Wheel performance

peepsalot

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Black 03 MSP
I don't know a whole lot about wheels, so I got a few basic questions.
I'm curious about the performance advantages of getting new rims. How heavy are our stock rims? Are they pretty heavy compared to other things out there? Would handling or acceleration be affected any noticeable amount with something lighter? Can rims be considered a performance upgrade at all really? I don't care about the bling factor much. How much would I have to spend, and does anyone have recommendations?
 
Your stock is about 22lbs. The standard ratio of unsprung to sprung weight is about 4:1. Therefore if you were to buy the wheels I have for sale in the 15-16lb range you would save from 6-7 lbs of unsprung weight which would equate to about 24-28lbs per corner. Now that is one corner times 4 so you're netting a loss in sprung weight of near 100lbs. Imagine taking a 100 lbs off of your body and that's what is driving your car.

This is a very laymen way of explaining it as there are mutiple benefits to a lighter and stronger wheel. Better handling, acceleration, and braking. Steering response will vastly improve as well. Most likely you will go to a wider wheel track so your car will feel more planted as well.

I have some very good lightweight wheel options for youl. Email me sales@autornd.com and i'll see what i can spice up for you. Let me know what you're doing with the car and what your budget is.

Thanks, Rishie
 
I'm just trying to learn a little about car performance really. This discussion could affect my purchases in the future, but at this point in time I don't have the cash for a new set of wheels, so it's all just a pipe dream for now.
 
Rishie, do the variences in tire wieght affect this greatly? Do tire weights vary enough to worry about how much your tires weigh?
 
How is handling affected when going to a smaller rim size? You can go smaller and still keep the same outer diameter by using thicker tires, right? So is one or the other supposed to handle better(low profile tires vs others)? I would assume this could make things lighter too?
 
peepsalot said:
How is handling affected when going to a smaller rim size? You can go smaller and still keep the same outer diameter by using thicker tires, right? So is one or the other supposed to handle better(low profile tires vs others)? I would assume this could make things lighter too?

Lower profile tires have a thinner sidewall. A thinner sidewall warps less in a turn so you will have a flatter, more wide contact patch with the road during a tight turn. The draw back is that low profile tires ride like s*** (because there's less rubber to obsorb the bumps in the road) and are generally more expensive. There are other factors to look out for. The original diameter of the factory wheels/tires dictate how the spedo works. So if you got tiny wheels on a car that came with 20s the car would think you were goind 140 when you might only be going 100. (There's a math formula to figure this out, but I can't find it right now. I bet someone else will google it on their first try.) A smaller wheel moves less per turn than a larger wheel. A larger wheel could (in theroy) give you a higher top end. Keep in mind you might not have the HP or the gearing to see the befits of this theroy. MORE ALSO: The farther the weight of the wheel is pushed away from the brakes, the harder it is on the brakes to actually stop the car. The farther the weight the more of a mechanical dissadvantage on the brakes.
 
peepsalot said:
Just to clarify, when you say 22lbs, you are referring to the mazdaspeed protege rims?

I would assume that this is referring only to the rims themselves. Because with the tires, there's no way they weigh only 22 lbs!
 
Offset simply refers to how far the mounting surface of the rim is from the true centerline of the wheel. If you took a look at a wheel with a 0 offset, it would mount dead-center from the centerline. A 7" wide wheel running a +45 offset, as per Rishie's fitments, means that the rim is 7" wide, and the center of the wheel is 45mm closer to the outboard (away from the center) of the car.

The key with offset is to get the wheels out on the corners as far as you can without rubbing. This allows you to have a nice stance, which affects how fast the car responds to turn-in, and how much it can balance on the outer tire. Loading up a tire that is more inboard (toward the center of the car) means that you have weight tipping over the center of the tire, which means it may be more likely to roll. Outboard more, the tire won't try and tuck as much.

Camber also comes into play here. Negative camber is very useful under hard cornering, as under neutral camber, when you're turning, your wheel and tire will tend to droop like this, where the /'s are the tires:

/-----/

That's if you had neutral camber, like this:

|-----|

Now, if you apply some negative camber, your wheels are facing like this (Though don't do this; This range would be what it looked like if you had over 3 degrees of camber or so. ;) This is just an example of the directions):

/-----\

So, when you cornered, this would happen instead:

/-----|

If you'll notice, your weight is now shifted toward the center of the contact patch more. Something to keep in mind with wheels and tires as well.

Typically, lighter weight wheels will afford you faster acceleration and better handling. However, tires are your actual INTERFACE between the car itself and the road, so that, too, is VERY important. Get good tires, in other words.

As for the size of the tires, it can be read this way:

195/50 R 16

The first number is the width of the tire in millimeters. This tire would be 195 millimeters wide.

The second number is the percentage of the width that dictates how large the sidewall is. This would be 50 percent. What this means is you take 50 percent, or half, of 195, and that leaves you with 97.5mm of sidewall. This is not the total height of your wheel and tire, but rather JUST one portion of the sidewall.

The last number is the diameter in inches of the wheel that you'll be mounting to. In this case, 16 inches.

Now, the larger sidewall you go with, the more sidewall flex you'll get, as was mentioned. More roll, and so-on. If you went with a 205/50R16 tire on the previous example, you would have 5mm more sidewall height, as it would be 10mm wider. That's 5 more millimeters that it has to flex.

ALSO, by doing this, you're increasing the diameter that the wheel has to travel to make one complete rotation, so the car will rev slower while going faster, which in turn also throws off the speedometer. Though a subtle change like that won't make much more of a difference, I generally try to go with an overall smaller diameter tire to try and shorten the gears, to increase acceleration further.

Whew... If you have any more questions, or you want links to sites where you can either read more of this stuff, or calculators to determine variances in tire size, and the effect on speedometer readings and so on, just ask. I'll post them here, if you want. =)
 
MORE INFORMATION: The farther the center of the wheel is away from the axel the more torque steer you encounter, or so I was told in Sport Compact Car. (The issue where they put wider wheels on the SRT-4 w/o a limited slip.)
 
flat_black, good info. some of that i got from tirerack.com, but i couldn't get my head around how offset would change handling.

could you post those links if you get a chance?
 
Here are some of the newer links that I have... I havn't looked at many of them recently, but there's lots of info to be had here:

http://www.miata.net/sport/Physics/index.html

Here is where I do quick tire/wheel size calculations, typically, if I can't do it in my head:

http://www.miata.net/garage/tirecalc.html

I just came to the realization that most of the stuff I have is books, actually, at this point, as I have about a billion books on physics, handling dynamics, and suspension tuning. Hehee.
 
lamp3 said:
Rishie, do the variences in tire wieght affect this greatly? Do tire weights vary enough to worry about how much your tires weigh?

They have the same affect as the wheels do. Lighter weight means lighter weight. If loosing weight at the corners are a big concern then yes the tires will affect the wheel/tire overall weight. In my opinion it's better to go on a diet and lose a few pounds if possible. hehe :p If you're looking for good light weight tires, give the Toyo T1-s (20.1lbs), Pirelli P-Zero Nero (21lbs), Falken Ziex Ze-512 (19.8lbs), Toyo Proxes 4 (21.6lbs). The weights given are for 215/45 17's. As I've seen in the past, most Yokohama tire are usually on the heavier side trade off being excellent traction.
 
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