[newhandle]

Basically, straight-cut gears are notorious for whining as is apparent in most GT race cars. Bikes got straight-cut gears too so where's all the whine gone? Here's an inspirational video:

I'd buy that whine over any muffler.

 

[jbreit]

interesting question.

the rigid driveline in the car will amplify it more. But, a bike has lots of other noises to drown it out to the riders ear. For example, I have a couple video's of bikes I'm selling...the gear and chain noise is all you hear in the drive by....one has a slip on, the other is stock exhaust.

Since you asked the question I suspect you have some background in it. Some gears will make more noise than others, even if they are all straight cut. If you get lucky designing a gear set, the contact ratio will be close to a whole number...2, 3 etc...(if noise is a concern, contact ratio of a whole number +/-.1 is the goal)...meaning there is a fairly constant meshing of teeth...this is obviously easier to accomplish if you have helical sets. You can play with pressure angle and pitch as well...but need to balance strength with width and gear centers and all the while get the ratios you want. If I was designing a gear set for a race car, noise would be the last of my concerns. How much power is going through the gear set will also impact noise.

 

[newhandle]

interesting question.

the rigid driveline in the car will amplify it more. But, a bike has lots of other noises to drown it out to the riders ear. For example, I have a couple video's of bikes I'm selling...the gear and chain noise is all you hear in the drive by....one has a slip on, the other is stock exhaust.

Since you asked the question I suspect you have some background in it. Some gears will make more noise than others, even if they are all straight cut. If you get lucky designing a gear set, the contact ratio will be close to a whole number...2, 3 etc...(if noise is a concern, contact ratio of a whole number +/-.1 is the goal)...meaning there is a fairly constant meshing of teeth...this is obviously easier to accomplish if you have helical sets. You can play with pressure angle and pitch as well...but need to balance strength with width and gear centers and all the while get the ratios you want. If I was designing a gear set for a race car, noise would be the last of my concerns. How much power is going through the gear set will also impact noise.

True that, but our bikes are race-prep as much as any race car. Tightening the chain helps with the whine a little, but it's dangerous of course. I don't have a thorough knowledge into gears that's why I asked the question. Good info btw.