r00st

I am on a pretty tight budget, TRYING to save for retirement..I am only 25 but I have been spending WAY too much "fun" money and the older I get the more I realize I am SOL come time to get my SS! I am at a job that has a state pension after 8 years so that will for sure help but I need to build a cushion.

Anyway...I have a bone stock 2012 Black 6mt GT that has an owner DYING for mods. The 3.31 gears are pretty steep! I enjoy being at super low rpm's but 90% of my driving is not free way (I drive 10 miles of 55mph two lane and about 3 miles of stop/go one way to work every day). I have heard most people actually increase their city MPG with the 3.73's.

My question is this: What is the RPM difference (at say..60mph) is the:
3.31
3.55
3.73

When I get new tires later this summer (Cant swing 600 for gears AND tires) I am considering going with a 295/35/18 (26.13 height) compared to the OEM 235/50/18 which is 27.25 height. If the one inch is too drastic of a drop I could also run a 305/35/18 which is 26.4 height but tires are 100 bucks more/tire than the 295's.

I realize this is not the best way to go about things but I will take the slightly harsher ride and less sidewall to fill the fender gap to gain the 3.55-3.73 performance!

I tried playing with various calculators online but did not get far. Once I know the revolutions per mile difference between 3.31/3.55/3.73 I can then compare the tire sizes to see what RPM difference those have to try and get close to the equivalent of 3.55/3.73.

Thanks!

clowe1965

Take the larger tire diameter D, divide it by the smaller diameter d. Then multiply it by your current gear ratio. so 27.25/26.13*3.31= 3.45. Sorry bud try again. You would probably have to go to smaller rims. or really narrow profiles. Also are you using the stock rims? I didn't think that 295 or 305 widths could fit the stocks. If you are going that width then you don't have to worry about rotations already. Anyway for your use D/d*3.31=Equivalent Gear Ratio.
Also if you can figure out the amount of rubber lost per revolution in a burnout, the constant being in inches/revolution, your gear ratio during burnouts becomes integral of 0 to time of D(start)/((D(start)-(Constant of wear)*time(in minutes)*average burnout rpm))dtime just for kicks and giggles.

scottmach

Remember if the difference in height between the fronts and rears are to great then you'll throw your ABS off.

r00st

ok thanks for the math. That does not seem like a good way to get the ratio down then!

As -1 inch on the tire is a pretty drastic change in ride/looks but not much of a gain in the gearing department. Should probably stick with tires that are as close to stock height as possible and just do gears when I get the money.

Did not think about the ABS either! Good point. Anyone know how much variance there can be front/rear before the ABS thinks your always skidding?