Slack Chains

[Briggsy]

For years now, I have noticed that many Thais seem to prefer having their chains at extremely slack tensions. I always considered this was a result of the "zero maintenance, fix it when it breaks school of thought". Lately, I have changed my mind. Often bikes which have had a lot of modification and prettification seem to have the slackest chains. It appears to be a fashion.

Is there any reason or benefit in having a chain slapping around? For me, a slack chain means it possibly coming off, sloppy, jerky gear changes and deceleration. I'm obviously missing something.

[BigBikeBKK]

Paraphrased from "All About Chains" A Conversation with A Chain Legend

Full article: All About Chains

An over tightened chain is a far worse than a loose one. Suspension movement increases chain tension. What is a fairly tight chain at standstill becomes impossibly tight when the suspension bottoms. These added and unnecessary tensile loads can exceed the chain's capacity and the increased friction will raise the chain's temperature sky-high.

Chain oil's main enemy is high running temperatures. The running temperature of a chain ideally should not exceed 160 degrees Fahrenheit (70 degrees Celsius). Above that, chain lubricant starts to thin, and the chances of it seeping out past the O-rings increase; eventually the film strength drops. (This is how I've "cooked" the low quality Thai-made DID chains on my locally built Kawasakis...)

A too-tight chain can, in no time at all, turn into history. The best way to check chain tension, the one used by many race teams, is too ask two of your biggest friends to sit on the bike and compress the rear suspension to the point where the wheel spindle, swing-arm bearing bolt and the front chain-sprocket centerline are all in line. That is the point of maximum chain tension. Or you can compress the bike's rear end with a ratcheting tie down. Free up and down movement at the middle of the chain's bottom run should be about half an inch (13 mm) with the suspension compressed.

Of course, a loose, dragging-on-the-floor chain is not too good either. A loose chain will rub on many static parts of the bike such as the swing arm rubber buffer and frame spacers. Besides, with the chain's ability to saw through anything in its path, the added friction will again raise temperatures. Also the sprockets will suffer. A loose chain will "ride up" into the higher and weaker areas of the sprocket teeth and slowly bend them into a wicked hooked shape.

Personally I always run my chains on the loose side and tighten as necessary.

Ride On!

Tony

[Briggsy]

Thanks.

At 61 kgs and riding a 10-year-old Sonic fairly smoothly, I don't think my suspension is ever close to bottoming out. Still, I take the overall point, loose chain less risky than tight chain & suspension movement effectively increases chain tension whilst riding.

I wonder if this extension of applying techniques used on the race track and/or in racing bikes and applying it to 125 cc scooters is really appropriate.

[ClareQuilty]

Not more than a week ago I had an old Tena of mine into the Honda shop for a new headlight, and the darn mechanic tightened the chain too tight - they're always doing this! Its the young guys I guess, don't know any better. When the chain is very tight it tends to make noises and vibrations.. when loose you don't notice anything.

Very irritating. They're always fussing over my bikes (no charge, but still, leave it alone!) I wish I knew how to tell a mechanic to loosen the chain.

[elkangorito]

Having raced motocross for many years, as well as having done lots of Enduro, I have never had to replace a chain or sprocket. Why?

I've always kept the chain at about a maximum of 25mm 'slackness' & used a graphite based lube. Minimum 'slackness' - about 15mm.

How do you measure the 'slackness'?

Place your finger in a central location on the return side (lower) of the chain. Push in an upward direction. If the chain moves a distance greater than about 25mm, it's too loose. If it moves less than about 10mm, it's too tight.

[Lancelot]

I replaced the chain and sprokets on my Honda Wave CZi at 14,500 km. Reason? Thai mechanics overtightening the chain and me not oiling the chain often enough. I bought a wrench and readjusted my new chain (loosened) and now oil the chain every 500 kms or daily on longer trips.

Time will tell

[neverdie]

OP, I know exactly what you are talking about. I have seen chains that virtually come off the front sprocket and then lay (when stationary) on the swing arm for almost the entire length until reaching the proximity of the rear sproket. In movement they bouce and clang around, iits great stuff .

LOS = Land of SSSloosechains.

[BSJ]

Super loose chains are stupid! With me sitting on the bike an assistant should see 2 fingers of movement....which should be about 30mm. Thank goodness I saw the light and got another bike with a shaft drive!