i'm planning on getting 17" Axis wheels for my xA....

Three of their 17's weight approximately 25 lbs. as opposed the the 17.5 lbs stock

How much will the extra weight affect handling?

They have one 17" that only weighs 14 lbs.

Will the wheels weighing approximately 3 lbs less have much affect on handling?

My fear is that this wheel will be very fragile....is this true? Will potholes and speed bumps and parallel parkings become nerve wracking?

 

A 17" that weighs in at 25lbs is pretty heavy--and it will affect handling somewhat, although it may be the opposite of what you think.

With a tire that has less sidewall and more contact patch, as well as a firmer compound, your handling will actually be better than stock. You'll have more grip and traction, although road noise may slightly increase.

Adversely, straight line acceleration WILL suffer from the added weight of the wheels. It's probably one of the worst areas to add weight, as the car has to move 4 pts. of rotational mass every time you hit the gas.

The one wheel at 14lbs from Axis is probably the Axis Mag Lite (4 spoke design), now I haven't heard any problems with this wheel being fragile or anything, but honestly I would personally not run this particular wheel (although others may, i'm just a paranoid kinda guy when it comes to things like this) because of 2 main reasons.

1. The design itself doesn't look all too sturdy...just look at the center of the wheel...it could be just cosmetics, but it just does not look strong at all!

2. Axis does not manufacture their wheels using a Forging process--instead, like many other wheel manufacturers do, use a Casting process to create their wheels. Forged wheels are scientifically proven to be stronger and more structurally rigid than their cast counterparts...the downside of course is the higher cost when creating a stronger, forged wheel. A cast wheel is ok if it is "typical" cast wheel weighted...in a 17", about 20+lbs...and a typical forged wheel is usually lightweight. So this worries me because of the Mag Lites relatively light weight--yet it's a cast wheel...
All in all, you probably would never have a problem running the Mag Lites--but like I said earlier...i'm the type that is uber paranoid...

All of the above is my personal opinion --and I can care less of what some of you others out there think. I won't tolerate any of this "Cmon man Axis is KoOL" type replies. Please, let's cut back on the BS that has been plaguing this forum.

 

Heavier wheels not only slow acceleration (like any added weight - but compound it because the wheel rotates), they'll also increase braking distance, bump steer, and wear brakes faster.

I wouldn't worry about the maglite. There are plenty of 4 spoke wheels that are just fine. A heavier wheel won't necessarily be stronger anyway.

Forging is definately stronger than casting, but there are multiple companies casting lightweight wheels. Rota is the most common that comes to mind. They have had some bending/breaking issues, but they've also replaced problem wheels for customers. Not sure about customer sevice/retention at Axis.

 

yeah, 25lbs would be pretty noticeable.

rota and others make some 17 inch wheels that are under 20lbs, I would go with that, they aren't very expensive and are strong enough.

keep in mind our scions are VERY light cars, wheels won't be seeing quite the stress that a normal sized car would anyway.

 

Thanks everyone for your reply...couple more questions....

How do i find out if a wheel is forged or cast?

Are all forged wheels the uber expensive type...ie Work, Volks etc?

Finally is there an easy way to find out the weights of different wheels? Axis only lists the weight of the Maglite and i had to email for the other weights.

 

I found this, and it might help you out. They don't have everything, but quite a bit...

http://www.wheelweights.net

 

And, if you can feel the difference in a street car you truly have the Golden Tush.

Let's say you put 25 pound wheels on your car, replacing the 17 pound stock wheels. You add 24 pounds total. You're right that some of this mass is rotating, and that part at the top of the wheel (8 pounds or so, total) will have a double effect, as the top of the wheel accelerates twice as much.

So, the effect of the "heavy" wheels is like adding 32 pounds to the weight of the car. The car weighs about 2400 pounds, so 32 pounds, or 1.3 percent. Awfully hard to feel that small difference.

Now, let's assume that your new large wheels increase the rolling diameter of the tire by an inch. That is a change of 1 inch in 24, or a 4.1 percent reduction in available wheel torque at the ground. Therefore, the difference in acceleration due to the larger tire size will be over three times as much as the difference due to weight.

Moral: If you want to go fast, keep your stock wheels!

George

 

It's my understanding that a smaller overall diameter (tire on the wheel) gets more torque to the qround, which should allow you to accellerate quicker. Also, a larger overall diameter would make the vehicle get a faster speed for the same engine RPM. Wheel & tire diameter is part of the overall end-result gearing, right?

