# Does chain weight really matter???

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I've read lots of posts and websites on this subject, but can't come to a conclusion. One guy said he dynoed a bike with a 420 chain and then with a 520 chain and got the same results. Yet, other guys swear they get better acceleration with a lighter chain.

I posted over at the physics forums what would be the required power to accelerate a motorcycle chain weighing 1 pound in 1 second to a speed that would equal 20mph at the wheel from a dead stop.

The wheel has a diameter of 20 inches.

The drive sprocket has a diameter of 2.25 inches.

The driven sprocket has a diameter of 8.5 inches.

If for some reason we need the length of the chain, I suppose that would be 100 links at 5/8 inch per link.

Assume all frictions are zero and all sprockets and wheels are massless.

What I got back was a mixed result of anything from 3 watts to 6 watts. Either way, that's negligible.

But what if you can actually spin a tire to 20 mph faster than 1 second? What if it only takes 1/10 of a second? Well, then it takes around 65 watts (almost 1/10 HP). If you throw your bike in 1st or 2nd and rev it up n dump the clutch, how long do you think it takes for the wheel to reach 20 mph? I know its pretty fast!

I guess what it boils down to.... Should I worry about 1/2 a pound on my chain?

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Remember that many folks actually prefer to add weight to the driveline for better traction, usually in the form of a FWW. A heavier chain would have the same effect in principle, but I don't think you will even notice the difference on a full size bike.

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well i think it does help, and helps a lot on small bikes,

my sons JR50 had a heavy DID chain, i bought the lightweight regina chain about 1/2lb lighter is all, and wow much better acceleration,

i dont think a 1/2 lb would make a difference on a big bike but on a small bike i can tell you it makes the difference in the holeshot or not.

less rotating mass equals more power to the rear wheel.

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I'm working with a quad, so less weight the better.

On a small bike, 5 or 6 watts is a bigger percentage of the total output. To a locomotive engine, even a few HP isn't going to be noticed, lol.

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It won't affect power output at steady state so it won't show up on a dyno as lower peak HP but it will affect acceleration just like heavier tires or more fat on the rider. So yes it can really matter since you are constantly accelerating/decelerating.

If one chain or the other has more internal friction, that will affect rear wheel output even at constant speed.

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YOU ARE LOOKING FOR AN EXCUSE FOR YOUR SORRY A\$\$ RIDING !!!!!!!!!!!!!!!!!!!!!!!!!

Don

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Heavier chain will transmit more torque to the rear tire.. (Conservation of Linear Momentum)

Lighter chain will transmit more horsepower to the rear tire.. (Impulse Reaction)

There a a few variables that come into play, things like bike weight to horse power ratio, rider weight on same, type of riding, terrain being ridden on.. on a heavy low horse power bike like a JR50, a lighter chain would make a difference, but on something with a real power like a KTM 530 you would probably never notice it unless you were looking at trap times on a drag race.. so it really depends on what your doing and with what.

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YOU ARE LOOKING FOR AN EXCUSE FOR YOUR SORRY A\$\$ RIDING !!!!!!!!!!!!!!!!!!!!!!!!!

Remind me to buy you a beer/soda/whatever if/when we ever meet. 👍

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The light chain will help with drag racing :-) Im not sure if you're into that but personally, it if has a motor and wheels, i'm drag racing it at some point in time so every little bit counts.

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The biggest factor with a chain is the amount of frction in the rollers. This creates drag and robs power. The weight of the chain does not affect the power of the machine, however it can trick the drum style dynos into showing increased horsepower numbers. This is where that style dyno can be inaccurate. In a real world situation a bike with a lighter chain will accelerate faster than one with a heavy chain, and it will feel like it has more power. However, all you really did was decreased the rotating mass of the system, wich allows teh wheel to accerate faster. It is really the same thing as decreasing the mass of the machine itself, except in a rotating sense. The power output of teh engine is the same, and the power at the wheel is the same, but the machine will accelrate faster due to less rotating mass in the system. Now, the difference in weight between most chains is so small that you will probably never notice a difference.

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Yep, and compared to the wheel speed, the chain does not rotate that fast, therefore the mass differences would be negligible. Lighter tires would make a bigger difference, and of course a lighter flywheel would be noticed.

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I've read lots of posts and websites on this subject, but can't come to a conclusion. One guy said he dynoed a bike with a 420 chain and then with a 520 chain and got the same results. Yet, other guys swear they get better acceleration with a lighter chain.

I posted over at the physics forums what would be the required power to accelerate a motorcycle chain weighing 1 pound in 1 second to a speed that would equal 20mph at the wheel from a dead stop.

The wheel has a diameter of 20 inches.

