ClassicVW_imp
Road warrior
Bob's physics statements can't be merely called an opinion, just as you can't call belief in gravity an "opinion".
Changed Final Drive Gearing 2013
- Thread starter CIP57_imp
- Start date
rboe
Road warrior
Yup. Physics is pretty much just measurements; no room for opinions. Advance a hypothesis based on facts (more the merrier); adjust the hypothesis until it fits the facts then you have a theory. Keep testing the theory until the facts don't back it up.
Lower gearing will let a motor spin up faster since you have given it better mechanical advantage for the given load, than a taller gearing. Which means at the top rpm you'll have to shift sooner. Unless you have geared it so low (think 4 wheel drive low) your speed advantage is nought (and don't think this is the case with the CB but if your times hold up, it could be).
Lower gearing will let a motor spin up faster since you have given it better mechanical advantage for the given load, than a taller gearing. Which means at the top rpm you'll have to shift sooner. Unless you have geared it so low (think 4 wheel drive low) your speed advantage is nought (and don't think this is the case with the CB but if your times hold up, it could be).
You have a fundamental misunderstanding of physics (which is not uncommon, so please don't be offended). If taller gears are "faster," why not just put in the tallest gears one can reasonably fit? Because taller gears reduce torque, lowering the rate of acceleration...CIP57_imp said:
We can use physics/mathematics to prove this: The formula for acceleration is a = f/m (from f=m/a, which is Newton's second law of motion). In other words, the rate of acceleration is the force applied to an object, divided by the object's mass. If the mass is constant (as is the case when considering two identical bikes/riders), increasing the force (torque) will result in a linear increase in acceleration. You can see an example of this for yourself: drop a rock of any size to the ground. Now, throw the same rock at the ground, releasing from the same height. The thrown rock will get there a hell of a lot faster because you applied more torque to it. Gearing is the same thing. It gives you the ability to apply more force (torque) to the same mass. Lowering the gear ratio increases the torque, as we all agree, which will increase the acceleration, since we know that increasing the torque will linearly increase the acceleration of the object.
An example using motorcycles: take two identical motorcycles of identical loaded weight, with riders of identical skill in standing start races. Gear one lower and one higher. Start out in first gear, and don't shift at the top of first and both riders will go to full throttle as soon as is practically possible. The race will be over for the bike when it hits redline and the rider will stop the bike. The lower geared bike will out accelerate the higher geared bike until it hits redline, but the higher geared bike will pass and travel further before hitting redline.
This example can be expanded to cover the situation we're talking about here: the fact that the lower-geared bike will out-accelerate the higher-geared bike will remain true regardless of the speed the bikes start off at, as long as both bikes start in the same transmission gear. So, if both bikes start off doing 50mph in 3rd gear, the lower geared bike will again out-accelerate the higher-geared bike, and the higher geared bike will again travel further before hitting redline in 3rd.
So, let's talk about a race between these two, identical (other than the final drive ratios) bikes and riders. As can be deduced from the example above, in a race between these two people then, the outcome, or winner, comes down to the rider with the lower-geared bike's ability to shift quickly and accurately (since he will likely have to shift more, or at least, sooner), and how far the race is (i.e. length, 1/4 mile, 1/8 mile, between stop lights, etc.).
(if the race is of a length that causes the lower-geared bike to hit top speed in top gear, the winner will then be a function of how long it takes the still-accelerating higher-geared bike to catch up to the now constant-speed lower-geared bike, and whether or not he can catch up before the end of the track/race course -- in its most simplistic, this is the situation called out in the dirt bike track, above, and is of primary concern when setting up a vehicle for any particular racing venue).
Randy B
Road warrior
I am sensing a spinning effect taking control.....
Bob, if two bikes with the same rider, same weight and same road conditions go head to head, from what you are saying the lowered gear bike should be faster 0-60 correct.
There is a sweet spot in gearing, you are assuming this situation or bike has that sweet spot. I'll give you the video, look at the 0-60 times what really matters here, the 19-38 gear ratio will outrun the stock gearing. I know i could have run a tenth or two better but I had a bad start off the line. The 0-100 times are faster as well, once i hit 3rd at 100 I'm long gone. Listen to the motor with the 19-38's it sounds sweet.
Bob, you seem like a nice guy and very knowledgeable, please take a look and give me your unbiased thoughts.
I have a 3.57 19-38's and 3.79 stock 0-60
Stock Gearing
http://vid1034.photobucket.com/albums/a423/cipolla57/Yoshi_zpsff50902b.mp4
19-38
http://vid1034.photobucket.com/albums/a423/cipolla57/new gears bri_zpslpqleggr.mp4
There is a sweet spot in gearing, you are assuming this situation or bike has that sweet spot. I'll give you the video, look at the 0-60 times what really matters here, the 19-38 gear ratio will outrun the stock gearing. I know i could have run a tenth or two better but I had a bad start off the line. The 0-100 times are faster as well, once i hit 3rd at 100 I'm long gone. Listen to the motor with the 19-38's it sounds sweet.