That's the point of + sizing, isn't it? What's the difference b/w a 195/60R15 and a 205/45R17 (nevermind whether it will fit in the wheel well or not)? 0.2%. I'd bet you'd never feel that difference, although you might notice something slightly amiss in your gas mileage.

So my rebuttal question is, what's the net effect difference between a 15" wheel and a 17" wheel, which both have a tire mounted that gives them the same overall outside tire diameter? Let's assume, for sake of argument, that both wheels weigh the same. Anyone care to tackle that one?

 

I wouldn't write off the difference that quickly ... I ran a few quick calcs that suggest the rotational kinetic energy of typical set of 17" wheels on an xB is somewhere around 6-7% of the total kinetic energy at freeway speeds. And I assure you that my scientifically calibrated tush can feel the difference :D

 

Changing the overall diameter changes the effective gear ratio. Going with a slighter smaller OD will make you slightly quicker off the line, but will run higher rpm at highway speed. The opposite is true for going with a larger OD.

Optimum, imo, is a plus 1 setup that's lighter than stock with a slightly smaller OD.

 

That one is relatively easy. Same diameter gives the same acceleration force applied to the ground gives the same acceleration.

However, many people who go for big rims end up with a couple of inches more tire diameter. I suspect that is why Scions are geared so short.

George

 

Hmmm, I don't see how that can be. Let's say that the wheels mass a hefty 10kg, and the mass is concentrated at the tire contact surface. This would give the wheel a surface speed equal to the speed of the car.

KEwheels=1/2mv^2=(1/2)(40)(25)^2=12500J

KEcar=(1/2)mv^2=(1/2)(1000)(25)^2=312500J

12500/312500=.04 or 4%

My assumption that all the mass of the wheel is concentrated in the contact surface tends to overstate the rotatinal KE of the wheels, so the actual proportion is more like 3% or so.

Also, cars don't run without wheels, so the difference in going from a 10kg wheel to a 7kg wheel would be very small, perhaps in the 1% range.

George

 

Changing the mass of the wheel effects the suspension and the accelleration.

The effect of the wheel weight is more important to the suspension. The wheels reffered to as "unsprung weight". If the wheels are heavier than what the suspension design calls for, the simplistic result is that the wheel is "lazy" to return to the proper position such that good handling (or grip ot the road) is acheived. This is not to say that good or better handling cannot be acheived with heavier wheels. It probably means that to get better handling that a different set of shocks and/or springs would be required since the stock ones are probably optimized with the stock weights. Any suspension has three basic components (spring-mass-damper). If you change any of these components (mass being the wheel), you can end up with a completely different ride charateristic. Lowering the weight of the wheel also has this impact. Suspension wise, the result of a lower weight wheel can be a more sporty, more responsive feel which may be good if you like that.

Now, the mass of the wheel also makes a differrence in acceleration. Acceleration of the wheel (a rotating mass) is a function of the wheels mass moment of inertia. This is essentially the center of mass of a rotating object. The bigger and heavier the wheel, the greater the mass moment of inertia. This makes the wheel slower to accelerate. Once at constant speed, there is not a significant difference since the drag of the wheels (road hp) is a relatively minor player. This moment of inertia can be reduced by reducing weight or reducing diameter of the wheel. This is why a lot of the smaller "drag cars" have pretty small wheels. They don't have the power to lose much grip so they find the best combination of just enough grip and the lowest mass moment of inertia. This will result in the best accelleration. Smaller wheels will also get you into the power band quicker which can result in quicker accelleration.

But, realistically, this is a car with 108 hp. The acceleration difference will not be much. The suspension impacts, however, is something to think about.

 

Wow, an old fashioned technical ____ing contest, just like I used to have at all the jobs where I got fired

In the kinetic energy calcs don't forget to add the weight of the tires. According to Overboost.com the stock wheel/tire combe weighs in at 34 lbs IIRC, which accounts for the difference between your calcs and mine.

As stated above larger rims will increase the moment of inertia of the wheel-tire combo by moving more of the mass to the outside. A low-profile tire will also have stiffer sidewalls, thus less energy will be dissipated through tire deformation under heavy braking. It's the same effect as overinflating your tires.

I'm not saying it's worth quibbling over a few ounces, but all in all I still say it's a non-negligible effect.