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Posted by Aaron (92 SE Auto) on June 21, 2002 at 22:49:27:
In Reply to: explaination -------> posted by Nismo87SE on June 21, 2002 at 22:36:26:
I will be pretty happy if I can knock off 3 tenths with some good smaller tires. I appreciate your help. : I got a question for you though... if I am not having any traction problems, how much do you think 2 smaller, lighter wheels will help me in the 1/4 mile? Is it just the smaller diameter helping the ratios? Of course they will be lighter, so I will have less unsprung weight. Which I know, makes a big difference. : The lighter the wheel is the less amount of power it takes to move it. If you were to lose around 6lbs on each wheel, in 1st gear that would be like dropping 75-100lbs off the car. As you get into higher gears it has less of an effect. However with smaller 205/50 tires that gives the car an effective 4.0 final gear vs 3.64 that is stock. : : I didn't have a problem in my car with wheelspin, however you would have more torque than mine did. They shouldn't give you much trouble, I know that BFG has drag radials in that size so those make a good strip only wheels. I'd suggest getting a higher stall convertor before doing a catback. AT the track you can always unbolt the muffler.
That's pretty impressive that you can explain to me how the gear ratios work. I will look into smaller tires one day when I get money. Also, maybe a higher stall... again, when I get money.
: What this means is that all the gears are shorter thus you get more torque multiplication. For example with a 4.0 final gear your speeds at redline in each gear would be: 41, 77, 118, 177.
: Since you stated the car bogs below 20mph that is around 2900rpm with stock tires, with smaller tires 20mph is 3200rpm. Basically there is more torque on tap at the start. Now combine these tires with lighter wheels and you have an effective weight reduction of 110-150lbs from the car in 1st gear. That much reduction is worth at least 1.5-3 tenths, assume you cut 2.0-2.2x 60's. It would be a 15.1-15.3 @ 90-91mph. I figure that 2 wheels from a junkyard are $25-50 and 205/50-15 tires are $100-140 for 2, it makes for a good mod. Or hell borrow a friends front or rear wheels if they have simular size tires.
: : Also, will these lighter wheels, that you prefer, cause the tires to spin more? Thanks Nismo87SE.