Gearing... why dont more people do this!

J

JRK5892

Over 1,000 Posts
man so on every one of my bikes i adjust the gearing, be that the main or the front sprocket (or pulley) the diff is unreal! i just did it last night again on my GSF600s bandit... went to a 14 tooth front sprocket from a 15... took me about 15 min start to finish and cost me 20 bucks... the bike is like a whole new bike, just a blast to ride has much more to roll on though the turns, all around great! i have regeared every bike i own and can not belive more people do not do this....
my RPM on highway did go up a touch... at 80mph i am at 7500, 70mph 68000, not bad before i was at:
80mph 7000, and 70mph at 6500, i have not had someone speed check me yet so i am not sure how that was affected yet, usuually it is 3 - 5 mph off. Now 6th gear is worth a crap on the highway... made a huge diff! i ride this bike every single day, rain, shine, snow... i am on it...

i tend to only go down 1 gear depending on the bike, on my HD it made a night and day diff on my launch, cafe made up for the flat spot in the throttle in sweeping turns, wifes bike made it so that off the line she is able to rip, and i could keep going... i have gone up a gear as well for better highway on a CB750 years ago as well...
just wanted to share... may be an option for some of the smaller bikes on here to get more UMPH out of your ride, being that alot of my smaller biked do not see alot of highway time
 
My garage peg board is full of stock countershaft sprockets that were one tooth too many. Simplest seat of the pants performance upgrade. Period.
 
yes a bigger front sporcket means lower RPM, i went from a 15 to a 14... prob going to take this bike to Missouri this weekend not the Harley so i will prob toss back in the 15 or maybe a 16 for the long road trip, 5 hours highway riding ya know
 
For the current build on my 360 I went from a 16 to an 18. I'm hoping the other mods I've added will create enough power that the increasing in gearing won't take all the fun out of the bike.
 
Yeah... I am worried about that... I put on a fairly radical cam as well, so the power is a lot higher in the band, too.

I'll reserve judgment until I actually get her on the road though. Provided she has enough oomph to overcome the new gearing, she should top out in the 120s. :D
 
Hell, I jumped very far the opposite way with my 175.......17/36
175 is already slow off the line, so might as well embrace it to gain some highway speed......much better all around bike now
 
I have been thinking about this for my cb350K but i don't really know were to start. Any ideas?
 
depends what you want, i would sugest going down a tooth in the front sprocket would rip in the turns
 
My bike is going to see a lot of DD duty. I went up on the main sprocket to drop revs and help fuel economy.
 
i went from 15 to a 17 on my cb450 which helped a lot on the vibrations and cruising speed on the highway. It's not bad at all from light to light either.
 
From what I've read a cb500t is very similiar to the 450t. I wonder if the same would hold true for my build. Its still a couple winters from completion, but hey its good to know!

I dropped a tooth in the front and added one in the rear of a 87 ninja 750 once, made it pop the front up a bit easier :)
 
I haven't messed with the DS7 yet, but the 'busa is up two on the rear. Yea, I'm sure I lost some top end, but how often am I doing 180mph?
It sure made it fun out the hole though. And as stated above, the acceleration is where all the fun is ;)


And just for reference, for those that don't know...
Dropping one in the front is equal to going up two on the rear.
Up rear/down front= acceleration>top speed.
Up front/down rear= top speed>acceleration.
You can mix and match to fine tune to your needs/riding style.
 
Going up a tooth (or two) on the rear sprocket will not have as radical effect on accelleration as changing the tooth count on the front sprocket.
 
I plan on dropping one on the front and going up one on the rear of the 750 this summer. Ill still be able to cruise at 70+ on the highway, but also allow for a little more grunt on the PA hills.
 
Also.. for what it's worth... the lower the number of teeth on a sprocket, the greater the effect of changing the number of teeth will have.

Final drive ratio is actually determined by dividing the number of teeth on the rear sprocket by the number of teeth on the front. For my CJ360, final drive is 33/16 or 2.0625.

Going -1 on the front changes this to 2.200 whereas going +2 on the rear bring me to 2.1875.

Multiplying the final drive ratio by the primary drive ratio and again by the gear ratio will tell you how many rotations the engine undergoes per revolution of the rear wheel.

So by going +2 to the front (as I mentioned in an earlier post) this gives me a new final drive of 1.8333. Multiply that by the primary ratio of 3.714 and the fifth gear ratio of .965 and we arrive at 6.5705 revolutions of the engine per revolution of the rear wheel. Given that my rear tire is 3.75-18 this means the bike is traveling 68.330 inches per revolution of the rear wheel or 10.399 inches per revolution of the engine.

Now, by choosing an arbitrary engine speed such as 11,000 RPM, we can calculate the speed of the in a given gear, for a specific RPM. I know the bike travels 10.399 inches per engine revolution, so we multiply the number of inches by the RPM to get our speed in inches per minute and then again by sixty to get inches per hour (10.399 * 11000 * 60 = 6863642.4231). Now divide this number by the number of inches in a mile in order to convert to MPH: 108.33 mph
 
I hear ya, Joe. I went up 3 in the rear, instead of going down in the front. I just wanted an aluminum sprocket though...
 
Yeah, I have a 16T front to throw on my 350F as per TwistedWheels (isn't there a z in there somewhere?) recommendation in Carolines build thread. Should be a blast in the twistys around here. Light bike+power in the corners=ultimate win.
 
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