Gear ratio chart

Bubby

Member
In the process of moving my little guy up from a predator beginner class with gear rule to a clone class with no gear rules. I'm a lost ball in high weeds again. Just looking for a primer on gear ratios and how they will affect us now that we aren't rule bound. Any basic info/help in understanding the effects of gearing would be appreciated. Thanks
FWIW, running a Jr sportsman champ on dirt oval.
 
That's going to be real tough because most all gear rule gearing used is never even close to what it should be, so comparison off it I won't take much into, Best would be find out proven on track results on gearing for other classes there and go from there, of course the closer the classes are to your plate size the better But if you cannot get that even If you can get Sr Clone we can get ya close.
 

Bubby

Member
We aren't bound by any gear rule in the new class. I guess I'm just looking for a chart/primer on how different gear/driver sizes affect performance. Ones we've talked to in our class seem to be running 16/64. I'm just curious what the effect would be going with a smaller driver vs a larger rear etc.
 
We aren't bound by any gear rule in the new class. I guess I'm just looking for a chart/primer on how different gear/driver sizes affect performance.
I understand no gear rule in new class, just giving you a heads up not to compare gearing now going to need based on your old gearing under a gear rule, there is no chart that will give you the info your looking for, there are ratio charts that give general info on ratio relations alone, as far as proper gearing some general info on helping figure out starting point you must factor in Track size, turn radius, momentum you can maintain, class engine, total weight, with gearing experience is best gauge.
You have a PM.
 

paulkish

old fart
In the process of moving my little guy up from a predator beginner class with gear rule to a clone class with no gear rules. I'm a lost ball in high weeds again. Just looking for a primer on gear ratios and how they will affect us now that we aren't rule bound. Any basic info/help in understanding the effects of gearing would be appreciated. Thanks
FWIW, running a Jr sportsman champ on dirt oval.
You need to know what top rpm you can realistic expect to get from your engine per your engine builder or experience.
Then make your best guess and from what you might learn from others put a best effort gear on.
If you hit your expected rpm take gear off until it will normally fall below what you expect.
Then put just enough gear back on to again hit your expected rpm.
And your all set with the only thing left being to set your clutch to engage as near as you can to peak torque.
If you have to fudge peak torque engagement up or down it's usually better to put engagement a small amount above peak torque.
If you put it below you'll lug your engine on the starts.

Last but most important is if you cannot hit your expected high rpm even with a ton more gear then you need, you have other issues to fix first.
If you have that problem when you fix an issue you'll find your rpm will go up.
Keep fixing stuff until you can get your rpm up probably taking gear off in the process.
Once your satisfied your at maximum rpm reliably the you start taking even more gear off so you can go faster.
With experience you will hit a point where your just as fast as others and then it becomes very fine tuning to gain even a fraction of a tenth.
At that point you'll either be the front runner or be running with them consistantly

It doesn't matter what engine you use I think the above thought process will be correct.
That is until you get to having so much hp as in a 410 sprint car that even without a clutch you can spin the wheels at low speed most all of the time.
At that point even if your in a 410 it will be about your driver learning how to not apply hp to go faster.
In your low hp arena it's about free the thing up with the grip of the track to the minimum needed and maintain momentum.
When you get to the top of your game be it a predator or a 410 it becomes a game of driver skill maintaining momentum.
If you were flying a plane it would be maintain thy momentum less the ground come up and smite thee.
With an oval racer it's maintain thy momentum less the wall come down and smite thee. ... :)

edit: The only difference in the process is between how long it takes someone new to go thru the process and how long it takes experienced racers.
Top racers are able to look at a track knowing their equipment and put what's needed now on the track.
It takes longer depending on your experience and don't worry or fret about it everyone goes thru the same process.
 
Last edited:
We aren't bound by any gear rule in the new class. I guess I'm just looking for a chart/primer on how different gear/driver sizes affect performance. Ones we've talked to in our class seem to be running 16/64. I'm just curious what the effect would be going with a smaller driver vs a larger rear etc.
On a clone you can't go to wrong keeping rear between a 58 and 62 with whichever front driver matches up for that to happen.
 

paulkish

old fart
and a question brought about because of my long winded bs, what rpm can he expect to get from a legal clone?
 

