How do we gear this beast?

[Guest]

Over the last couple months I've read to drop 1 in front, add 2, 3, or 4 in rear. Even remember someone doing all the above. I read a couple say no more than +2 on rear and was wondering why. Seems like several have dropped 1 on front and +3 on rear is close to same. Is the "no more than 2" due to usable traction or can the motor not rev quick enought to use more gear? Just curious as to the reasoning. Bike not here, but gathering parts and info to help pass the time. Beats pacing floor like expecting father!

 

[OB_RobBase]

Its usually better to not make the front sprocket smaller because the smaller it is the more the chain has to bend around it and the quicker you will wear out the chain. Nevertheless the most popular gearing change on this board is to change from 17/40 to 16/40. Most like it and it helps at the dragstrip. However you can get almost the same ratio by going to either 17/42 or 17/43.
You'll save wear on the chain but ironically you'll have to buy a new longer chain because the rear sprocket is larger.

 

[OB_RobBase]

A simple way to figure out gearing is to remember the closer in size/teeth the front and the rear the more "overdrive" your bike will have. Example 20 tooth front/30tooth rear would probably take you to 500mph if you could ever get it rolling. Other extreme would be something like 14 front/50 rear, same as granny gear, your bike would top out at 100mph.
To summarize, if you want quicker acceleration in all gears but lower top speed then go down in the front or up in the rear. Also your bike will be turning more rpms at any given mph. If you want the bike to rev lower while droning on the highway or you want a higher top speed and less acceleration then go up in the front or down in the back.

 

[Guest]

I understand how the gearing works, and the 17/43 is very close to 16/40. Am just curious why some of the members were thinking no more than +2. I also am from the school of bigger on rear better than smaller on front. Not worried about top speed, only want to get from point A to point B, in a straight line, as quickly as possible. Thanks for the info.

 

[Guest]

Plus 2 in the rear would be just about the limit of the stock chain. I imagine you could go as big as you want in the rear as long as you could find the sprocket and a chain to go around it.
Just my .02

 

[OB_THE MOTORHEAD]

17 44 i put on works good but if you put pipe etc. 42 is better i have to stand up ahead of fairing through first and early second at track to keep from flipping.fun gear though.

 

[OB_bimmerbusa]

What does this do to your speedo reading.
How far off will it be going to a 42 or 43.

 

[OB_THE MOTORHEAD]

you can calculate it by the percetage you change yourfinal drive ratio they are overly optomistic stock any way.

 

[OB_jeffw]

I initially did 16/43 when I converted to a DID 520 chain (no drag racing here). I used the yellow box to correct my speedo, it worked just fine.

I have since gone to 17/43, it gave me less chain noise. I did not shave the chain guard on the swing arm. I guess if I had some of the noise would have gone away.

I wanted roll on acceleration (like riding next to a R1 and watching his eyes as I pull away). On the down side, the front end was hard to keep down, not to talk about the rear tire spin.

 

[rotts4u]

To compute the effective final ratio of a sprocket combination simply divide the rear sprocket by the front to get the ratio.

Stock= 40/17=2.3529
41/17=2.4117 top speed decreases by 2.499%
42/17=2.4705 top down by 4.998%
40/16=2.50 top down by 6.251%
43/17=2.5294 top down by 7.501%
41/16=2.5625 top down by 8.908%
42/16=2.625 top down by 11.564%

Torque multipication will INCREASE by the same percentage listed above for each ratio. Also top speed will only decrease by this much at redline in top gear assuming your bike would pull redline in 6th. If it would not with stock gearing a small change in gear may effect your top speed by very little if at all because it will now pull higher rpms due to the effective higher ratio.

So if you assume the therotical 199mph at redline you can compute your new top speed by reducing the 199mph by the percentage listed by the gear you choose from the above chart.

One other thing to think about chain makers prefer an odd number of teeth in front and rear to get max chain sprocket life. This is because the chain has an even number of links and will therefore have each link always hitting different teeth of the sprocket on each revolution of the chain.

Ok math class is over lets ride Busas now.

Don
RoadDog not MATHDOG

 

[OB_Animal]

RobBase,

I went 17/44 (so up 4 rear) with stock chain (length) and this was juuuuuuuuuuuuust a bit tight but +3 will definitely go with stock chain and no problems whatsoever, apart from the increased torque.

 

[OB_GSX1360R]

Keep in mind that the Hayabusa looses speed in the quarter mile when lowering the gear ratio... I've seen this personally.

 

[Guest]

GSX1360R, If going to a 42 or 43 tooth rear makes the bike pull stronger, how do you lose speed? I would think the bike would rev quicker and run thru the gears quicker, and end result would be gaining speed quicker. I thought it would make the bike quicker but would think that it would be at a higher speed also. I'm I thinking about this all wrong, or just thinking too much?