what are the advantages of chain over a belt?

maybe for an off road bike but i don't think that is this machine's intended purpose.

hey, the only dumb question is the one you don't ask.

Keep production costs down? Cheaper to replace? I still think belts look a little weird, but that's just me. All I can think of.

The design was based on Chris Peiffer's stunt bike, so I would trhink with a chain, other stunters can change sprockets to increase torque for pulling wheelies and whatever. Much easier to change out as well as much more readily available than trying to find pullies. A broken chain can also be repaired, a broken belt probably not.

f14rio said:

maybe for an off road bike but i don't think that is this machine's intended purpose.

hey, the only dumb question is the one you don't ask.

Click to expand...

For the big picture you might get your answer by looking at the type of drives used on the race track.

I think of the F800R as a bike that someone would want to have the ability to use on and off road.

Easy

I like belts a lot, but you have to consider their width when dealing with a wide rear tire. The real estate used by the belt eats into the tire width options.

Chain;
Easily changed and repaired, efficient transfer of power, noisy, requires constant attention as far as cleaning, oiling, and adjustment for stretch.

Belt;
Clean, wears well into 50K miles, quiet, seldom needs adjustment, vulnerable to embedded road debris, non-repairable, complicated replacement in many designs.

This is as I see it after owning both. Off road should use chain unless effective belt shielding is present.

http://www.scootworks.com/scootworks/beltdrives.htm

A list of belt to chain differences (admittedly they are biased) at the bottom of the page.

Note, my old Roadstar had belt drive and the white walls were STILL never white.

AKBeemer said:

Be nice if the belt was offered as an option or a retrofit kit. I'd like to belt on my wife's GS since it will be her road bike.

Click to expand...

They have some cruiser retro fit kits - maybe they would work with you on designing one.

Strictly from an "on road" point of view, and my opinion of course...

Chain:

- Heavier, greater inertia while rotating and greater hp transmission loss = noticeable backlash when decelerating
- lower mileage
- noisy operation (nothing beat the "chain song" of a 750 Honda ... nothing)
- constantly requires adjustment
- constantly requires lubrication
- creates a mess on the bike and rider
- usually failure is catastrophic, but less likely to break than a belt
- creates real havoc when they do break, including destroying engine/trans cases (my old Honda 750 went away like this)

+ most economical way to manufacture (old technology/no molding required)
+ easily repaired with a master link carried in the tool pouch
+ bulk chain is readily available at most bike shops/ industrial supply companies and developing third world nations.
+ essentially impervious to heat, oil and solvents (hostile environments)
+ easier to change "gearing" ratios
+ basically no "shelf life", kept oiled a chain will last a hundred years (rubber degrades)

Belt:

- expense
- "universal" replacement belts are not readily available on the road
- susceptible to severe service environments - heat, oil and solvents
- can not be repaired

+ lower weight
+ lower inertia = lower hp transmission loss, smoother transmission of power and dampens shock loads
+ quieter operation
+ higher mileage
+ wear on pulleys is much lower than that on equivalent chain sprockets
+ minimal maintenance
+ easier to visually inspect for wear

At this point in time, belts of a reasonable size cannot handle as much power as chains. Slap a belt on a S1000RR and it would fail.

Motorcycle belts also seem to be a single vendor (OEM) item. You can source a chain from quite a few vendors.

Anyname said:

At this point in time, belts of a reasonable size cannot handle as much power as chains. Slap a belt on a S1000RR and it would fail.

Click to expand...

not so sure about this, but i have no real data.

the only thing i have is anecdotal, but good. I worked with the guy who did all the finite element analysis (stress testing) on the original belts designed for HD by Gates Rubber Co.

He said that the HD guys didn't give a crap about what some FEA on a computer said. But they were won over by the rider pulling huge wheelstands on an HD in the Gates parking lot.....

those belts are pretty darn strong.

i am hoping that some day BMW comes up with a workable enclosure system so that belts can be used off-road. from what i understand, a rock getting stuck between the wheel and the belt can be fatal for the belt.

ian
.

You know, there are these shaft drive motorcycles

Chains are the most efficient in delivering power from the engine to the rear wheel - hence their overwhelming popularity in sport bikes and racing venues.

Shafts only advantage is that the drive system is enclosed and supposedly, low mnaintenance. Hardly describes the current BMW drive train. They are heavy, unreliable, expensive when you buy, and astronomically expensive to repair / replace.

Best bet: The Belt. As for "Can it handle transfering fistloads of power to the rear wheel or accomodate large tires?" , I think Kawasaki (Vulcan series) and H-D (nearly their entire line) have answered those questions.

When I run BMW (OK - just daydreaming here under the influence of way too much caffeine!), shafts will be done away with - replaced with aramid-fiber belts that require no maintenance other than occasionally self-checking and adjusting tension, and every 100,000 miles - you just throw the old one away and replace it with a new one.

