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Why are we running 3/32 chains for BMX?
CWracer
post Oct 13 2012, 07:52 PM
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I'm redoing a lot of parts on my bike and rethinking a lot of things. Other than weight being a factor a 1/8 chain seems more appropriate for BMX, especially for bigger stronger riders than 3/32. 3/32 are prone to stretching and designed for lateral movement between the gears on a road bike which means they are more susceptible to being thrown from the gear on a single speed. I'm probably going to switch.

I'm curious about other opinions on this. Who else is running a 1/8?
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sxebmx
post Oct 13 2012, 08:08 PM
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I've run both, and prefer 1/8th because i am deathly afraid of breaking a chain because I don't really do much(note, none at all) bike maintenance. That said, 3/32 feels way smoother. 1/8th has a bit more wiggle room and feels sloppy and get kinks easier(the lack of bike maintenance prob doesn't help.)

But that's just one dude, whose sitting next to a cat, doesn't really race very much, and is wearing pajama pants' opinion.
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cruiser247
post Oct 13 2012, 08:18 PM
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QUOTE (CWracer @ Oct 13 2012, 08:52 PM) *
I'm redoing a lot of parts on my bike and rethinking a lot of things. Other than weight being a factor a 1/8 chain seems more appropriate for BMX, especially for bigger stronger riders than 3/32. 3/32 are prone to stretching and designed for lateral movement between the gears on a road bike which means they are more susceptible to being thrown from the gear on a single speed. I'm probably going to switch.

I'm curious about other opinions on this. Who else is running a 1/8?


I've thought about this myself...the only thing is that most race sprockets, cogs, etc are 3/32...seems like there would be some slop (for lack of a better word) mixing the bigger chain with the thinner drive train parts.
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cwstnsko
post Oct 13 2012, 08:19 PM
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I run 3/32nds chian because I run 3/32 chinrings and cogs. I don't think there is anything inherently stronger about 1/8" chains. Good quality 3/32 chains are very strong. Many of us run 8 spd SRAM chains, but KMC makes many of the same chains they market to freestyle for racing applications in 3/32 width. http://www.kmcchain.us/kmclandinga.asp?bsid=55&ssid=643
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joelwitte
post Oct 13 2012, 08:50 PM
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i run 1/8" cause i'm not a weight weenie, i also run 1/8" cassettes and front gears, there is a big difference in chain strength, provided its a reputable chain, as you go to the larger widths, the main thing is making sure the side plates are thicker but all racers care about it saving fractions of an ounce cause you know, it makes you faster
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MikeCarruth
post Oct 13 2012, 08:58 PM
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Arielle Martin cites a 1/8" chain, installed on her race ride, for the crash that ended her 2012 Olympic hopes and almost killed her.

Her chain alignment was off, but because of the play, it made it appear OK. And it threw off the rear cog.

I think that is a pretty powerful endorsement to run a 3/32

From ariellemartin15.com

(IMG:http://www.bmxnews.com/hosted_images/amv_chain.jpg)

QUOTE
The day after I was released I examined my bike for the first time. My chain had dropped off the rear cog on the inside and jammed my rear wheel. I looked it over with the five other men in the room and we tried to spin theories as to how it happened. We put the chain back on and it was in alignment, not too lose, not too tight. I was hoping for some sort of vindication, an answer, a reason other than my chain just came off but we couldn’t find it. Current theory is that the particular chain I was running was too wide, too stiff, but I’m still not satisfied with that answer. Might as well call it an act of God because I found no solace in seeing the bike.



M
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CWracer
post Oct 13 2012, 09:11 PM
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I thought this was an interesting read.

http://velodrome.org/mva/sites/default/fil...oad_v_track.pdf

I understand a heavier chain has greater rotational weight but I think a 3/32 is probably more appropriate for younger riders who make up the bulk of our sport. When you get into big guys with strong legs why not run a 1/8? My 3/32 chains are good for about 6 months before I noticed significant stretching. I've never broken one, but given that they develop loose spots and are designed for lateral movement between gears, I think the risk of throwing a chain during a sprint merits concern.

Just my opinion of course. But what are the velo guys running?
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bmxundergrounddo...
post Oct 13 2012, 09:44 PM
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I'd never really thought about it before, but I can't see why a wider chain would be stronger. Counter-intuitive, I know.

Anyone with an engineering background?
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CWracer
post Oct 13 2012, 09:44 PM
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QUOTE (MikeCarruth @ Oct 13 2012, 09:58 PM) *
Her chain alignment was off, but because of the play, it made it appear OK. And it threw off the rear cog.



I don't know what her rear cog was but her front chainring was a Rennen and I don't think they make them in 1/8. So was she running a 1/8 chain on 3/32 gears?

This from the article I posted above:
"While it is possible to do the reverse and use a 3/32nd inch cog or chainring with a 1/8th inch chain, it is not recommended because the narrower width of the 3/32” ring or cog will encourage the derailing of the chain from the system during riding. This could cause a crash or at the very least, ruin some equipment, even if you do not go down."

Again, I'm not an expert on this stuff but I think this sounds like a likely culprit.
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sxebmx
post Oct 13 2012, 09:55 PM
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Also, if her rear cog was just the tiniest bit out of alignment, it changes everything, maybe a 3/32 chain would have just snapped? Pro's change their chains more often than I was my favorite pair of pants(a sad but unfortunate truth, I know, but still, monthly at worst) but it's impossible for anyone aside from the person who lines up your front and back sprocket to know anything.
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