How much will adding 16 lb to my car affect ET/mph(rotating weight)

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Cudafever

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Our track has divided all the races in half. Half d.o.t tire, half slick only races.
So i dug up my old street tires and rims as the first race is d.o.t only race.

The street tire/rim combo weight 8 lb more per tire. so 16 lb total
The plus side is that the tires are two inch shorter. So i should be closer to the rev limit,at the finish line, with these tires.

The bad news is that i don't think i can get them to hook off the line. Even if i leave at a idle.
 
Obviously the tire spin will hurt but the weight difference will be next to unnoticeable just a little more stress on parts (not much)
 
The weight will have a whole lot less affect than loss of traction. I would find some cheap aluminum wheels, and some good drag radials, if you want to be competitive.
(My race weight wheels and tires are a hundred pounds lighter than my street stuff).
 
Unsprung weight is much harder to figure mathmatically (for me). Sprung wieght is approx. 100# per tenth.
 
The weight will have a whole lot less affect than loss of traction. I would find some cheap aluminum wheels, and some good drag radials, if you want to be competitive.
Beleave it or not the slicks and the street tires are on alu rims.

The street tires are on a set of turbine or fined rims that came on a old ford like a thunder bird. had to grind the center out so that they would fit on my axles.

If i had the money i would go by some nice light weight rims and some real sticky d.o.t tires........So have to make do with what i have kicking around.
 
I thought reciprocating Wright was connected to the crank. Your wheels are unsprung weight.
It's rotating weight,..... so it adds 16 lb to the weight of car but also adds 16 pound of unsprung Weight that the eng has to push or drive.
un and sprung weight i get confused on so i may have them backwards.
 
Beleave it or not the slicks and the street tires are on alu rims.

The street tires are on a set of turbine or fined rims that came on a old ford like a thunder bird. had to grind the center out so that they would fit on my axles.

If i had the money i would go by some nice light weight rims and some real sticky d.o.t tires........So have to make do with what i have kicking around.
My bad, i assumed steel wheels, lol. My steel 8x15 steels, with t/a radials, are almost thirty pounds apiece more than my slicks on autodrags.
You could look at it as a challenge, learning to race on street tires.
 
The old rule of thumb is 100 pounds = 1/10 of a second.
 
The old rule of thumb is 100 pounds = 1/10 of a second.
True, but that is for static weight. The more weight that has to be rotated, the harder it is to accelerate that weight. Its a lot harder to accelerate a 60 lb flywheel, than a 12 lb one, for example.
I will admit, i dont think 16 lbs at the wheels would be very noticable.
 
ok so my verbiage still is not right
sprung weight is a tire on suspension
un sprung weight is a lighter race seat so neither one is rotating weight.
 
I bet he could cross the stripe a dozen times and still wouldn't be able to tell the difference. lol
Any takers ?
 
So i found a sight that said that 1 gram of rotating weight was equal to 2 grams of chassis weight.
this was a dirt bike forum so if that theory holds true on a car. That means that my addition of 16 pound X 2 is 32 lbs
a tenth (.010) take 100 pounds..........So 32 pound would equal ruffly .003 of et..........Fishmens67 you, and most every on else may be right and it just don't matter.

I thought that it would have had a bigger impact.

Come on all you Mathematicians show us a formula :)
 
I think it depends on where the extra weight is. If it is closer to the axle center line (heavier wheels) it matters less. The farther out it is (heavier tires) the more difference it makes. The heavier the weight, and larger radius, the more energy it takes to accelerate it.

I believe what you are talking about is centrifugal force. For a fixed radius, the force increases proportionally with the weight and increases with the square of the wheel speed. More of your horsepower is stolen as the centrifugal force goes up.

I believe this is the general path you would need to follow to get a real answer. If you could figure out the weight distribution across the radius of your wheel and tire and a wheel speed of interest, you might be able to come up with some estimates, but I don’t know how to do that.

I am guessing that the easy way to do this is just try it, as the math and measurements you would need to figure it out look complex.
 
ok so my verbiage still is not right
sprung weight is a tire on suspension
un sprung weight is a lighter race seat so neither one is rotating weight.
Sprung weight is the body etc. of the car, the stuff above the springs.
Unsprung weight is the rearend, wheels and tires, a % of the front suspension.
Rotating is part of the crankshaft, flywheel, flexplate, converter, trans internals, driveshaft, gears, axles, brakes, wheels and tires. Weight after the gears has less effect than in front of the rearend.
Reciprocating is the pistons, rods, part of the crank, valves,part of the rockers, etc.
 
Lord Jesus, just bolt the other wheels on and make a few test and tune passes to see where you are.
 
That much weight will slow it down so much a old Diesel Rabbit will give you a run for the money.
 
How would you ever know, you will probably run a 10th or more slower than your last pass. lol
 
ok so my verbiage still is not right
sprung weight is a tire on suspension
un sprung weight is a lighter race seat so neither one is rotating weight.

You got the verbiage correct and I understood what you meant, I simply gave "all" and the "only" information on the subject that I knew.
 
So i found a sight that said that 1 gram of rotating weight was equal to 2 grams of chassis weight.
this was a dirt bike forum so if that theory holds true on a car. That means that my addition of 16 pound X 2 is 32 lbs
a tenth (.010) take 100 pounds..........So 32 pound would equal ruffly .003 of et..........Fishmens67 you, and most every on else may be right and it just don't matter.

I thought that it would have had a bigger impact.

Come on all you Mathematicians show us a formula :)
A tenth is .100, so a third of that would be .033. So for example, slow from 12.500 to 12.533. Not a whole bunch, either way.
 
33IMP
Thanks for the correction and yes i agree.

Rusty that statement was not pointed at any on.
Just me trying to correct my self
 
Beleave it or not the slicks and the street tires are on alu rims.

The street tires are on a set of turbine or fined rims that came on a old ford like a thunder bird. had to grind the center out so that they would fit on my axles.

If i had the money i would go by some nice light weight rims and some real sticky d.o.t tires........So have to make do with what i have kicking around.

Sounds like cast alum rims , they are heavy !~
 
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