PS: You can actually carry a spare drive system on tour with you in your tank bag!

Greenwald said:

PS: You can actually carry a spare drive system on tour with you in your tank bag!

Click to expand...

I can remember carrying spare tires, too. I started buying BMW's because I was tired of carrying spare parts and adjusting chains. But, the idea that BMW has apparently managed to "design in" drive shaft failures, is pretty amazing. Advancing an idea to the point of reduced reliability is something only an MBA could appreciate.

Is a chain or belt cheaper? Of course they are. Is that a selling point for a premium priced motorcycle? I doubt it.

But, that is just my opinion.

Have a good one.

Chains allow gear ratio changes far easier than what a belt system will allow and do not require tensioners. If you are targeting a yourger audience, more prone to modifying their bike for stunting or the track, I'd opt for a chain drive. I think it is something that needs to considered based on the model and intended use / customer.

Shafts get paid for with weight, cost and complexity but require infrequent maintenance and can run for a long time on "simple" fluid changes, even in dirty conditions. Ratio changes are difficult and expensive.

Belts are a compromise that are less complex than a shaft, but more so than a chain. They may weigh slightly less than a chain drive and can last a long time with no service as long as they aren't used in dirty environments. They do require service that can be more complex and costly than a chain or shaft drive, but it is infrequent. Ratio changes are more costly and complex than with a chain, but less than a shaft drive.

Chains are the least complex and expensive of the three, but require frequent maintenance. They work well in dirty conditions and ratios can be changed relatively easily and inexpensively.

Pick your poison - not one of them is perfect, but each lends itself to certain applications more than others.

Greenwald said:

Best bet: The Belt. As for "Can it handle transfering fistloads of power to the rear wheel or accomodate large tires?" , I think Kawasaki (Vulcan series) and H-D (nearly their entire line) have answered those questions.

Click to expand...

I dunno Kevin, when I see road tests of the large engined cruisers, I see quarter mile times that look pretty meek compared to any 600cc sport bike. Come to think of it, none of those bikes are much in the leaning into corners arena either, so a huge sprocket and wide belt don't make much difference to them.

Belts are generally a lot nicer than chains, but none of the manufacturers seem to trust them on really powerful machines.

36654 said:

But, the idea that BMW has apparently managed to "design in" drive shaft failures, is pretty amazing.

Click to expand...

It does seem a bit odd that the drive shaft issue has been going on for some years. Every car and truck I can think of has wheel bearings on only one side of the wheel and bearing failures are rare on both cars and trucks. Seems like someone BMW knows should be a wheel bearing expert.

Anyname said:

I dunno Kevin, when I see road tests of the large engined cruisers, I see quarter mile times that look pretty meek compared to any 600cc sport bike. Come to think of it, none of those bikes are much in the leaning into corners arena either, so a huge sprocket and wide belt don't make much difference to them.

Belts are generally a lot nicer than chains, but none of the manufacturers seem to trust them on really powerful machines.

Click to expand...

in the case of cruisers, "power" means torque, not hp.
have you looked at the back end of most modern large-engine cruisers? those tires are mega-wide!

back to the original question- belts are not a good plan in an environment where a rock can get wedged between belt and pulley. Results could become rubber and metal shards everywhere, but no belt in sight. So- not a plan on a GS bike.

For the R model - i dunno, belt should have been just fine.

A belt (or chain) wouldn't make as much sense on an R or classic K because of the engine layout. Possible, but a shaft is a good solution. On the other hand, with a transverse engine shaft drive, the power train would make 2 right angle turns, not an elegant engineering solution. As for belt vs chain, many similiar trade-offs go on with cam-drives in the automotive world, with no clear winner.

Anyname said:

It does seem a bit odd that the drive shaft issue has been going on for some years. Every car and truck I can think of has wheel bearings on only one side of the wheel and bearing failures are rare on both cars and trucks. Seems like someone BMW knows should be a wheel bearing expert.

Click to expand...

Wheel bearings in cars / trucks are generally centered near the tread center and don't have to serve as a bearing for a differential carrier at the same time.

bikerfish1100 said:

in the case of cruisers, "power" means torque, not hp.
have you looked at the back end of most modern large-engine cruisers? those tires are mega-wide!

back to the original question- belts are not a good plan in an environment where a rock can get wedged between belt and pulley. Results could become rubber and metal shards everywhere, but no belt in sight. So- not a plan on a GS bike.

For the R model - i dunno, belt should have been just fine.

Click to expand...

I agree. Off-road, there are concerns with debris getting entangled in belts - but also in chains, and they've survived nicely in that environment for decades?!

Where I envision belts as finally solving the FD issue with BMW would be on the touring and sport-touring models - the R (GS excepted) and K bikes that will spend their lives on the pavement - not on the fire road.

Certainly not holding my breath for BMW to move away from a shaft system that too many have lost confidence in, but the alternate path is there.