Last wednesday i was at the track first time...and i got 3 runs. First run was 15.1 (didn't know where to launch). 2nd run was 15.5 (VDC was on) 3rd run was a 14.5 i launched at about 1800 rpm. my 60 foot was 2.25. Now my mods consist of cold air intake andand clutchmasters stage 3 clutch and lightweight flywheel. i also ran with my 20 inch heavy maya mrs on. People at the track were telling me if i came with slicks or maybe even stock 18's i would probably break into 13's with a 2.0 60 foot. i just wanted to know if their was a mathimatical way to figure what my time could be with smaller wheels. temp was also 80 degrees. I went with my friend who has a lightning and he told me with his slciks he runs low 12's with his 20's he runs 14's. i didn't think rims would slow a car by that much but if it does than i basically high 13's with just intake and clutch combo?

 

Im not sure if you took physics or not, but the bigger the rim the longer it takes for the rim to make one turn, as compared to a smaller rim.

Say you have 18 inch rims on and you are going at say...80MPH, those 18 inch rims are spinning faster as compared to 20 inch rims at 80 mph. The mathematical way is really long and confusing. Lets just say the smaller the rims the faster your time will be, maybe not breaking into the 13s but you will notice a difference. Hope this helps.

 

okay i guess i will just have to experiment than

 

I'd hate to spoil GinFLA's explanation, but it's not completely correct. The overall diameter of your 20" wheel plus tire should be the same as a stock 18" wheel plus 245 ratio tires (around 26"). Therefore the rate at which the tires turn ideally should be the same. I doubt you are running 20s with monster walls? That would mess up your speedo too.

Here, you can't go wrong with this.
http://www.wheelsmaster.com/rt_specs.jsp

NOW: the reason you have slower times with monster wheels is due to the fact that the power/torque needed to turn them increases as the concentration of mass moves further from the axis of rotation. (Rotational inertia Iw^2) Keep in mind all the mass of the wheel is 10" from the center on a 20" wheel versus 9" from an 18" wheel. Sure that doesn't seem like much, but 20^2 is > 19^2. The only way to combat the rotational inertia in larger wheels by getting ultra light ones.

Where GinFLA is correct (or what I think he was getting at) is if you step down to smaller, lighter wheels, with "lighter" tires, you'll get the best drag times possible.

 

Thats what I was getting at lol, its been awhile since physics class and we actually did some problems just like this. lol thanks for clearing it up

 

thank you i did already understand that the 20 inch wheels+tires equals the same as my 18'+tires but i was looking for some formula that can convert the difference in weight into a difference in time so i can try to calculate what my time would be with stock 18 inch wheels on. That site is cool. would have been very helpful a year ago before i bought rims