Gear selection

Smr#17

Member
If your running a 15/59 or a 14/55 both are a 3.93 would one have a faster acceleration or would the weight of the gears be the only difference between the two choices. Just wondering if there are any advantages to different gear choices that equal close to the same ratio
 

racing promotor

Moderator
If your running a 15/59 or a 14/55 both are a 3.93 would one have a faster acceleration or would the weight of the gears be the only difference between the two choices. Just wondering if there are any advantages to different gear choices that equal close to the same ratio
The 15/59 and 14/55 you mention are you using them ? Or just an example, if your racing them with which motor and class ?
 

Smr#17

Member
I’m on a 15/59 it’s in a kids class on box stock predator. Just seeing if there would be any difference by going to a 14/55
 

Smr#17

Member
She is doing pretty good, stays part throttle though corner. Could possibly be on the throttle alittle more through the corner but overall Pretty smooth on throttle and the wheel she has less than 10 races under her belt and has picked up a couple wins and is usually in top 3
 

racing promotor

Moderator
If she's not maximizing momentum and your turning 5150 your geared wrong, which is ok for now it will take off slightly quicker and recover quicker on a 14 driver, keep an eye on it as once she does maximize momentum you'll likely only need a 57 rear to turn same rpms, then at that point I would try a 16 driver with 60 rear, also at that point I think you'll find 5000 rpm max will be faster.
 

alvin l nunley

Site Supporter
If your running a 15/59 or a 14/55 both are a 3.93 would one have a faster acceleration or would the weight of the gears be the only difference between the two choices. Just wondering if there are any advantages to different gear choices that equal close to the same ratio
If you measure "pitch diameter" and calculate the ratios, you will find that the larger gear set is a slightly lower gear ratio. This chart will show you how much.
pitch ratio.jpg
 

Smr#17

Member
So I know 14/55 15/59 and 16/63 are basically the same final ratio so which one would pull out of the corner harder and still have the same top speed. The track has tighter corners and at 251 lb so they pull her out of the corners alittle but she’s a lot faster by the end of straightaway and still hasn’t mastered the art of passing
 

alvin l nunley

Site Supporter
Look at the pitch diameter ratios, the 16/64 will get you out of the corners faster, very slightly, but you'll need to turn a few RPM more to be going the same speed it the end of the straight.
Pitch diameters do not grow linearly as the tooth count increases.
 

paulkish

old fart
deleted because I need to understand Al's first post better on pitch diameter ratio being different then gear ratio and not changing proportionally like gear ratio.

Al I think a spread sheet where racers can input gear ratio and get an answer back on pitch diameter ratio would come next?

Or is the difference in pitch diameter ratio only an interesting fact which has nothing at all to do with gear ratio? I don't know?

At this point not understanding it fully I think either pitch diameter ratio is correct or gear ratio is correct for giving the mechanical advantage. If there different they 'both' can't be correct.

got to read more on it
 
Last edited:

flattop1

Dawg 89
So I know 14/55 15/59 and 16/63 are basically the same final ratio so which one would pull out of the corner harder and still have the same top speed. The track has tighter corners and at 251 lb so they pull her out of the corners alittle but she’s a lot faster by the end of straightaway and still hasn’t mastered the art of passing
herein is the problem .
the gear ratios provided will alter low speed take off or top speed.
they can not provide both .
you have to give up one or the other at a stated rpm .
 

racing promotor

Moderator
So I know 14/55 15/59 and 16/63 are basically the same final ratio so which one would pull out of the corner harder and still have the same top speed. The track has tighter corners and at 251 lb so they pull her out of the corners alittle but she’s a lot faster by the end of straightaway and still hasn’t mastered the art of passing
Until she figures out the art of passing that is hindering MOMENTUM your just chasing your tail with gearing, pick whichever one you feel helps her the most and stick with it as long as your hitting close your RPM target, work on her PREACH MOMENTUM, MOMENTUM, did I say MOMENTUM.

Good Luck !!
 

Smr#17

Member
Ok thanks for the info I think I’m understanding it better. I’ve really been working with her on momentum. The only place I feel she is really losing any is easing off the gas in the corners. But she says if she stays in it more she can feel the tires start sliding. The only class that can really hold it wide open all the way around are stock and AKRA adult classes. I figured with her weight she would have a lot less available traction because a lot less weight on the tires. I’ve changed my prep this week to try and make up for that. Track has been pretty hard but keeps moisture in it all night. And with rain this week I figure the track will be soft and wet all night. I have a set of 33b’s that don’t have much life left I may just go ahead and use goat on them
 

racing promotor

Moderator
Ok thanks for the info I think I’m understanding it better. I’ve really been working with her on momentum. The only place I feel she is really losing any is easing off the gas in the corners. But she says if she stays in it more she can feel the tires start sliding. The only class that can really hold it wide open all the way around are stock and AKRA adult classes. I figured with her weight she would have a lot less available traction because a lot less weight on the tires. I’ve changed my prep this week to try and make up for that. Track has been pretty hard but keeps moisture in it all night. And with rain this week I figure the track will be soft and wet all night. I have a set of 33b’s that don’t have much life left I may just go ahead and use goat on them
If the adult classes can flatfoot it so can the rookie classes added weight has nothing to do with it, if sliding whole kart to much air pressure, not enough bite in tires, set up is off, or all of the above, if just rear is breaking out could be to much wheel input, if front sliding middle off if she entering to low to straight and to soon it will not exit right, if indeed it's wet soft yes you need an aggressive prep but don't do it in anticipation wait and see what you get.
 

Smr#17

Member
So does added weight not make more traction? On a regular night the fast adults are on tires duro 40-45 so does a light kids class need a lower duro and more bite to make the same traction? I figure a kids class could duro lower because there not putting the same stresses and loads on the tires as the adult classes
 
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