Bob, you seem like a nice guy and very knowledgeable, please take a look and give me your unbiased thoughts.
I have a 3.57 19-38's and 3.79 stock 0-60
Stock Gearing
http://vid1034.photobucket.com/albums/a423/cipolla57/Yoshi_zpsff50902b.mp4
19-38
http://vid1034.photobucket.com/albums/a423/cipolla57/new gears bri_zpslpqleggr.mp4
808_rider_imp
Running like a top
I have no personal experience as to the effects of changing the final gear on motorcycles but my experience from riding multispeed street/mountain bicycles is in agreement with Bob. From a standing start, the lower the gearing, the quicker I can accelerate. On the rear wheel of my bicycle, if the chain is on a sprocket with 17 teeth, my bicycle will accelerate quicker than if the chain was on a sprocket with 12 teeth.
Not sure if my experience on bicycles translates over to motorcycles, but I just wanted to throw that out.
Not sure if my experience on bicycles translates over to motorcycles, but I just wanted to throw that out.
the Ferret
Road warrior
Same vid isn't it?
rboe
Road warrior
In physics, to cover your butt and to make sure other folks can do the same experiment to see if they get similar results you need a measure coarse, accurate clocks/timers, a means of accurately weighing the bike and a record of atmospherics. All variables have to be taken into account and the more runs you can do so you can average the results the better.
Unfortunately, and I don't want to sound mean here, but those videos are no better than hearsay. No attempt to show a measured distance nor any timing device. They neither support nor dispute your claim or Bob's.
Now it you two could meet at a drag strip, make several passes, swap sprockets and repeat more runs, then we'd have some real data. Plus the opportunity to sling mud in person.
In good jest of course. 
Unfortunately, and I don't want to sound mean here, but those videos are no better than hearsay. No attempt to show a measured distance nor any timing device. They neither support nor dispute your claim or Bob's.
Now it you two could meet at a drag strip, make several passes, swap sprockets and repeat more runs, then we'd have some real data. Plus the opportunity to sling mud in person.
In good jest of course.
the Ferret
Road warrior
I watched two vids..both you were stopped with your turn signal on, both a silver car turned in front of you and headed up the street, both you rocketed up the road with your turn signal on...both looked the same..
Doh... I watched the same vid twice. We really need a head pounding against wall emoticon for times like this.
Doh... I watched the same vid twice. We really need a head pounding against wall emoticon for times like this.
Robe, i have been documenting runs since the bike was stock to see what gains are made with certain mods. It gives me a real good idea of whats happening. I'm not challenging anyone my post was just for information which i think i presented in an honest fashion.Rboe_imp said:In physics, to cover your butt and to make sure other folks can do the same experiment to see if they get similar results you need a measure coarse, accurate clocks/timers, a means of accurately weighing the bike and a record of atmospherics. All variables have to be taken into account and the more runs you can do so you can average the results the better.
Unfortunately, and I don't want to sound mean here, but those videos are no better than hearsay. No attempt to show a measured distance nor any timing device. They neither support nor dispute your claim or Bob's.
Now it you two could meet at a drag strip, make several passes, swap sprockets and repeat more runs, then we'd have some real data. Plus the opportunity to sling mud in person.
I'm just a normal self employed guy, my son is a mechanical engineer and teaches night school. He read through these post with a grin. He said he may give this project to his senior class next year, his comments where there are to many factors to consider to make a decision based on physics alone.
pekingduck
Road warrior
Well, correct in a perfect world. Using your mountain bike's largest rear cog on loose level dirt means you'll spin the rear wheel and crank way too fast.808_rider_imp said:
On a motorcycle I think that too low a 1st gear means you have to modulate more between spinning the tire and a wheelie, and the time spent in 1st is too short. Most real accelleration takes place in 2nd and 3rd.
Production class vintage road racers gear up for top speed, and generally take off in 2nd gear. I think the same is true of drag racers - too much time lost in the 1-2 shift.
Inspection of transmission gears on a hard-ridden bike would almost always show wear or fatigue on 2nd gear teeth, not 1st. I can't recall ever seeing a blown up 1st gear - it's always 2nd.
Randy B
Road warrior
This is not due to not accelerating hard in first, but is due to the hard shock 2nd gear takes on the redline shift from 1st.pekingduck_imp said:
Interesting thread that seems to be dealing with an argument involving theory v.s. application.
In terms of pure theory, I would agree with the physics junkies. However it is possible that given the average riders skill set, gearing changes such as the one CIP has made could provide for an easier application of torque/power in tests such as this. It is certainly conceivable that the lower stock gearing makes it harder to get a good launch — ironically, due partially to the faster acceleration. You also have to be prepared to make that first shift much sooner and if you make a less than perfect shift you'll cost yourself a measurable amount of time. Such variables have quite an impact on short runs like those that CIP is making in the videos.
