Could someone explain to me the difference between using a bigger clutch driver vs. just going to a different rear sproket assuming the either change would be the same gear ratio. I have always just changed my rear sproket top switch ratios. I hear people talking about changing the driver and shoe speed. I need some enlightening. Thanks
rear sprocket or clutch driver
- Thread starter davis20
- Start date
When you change to a smaller front sprocket and leave the rear the same, you will be changing your ratio and either gaining acceleration or top end, depending on which way you go with the change. But, if you have say 15-65 on your kart now and you want more pull out of the corners, instead of putting a 66 on the rear and changing your gear ratio, you can also choose to put a 14 on the front and 61 on the rear and keep the same ratio but have more acceleration out of the corners. When changing gears and keeping the ratio the same, a bigger front driver will give you more top end, and a smaller front driver will give you more acceleration/torque. My rule of thumb is to always run the biggest front driver i can get away with running. For bigger momentum tracks or tracks with wide sweeping turns and no lifting of the throttle in turns, you want a bigger front driver, and for small tracks or tracks with tight haripin type turns where your in and out of the throttle alot, a smaller driver would give you better speed and more pull off the corners. In other words, if you have your gear ratio right where you want it and just want a little more speed or a little more pull off the corners, you can change the front driver up or down one size then change the rear gear to compensate. For each size you go up or down on the front driver, you will change the rear gear 4 teeth to compensate and keep the same ratio. For each tooth you add to the front, i believe you turn about 300-400 more rpms, and for each gear you add to the rear, you gain 75-100 more rpms.
alvin l nunley
Site Supporter
15/60 = 4.0-1
14/56 = 4.0-1
6000 RPM W/34” tires = 48.3 MPH with both.
6100 RPM = 49.1 MPH with both
I use those gear ratios because they both equal 4.0-1.
Yet it is a monumental waste of time trying to convince some people that changing drivers, with the same gear ratio, makes no difference. I’ve given up trying to convince people otherwise. True or false, it’s not going to hurt you.
It is equally as hard to convince people that air density really does make a difference in horsepower.
While there are horsepower correction factors for changes in barometric pressure and temperature, (air density) and gauges for tracking changes in air density, few pay any attention to these factors at the track. HP correction factors are what they’re called.
Any dyno software that lacks the ability to enter these correction factors is worthless, they’re that important.
So if you’re going to believe a changing of gear sets, with the same ratio, can make a difference in lap times, even though there’s no demonstrable methods to prove it one way or the other, why would you not believe the air density could make a difference. It is easily demonstrated, on the dyno, that any change in air density can effect readings for HP.
So it’s a myth vs. hard proven fact.
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory.
14/56 = 4.0-1
6000 RPM W/34” tires = 48.3 MPH with both.
6100 RPM = 49.1 MPH with both
I use those gear ratios because they both equal 4.0-1.
Yet it is a monumental waste of time trying to convince some people that changing drivers, with the same gear ratio, makes no difference. I’ve given up trying to convince people otherwise. True or false, it’s not going to hurt you.
It is equally as hard to convince people that air density really does make a difference in horsepower.
While there are horsepower correction factors for changes in barometric pressure and temperature, (air density) and gauges for tracking changes in air density, few pay any attention to these factors at the track. HP correction factors are what they’re called.
Any dyno software that lacks the ability to enter these correction factors is worthless, they’re that important.
So if you’re going to believe a changing of gear sets, with the same ratio, can make a difference in lap times, even though there’s no demonstrable methods to prove it one way or the other, why would you not believe the air density could make a difference. It is easily demonstrated, on the dyno, that any change in air density can effect readings for HP.
So it’s a myth vs. hard proven fact.
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory.
MercerEngineering
New member
Alvin not disputing the fact that it would be hard to measure but it does seem to make a difference. Especially noticeable on restarts. One FACT you can't ignore is the effect of inertia, you are making both gears smaller so there is definately a reduction in inertia, maybe small but definately there! Have a blessed Day!
David Mercer
David Mercer
jsstump#70
Member
For the most part as a rough rule of thumb, Davis20, a smaller front gear will "pull" you off the corner better and a large front gear will equate to more speed at the end of the straightaway IF both ratios are the same. At least thats seems to be the prevailing opinion of those that believe such things. Another common opinion is to use the largest front gear (driver) possible and still get the ratio you want. Some think ratio is ratio, how you get it is not important. Good luck forming your own opinion. Time will aid you in this. I do know air density plays a very important role in setting a carb. Ive known this waaaaay before hearing of Bobs or Al. back in race season saw 4 different air density gauges used at a track. Heard several others discussing it. thats just what i saw. Not sure why Al thinks no one cares about it or understands it. Its a fact, not a myth, that racers I know pay it the attention it deserves.
alvin l nunley
Site Supporter
I have thought about it, quite a bit, and I've come to this conclusion; it makes no difference.
On the starts, or restarts, compared to the weight of the kart and driver, the difference between the two sprocket sets is virtually nothing.
alvin l nunley
Site Supporter
I have never thought that, quoting you; " Al thinks no one cares about it or understands it". C'mon, you don't know what I think, and it appears you don't know what I said. What I said was, " virtually nobody" uses the air density gauge. In my way of thinking, if there are 150 people at the race and only four are using the air density gauge, that's " virtually nobody".
