magic gear' is lost when the chain just gets a hair too long. I suppose you could change out the cog/chainring, but I really like the gear ratio I'm in now. I also failed in my attempt to install the SKS chainguard because the plastic guard is just absurdly thick. I am using a Sugino RD2 crank with the chainring on the outer position to minimize Q-factor and the plastic is thicker than the space between where the chain sits on the chainring and the crank arm. If I were to switch it to the inside position it would fit, but it is something to note.

  20. #20
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    Good job!

    Years back when Sachs made chains called Sedis...

    ...they lasted much longer. Now with Sram, I snap more chains now and have gone to BMX width chains on my single speed, also switched to KMC brand.

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    Quote Originally Posted by crazylemurboy View Post
    I'm at the 1900 mile mark and the chain has just begun to stretch.
    I'd say you've earned a new chain. The thing I hate about tensioners is the noise they make. It ruins my beautifully silent alfine experience. That's why I'll mess with the cogs before going back to a tensioner.

  22. #22
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    On my rohloff I run wipperman IG8 with a Phil cog.. , No stretch, and rocks and logs are not a worry.. people laugh when they see it.. But i can run it without a rock ring. Its a good east coast setup..

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