chain stress

Stephen Harding

Peter Cole wrote:
> Stephen Harding wrote:
>
>> I had two SRAM PC-48 chains break at the side plates.
>>
>> I think its just cheap manufacturing for that model of
>> chain. I now use PC-68s.
>>
>> Probably most likely chain failure is because the pin
>> wasn't properly installed. Chains for the most part
>> don't break, no matter how much torque you are able to
>> apply to it.
>>
>> I stay away from "pinned" chains now too. The master
>> link is much superior IMHO.
>
> I've had god luck with the PC-48, never breaking one (out of perhaps a
> dozen) despite my weight (230), long cranks, low gear (20T on MTB) and
> often towing ~100lb trailers.
>
> I typically never repin a chain any more, no need to with quick links,
> but when I did, I found it was a pretty fussy job, you have to have a
> good tool and be very careful to get exactly the right amount of pin
> protruding on both sides of the late.

I used the PC-48s for years with no problems.

The failures were quite recent so I'm wondering if their
manufacture has changed for the worse?

When buying a new chain, the LBS guy told me he won't
sell the PC-48 any more because they've had too many
problems with them. Just "too cheaply made" whatever
that means.

At any rate, the PC-68s are still going good and they
aren't terribly more expensive.


SMH

DennisTheBald

Serious question, serious answer...
No F.N. way that the weight of a bicycle & the bicyclist breaks a
chain, not even if they were suspended by that chain and then
bounced. You and your horse together can not produce enough torque to
break that chain; big gear, little gear - no way, no how.

Having a chain come apart is quite another matter altogether tho, you
can probably take one apart without even breathing hard. Should one
slip apart while you're riding trying to put it back together by the
side of the road with nothing but a pair of pliers will make you sweat
and curse. If you fear a chain failure and wish to mitigate that
situation you might slip a powerlink (r) into your purse.

http://www.rei.com/product/751366

DennisTheBald

I'm having a little trouble following you here, did the side plates
break or did the pins slip out of the side plate? One of those things
seems quite believable and the other completely not. I would even
entertain that the plastic replacement pins that Shimano provides to
put a chain back together with could break...(never seen it happen but
I didn't like the idea and refused to use them for any length of time
myself) Why would one put plastic bits in their drive chain...crack,
either smoking it or having one's head up it? Then again, the pin is
pretty much just to hold the inner and outer side plates together and
the real stress should be on the flanges of the side plates
themselves, not the pin... but I don't trust plastic pins on my chain.

I wouldn't use these: http://www.rei.com/product/544076

I maintain that the gear ratio used when starting from a stop has no
bearing on the life of the chain, maintenance on the other hand does.

I further assert that side plates don't stretch either and that the
actual cause of what people tend to call 'chain stretch' is actually
the side plates wearing into the pins. I'd like to take credit for
that idea, but I'm pretty certain I heard it from Sheldon Brown
first. I have personally confirmed it by careful disassembly,
inspection, and measurement of a 'stretched' chain. There is
certainly some evidence to support the idea that repeatedly rubbing
two pieces of metal against each other will cause a loss of mass in
one or both pieces and this seems to be what has happened rather than
the side plates becoming elongated.

Would flipping your chain around say every 20k miles extend its life?
You would be wearing down the other side of the pin and wallowing out
the other side of the side plate hole. Rotating your chain will have
more of a bearing on its usable life span than not shifting to low
before stopping will.


> I had two SRAM PC-48 chains break at the side plates.
>
> I think its just cheap manufacturing for that model of
> chain. I now use PC-68s.
>
> Probably most likely chain failure is because the pin
> wasn't properly installed. Chains for the most part
> don't break, no matter how much torque you are able to
> apply to it.
>
> I stay away from "pinned" chains now too. The master
> link is much superior IMHO.
>
> SMH

Paul O

DennisTheBald wrote, On 6/18/2008 1:55 PM:
> <snip>
>
> Would flipping your chain around say every 20k miles extend its life?
> You would be wearing down the other side of the pin and wallowing out
> the other side of the side plate hole. Rotating your chain will have
> more of a bearing on its usable life span than not shifting to low
> before stopping will.
>

20,000 is a lot of miles for a bicycle chain! Are you sure that you
didn't mean to say 2k miles?


--

Paul D Oosterhout
I work for SAIC (but I don't speak for SAIC)

recycled

"DennisTheBald" <DennisTheBald@gmail.com> wrote in message
news:ba379f4b-74e5-4df7-a4b9-827144965fbb@r66g2000hsg.googlegroups.com...
> Serious question, serious answer...
> No F.N. way that the weight of a bicycle & the bicyclist breaks a
> chain, not even if they were suspended by that chain and then
> bounced. You and your horse together can not produce enough torque to
> break that chain; big gear, little gear - no way, no how.

Ok. I assumed the chain might well be the... errr... weakest link.

Let me rephrase: What component would be the most stressed from a standing
start in a high gear?


> Having a chain come apart is quite another matter altogether tho, you
> can probably take one apart without even breathing hard. Should one
> slip apart while you're riding trying to put it back together by the
> side of the road with nothing but a pair of pliers will make you sweat
> and curse. If you fear a chain failure and wish to mitigate that
> situation you might slip a powerlink (r) into your purse.

I don't fear it. Just something I wondered about.

Tom Keats

In article <g3dgd2$u3m$1@news.datemas.de>,
"recycled" <u-lock@hotmail.com> writes:
>
> "DennisTheBald" <DennisTheBald@gmail.com> wrote in message
> news:ba379f4b-74e5-4df7-a4b9-827144965fbb@r66g2000hsg.googlegroups.com...
>> Serious question, serious answer...
>> No F.N. way that the weight of a bicycle & the bicyclist breaks a
>> chain, not even if they were suspended by that chain and then
>> bounced. You and your horse together can not produce enough torque to
>> break that chain; big gear, little gear - no way, no how.
>
> Ok. I assumed the chain might well be the... errr... weakest link.

