berlinetta1

Hi,

I have read on the net that with import cars people who put wider ( and larger) rims and tires on have really hurt there exceleration. In fact, this one guy (I'll see if I can find a link to this) by putting his stock rims and tires on the front and 2 temporary spares on the back was able to go from 16.1 to 15.8 in the quarter.

I have American Racing Equipment wheels on it, and I have traction problems. I am thinking that a change of rims and tires could shave off some time.

My questions are:

What do stock 16 inch iroc rims and tires weigh?

What do 89 15 inch iroc rims and tires weigh?

What do 15 inch Z28 rims and tires weigh?

Would having a larger after market wheel with an extremely low profile tire reduce weight?

Would having what I have seen on 2nd gen cars with 14'' front (smaller and narrower but not really a skinny) and 15'' in the rear be lighter and better for handling.

Should I have a standard drag race setup for tires?

I only drive this car on the street, so handling is important too. But hey everyone want to be fast and I would really like to solve my traction problems.


Thanks!

Orr89RocZ

iTrader: (20)

with standard 245/50/16 Zrated street tire, they weigh about 50 lbs each.

with a 26x11.50x16 ET street, no tube, it weighs about 46lbs.

15's probly would be only a few pounds lighter if anything at all. depends on tire size.

with my lighter weight 15x8 prostars and 26x10.50 et streets, they weigh about 30lbs each. i saved alot of weight, about 70-75lbs overall with the skinnies up front and i think i gained about .1-.2 at the most...hard to say tho, i never got consistent weather runs to compare.

So there is a benefit of running lightweight wheels and tire combos.

chevyracingrox

if your concerned about weight of wheels you could get aluminum alloy rims, they're pretty light without being extremely expensive. a larger rim with lower profile tire will weigh more. people put lower profile tires to improve handling by reducing the amount of flexing in the sidwall. its a noticeable difference. if you get the right size rims you'll know it cause your car will make your old profiles feel like they belong on a silverado instead of a camaro. there is such a thing as too little sidewall (19-20something inch rim guys, its a camaro. who are you kidding? its not "high performance" you just like the look). getting more rim and less tire does add enough weight to effect gas milage too. i have seriously considered getting 16"s before though, and reducing the sidewall accordingly. its a real difference if you like good handling, but of course you probably like drag racing more than anything so i guess everything i just said is why you'll consider drag radials.

rx7speed

it's also not all about just static weight.
I can give you a 30lb tire/rom that is harder to rotate then a 50lb tire/rim

where the weight is located also makes a BIG difference.

TraviZ

iTrader: (2)

I love my heavy *** zr1's. I just make more horsepower to carry my weight.

robertfrank

iTrader: (27)

I know my GTA's with mt kuhmo's 245/50/16 tires weigh in at 41 pounds, That's pretty light for a street tire if you ask me.

joshh44

this got me woundering how heavy my rims are. i might weigh them tommorrow just for the heck of it.

they are 15" American outlaw series II rims and the tire is 235/60/15

25thmustang

I had more power (272/316), 245/45/17s with 165/15 radials out front on lightweight wheels and ran 12.99 @ 107.6.

With less power (256/295), running 285/35/18s out back and 255/35/18s up front on heavier wheels I ran 12.95 @ 106.7.

Very very similar track conditions, as well as the same track (same event a few years apart). There is a lot of variables that dictate, but less weight 95% of the time is better!

Mike-in-Orange

The lighter a car is, and the less power it makes, the more important lightweight wheels becomes. When you're talking about something like a Mazda Miata that weighs a mere 2300lbs and puts out 140HP/110ft-lbs at the crank, then gaining just 5lbs per wheel can be a very bad thing. A very bad thing. Acceleration will suffer, stopping distances will increase, lap times will rise, and ride quality will be compromised.

But adding 5lbs per wheel on a 10 second drag car won't make anywhere near as much of a difference.

