final drive 101

[Max D]

I read in previous post that belt drives are the most efficient form of a final drive. I was a little confused by this. I have been told by many motorcycle mechanics that a chain is the MOST efficient. They explained that a belt can and will slip as well with a chain every degree the front sprocket turns will directly transfer to the rear sprocket where with a belt some of it will get lost in belt stretch assuming it doesn?t slip. However the other post mentioned that the chain has sooo much more friction it will hinder the power transfer. Both reasons seemed logical to me so which is more efficient. I?ve never owned a belt drive bike (mostly because it is exclusive to Harley??? and a few Yamaha?s). Now the whole belt slipping I am just going off of what I have herd. So how bad is this alleged belt slippage. It goes without saying that the shaft drive cannot compete with either in terms of efficiency.

 

[maleko89]

If chain slips then it's either time for a new chain or sprockets. Chain is the most efficient in my book. Stronger too.

 

[Rhoy Carter]

The belts I have seen have teeth on them so they dont slip either

 

[modnrod]

Power transfer has to over come losses of many sorts. Toothed belts (like cam timing belts) dont slip, and have much less weight than chains, so less momentum to overcome in driveline speed changes.

 

[4gasem]

Agreed! Never seen anything but a toothed belt on a bike. Heck... My '81 Kawasaki 440 had a toothed belt.

Quiet, light, efficient, and didn't need lubed. Wins in my book! There's one big down fall which with technology isn't such an issue. STRENGTH! Sure they'll take a ton of torque but do they last as long as a chain in the same conditions?

Chris

 

[Max D]

I know all them motorcyle belts have teeth on them but when its all said and done it is still made of rubber so couldnt it still slip and will stretch when power is applyed which would = efficency loss correct?

 

[modnrod]

Most drive belts are made of Kevlar with outer rubber bonded, so they actually don't stretch much really. The stretch that is there is similar to a chain on sudden throttle, you'd be amazed how much chains stretch and flap about!
They don't last as long as a chain generally, but still a mate with a S&S 124 normally still gets about 20K miles on one.

 

[PATMAX]

Max D, one needs only to look at what the pro-drag guys are running and your argument is settled. They have collectively spent more money tested out the various technologies to the limit so rest assured, what they are doing is the best performance drive systems.

 

[modnrod]

I reckon if I had a 400RWHP engine I'd use a chain too..........much easier to change sprockets and gearing to suit the track conditions and atmospherics, and very limited availability of toothed pulleys and belts to take the grunt.
More to do with ready parts access than strength.
For streeter, belts are OK.

 

[one2dmax]

As far as efficiency the cogged (tooth) belts are going to be the best. Light, no slip, minimal stretch (if they stretched they would skip a tooth and time to replace) and quiet. They aren't the strongest but that doesn't mean they won't work for most applications seen by a street bike.

The chains will vary on efficiency. The non-oring chain is the better one here. They don't have as long a life but they do have less drag. The o-ring (and variants like "X" and "W" chains last much longer especially in street riding environments.

The shafts advantage is quiet operation and almost unlimited life (when driven normally). But of course the extra gears just eat more of the available power generated by the engine.

Sean

 

[Max D]

Soooooooooo to kind of sum up everything we all relatively agree that belts are the most efficient but not much more than a chain which is much more durable.

 

[jedi-]

Soooooooooo to kind of sum up everything we all relatively agree that belts are the most efficient but not much more than a chain which is much more durable.

Actually they aren't. In general terms chain is slightly more efficient than belt.

 

[Max D]

Could you explain your reasoning behind the chain being more efficent because the fact that the belt is lighter is a compeling argument.

 

[naughtyG]

Could you explain your reasoning behind the chain being more efficent because the fact that the belt is lighter is a compeling argument.

I too thought that the belt drive was lighter - in fact I found out it is not, and by a long shot, when playing with my Kawi 454LTD.

Sure the belt itself is lighter than a chain (although not as much as you'd think), but the big difference is that the sprockets used with a chain are WAY lighter that those cogged wheels used with a belt. We're talking many lbs difference here.

When I removed them from the bike, I could not believe how heavy the front and rear toothed wheels used for the drive belt were - definitely a helluva lot more than any sprockets I've ever handled.

As a result, I don't think a belt drive is more efficient at all, but it is quieter and a little smoother, and also cleaner than a chain as it does not require constant lubrication that splashes all over the bike with centrifugal forces.. :confused2:

 

[m-cman]

Had a belt drive on a 91 HD Sturgis for 8.5 years. Absolutely no problems and after 10,000 miles only required one minor adjustment after the initial new belt stretch. Supposedly will last up to 100,000 miles. Had to buy a belt tension measurement tool to monitor tension which determines when adjustment is needed. Was about $15 then. No lube mess or noise. I am sold on them. Really high horsepower motors would need a chain though. A belt that would handle really high hp would have to be too wide.