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View Full Version : How sprocket affects top speed



han
07-13-2017, 08:27 PM
I keep hearing to change my sprocket up in teeth.Doesnt this improve low end acceleration but cut the top speed? I ride top end frequently and just want to know the best set up for my riding style.Im guessing stock is best for low mid and high range

1190SX
07-13-2017, 09:33 PM
Its not changing the power band of the engine, its changing how fast or slow the wheel rotates in a given gear in relation to the engine speed. The engine still has the same performance characteristics, making peak power at the same point(RPM). So basically if you go up on the rear sprocket or down on the front sprocket you will have improved acceleration, and in many cases be able to keep the bike in the power band through more gears if riding on the street. You do not gain "torque" as some term it. The stock setup is setup for the track IMO, which is what Erik wanted, a no nonsense track machine. As far as losing performance in the top end: if you mean losing top speed, then yes, if you are using that 170 mph top speed on the street than yeah, I wouldn't mess with the gearing because it will reduce top speed. Reality is even if you install a 46 tooth rear sprocket the bike will still do at least 140. I don't know about you but I don't regularly go 140 on the street. With the factory gearing you can barely use 6th gear on the street if at all, and it won't be in the power band if you are within the speed limits. The other concern is affecting fuel mileage, however, in light of the fact that you can't use 6th gear most of the time, I would think the impact on mileage going to a 43 or 44 rear would be minimal. If I was keeping my bike, I would have no problem going to a 45 or 46 rear, however I would prefer to install a 15 T front sprocket and retain the stock 41 rear to reduce chain and sprocket wear. Uneven number tooth sprockets reduce chain wear.

Hughlysses
07-14-2017, 08:51 AM
Remember that a change to a higher ratio final sprocket doesn't necessarily reduce top speed. If the engine can reach redline in high gear with the stock ratio, then obviously a change in overall ratio reduces top speed. However, a lot of cars and motorcycles are geared such that the engine can't reach maximum RPM in top gear. Some bikes can go faster in 5th gear than in 6th for instance. This is often done to promote fuel economy, reduce emissions, etc. Occasionally, installation of a higher ratio rear sprocket actually increases the top speed capability if it works out that the maximum engine RPM and maximum vehicle speed coincide with the new overall drive ratio.

All that said, I don't know where the EBR falls on this. Does anyone know what the RPM is with stock gearing in 6th gear at maximum speed?

EBRRider
07-14-2017, 09:23 AM
This shows just what you are asking . About 10.5 K

https://www.youtube.com/watch?v=HCzIBxZU9ww

TerryS1980
07-16-2017, 09:22 AM
Going from 41 to 44 tooth rear sprocket, the bike will lose an average of 10 mph above 7500 rpm and in 4th-6th gear

Top speed in six gear is dependent on available HP and wind resistance...

Doug Porcaro
07-17-2017, 11:51 AM
In 6th my SX hits the limiter at 169 with a 44 tooth.

Kid Thunder
07-17-2017, 11:16 PM
In Rhode Island that's no problem!! Never can I top out anything!!

noone1569
07-18-2017, 07:38 AM
In 6th my SX hits the limiter at 169 with a 44 tooth.


Whew bet that was fun on a naked!

TerryS1980
07-18-2017, 08:31 AM
On top of loss of top speed, hp and torque goes down as the drive becomes less efficient with more teeth...
http://www.superstreetbike.com/how-to/bigger-rear-sprocket-makes-more-horsepower-mythbusters#page-3

Doug Porcaro
07-18-2017, 11:16 AM
Whew bet that was fun on a naked!

Certainly :)