The original post here specifically mentioned imports, and most of those engines make very little torque. Take for example a Honda S2000 versus a Dodge SRT4 (with the Mopar Stage 1 ECU). Both are 4 bangers and both make 240HP (give or take) but the Honda makes 165lb-ft to the SRT4s 265lb-ft. Guess which one will feel a 5lb per wheel increase the most?

rx7speed

mike if you want to make that comparison can you do so in how much torque it makes to the wheels and in what gear you are giving that at?

mike_c

iTrader: (13)

Here's a good write-up on the subject:

http://www.sportcompactcarweb.com/te...ht_wheels.html

Orr89RocZ

iTrader: (20)

all i know is i dropped around 70-75 lbs of rotating weight off my car and didnt gain as much as i was hoping/expecting. I think in similar conditions, i only gained a tenth or so, maybe a tenth and a half. Mph wasnt much different. i was hoping for near 2-3 tenths since i was hearing that 1 lb of rotational weight was like 2-4 lbs of dry weight, depending on the source so if i dropped 70 lbs rotating mass, the car should act like it lost 140-280. 200 lbs is close to 2.5 tenths.
i was about 2 tenths slower with a 170 lbs passenger at the track as well.

Mike-in-Orange

I was using numbers from memory, but here's what each manufacturer says:

From Honda's website: An impressive 237 hp at 7800 rpm and 162 lb.-ft. of torque at 6800 rpm

From the Mopar website regarding Stage 1: The Stage 1 Turbo Kit for the SRT4 boosts power to 240 hp and 260 ft.-lbs. of torque.

Mopar has changed their website and no longer shows the dyno charts, but since the engine redlines at 6200 those numbers are obviously at revs well below the Honda's stated numbers. I believe peak HP was around 5800 and peak torque closer to 5200.

Neither site specifies if the numbers are at the wheels or at the crank, but practically every SRT4 I've ever seen dyno'd is making those numbers at the wheels.

rx7speed

guess I should rephrase it.
real torque to the wheels. not what the dyno shows as it doesn't give you real torque but rather engine torque taking into account drivetrain loss.

sorry not trying to be a pain but I don't know for sure on this and it can make a big difference.

Mike-in-Orange

I'm not really sure what you're looking for here. The numbers I posted are straight from the manufacturer's respective websites but I can't guarantee one way or the other if they are engine or chassis dyno numbers.

How do you figure that a dyno doesn't give you torque to the wheels? A chassis dyno has no way of knowing what the engine torque is, or specifically what's going on in the drive train. It is interfacing with the wheels and taking the measurement there. Unless you're talking about an engine dyno, in which case the dyno is hooked up to the crankshaft (effectively) and measuring at that point. In the case the engine isn't even mounted in the car, so there is no drivetrain loss at all.

But in a nutshell, when comparing the S2000 and SRT4, HP numbers are extremely close, but the SRT4 generates roughly 100lb-ft more torque. Most manufacturers quote crank figures, not wheel numbers. A quick Google search for some real world numbers (guys on forums who have actually dyno'd their cars) shows one guy's S2000 putting out 218 WHP and 151 torque (at the wheels) and his buddies saying those numbers sounded high! There are plenty of guys out there posting dyno numbers for a bone stock SRT4 in the neighborhood of 230 WHP and 241 lb.-ft. of torque (these specific numbers come from Grass Roots Motorsports Magazine's dyno test).

Yes, there are going to be variations from car to car and from dyno to dyno, but when you see a clustering of numbers from a wide range of cars, you can safely say that the HP numbers between the S2000 and SRT4 are very close, but the SRT4 just kills the S2000 when it comes to torque. At the wheels.

rx7speed

when torque is produced in an engine it gets multiplied by the gears. so if lets say you are running 100lb/ft of torque through a 2:1 gear then on the other side of the gear you have 200lbs/ft of torque. a chassis dyno takes that into account and takes the gearing back out of the numbers it gives you so it doesn't give you real torque to the wheels.
so with the above example even though the car is putting down 200lbs/ft of toque to the wheels due to the gearing the dyno will still only give you 100lb/ft. well less actually because you have drive train loss. that is what I was refering to with it gives engine torque minus drivetrain loss (roughly)

25thmustang

Thats why they dyno cars in their 1:1 gear. Granted the rear gear, tires and everything else play a roll, but putting each car in 1:1 is a good way to base one particualr car vs another with as few varibales as possible.

91z28ss

iTrader: (4)

Sorry for the late response! I was talking about the ROH Drift-R. You can get them in either silver or graphite color with a choice of 18X9 on 4 corners or staggered 18X8 fronts & 18X9 Rears.
They remind me the ROH ZS wheels found on the Stang's and our Maro's... They are made out of magnesium which I think are lighter than aluminum cast. If I remember they were selling for 1250$/Set on Fleabay

Please diseregard I don't know why I ended up on this topic sorry...