Track Tac

Gear selection

alvin l nunley said:
still, if you had done the math, the amount of rpm you would need to pick up or lose depends on the gear ratio your running. In the area of 4.0 – 1 ratio, one tooth on the axle equals about 100 RPM to be going the same speed. As a ratio goes up and down the number of rpm's you'll need to pick up or lose, to be going the same speed, changes. For instance; at 6000 RPM, 15/60 gear ratio, you'll be going, with 34 inch tires, 48.30 miles per hour. If you add one tooth to the axle, you'll need to pick up 105 rpm to be going the exact same speed. The higher the gear ratio the less RPM with a one tooth change, the lower the ratio, the more RPM to be going the same speed. You have my Excel spreadsheet, easy enough to check my math.
Comments compliments criticisms and questions always welcome.
Click to expand...

Let me ask this Al, does this take into account gearbound?
 
I'm new also and I'm running a predator 212 with no gov, header muffler and that 10.8 springs stock jet and air box...I put a max torque 12 tooth on it the other day and drove it around a parking lot and it had a 64 on the rear and i could hold it floored through the turns no spin...but I got a mychron 3 today hooked it up and put a 16 on the front and 59 on the rear per what the track tech said predators are running it won't even reach 4000rpm unless that tach is wrong but I just put it on the street and tried it ....it takes off a lot slower but seems to run faster on top end...what do y'all think the top rpm on that motor should be and do I need a little slippage when racing or will that 12 t driver just slow me down
 
alvin l nunley said:
I'll answer that question if you can answer this question; what is gear bound?

Comments compliments criticisms and questions always welcome.
Click to expand...

Gear bound is when you have a gear on, and the kart just wont turn more RPM, just is flat. Youre not even turning the RPM you should be just because the motor wont. You add a tooth, and you get the same RPM, or maybe even lose some.
 
You are only at the gear ratios ,max rpm and max mph full potential for a milli second at the end of the straight if your perfect , navigating the corners scrub off your rpm ,mph and the rest of time your winding / building back up down the straights over and over again . Choose the gearing based off what yields the overall fastest lap times and then you also have a choice of if your going to be beating and banging starting in the rear or if your going to be out front and plan to lead . That might dictate a driver change and or adding a tooth or two on the rear .You never hardly out there by yourself so also have to think about that in your gearing choices.
 
This is why you hear guy's at the track I went smaller on rear and picked up RPM's with same driver, I've helped guy's actually take off 4 teeth and pick up RPM, there was a post somewhere asking about a 12-74 for Jr Rest on a quarter mile, that would of defined gear bound.
 
SoCo Tire Treatments said:
Gear bound is when you have a gear on, and the kart just wont turn more RPM, just is flat. Youre not even turning the RPM you should be just because the motor wont. You add a tooth, and you get the same RPM, or maybe even lose some.
Click to expand...
X'S 2, This happens all the time if your not very careful =volumetric efficiency of the engine is at its max to early down the straight. Also listen for valve float it will kill you too!
 
SoCo Tire Treatments said:
Gear bound is when you have a gear on, and the kart just wont turn more RPM, just is flat. Youre not even turning the RPM you should be just because the motor wont. You add a tooth, and you get the same RPM, or maybe even lose some.
Click to expand...
This never happens. Your engine will turn 10,000 RPMs if you let it. LOL There area so many varibles. Gear bound, kart bound up, and the list goes on and on. I always like when you dont change any gearing only tires and pick up RPMs. Watching your drops has be helpful to us.
 
racing promotor said:
Which proves that what works on paper does not always apply to the track !!
Click to expand...

I like to win to much to be narrow minded about this subject. It's a huge difference not a tiny in my experience running state and national races in the past . I have been karting for over 25 years and I'm a Gearoligist for a cup team and have been for 15 years!! I see it ! I use to my advantage!
 
Gearhead said:
Been there many times also pulling teeth off the rear and gaining RPM's and lap times start jumping!!!!
Click to expand...

ditto, Except for a win, that's about the BEST and most FUN kart racing experience you can have. It don't get much better then taking gear off AND having the rpm's go UP !

double ... :) ... :) on that one
 
SoCo Tire Treatments said:
Do not take any teeth off for Jasper when it turns night!! You may even be adding a tooth. What Al dont understand is a dirt track will change, and by the end of the night this track will slow up just a bit.
Click to expand...
not saying you’re wrong, the dirt can change, very true, but so can the air density. Just a guess, but I wonder how you would know the difference.

I can only imagine how hard it would be to estimate how much a track can change. On the other hand, with an air density gauge, I can tell exactly how much the air is changing. And I wonder; if you don’t have an air density gauge, how can you determine if it’s track or the air density that is slowing you down or speeding you up.

I have never heard where anybody was splitting the track for lap times. If the track is better, wouldn’t the times improve in the corners? If the air density goes up, but your slower in the corners, what would that tell you? I believe it can tell you one of 2 things; either the track is going away, or you’re a little lean.


Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
 
alvin l nunley said:
not saying you’re wrong, the dirt can change, very true, but so can the air density. Just a guess, but I wonder how you would know the difference.

I can only imagine how hard it would be to estimate how much a track can change. On the other hand, with an air density gauge, I can tell exactly how much the air is changing. And I wonder; if you don’t have an air density gauge, how can you determine if it’s track or the air density that is slowing you down or speeding you up.

I have never heard where anybody was splitting the track for lap times. If the track is better, wouldn’t the times improve in the corners? If the air density goes up, but your slower in the corners, what would that tell you? I believe it can tell you one of 2 things; either the track is going away, or you’re a little lean.


Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
Click to expand...

One word....experience.
 
SoCo Tire Treatments said:
One word....experience.
Click to expand...
that really says it all. I agree. Still, I always had to fight the idea that I had so much experience nobody could tell me anything new.

Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
 
alvin l nunley said:
that really says it all. I agree. Still, I always had to fight the idea that I had so much experience nobody could tell me anything new.

Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
Click to expand...

I learn new things quite a lot actually, and that helps with the experience i have.
Im not afraid to admit when im wrong or dont know something, im 51 and i do not know everything. But that i did know about.
 
You must log in or register to reply here.
Back
Top