Hey guys, I'm think I've read both things on the forum, so I thought I'd ask. Is the .8"-1.2" on sidestand for chain tension when the chain is cold, or when the chain is warmed (by a short ride)?

Thanks,
-UnSaniTiZ

BTW, just changed my oil, rear brake pads, and I cleaned, lubed, and tightened the drive chain successfully (assuming warm .8"-1.2") for the first time. Also changed my bar ends.

i do mine warm ... chain does't get that hot that it makes that much of a differece

my 2c

I learned from a successful racer (GaryJ on BayAreaRidersForum) to do it warm, since that that should be the amount of slack when riding it, and the chain is warm when you ride it.

alright cool. It's at an inch warm now... So I'm happy...

Whether it's warm or not isn't too important unless it's a roller...but better warm than cold.

The difference in overall length between a warm and cold chain will be a few thou` of 1 inch at most, its negligable. Hot or cold it will make no difference whatsoever.

Not on a roller.  The 120 links on my TL add nearly half an inch of play after they're warmed up.  Ringed chains will do the same once the rubbers start wearing down.

http://gstwins.com/gsboard/index.php?topic=28402.msg304624#msg304624

^exactly.  The tolerances of metal at varying temperatures should not be underestemated.

Metal expands when hot......we all know that but there is no way that the apparent increase of 1/2"in the chains length is due soley to thermal expansion of the metal. You could heat it till it reached melting point and it wouldnt grow by that much. The chain will become warm, not mad hot in normal operation depending on ambient conditions and that heat leads to increased flexibilty in the chain. The rollers and joints will expand slightly but not by a cumulative1/2". Tensioning chains is not an exact science, far too many variables, hence the min and max tolerances quoted by Suzuki.

umm, gaining half an inch of slack is less than a .001" stretch per link (120 links).  I'd say that's WAY within normal spec for a chain that operates at 185*f (roller).  I've seen similar stretches on ALL varieities of chians in a variety of circumstances.  I believe you're speaking without ever having done any research.

(.49" increase in slack on my TL with 120 link D&D rollor [4140 steel] with steel sprockets [also 4140] = .000373" per link.  Temp at time of measure = 153*f.  Ambient temp = 83*f, no change in cold slack.)

I believe warm or cold is insignificant.

Neither my Owner's Manual nor my Service Manual specify a temperature when adjusting the chain.

I am well aware of the effects and coefficient rates of thermal expansion, however your figures confuse me. How exactly do you come to the conclusion that each link will grow by almost 0.004"

Like Sledge said, can't see the thermal expansion making any noticeable difference at all in the chain length,  but .004" per link wear would make a 120 link chain about 1/2" longer.

For years it has been recommended to lube the chain when hot so the lubricant will penetrate into the chain better, but this mostly applied to the old standard non o-ring chains.  The chain lube can get stiff real fast in cold weather though.

I'm sure the chain wouldn't care what the outside temp is when it's adjusted, but it might be more pleasant for the adjuster to do it on a warm day.   

I have looked in some reference material I have, cant find anything on thermal expansion and chains. I cant see it being a real issue as chains are intended to operate with slack in them and a small increase in length would be non influencing. Not exactly sure how you would calculate the expansion of chain as it is not a solid mass rather an assembly but I did a rough calc` for a grade of mild-steel with dims of 12x12x1250mm which I think is near enough to the dimensions of the chain and got a figure of just under 1.2mm assuming a rise of 60degC from an ambient of 40degC. 100degC is the figure recomended by most bearing manufacturers as the temperature required to overcome the interference between rolling element bearings and journals, (usually about +0.03mm). Bear in mind though chains get nowhere near this temp` in normal use, if they did the grease would start to smoke and the seals probably start to melt. If you left a 10 ft girder in the sun all day it might just grow by 1/2" but it wont happen to a bike chain. You dont see the cylinder block/head or exhaust headers/pipes grow by that much and they get a lot hotter than the chain! You are getting that extra 1/2" because the chain becomes slack in use at each riveted joint due to the small amount of heat generated, not because of the overall thermal growth. Question? Lets assume they do grow by 1/2" in normal use and you tensioned it when warmed up.....what would happen when it dropped down to ambient OR it went really cold and froze overnight?