The drive sprocket has a diameter of 2.25 inches.

The driven sprocket has a diameter of 8.5 inches.

If for some reason we need the length of the chain, I suppose that would be 100 links at 5/8 inch per link.

Assume all frictions are zero and all sprockets and wheels are massless.

What I got back was a mixed result of anything from 3 watts to 6 watts. Either way, that's negligible.

But what if you can actually spin a tire to 20 mph faster than 1 second? What if it only takes 1/10 of a second? Well, then it takes around 65 watts (almost 1/10 HP). If you throw your bike in 1st or 2nd and rev it up n dump the clutch, how long do you think it takes for the wheel to reach 20 mph? I know its pretty fast!

I guess what it boils down to.... Should I worry about 1/2 a pound on my chain?

No. 8 ounces are what you are speaking about let say bike /rider weighs 300lbs...hmmm, me..450f +6ft rider..240 +210=450..anyways.....at 300 lbs,that is a 600 to 1 ratio...I wouldnt think you get past on an uphill cause the chain was too heavy..The weight is unsprung,meaning it doesnt directly affect the suspension,like say a full tank of gas does . Assuming gas weighs approx 7 lb per gallon..removing about 2 ounces pretty much make up for the 8 ounce heavier chain . Now many years ago..(as a teenager).I came close to this problem on a 125 ..back when they were aircooled (yea,ancient) turns out I was comparing a stock oem chain against a heavier (and an O-ring) chain .

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Yeah, its pretty obvious 1 lb chain weight will make no difference whatosever at any point in time except if the acceleration of the chain approaches 38 m/s/s. That's the point that the power needed to accelerate the chain that quickly becomes equal to that of a light bulb. I guess the only question now is can a bike accelerate a chain that fast? And would that be something anyone would want to do on a regular basis? Sounds like a good one for mythbusters.

From different perspective... You can sure feel the difference in a 12 ga bird shot and a slug. Of course a chain won't accelerate nearly as fast as a shotgun blast, but the weight difference is only a matter of grams too.

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But we all know rotatioanl mass is much more beneficial to reduce than static mass (for drag racing...not holeshot purposes etc) Like he said, losing rotating mass helps acceleration, but the bike makes no more power than before. What happens is the reduced rotational mass DECREASES the parasitic and drivetrain losses that your machine has, which basically allows more hp from your engine to make it to the ground...a good thing in my book I get happy with a 5lb rotational reduction on my car...i'll take a 1/2lb on a bike anyday.

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So,,, you'd pay \$30-\$40 more for a chain that weighed 1/2 lb less? That's basically what I'm up against.

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YOU ARE LOOKING FOR AN EXCUSE FOR YOUR SORRY A\$\$ RIDING !!!!!!!!!!!!!!!!!!!!!!!!!

Don

Right On.

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Me personally, yes I would anyday, but like I said, I come from a drag race background so I take every bit I can to give me the edge, even when the edge is very small. I lose rotational mass in all my vehicles when possible. Lowering rotatioanl mass has many benefits including less strain on engine/drivetrain, more power from engine to ground, better acceleration, better fuel efficiency. I do this on all mustangs I build. I replace rims, tires, flywheels, driveshafts, rotors, pinon flanges, gears, and even bolts with light weight pieces to achieve all of the above stated things, and I do this with motorcycles as well. BUTTTTTTTT, there is a couple downfalls as well. Driveability is sometimes affected by lowering the rotational mass alot. Sometimes, the bike is harder to start out on, requring more clutch control. Stalling may become easier until you get used to it. If you can deal with that, then you'll be ok...but a 1/2lb chain lighter chain will not induce this...but the chain with a light flywheel etc etc might.

Thanks,

Mike

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BUTTTTTTTT, there is a couple downfalls as well. Driveability is sometimes affected by lowering the rotational mass alot. Sometimes, the bike is harder to start out on, requring more clutch control. Stalling may become easier until you get used to it. If you can deal with that, then you'll be ok...but a 1/2lb chain lighter chain will not induce this...but the chain with a light flywheel etc etc might.

Thanks,

Mike

Don't confuse a lighter flywheel with a lighter chain (or wheels, tires, hubs, etc) at start. With everything stopped but the engine the bike will be harder to stall with the lighter chain. Once its all moving then the effect you're talking about comes into play. Only a lighter flywheel will make it easier to stall at start.

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Ok KLXD...but I think you got the point I was trying to convey. Thanks for the correction.

Mike

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The only reason I would get a lighter chain is to lessen the unspring weight to help the rear suspension do it's work. But there are better ways to do that - a lighter tire, rim, sprocket, hub and rotor will give you a better gain then the chain.