Why 8 Tooth Drives??

[Ruggybuggy]

Why would Yamaha put a 8 tooth on the MTX and 9t on other Phazers. If my thinking is right a larger drive would be a gear reduction, something you would want for more grunt down low. Why not just run the 9t in the MTX then make a gear change in the chaincase. Wouldn't 9t give you a better approach angle and better front hyfax wear?

 

[3wheelerdude]

The 8 tooth being smaller in diameter allows for extrovert (anti-ratchet tooth), which would hit the rail tips on a 9 tooth.

 

[..SNAKEBIT..]

If you ran the 9t drivers you would need a more gear change
the larger the driver the more speed
so in the mountains the smaller driver is better geared and fits deeper tracks

try this
http://www.ty4stroke.com/download.php?id=24663

 

[blueironranger]

8 tooth is 12.5% slower that 9 tooth at driving a track. This basically makes an 18t upper gear act like a 16t upper gear in the chain case, and the same reason my 19t in my MTX is just about identical to a 17t on a shorty. No reason to go 8 tooth on a shorty unless the track is a touch short for some reason. The 9t clears a 2" paddle on shorty sleds.

 

[Ruggybuggy]

8 tooth is 12.5% slower that 9 tooth at driving a track. This basically makes an 18t upper gear act like a 16t upper gear in the chain case, and the same reason my 19t in my MTX is just about identical to a 17t on a shorty. No reason to go 8 tooth on a shorty unless the track is a touch short for some reason. The 9t clears a 2" paddle on shorty sleds.

Going to the 144. So 9 tooth drives and 20 teeth on top gear should be close to 8 tooth drives and 17 top gear?

 

[blueironranger]

8 tooth is 12.5% slower that 9 tooth at driving a track. This basically makes an 18t upper gear act like a 16t upper gear in the chain case, and the same reason my 19t in my MTX is just about identical to a 17t on a shorty. No reason to go 8 tooth on a shorty unless the track is a touch short for some reason. The 9t clears a 2" paddle on shorty sleds.

Going to the 144. So 9 tooth drives and 20 teeth on top gear should be close to 8 tooth drives and 17 top gear?

Other way around, a 9 tooth drive with an 18t would be the same as 8 tooth drive with a 20t. If you can't crack 85 on the speedometer you ideally need a 9 tooth driver + 17t upper gear combo OR 8 tooth driver + 19t upper gear (which is what I have)

 

[Ruggybuggy]

So the question still stands. Why didn't Yamaha just have one 9t drive then use the 17t upper gear on the MTX? The 9 tooth has the advantage of a better approach angle, less front helix wear and cheaper production costs (only one drive gear).

 

[Ding]

Track clearance.

 

[blueironranger]

So the question still stands. Why didn't Yamaha just have one 9t drive then use the 17t upper gear on the MTX? The 9 tooth has the advantage of a better approach angle, less front helix wear and cheaper production costs (only one drive gear).

because the Phazer, when in the mountains, only makes ~60hp and it needs the low LOW gearing to turn the track. If I feel like some of my buddies 600's I toss my 17t gear in and race them, 0-60mph goes by dang quick geared that low but ~78mph on the speedo = rev limiter.

 

[cannondale27]

I run 17 t just have to clutch for top end.

 

[SnoXer18]

So the question still stands. Why didn't Yamaha just have one 9t drive then use the 17t upper gear on the MTX? The 9 tooth has the advantage of a better approach angle, less front helix wear and cheaper production costs (only one drive gear).

The MTX did come with 17t factory, the 19t was for low elevation setup.