FWIW, the carriages of forklifts are chain driven.

> Let me rephrase: What component would be the most stressed from a standing
> start in a high gear?

I believe it is the rear axle. I've broken a number of them.
And it's actually /lower/ gears that apply more torque -- or
rather, allow the rider to apply more torque.

Higher gears actually work to prevent a rider from
applying very much torque. That's why it's so hard
to give the pedals that first push from a dead stop
in a high gear. On the other hand, jack-rabbit starts
in low gears sometimes manifest as spontaneous wheelies,
especially on inclined planes. Then you might hear some
rearward component go "crack!" and you tersely think: "Oh-oh."

>
>> Having a chain come apart is quite another matter altogether tho, you
>> can probably take one apart without even breathing hard. Should one
>> slip apart while you're riding trying to put it back together by the
>> side of the road with nothing but a pair of pliers will make you sweat
>> and curse. If you fear a chain failure and wish to mitigate that
>> situation you might slip a powerlink (r) into your purse.
>
> I don't fear it. Just something I wondered about.

When reassembling chains, I've learned to drive the pin in
a little too far, and then drive it into the sweet spot
from the other side of the chain. And then still visually
inspect to ensure the sideplates aren't splayed, and tactilely
inspect to ensure the link isn't stiff. It's really quite
easy to properly reassemble a chain, and not doing so is just
inexcusable sloppiness (mea sometimes culpa.)

If you use a PowerLink and suffer chainsuck or
over-shifting fall-out, the PowerLink will always
be in an inaccessible spot. It's a Murphy's Law thing.

If you wish to avoid disaster: when installing pedals,
always take care to ensure they're tightly in there.
/That's/ where there's no room to be perfunctory.

There's an interesting article in the FAQ about broken axles.


cheers,
Tom

--
Nothing is safe from me.
I'm really at:
tkeats curlicue vcn dot bc dot ca

Peter Cole

DennisTheBald wrote:
> Serious question, serious answer...
> No F.N. way that the weight of a bicycle & the bicyclist breaks a
> chain, not even if they were suspended by that chain and then
> bounced. You and your horse together can not produce enough torque to
> break that chain; big gear, little gear - no way, no how.
>
> Having a chain come apart is quite another matter altogether tho, you
> can probably take one apart without even breathing hard. Should one
> slip apart while you're riding trying to put it back together by the
> side of the road with nothing but a pair of pliers will make you sweat
> and curse. If you fear a chain failure and wish to mitigate that
> situation you might slip a powerlink (r) into your purse.
>
> http://www.rei.com/product/751366

A quick link doesn't usually help without a chain tool. The common
failure scenario is pin pull out, leaving you with a damaged link that
must be removed before you can use the quick link. Of course if you have
the tool, you don't really need the quick link.

Peter Cole

DennisTheBald wrote:
> I'm having a little trouble following you here, did the side plates
> break or did the pins slip out of the side plate? One of those things
> seems quite believable and the other completely not.

Both are known to happen. The pin pull out is the more common, and
usually an assembly error, the other is likely a manufacturing defect.

I would even
> entertain that the plastic replacement pins that Shimano provides to
> put a chain back together with could break...(never seen it happen but
> I didn't like the idea and refused to use them for any length of time
> myself) Why would one put plastic bits in their drive chain...crack,
> either smoking it or having one's head up it? Then again, the pin is
> pretty much just to hold the inner and outer side plates together and
> the real stress should be on the flanges of the side plates
> themselves, not the pin... but I don't trust plastic pins on my chain.
>
> I wouldn't use these: http://www.rei.com/product/544076

I've never used them, I just used quick links with Shimano chains. When
SRAM started including them, I switched.


> I maintain that the gear ratio used when starting from a stop has no
> bearing on the life of the chain, maintenance on the other hand does.

If by "maintenance", you mean cleaning, a guy here (list) did an
experiment a few years back and found no difference in chain wear
cleaned vs, not cleaned. It seems no one has bothered to repeat it
(despite endless talks about cleaning/lubing methods). I don't clean my
chains any more.

One knowledgeable poster reported a large difference in chain life
between regions with different geology, reasoning that the makeup of the
road grit (say limestone vs. granite) affected wear rate significantly.

> I further assert that side plates don't stretch either and that the
> actual cause of what people tend to call 'chain stretch' is actually
> the side plates wearing into the pins.

The term is accurate in the sense that the length of the chain changes,
and in doing so, the pitch changes (the only important dimension). I'd
be surprised if anyone who care to think about it at all believed the
stretch was literal.


> Would flipping your chain around say every 20k miles extend its life?
> You would be wearing down the other side of the pin and wallowing out
> the other side of the side plate hole. Rotating your chain will have
> more of a bearing on its usable life span than not shifting to low
> before stopping will.

Chains have inner and outer links, pins and rollers. The pins, rollers
and inner link bores all wear. The roller wear doesn't affect the pitch,
only the pin and inner link wear. See the FAQ. Flipping your chain won't
help.

Bill Sornson

Peter Cole wrote:
> A quick link doesn't usually help without a chain tool. The common
> failure scenario is pin pull out, leaving you with a damaged link that
> must be removed before you can use the quick link. Of course if you
> have the tool, you don't really need the quick link.

I thought the pins in "modern" chains can't be pressed back in like in the
good old days? Can certainly reconnect the chain ends, but I'd be hesitant
to really hammer on it.

Bill S.