STREETREBEL said:I THOUGHT THE MORE GEAR YOU HAVE THE MORE
TORQUE MULTIPLIED! ALSO WITH A TALLER TIRE
THE BIGGER THE FOOT PRINT AND BETTER
THE TRACTION. :xpl:
you also have ot remember when u go to a bigger tire, u reduce the gearing also
STREETREBEL said:I THOUGHT THE MORE GEAR YOU HAVE THE MORE
TORQUE MULTIPLIED! ALSO WITH A TALLER TIRE
THE BIGGER THE FOOT PRINT AND BETTER
THE TRACTION. :xpl:
Yes, the “more” gear you have (higher numerical ratio), the more torque multiplication and hence, the larger the force applied by the tire to the pavement. However, the larger the diameter (and radius) of the tire, the lower the force applied, i.e., F = TQ*GR/Rtire. And of course, the higher the force, the higher the acceleration. Does that help?STREETREBEL said:I THOUGHT THE MORE GEAR YOU HAVE THE MORE
TORQUE MULTIPLIED! ALSO WITH A TALLER TIRE
THE BIGGER THE FOOT PRINT AND BETTER
THE TRACTION. :xpl:
Black2003Cobra said:For your case, the numbers do support your gut feeling. In theory, if you are currently trapping 127 mph on average w/ 504 rwhp, then with 600 rwhp you’d be trapping 127*(600/504)^(1/3) = 134.6 mph, (all else being equal.) So if you’re running 26” slicks and haven’t changed your rev limiter, the highest numerical ratio you could get away with is 3.73, (which tops out at about 135 mph in 4th as Bob said.) If you go with a 28” tire, then you could go with the 3.90’s, but the taller tire is canceling out the advantage (in terms of acceleration) of the “shorter” gear, and then some. So as mentioned, you really have to look at each situation case by case and work through the numbers to figure out what gear is best using the rule of thumb that Bob mentioned earlier.
Good point, (although of course, I was assuming traction was not a limitation/problem. I was addressing the tradeoff of using a taller tire to overcome the problem of going through the traps and having to shift out of 4th when using the shorter gears.)11secCobra said:when people run 28" tires, its for traction purposes. the 28" tire has more sidewall to take up the shock to the drivetrain when u drop the clutch, and they also have a lot more rollout for more tire on the asphalt.
WS6JJP said:another thing i never understood...there was a thread awhile back talking about gears/gearing and how they have never really seemed to help on our cars(i wish i could find it)but basically everyone that runs really good times (above average drivers and E.T.'s) are still using the stock gears and....quite of few of those people have tried going to a steeper gear and have slowed down(E.T wise , not trap) They were sayin that with our cars having so much torque throughout the RPM range that you didnt need any type of lower gearing, and that the engine does better letting it stay (and pull) through each gear longer, like somehow it accelerates better that way then if you had to constantly bang the next gear because the gear ratio is so short. Almost what Bob C was saying with the old N/A cobras: not much torque so you need the gear, but with a lot of torque and a lot of gear you're not giving the engine chance to pull through each gear.
Now when i was reading this thread i DIDNT really agree with it, simply because anytime you change the gearing for the better it seems it would always have to help you. Even when "calculated" on paper it would almost HAVE to help....but....these people have been at the track and somehow (or maybe not) proved different. Like i said some of them have seemed to be above average drivers so they know you have to get traction to reap the benefits of the steeper gearing or else you'll slow down (E.T.'s) so how is this true?? Their "facts" are right there in black and white (timeslips)
redstaf426 said:You know,after talking to projektZero about his 4.10s I'm kind of leaning towards the gears,but I also notice he has a hell of a time trying to hook up.what kind of tires are you running,ET streets,DRs??could you update us with your 60ft's times,thanks.
CobraZb said:This is confusing
jtfx6552 said:Gears are the best seat of the pants mod ever envented.
However, that is where they make the biggest difference.
I know I shouldn't post into this thread, because it will get into a long dawn out discussion of torque vs. horsepower.
Gears do little to make your car faster because while they add peak rear wheel torque, they do not add any power. What gets you car down the track is the amount of power it has.
Torque in an of itself is a meaningless number, without knowing the RPM. I can generate 1,000,000 lb ft of torque, just give me a long enough wrench...
Here is why torque matters. Not engine torque per se, but torque at the rear wheels that matters. Since horsepower is conserved, and torque is not, the best representation of torque availibilty at the rear wheels is HP, as it accounts for the various gearing vs speed multipliers.
Simply put, if you had two engines whose torque curve looked like a flat line, 330 ft lbs from idle to reline, but one redlined at 3000 RPM ad the other redlined at 6000 RPM, what engine would make the same car faster?
In order to race to the same speed, the car with "twice the redline" engine could have twice the rear gears and still make it to the desired speed. That car would have twice the torque at the rear wheels for the whole race. That would not be much of a race.
But with our cars, when you take the typical positive displacement blown Cobra, it is traction limited. When you do suspension and or switch to a solid rear things may be different. But for the typical IRS car, adding gear will give more torque than you need in 1st, and depending on boost level and blower type, maybe second or third, too. Once you have enough torque at the rear wheels to spin the tires in low gear, adding more won't help.
If a 4.10 or 3.90 car lines up with a 3.55 car, when both are in the same gear, the higher numerical gear car will have more rear wheel torqe, but will hit redline and need to shift, then the lower numerical geared car will have more rear wheel torque because he is still one gear lower. It will be a see-saw back and forth as the cars go through the gears, and shift at different points.
Obscenely high numerical gears got popular with N/A cars that had very limited low end torque, and usually a transmission that only was low 2.x to 1 first gear. In that case, high numeric gears got the car into the powerband on launch quickly.
With the positive blown cars "shelf" like torque curve and the stock suspension, there is no need for higher numericals. My car makes almost peak torque from about 2000 rpm upward. With about 500 lb ft available, the car can pretty much be on the verge of spin all through first. If I added more gear, I'd still be traction limited, but need to shift into the next gear sooner, loosing rear wheel torque vs staying in the previous gear.
combatstang said:if you had two cobras with thee same power, same driver skills, and one had 3.55's and one had 3.90's the geared cobra will walk the other cobra.. not by much but it will.. PERIOD!!... That's the bottom line, thats why I did it...
Marc
Bob Cosby said:The idea is to maximize average HP in each gear. In 1st, 2nd, and 3rd gear, that means calculating optimum shift points, for which rear gearing has little or no effect. However, for 4th gear, it means gearing the car as described above.