Ugh... 

Chain stretch is not the same as chain slack.  When you argue about .001mm, make sure you know which figure you're talking about.  Chain stretch can be super small and cause a big amount of slack.

If you look at the chain as a system of right triangles (it should be close to that when you pull the chain taut in the center) you have a length approximately half the distance from the front and rear sprockets, a height equal to the chain slack, and a hypotenuse that is the chain's length.  Pythagoras says your chain slack will be roughly approximated by sqrt(length^2 - dist^2).  So if the distance is 18 inches (half a swingarm) and length is 18.01 inches (that's just the length of chain from one sprocket to the halfway point), you'll have a sag of about 0.6 inches.  If the chain "stretches" (by whatever means) to 18.04 (0.03 inches of stretch) your sag becomes 1.2 inches.

You don't need nerdy math to figure this out.  Just turn your adjuster nut about half a turn and watch your half inch of chain slack disappear.  Your axle only moved half a mm.  It's clear that miniscule amounts of change in chain length or axle distance make a great deal of difference in slack.

It's not a "stretch"  for me to believe that the miniscule differences in length due to temperature can cause a noticable effect on slack.  If others have claimed to have noticed it, I wouldn't call them liers.  I'll probably start checking my chain warm, as it makes sense to me.

Here's what I meant by all that trigonometry stuff:


Do the math.  It works.  It's shocking.

Not wanting to get into this too deeply, I went right past my copy of Marks and blew some dust off my half century old copy of Machinery's Handbook to find the coefficient of linear expansion for carbon steel to be .00000633 inches per inch per degree F. 

Most of us wouldn't be adjusting or even using the chain much below 32F and if it got up to 130-140F in use it would be too hot to touch and I've rarely experienced that on my modestly powered bikes.  So let's see how much 120 links of 520 chain would grow if the temp was to increase by about 100 F. 

.00000633 x 120 links x.625 pitch x 100 degrees F = .048" growth

So the chain would be about 3/64" longer and the center distance change about half that or about 1 mm for the same chain tension or should I say same slack. 

I think I'll continue to adjust my chain cold on the centerstand to about an inch of slack, but I won't loose any sleep if I have to do it hot.  What works for me for 22 years and 350k miles is good enough for me and besides my head is starting to ache from being forced to think and it deserves to rest at it's age.   

Quote from: gsJack on October 16, 2006, 12:22:13 PM
.00000633 x 120 links x.625 pitch x 100 degrees F = .048" growth

So the chain would be about 3/64" longer and the center distance change about half that or about 1 mm for the same chain tension or should I say same slack. 

You assume that expanding steel is the only factor.  That's probably wrong.  There's viscosity of the lubricants at play, as well as friction in the rotation of the links, which is far more a factor in a O-ring or X-ring chain.  A cold O-ring chain can keep some small amount of bend on it more so than a warm one and appear shorter.

But anyway, let's assume that expanding steel is the only factor.  Then let's try doing the math correctly.

120 links is 75 inches.  (120 x 0.625")

If the sprockets were points, there'd be 1/4 of that length as one of the legs of that triangle.  The sprockets are not points, so I'll say 1/5 instead.  That's conveniently 15 inches.  And the stretch in that section would be .01".

If you had zero slack at 15 inches, then you'd have:

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


Now, your chain will never raise by 100F, but this shows that the temperature can have a measurable/noticeable effect.  As to how measurable the other effects may be, I don't know.

Practically?  Yeah, if you can get your chain slack close, you'll be fine.  If you're being pedantic, you'd do it with a warm chain.  We all need an excuse to ride more.

Oh yeah... and sorry for making you think.