Track Tac

gearing question

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bayne28

New member
Ok gear gurus this might be a dumb question but the track I always run at i run a 15/65 in champ heavy. My question is what is the difference in a day and night rave because I hear some people say they're gonna get down to 62 and 63. And would this matter if you ate a heavier driver I cross the scale at 44
435 instead of 425 seems like I'm always running bigger gears in the back than the other guys
 
At night, if the temperature drops, the air density can go up, and depending on where you're at, sometimes substantially, and your engine will be making more horsepower. (If the mixtures right) More horsepower can pull a higher gear ratio.

From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
 
bayne28 said:
Ok gear gurus this might be a dumb question but the track I always run at i run a 15/65 in champ heavy. My question is what is the difference in a day and night rave because I hear some people say they're gonna get down to 62 and 63. And would this matter if you ate a heavier driver I cross the scale at 44
435 instead of 425 seems like I'm always running bigger gears in the back than the other guys
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Are you saying you put on a 15/65 and never change it ? if so do you not have a tach ?
To answer your question in general for a day race the track will be freer thus less rolling resistance in turn higher RPM's in turn lower rear gear, in fact most cases 1 higher front driver for a day race.
 
No I've changed them before and I have a tach last time I ran I did good on the 65 at night but Saturday is a day time race and from what I've heard some of the guys said they would get down to a 62 or 63 and was wondering why day and night races are different
 
bayne28 said:
No I've changed them before and I have a tach last time I ran I did good on the 65 at night but Saturday is a day time race and from what I've heard some of the guys said they would get down to a 62 or 63 and was wondering why day and night races are different
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Because Track will be different if prepared right a bunch different more Bite ( grip ) in track so it will generate more RPM's thus lower rear gearing, If you find yourself reaching for that 62 change Front and rear to a 16-66 instead ya might just catch em all sleeping !!

Good Luck !!
 
racing promotor said:
Because Track will be different if prepared right a bunch different more Bite ( grip ) in track so it will generate more RPM's thus lower rear gearing, If you find yourself reaching for that 62 change Front and rear to a 16-66 instead ya might just catch em all sleeping !!

Good Luck !!
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Cool thanks
 
Some tracks are faster at night and some tracks are faster in the daytime. It depends on moisture, dirt, calcium, preparation, number of karts, etc. While air density and engine performance is an issue, surface conditions are always a bigger issue.
 
15/62 = 4.13. 16/66 = 4.13 In that gear ratio range, one tooth on the engine, (+/-) equals four teeth on the axle. The smaller the driver, the greater the change, the bigger the driver, the less the change. For instance; 10/80 = 8.0. 11/88 = 8.0. An eight tooth difference on the axle with a one tooth change on the engine. 20/60 = 3.0. 21/63 = 3.0. A three tooth difference on the axle with a one tooth change on the engine.

Without knowing all the contributing factors, (i.e. being there) it would be impossible for me to say why others are changing their gear ratio. I do know one thing, as important as knowing the track condition is, knowing the ambient weather conditions is very important too. There are people who dismiss the weather as not being very important when compared with the importance of track condition. One only needs to look at the ambient condition correction factors , that are used when dyno testing, to see the error in that assumption. No serious dyno operator would ignore the ambient conditions.

From the desk of Al Nunley
Comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory. (Al Nunley)
 
Main reason they are taking gear off the rear is because tracks are generally harder and faster during day races than night races. I would also reccomend you take some harder tires with you for the day race
 
warm night, 18/56, turned 8400.....cold night, same gears, turned 8190.....ran real lean because i didn't compensate for the air temp or density and swap the jets. so the rpm's were way down....not a big fan of all the math involved or the technical side of air density/air-fuel mix...but i'd listen to what al is saying.....it does make a big difference! it all has to play together to get the most out of your engine and develop the power you need to propel you forward.....

ENGINE + SET-UP + TIRES = WINS AND TOP FINISHES.......
 
mikey56 said:
warm night, 18/56, turned 8400.....cold night, same gears, turned 8190.....ran real lean because i didn't compensate for the air temp or density and swap the jets. so the rpm's were way down....not a big fan of all the math involved or the technical side of air density/air-fuel mix...but i'd listen to what al is saying.....it does make a big difference! it all has to play together to get the most out of your engine and develop the power you need to propel you forward.....

ENGINE + SET-UP + TIRES = WINS AND TOP FINISHES.......
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Your not analyzing your RPM drop properly by only looking at motor, Cold night less grip in the track so if you did not compensate Tire prep to get in the track enough to generate same forward drive as a warm night your RPM's will be low, Yes what you point out most likely contributed but I bet like 20 % the reason for the other 80% of lacking RPM's was TIRES. All the motor in the world does NO good if the tires are not in the track enough to generate forward drive. Of course you can over do it and have them in the track to much as well, both cases will greatly effect RPM's.

More Forward Drive makes you competitive, Perfectly tuned ( better balanced ) forward drive WINS races !!
 
Isaac, the reason will be a higher kart count. Do not go over a 64 on the rear, even at night. Free that kart up and get on same gear as the leaders.
 
bayne28 said:
Ok gear gurus this might be a dumb question but the track I always run at i run a 15/65 in champ heavy. My question is what is the difference in a day and night rave because I hear some people say they're gonna get down to 62 and 63. And would this matter if you ate a heavier driver I cross the scale at 44
435 instead of 425 seems like I'm always running bigger gears in the back than the other guys
Click to expand...

"My question is what is the difference in a day and night rave because I hear some people say they're gonna get down to 62 and 63."
________________________________________

There is only >>>one<<< reason for them to go from a 65 on the back to a 63. The reason is they expect to be going faster out on the track.

That's it IMHO, there is no other reason.

If they think they can make a 62 work, the only reason is they think they will be able to go a lot faster, because of changing track conditions and to possibly to some part having better air and getting a little more hp out of the engine.

But, if a 65 was right and something changes to make a 63 right, to make it right you have to go faster, no if's, and's or butt's.
 
paulkish said:
"My question is what is the difference in a day and night rave because I hear some people say they're gonna get down to 62 and 63."
________________________________________

There is only >>>one<<< reason for them to go from a 65 on the back to a 63. The reason is they expect to be going faster out on the track.

That's it IMHO, there is no other reason.

If they think they can make a 62 work, the only reason is they think they will be able to go a lot faster, because of changing track conditions and to possibly to some part having better air and getting a little more hp out of the engine.

But, if a 65 was right and something changes to make a 63 right, to make it right you have to go faster, no if's, and's or butt's.
Click to expand...

Your CORRECT Paul you would be going faster, Provided your on the right tires.
 
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