OVALTECH1

Premium User
The smaller driver will help you regain some you lost quicker off the bottom whether it be from a break in momentum or a bad start etc. The bigger drivers will help your middle to top and give you that extra pull up top you need to say run em down before the next corner.
 

Randy Major

Member
You need to know what top rpm you can realistic expect to get from your engine per your engine builder or experience.
Then make your best guess and from what you might learn from others put a best effort gear on.
If you hit your expected rpm take gear off until it will normally fall below what you expect.
Then put just enough gear back on to again hit your expected rpm.
And your all set with the only thing left being to set your clutch to engage as near as you can to peak torque.
If you have to fudge peak torque engagement up or down it's usually better to put engagement a small amount above peak torque.
If you put it below you'll lug your engine on the starts.

Last but most important is if you cannot hit your expected high rpm even with a ton more gear then you need, you have other issues to fix first.
If you have that problem when you fix an issue you'll find your rpm will go up.
Keep fixing stuff until you can get your rpm up probably taking gear off in the process.
Once your satisfied your at maximum rpm reliably the you start taking even more gear off so you can go faster.
With experience you will hit a point where your just as fast as others and then it becomes very fine tuning to gain even a fraction of a tenth.
At that point you'll either be the front runner or be running with them consistantly

It doesn't matter what engine you use I think the above thought process will be correct.
That is until you get to having so much hp as in a 410 sprint car that even without a clutch you can spin the wheels at low speed most all of the time.
At that point even if your in a 410 it will be about your driver learning how to not apply hp to go faster.
In your low hp arena it's about free the thing up with the grip of the track to the minimum needed and maintain momentum.
When you get to the top of your game be it a predator or a 410 it becomes a game of driver skill maintaining momentum.
If you were flying a plane it would be maintain thy momentum less the ground come up and smite thee.
With an oval racer it's maintain thy momentum less the wall come down and smite thee. ... :)

edit: The only difference in the process is between how long it takes someone new to go thru the process and how long it takes experienced racers.
Top racers are able to look at a track knowing their equipment and put what's needed now on the track.
It takes longer depending on your experience and don't worry or fret about it everyone goes thru the same process.

Hello Paul!!!! How ya been?
 

alvin l nunley

Premium User
Any basic info/help in understanding the effects of gearing would be appreciated. Thanks
FWIW, running a Jr sportsman champ on dirt oval.
Basic/basic I always went with the idea that you run the lowest gear possible without going over the HP/RPM peak. Or, and this applies only to 2 cycles, before the HP curve starts falling off. 2 cycles have a totally different power curve from 4 cycles.
I always set the clutch at peak torque RPM and geared to that point just before you reach the falloff at the end of the straight. One way to find that point is; if you add a tooth, and don't pick up about 100 RPM, you're at the peak. Of course that pickup will very depending on the the gear ratio. Remember; "don't pick up!!" As long as you pick up that hundred RPM with every addition of one tooth, you're going the same speed, approximately. Now sometimes you have to go over that just a little and that will help you off the turns. It really depends on the track. If you don't pick up 100 RPM with each tooth you add, you're going slower on the top.
There are spreadsheets in my "free" collection of Excel spreadsheets that show you, precisely, speeds as they relate to gear ratios and RPM changes.
For your free copy, email; alvinnunley62@gmail.com ask for "nine sheets" about 44 pages of karting related spreadsheets. Try it, you'll like it.
 

alvin l nunley

Premium User
Interesting, I wonder if there's anybody out there with eyes good enough to see this gear ratio chart from 15 feet away! I designed it to print on a 5 x 8 piece of paper. I had photo paper in mind because it's heavier than regular paper.
 

Randy Major

Member
Gear ratios are just simple math:

60 rear gear divided by 15 front driver equals a ratio of 4. If you want to change to a 14 front driver and keep the same ratio multiply 4 x 14 equals a 56 rear gear.
 
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