axelaspeed

haha, well i love my 3, best investment i made, saves me on gas too which is another reason i love, but other than that haha must be fun to drift, one of these days i'll do that, but im sure once u drive that 3 u'll never wanna leave till u buy one, thats how i was when i test drove one, good luck

crossbow

Not to go too far off topic...

But technically you can get 6's cheaper then 3's currently. The 3's tend to have little negotation (they sell really well), while the 6's have some crazy negotiation rooms.

Some individuals have recently gotten (v6) 6s MTX's (NEW) for 16k with employee pricing (some dealerships offering it) and about 3k in rebates.

And if it matters, even after being out a year longer then the 3, the 6 still has less MRI's and TSB's. The dealers don't call it the TSB3 for nothing!

Still a sweet zippy car though. Just make sure to get an 05 or 06 to skip alot of the inital issues. If you are getting a 6s ATX, make sure to get an 05 with the 6spd ATX to avoid all the inital problems with the 5spd Jatco ATX.

theboy

Great thread manz~

Jeromie

hey i gots a question... will my 225s fit on a 18.5 rim??? i got some new rims and wanna use the stock tires. havent been able to search this....

IZoomZoomI

you mean 8.5? Yes it would. But ideally you should go with a 245 tire.

StealthTL

iTrader: (1)

Just put the "snows" back on, and noticed that they were noticably lighter than the summers, so got the scale out.....

Summers (stock Bridgestone RE040, very worn) on stock wheel - 50.6 lbs.
Snows (new Toyo Garit HT) on cheapo-cheapo 17" FRD rim - 44.6 lbs.

Wow, 6 pounds per wheel, that's huge!

S

theboy

did someone with both OEM 16'' and 18'' wheel tried launching them and get the 1-100 time?

rotorhead335

I'll just take a wild guess here and say he's an American.

surgictube

Are there adverse effects of increasing the front tire width too much? Like increased required turn in force?

imput1234

iTrader: (6)

I just finished reading through most of the links, VERY VERY helpful. Thanks crossbow for taking the time to find and put all this together!

Mazdaspeed 88

This is really helpful with all the links and articles in place. Thanks ;-)

Backstyck

I didn't realize so many people only installed lightweight flywheels to only decrease the weight of the CAR. I always thought the purpose of a lightweight flywheel was to decrease the inertia of the flywheel and fix delay problems that seem all-too-common for the overly-heavy stock flywheel.

SolarYellow510

Sorry, this is off topic a little, but I couldn't help responding to this:

No matter what you do to your car, no matter how much money you spend, someone else can always spend more and find a more talented fabricator to one-up it. Maybe even before you're finished with your vision.

The only thing you can do with and to your car that's totally unique and a reflection of you that nobody else can do exactly the same is drive. Maybe someone else will be better, but how you drive will follow you into any car you're in, unlike the money you spend on mods.

SolarYellow510

Yeah, what Team said. I'm not going to say Rob from Robispec knows everything, but he's done a lot more with suspension than I have, and he is adamant that a slightly heavier but stiffer wheel he changed to had given him more consistent suspension setups. He was able to get a car really dialed in, rather than chasing an unpredictable target, making the car ultimately faster.

This was actually the NTO3-M, which in 17x9.5 is able to clear StopTechs, whereas the 18x9.5 RPF-1 can't, due to the dish of its spokes. Not to take anything away from Goodwin. There are some good 275/40-17 tires out there, too. 255/40-17 is a Porsche OE rear size, so basically every serious performance tire in the world comes that size, and it's a really good match for a 9.5-in. wheel. I guess that's a suggestion for track rubber. There are fewer 255/45-18 tires, but that may be a nicer street size to keep the revs down on I-5.

The moment of rotational inertia is what you're concerned with in straight-line acceleration. Every bit of mass contributes by the square of the radius from the axis of rotation to its location. So an 18-in. wheel with the same weight as a 17-in. wheel will still slow you down more. SCC found this when they did a 16-17-18 test because they couldn't think of anything else that was worth doing with their long-term Mitsu Eclipse (gen 3).

Reducing your tire OD by an inch or more takes you out of the discussion, because your observed increase in vehicle responsiveness is likely due significantly to the advantage gained in gearing.

Remember the Sport Compact Car Technical Assistance Program, where they took some poor schmuck's Sentra to the drag strip and turned it into a golf cart? By far the biggest improvement in ET they were able to achieve was going from heavy 19" show wheels to stock 14s with shyte tires off a G20. I still can't decide what part I liked better: where they Sawzalled off the wing or when they had a big galoot jump on the fiberglass rear bumper one time to remove it.

On my BMW, the light weight of the SSRs makes near-race spring rates tolerable on the street. Heavy wheels would make it suck.

I have driven many, many cars with a lot of different wheels. I have homed in on a particular set of crappy characteristics that represent "heavy wheel feel." It's real.

I have also done skidpad tests on another vehicle, where we over-tired a wheel. With 18x10.5 wheels, we tried 295/30-18 and 315/30-18. The tire temperatures were more even with the wider tires, but the lowest one was higher than the highest temperature with the 295s. With the wider tires, the tires were making more noise and the car was going slower. So even beyond saying you should have a wide enough wheel to support the rubber you're using, it may be that using a narrower tire on the wheel you have could actually be better.

My theory on wheels is that their job is to connect the tires you want to use to the vehicle and support them properly, while clearing the brakes you want to use.

