View Full Version : busa final drive ratio

09-10-2006, 06:30 PM
You guys that have running busa rails. What is your final drive ratio? I've only run mine a little but with a 4.4:1 final coupled to the 1.596:1 primary=7.02:1 it accels like a rocket with 27" tires @ 1200# and I don't need to run at redline. It's a little steep on takeoff tho. What is your experience??????

09-10-2006, 10:00 PM
14 countershaft, 64 rear sprocket. 1300 Padla traks on 15 inch wheels so maybe 30 or 31 diameter. Gear ratio 4.5:1 based on countershaft and rear sprocket. Too high. IMO - shoot for 6.5:1 to 7:1


09-10-2006, 10:06 PM
So adding in the primary drive reduction(1.596:1) a final rear ratio of about 11:1? Really?

09-10-2006, 11:17 PM
not a busa powered but I had a 5:1 in my cbr 900 and it was way to high 4,5 and 6 gears were unusable . 6.75 :1 in the old diff and the ratio was a little low but fun as hell to shift all the time....Going with 6.25:1 this time should be spot on for my little cbr

edit-based on sprocket sizes or internal reduction in the diffs not counting the tranny ratio 5:1 = 14/70 sprocket combo both diffs are using a 14 tooth counter sprocket

09-11-2006, 06:41 AM
Just trying to get a handle on this.hotwheels,Gene,what is your total reduction from engine to wheels? Ican be very wrong here but isn't a total reduction(for a busa-maybe not with the higher revs of the 900)of approx 8.-8.5:1 enuff?

09-11-2006, 07:37 AM
I have no clue about the overall ratio and such, but Desert Dog uses a 1:1 input from the busa counter shaft into an RPM tranny - the tranny is 4.6:1 input to output.

He's running 31" tall tires and first gear is good for putting around the parking lot. Step on the pedal and you hit red line almost immediately. Second gear is a better "first" gear. The car will top out right about 120.

When he first started putting this drive train together, an 8:1 tranny made first and second gear pointless and third was short and quick.

09-11-2006, 08:07 AM
That's more in line with what i was thinking.4.6:1xTranny primary reduction 1.596:1=7.34:1. That's approx. what I have now and it accels like a rocket. Can't see why anyone would need lower unless they want to do some crawling. I can see lower being neded with higher revving/lower torque smaller bike motors tho. Thanx!

09-11-2006, 10:33 AM
5.5:1 on my setup, 1st. gear is fairly quick but not too quick. Seems ok but I might gear it a bit higher, it's seems a hair low right now but I'll wait till I get some dune time on it to see how it handles. The sand at the dunes is different than below the dam so I know they handle different. The sand at the dunes lugs my motor more......

09-11-2006, 01:35 PM
What I'm looking at now works out to 5.2:1. Damn we agree on something! :lol:

09-11-2006, 02:21 PM
So adding in the primary drive reduction(1.596:1) a final rear ratio of about 11:1? Really?

were are you getting this from? 1.5961:1

09-11-2006, 02:25 PM
The specs I got were 2.352-1 for the primary reduction.

09-11-2006, 02:27 PM
were is that coming from tho, reduction at each gear, then another to the outputshaft? 8)

09-11-2006, 02:39 PM
2.352 between the crank and the clutch basket.

So to get your final drive ratio you would have to times 2.352 and the gear ratio.

1st gear is 2.615 X 2.352 = 6.150 at the output shaft.

09-11-2006, 02:41 PM
ok, i think what most guys like gene etc, are defining there final gear ratio, after the output shaft, not from the crank..

09-11-2006, 03:03 PM
1.596:1 is the primary internal reduction from the crank to the trans.on a busa. Don't confuse this with first gear of 2.615:1. When we talk of total reduction we are refering to the primary x final drive ratio usually. That was what I was interested in.

09-11-2006, 03:13 PM
most people listing there gear ratios, are listing from sproket back, so it not be confused.... 8) i am shooting for appro 6:1 thats from the output shaft.... 8)

09-11-2006, 03:38 PM
That's what I call final drive ratio. I think we are all in agreement here.

09-12-2006, 06:16 PM
is what I'm talking about. Right or wrong I tend to ignore the tranny ratios and focus on countershaft and sprocket for chain drive and now the ring and pinion for my diff.

All I have is experience to share on my chain driver with 14/64, which works out to be 4.5:1 final drive. I could feather the clutch and get going but it would hit at least 50 or more in first gear. I swear I have driven that car 100 MPH in third. My pals at Sick Sand Travel said they have driven their cars 140 MPH.

That's a bit outside my comfort zone. My Belmore rail buddies find 6.5:1 optimal. I have ridden in one of their cars and it was sweet.

My spreadsheet says my car will go about 30 MPH at 8500 RPM in first geat with a6.94:1 final drive ratio. I'd hardly call that a stump puller and believe it is going to give me the performance I want.

09-12-2006, 07:33 PM
I tend to think I want a compromise between the two since I like speed and don't think I want to be within the 20 percent of redline when cruising at higher speeds. Think I'm going to try about 5.5:1 for now.Thanx everyone for your opinions!

09-12-2006, 08:16 PM
see, i would ratjher cat walk up a very large hill than sprint to the top myself, lot more thrill going uphill at 80 degrees than 80 mph i think.... 8)

09-12-2006, 08:36 PM
Whatever pumps your adrenaline. 8)