In a perfect world, a lower geared bike is going to outperform the higher geared bike in terms of pure acceleration. But insert less-than-perfect humans, road-surfaces, etc. into the mix and you begin to throw things off balance. A professional racer that can achieve a perfect launch and make lightning-quick shifts is going to have different results than the average guy trying to mimic the more skilled rider. Three different riders might well prefer three different gearing setups to achieve their best times from 0-60mph, 0-100mph, etc..
Another way to look at it: If the CB1100 came with an eight speed transmission and lower gearing, in theory you would have the potential for impressive acceleration. In reality the difficulty of launching and the inefficiency of shifting would overcome the gains provided by the low gearing in a test of 0-60 times for example. In terms of real-world applications, I'm guessing the average rider is much more concerned about roll-on acceleration at varying speeds than 0-[insert speed here] times. But tests such as those CIP is running makes for an interesting conversation.
Bottom line: Others might experience different results, but this gearing change works out better for CIP57 and makes his CB1100 experience even more enjoyable. That's good in my book.
All of the above is simply my own opinion of course and it's worth the same $.02 as anyone else's.
I just realized that I somehow missed AzBob's post (#23) which makes much of mine appear rather redundant and much less eloquent. I'll just scramble back into my cave now. :blush:
In terms of pure theory, I would agree with the physics junkies. However it is possible that given the average riders skill set, gearing changes such as the one CIP has made could provide for an easier application of torque/power in tests such as this. It is certainly conceivable that the lower stock gearing makes it harder to get a good launch — ironically, due partially to the faster acceleration. You also have to be prepared to make that first shift much sooner and if you make a less than perfect shift you'll cost yourself a measurable amount of time. Such variables have quite an impact on short runs like those that CIP is making in the videos.
In a perfect world, a lower geared bike is going to outperform the higher geared bike in terms of pure acceleration. But insert less-than-perfect humans, road-surfaces, etc. into the mix and you begin to throw things off balance. A professional racer that can achieve a perfect launch and make lightning-quick shifts is going to have different results than the average guy trying to mimic the more skilled rider. Three different riders might well prefer three different gearing setups to achieve their best times from 0-60mph, 0-100mph, etc..
Another way to look at it: If the CB1100 came with an eight speed transmission and lower gearing, in theory you would have the potential for impressive acceleration. In reality the difficulty of launching and the inefficiency of shifting would overcome the gains provided by the low gearing in a test of 0-60 times for example. In terms of real-world applications, I'm guessing the average rider is much more concerned about roll-on acceleration at varying speeds than 0-[insert speed here] times. But tests such as those CIP is running makes for an interesting conversation.
Bottom line: Others might experience different results, but this gearing change works out better for CIP57 and makes his CB1100 experience even more enjoyable. That's good in my book.
All of the above is simply my own opinion of course and it's worth the same $.02 as anyone else's.
I just realized that I somehow missed AzBob's post (#23) which makes much of mine appear rather redundant and much less eloquent. I'll just scramble back into my cave now. :blush:
DGShannon_imp
Been there
In debates, I often find that people are saying the same thing but in different ways. Because it sounds different to the ear, we think there is disagreement. Regardless of which side of this debate you fall on, the meat is contained in the statement above.AzBob_imp said:
There is a difference between acceleration and top speed. When debating, and using the word "faster" you have to be clear which one you are talking about.
In debates, I often find that people are saying the same thing but in different ways. Because it sounds different to the ear, we think there is disagreement. Regardless of which side of this debate you fall on, the meat is contained in the statement above.DGShannon_imp said:
There is a difference between acceleration and top speed. When debating, and using the word "faster" you have to be clear which one you are talking about.
D,
There is meat in the above paragraph if you change the word Bike to Motor. Stop both bikes when the first hits redline and measure F/T (feet traveled)
The bike with the lower gears will have traveled further (i.e. be ahead of the other bike) and have a higher trap speed, all other things being equal.CIP57_imp said:
Lower final drive = more acceleration at the cost of top speed.
Higher final drive = higher top speed at the cost of acceleration.
In an actual race, the winner will be the person with more skill/experience in that type of race, and/or more luck.
Usually, to eliminate the variability of the start, people will race from a rolling start. E.g, they both get on the road doing 20mph, look at each other, agree to start via some head nodding or whatever, and punch it.Guth_imp said:
nhawk7504_imp
Been there
I wrote to Honda in Japan and the engineers said if you change to a smaller rear sprocket, the chain could scrape on the swingarm which would not be a good thing in their opinion. He said to leave the gearing as is and enjoy. The original concept was too slow down and enjoy torque rather than horsepower. But of course they have since added the sixth gear once the market moved out of Japan. I rode a 919 yesterday and it was very smooth. Vibes are character. Not to me. A sewing machine is fine for me. - Anyway, change the front and leave the rear alone, or at least keep and eye on the swingarm to see if it is being altered by the chain at all.