Step 1: What brakes do I want to use?
Step 2: What is the smallest diameter wheel that will fit over the brakes?
Step 3: How wide is the widest tire I can fit, and what OD is appropriate?
Step 4: What is the widest wheel I can fit, and what offset range do I need to have it clear the suspension and the tire clear everything?
Step 5: What tires do I want to use that work with 2, 3, and 4? Are they available? Can I afford them?
Step 6: Shop for wheels of the correct diameter, width, and offset, with sufficient clearance for the brakes and decently light weight that I can afford.

So what did I do?
I have a set of 18x10.5 +43 et wheels in the garage waiting for my 8 to get here. Not quite as light as Team's, but close. There aren't many lightweight 17x10 or 10.5 wheels out there that fit the 8, fewer that clear StopTechs (I always try to leave that door open). In fact, the only ones I can name are Volk$.

I also have a set of 17x8.5 SSRs left over from my last project, which will be my street wheels.

SolarYellow510

The reasons you state are good ones, but anything you do to remove mass from a vehicle helps. Other than the money spent, light flywheels are generally low-compromise items.

As far as straight-line acceleration, the benefits are greatest in first gear, diminished in second, diminished still more in third, and basically hard to measure in fourth.

Hannu Prettner (sp?) was a multi-time world champion in R/C airplane aerobatics when I was a kid. His single piece of advice for anyone wanting to build great airplanes? Build with a gram scale. Think about the weight of the plastic film you're covering the plane with, think about how much glue you're using. Buy more wood than you need to, and sort it for lightness.

The point is that small differences often don't by themselves mean much, but the accumulation of many very small differences can yield a real advantage. It's how an Evo gets down to 2200 lb and becomes magic.

rollerbldes

Broken links make me sad. =(

Bradleydrivn

I agree, but I think there is more of an equation that that; or at least fill in a blank for me:

Rather than undefined rotational mass to some form of power measurement (at a rate between 2.2 and 3)... Pounds of rotational mass to horsepower equation maybe?

An equation like that would be very useful if you or someone has it.

Hope you don't see this as a dick move. I'd really like to know.
Thanks

SolarYellow510

The basic problem with most of these discussions is they are based on a woefully incomplete application of the simple F=MA. Acceleration is the force available to accelerate the vehicle at the speed it's going (subject, of course, to the limit of traction; also, this is really torque geared to the speed you're going - power is the common expression of this) minus the force of resistance such as aerodynamic drag and rolling resistance, divided by the total of inertial effects (mass to be translated plus rotational inertia of the spinny parts).

The "pounds of rotating mass to non-rotating mass" relationship depends on how much of the inertial effect is accounted for by the rotational inertia, how the pounds of each rotating item are distributed to contribute to rotational inertia, and how much power the car has. It's all percents.

To take this to an extreme, if you had 10 hp, and added 10 hp, the change would be massive. If you had 400 hp and added 10 hp, you may not even be able to isolate the change at the drag strip.

It's still a pretty simple equation. The hard part is knowing what values to put into it to get a real answer. It's impractical for anyone but the OE manufacturer of a vehicle to assemble the data. Extensive road tests can approximate aero and rolling resistance values if analyzed with a good model. Rotational inertia of the complete vehicle pretty much needs a complete vehicle model. If we have a good chassis dyno plot and good data on actual vehicle performance, then predicting the effect of a change in inertia should be within reach.

It should be possible to build a test rig to determine the rotational inertia of things like wheels and brake rotors, but I've never seen anyone do it. The manufacturers of these items will have CAD models and should be able to get a number for rotational inertia with a few clicks, but good luck getting them to tell you what it is.

In the real world, where people care more about making cars go fast than about talking about it, the six-step plan I outlined above is pretty good.

If you do have the resources to test multiple setups accurately (measurement equipment, consistent and fast driver, track time, parts to swap out, etc.), then you can certainly choose between them and even understand the differences. There is a lot more than lap times. If you understand where one setup may give you better braking or cornering, and another may give up some of that but through lower inertia, rolling resistance and drag, give you higher speed on longer straights, you may be able to predict where one setup would be favored over another. More likely, you'll make a choice on parts and invest in it, then work on optimizing the setup of those components at each place you go.

If that seems too hard, then you should probably do what everyone else does (including me and the author of http://www.nerocam.com/SCC_TAPnew.asp), which is look at what fits, pick out the ones that look good to you, weigh your own values of price versus weight, and lay down your dollars. Then go work on optimizing the nut behind the wheel.

upstate_T-RX

holy crap all this reading is killing me, i feel like im reading a book about the citric acid digestion process. can any one simply tel me whether or not : a. putting new 18' wheels on stock tires will work and b. does lighter tires and wheels affect acceleration performance ...thank you and no einstein answers please

Spin9k

Sure - I'll tell you

- Putting new 18" wheels on stock 18" tires will work.
- YES! Lighter wheels and tires affect accelerative performance.

Bong! That was easy!

Endless Rotaries

iTrader: (6)

Well i did a fuel economy experiment.

Basically everytime i did a +1 on diameter and width i lost about 10% of the fuel economy. FYI.

Tested on my RX8 and Miata.

Rishie

parkpy

iTrader: (1)

a lot of the links in the first post are broken

Goofy

Did you account for the fact that your odometer is reading low?

rXter

Anyone know what the OEM Chrome wheels weigh on a 2004?

matt13b

I have Gramlites-18x8.5. Does anyone happen to know how much they weigh??