In my 40 years of active participation in karting, in California, to the best of my knowledge, I was the only person at the races with the air density gauge. I only have my own experiences to go by. I'm happy to hear more people are using them. Cash
Comments compliments criticisms and questions always welcome.
jsstump#70
Member
Al, what you said was "nobody seems to care what the air density is". http://karting.4cycle.com/showthread.php?8441-Animal-blue-to-gold, post #4 I dont understand why you would type it if you didnt "think" it. I figured your grandiloquence here would logically be your thoughts. There was 150 people at the race I spoke of? How do you know this? I only SAW 4 using one. I dont know how many more may have. Either way, "nobody" is not an accurate description. Now back on topic, I too believe ratio is ratio, for the most part. See we are so much alike!! LOL
alvin l nunley
Site Supporter
It amazes me how many people can misquote me and use that as the basis of their argument.
Please keep this guys thread on topic guys, he is just trying to learn about gear ratio's, not air density or how many people use them, no offense to either of you but arguing will get everybody nowhere. That said, my experience has proven to me that a ratio is not just a ratio when it comes to gearing on a kart. Put a 16/68 on your kart, go record lap times then come back and only change gearing to 13/56 and tell me you had the same lap times and did not notice a bit of difference. You will see that with the smaller front and rear gears, you have alot more acceleration on starts and off the corners, and alot less speed at the end of the straitaway and on the starts. It has been proven time and time again that the smaller front gear improves acceleration and low end power while bigger front gear improves speed. Finding the perfect balance and ratio will give you the fastest lap times on that particular track and those particular track conditions that day.
i did say 16-68 and 13-56 earlier, but did not do the math to make sure that was the same ratio. I should have said to try a 16-68 then try a 13-55, that is literally the same ratio just with different drivers.
i did say 16-68 and 13-56 earlier, but did not do the math to make sure that was the same ratio. I should have said to try a 16-68 then try a 13-55, that is literally the same ratio just with different drivers.
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Of course they arent the same gear, but they are basically the same ratio, plus or minus 1-2 points. Those of you who believe a ratio is just a ratio and your speed or accelleration doesnt change no matter what gears you have on the front or back, need to actually get out on the track for practice and try a few different gear combo's and see for yourself. You cant possibly tell me you actually believe that you have the same acceleration on the starts or on takeoff using a say 15-65 and whatever gear you need to have to keep the same ratio while using a 13t front driver, and cant tell a difference. I dont see how anyone can actually believe that if they have actually tried it. Seems like most are just stating their opinion, and havent really tested that theory. If you travel to different tracks and are changing front drivers to suit those tracks, you know a ratio isnt just a ratio. If your going to different tracks and running the same front driver no matter where you race, and are actually competitive, then you must be one lucky guy. Try running the same front driver you would use on a small bullring but instead use it at a momentum track, and only change the rear gear to get the rpms you need or speed you need, and see if your competition isnt running bigger drivers and pulling you down the straits. I bet they are.
I added this to the post i made above because i didnt check to make sure they were the same ratio before putting it out there, that is my fault, sorry. But i stand by what i said
i did say 16-68 and 13-56 earlier, but did not do the math to make sure that was the same ratio. I should have said to try a 16-68 then try a 13-55, that is literally the same ratio just with different drivers.
i did say 16-68 and 13-56 earlier, but did not do the math to make sure that was the same ratio. I should have said to try a 16-68 then try a 13-55, that is literally the same ratio just with different drivers.
Arc Angel 18
New member
im with weddle on this subject an heres why. at one of my local tracks i normally run a 19t driver as does the competition. anyway another racer forgot their 19t driver at home so let them borrow mine an id just use an 18t and adjust the rear accordingly thinking it wouldn't make a difference. i was sure wrong on that, not only was i being out pulled on the straights but at the end of the straights someone said it was like i hit the brakes cause other karts would clearly increase there distance from me. i definitely learned my lesson that day. lol
Dont people ever wonder why you always see people on here asking what front driver or what gear everybody uses at a certain track? If it was really like some people believe, then at any given track you go to, there should be a bunch of different gearing used, rather than 90% of the racers on the same front driver and a few teeth difference in the rear gear. Or in other words, everybody is on close to the same ratio using the same front driver just a different rear gear to get the rpm they need. The wrong front driver at most big races can make the difference between you being in the front row on pole for the feature, or dead last, itll put you in left field without a doubt.
x's 2 , Those non believers are easy money !
DepDaddy
Member
Here's the solution...
Error on the side that the driver gear makes a difference. If you are wrong it won't matter. If you're wrong then you're running the same ratio either way.
I do not know who is right or wrong on this, but it sounds to me that you can't go wrong with the bigger clutch gear.
Error on the side that the driver gear makes a difference. If you are wrong it won't matter. If you're wrong then you're running the same ratio either way.
I do not know who is right or wrong on this, but it sounds to me that you can't go wrong with the bigger clutch gear.