Chain tension, warm or cold?

[makenzie71]

You're looking at it 2-dimensionally. 5/100" of a gain in length is nearly 3/5" in lateral play.  We're not discussing the gain in length...we're discussing slack.  They're very different.  Pay attention.

[gsJack]

pe·dan·tic:
Pronunciation: pi-'dan-tik
Function: adjective
1 : of, relating to, or being a pedant
2 : narrowly, stodgily, and often ostentatiously learned
3 : UNIMAGINATIVE, PEDESTRIAN
- pe·dan·ti·cal·ly  /-'dan-ti-k(&-)lE/ adverb

Mmmmmmmmm, haven't heard that word used around here since Sledge used it a while back, had to look it up again before commenting.  

OK, I'll just say that whether being practical or pedantic, my recommendation is still to adjust the chain cold.  Accepting your speculation based on my 100 F temp increase estimate that a warm chain might gain as much as 1/2" additional slack, my experience tells me that a motorcycle chain with 1 1/2" of chain slack is much better to ride than one with only 1/2" of chain slack; assuming starting with adjustment to 1" slack.  I'd rather start with 1" cold and get a little more slack as it heats up than start with 1" of slack hot and have it get tighter.  Doubt if it will make a whole lot of difference either way though.

I'm not even going to speculate on the real possibility of the sprockets and possibly even the swingarm getting a bit warmer as the chain does cancelling out some of the possible chain length increase.

So, lets try to do the math correctly again after taking a look at your triangulation.  Assuming standard 16/39 sprockets and a 520x120 link chain, I'd say there were about 20 links wrapped around the rear sprocket and a tad under 8 links wrappped around the front sprocket.  So 120-20-8=92 links approx divided by 2 runs would give a sprocket center distance of about 46x.625=25"

So rather than

sqrt(15.01^2 - 15.00^2) = 0.56 inches  

I'd guesstimate the slack increase to be only about:

sqrt(12.51^2 - 12.50^2) = 0.50 inches

And if my 100 F temp change turned out to be only about 50 F, then the slack change would only be about .25 inches or equal to the approx +/- .25" allowed.

In the words of the Bard, perhaps it's Much Ado About Nothing.  

[Chuck]

But it sure is fun.  First of all, I bet the differences that arise from lubrication is way more than the differences due to metal expansion.  But I also bet it doesn't matter.  I was just trying to explain the difference between length and slack because it looked like some folks were confusing the two.  And I wanted to put some cool math behind it.

But I'll bet there is the danger to adjusting the chain while warm that if you're on the tight side of the tolerance, the chain will get even tighter when cold.  Vice versa when adjusting a cold chain.  A loose chain will only get looser.  The recommended spec almost certainly takes this into account, so most mortals won't give a care.

Given that most people barely lubricate their chain or pay any attention to slack, if you make any attempt to get it close, you're in the 95th percentile.

[sledge]

This issue will be nailed soon. I have e-mailed Renold Tech`support asking for the thermal expansion rates for 520, I told them it was required for part of a feasibility study for a major automation project and may well lead to a large order if the figures are within the specified limits 

[The Buddha]

Set the slack when lubed and cold, lube it when warm.
Like this, set slack, ride for 20 miles, dont even stop it for a second ... like stop and lut back in gear when on centerstand, and zip tie the clutch lever. The clutch drag will spin the wheel slowly ... lube it. Then shut it off.
Let it get cold. Then check slack again.
Cool.
Srinath.

[Chilly Willy]

Set the slack when lubed and cold, lube it when warm.
Like this, set slack, ride for 20 miles, dont even stop it for a second ... like stop and lut back in gear when on centerstand, and zip tie the clutch lever. The clutch drag will spin the wheel slowly ... lube it. Then shut it off.
Let it get cold. Then check slack again.
Cool.
Srinath.

Yeah, but keep your fingers off the chain if you're going to use Srinath's method.  Lube it only, don't try to clean it.  There's a pretty gross picture around here of the end of someone's finger or thumb that he had chopped off after getting caught in the chain.