chain stress

On Jun 15, 7:27 am, "recycled" wrote:
Is there any deleterious effect on a chain if you start from a dead stop in
a high gear such that you are putting a large strain on the chain and cog
wheels, chain rings and crank arms for that matter?

Serious question.

It should cause no problem.

The tension in the chain isn't hard to calculate. Your crank arm has
a radius of about 170mm. In "high gear," your chainring has a radius
of about 100 mm. So to find chain tension in high gear, multiply your
pedal force by 175/100. (The choice of rear cog doesn't matter.) And
your pedal force is probably about equal to your weight in that
situation. If you weigh 175 pounds, that's a chain tension of 306
lbs.

It's worse when your chain's on a small front cog. A triple crank's
small cog might have a radius of 50mm, so if you're standing hard on
the pedal in that gear, you get about twice the chain tension: 612
lbs. And my chain's stood up to that situation thousands of times.


Has anyone snapped a chain in this manner?

I once broke a chain mountain biking, but never road riding. I was
trying to grind past a sudden, steep obstacle and was in the process
of changing to the smallest front cog. I imagine the bending &
twisting of the chain during the shift is what tore the side plate off
the pin.

I've had to start in a high gear many, many times (and always kicked
myself for forgetting to "pre-shift"). But it's never, ever harmed my
chain. Don't worry.

- Frank Krygowski

On Jun 15, 6:27 am, "recycled" wrote:
Is there any deleterious effect on a chain if you start from a dead stop in
a high gear such that you are putting a large strain on the chain and cog
wheels, chain rings and crank arms for that matter?

Serious question.

Has anyone snapped a chain in this manner?

I can't believe that a bicycle chain can be broken by the weight of a
human & a bicycle, regardless of the gearing.

wrote in message
...
recycled at wrote:

Is there any deleterious effect on a chain if you start from a
dead stop in a high gear such that you are putting a large strain
on the chain ...

Note that the strain you can put on the chain will be greatest
when using your smallest chainring

And MTB riders do that all the time with no ill effect. This
sounds like one of those:

"If I hang my bicycle from the front wheel, won't that ovalize it?"

Troll!

I hope you aren't suggesting that I'm a troll.

You are a troll, possibly unwittingly. I suppose remainng anonymous
helps you live with it.

Believe what you wish.

I had that thought whilst taking off from a traffic stop in a high gear and
wondered about it.

I'm sorry it doesn't meet your posting standards.

I wonder what you find so trollish about the question.

BTW: I do not post as 'anonymously'. I post as 'recycled' at email
and have done so on this ng for years. Though I haven't
posted much at all recently. T'is true this is not my real name nor even a
fake name that would have the appearance of a real name. I'm sorry that does
not meet your posting standards either but I don't indiscrimately release
personal information on the internet. Identity theft and net-cook
cyber-stalkers might be a low order probability but I won't take that risk
simply to please you or anyone else.

DennisTheBald wrote:
On Jun 15, 6:27 am, "recycled" wrote:

Is there any deleterious effect on a chain if you start from a dead stop in
a high gear such that you are putting a large strain on the chain and cog
wheels, chain rings and crank arms for that matter?

Serious question.

Has anyone snapped a chain in this manner?


I can't believe that a bicycle chain can be broken by the weight of a
human & a bicycle, regardless of the gearing.

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

Stephen Harding wrote:
DennisTheBald wrote:

I can't believe that a bicycle chain can be broken by the weight of a
human & a bicycle, regardless of the gearing.

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.

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

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

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

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)

"DennisTheBald" wrote in message
...
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.