What are the lightest wheels for this car?

[autogyro]

SSR Type C-RS 18x7.5 is 17.4 lbs.

http://www.ft86club.com/forums/showthread.php?t=15918

[Suberman]

OZ Alleggeritta HLT are 15.2 lbs in 17x8.

Superleggera are no longer made. Ultraleggera are 17.2 lbs, same size.

Aluminum wheels can be light pressure cast with good results comparable to forged.

OZ HLT wheels are low pressure cast and the rims are spun out to final diameter. Pretty cool technology.

Search tire rack site for the description of this process.

[jflogerzi]

Originally Posted by WRB-DZA-BRZ

Here is what I'd like to see...

Enkei Racing RPF1 16x7
Offset: +35mm (will this fit??)
Backspacing: 5.35"
Weight: 13.7lbs
Price: $207 each on TireRack

Hankook Ventus R-S3
Tire Size:225/50-16
Weight: 25lbs
Price: $123 each on TireRack

Apparently Tire Rack shows 16" wheels/tires if you go to the winter section.

25LBS 16inch tire??!! WTH

[Suberman]

Originally Posted by jflogerzi

25LBS 16inch tire??!! WTH

Yup, smaller diameter wheels and same rolling total circumference means larger tires weighing more.

[Joakim3]

So essentially people...

small & light rim with a thick & heavy tire (assuming you try to stay close to OEM diameter)

or

larger & heavy rim with a skinny & light tire (assuming you try to stay close to OEM diameter)

Moral of the story is don't to stray away from OEM 17" 215/45 if you want true unsprung mass & rotational inertia loss... the above options essentially cancel each other out

[TRD_86]

18"

OZ Alleggerita HLT
Offset: +48mm
Backspacing: 6.18"
Rec. Tire Size:225/40-18
Weight: 16.2lbs.
---------
Has anyone experienced w/ this light wheel compare to enkei brand in quality for DD use only ?

[FReSh]

Originally Posted by Joakim3

So essentially people...

small & light rim with a thick & heavy tire (assuming you try to stay close to OEM diameter)

or

larger & heavy rim with a skinny & light tire (assuming you try to stay close to OEM diameter)

Moral of the story is don't to stray away from OEM 17" 215/45 if you want true unsprung mass & rotational inertia loss... the above options essentially cancel each other out

There's a distinction between unsprung weight and inertia. It makes a difference between these options listed. Please excuse (or enjoy) the science below...

The inertia refers to how difficult it is to accelerate the wheel (make it spin faster). Something with a higher rotational inertia will require a larger amount of torque to accelerate. Torque is basically a force multiplied by a lever arm. Hence the units of LB*ft. For example: you have a 2 foot long breaker bar on a bolt and you exert 12 LBS of force on the end of it with your hands. You have now torqued that bolt to 24LB*ft. With more of the weight concentrated farther away from the axis of rotation (a longer lever arm), the torque will be higher for the same given weight. This is why a longer breaker bar makes it easier to tighten/loosen the same bolt. This is also why a heavy rim with light tire will have less inertia than the opposite case (since the tire is at a farther distance from the center).

The unsprung weight is just how much it weighs (the unsprung part means that it is not supported by the suspension of the car). Assuming the tire/wheel combo weighs the same in each case above, they will be equal as far as unsprung weight goes.

All said and done: If you have the choice to save an extra 2 pounds on either the tire OR the rim, save it on the tire. (that is assuming you don't care about the fact that the tire is a wear item and will need to be changed eventually.)

[Admiral Ballsy]

Originally Posted by FReSh

If you have the choice to save an extra 2 pounds on either the tire OR the rim, save it on the tire.

I don't believe it's really that simple.

Assuming you're comparing two setups, same section width tires and same wheel width, but different wheel diameters, I think the change in centroid would be extremely minor. The tire gets heavier, but its centroid will shift closer to the hub center.

Since you're only adding sidewall to the tires, the tread mass stays the same and stays in the same location WRT hub center. You're making the sidewalls taller, which effectively shifts the center of their mass to towards the hub.

Obviously if you're changing widths of the tire or wheel or both, then it really comes down to the measurements.

How much it matter depends upon a lot of things - how much heavier is the tire being the main one. But it's not necessarily true that going from, say, 255/50-17 to 255/40-18 significantly changes the moment(s) of inertia.

[FReSh]

Originally Posted by Admiral Ballsy

I don't believe it's really that simple.

Assuming you're comparing two setups, same section width tires and same wheel width, but different wheel diameters, I think the change in centroid would be extremely minor. The tire gets heavier, but its centroid will shift closer to the hub center.

Since you're only adding sidewall to the tires, the tread mass stays the same and stays in the same location WRT hub center. You're making the sidewalls taller, which effectively shifts the center of their mass to towards the hub.

Obviously if you're changing widths of the tire or wheel or both, then it really comes down to the measurements.

How much it matter depends upon a lot of things - how much heavier is the tire being the main one. But it's not necessarily true that going from, say, 255/50-17 to 255/40-18 significantly changes the moment(s) of inertia.

Yeah, if you're choosing the same tire model/wheel model combo and just changing the size of the wheel, then you won't notice a huge difference. The smaller wheel would probably be more beneficial. I was referring to if you had rim size in mind already and were wondering whether you should spend more on lighter style rims, or lighter tires...

also... the centroid of your wheel/tire should ALWAYS be in the center... otherwise you'll get some nasty vibrations. Unless you were talking about the centroid of one side of the cross-section of the tire. Then you're statement is correct, closer to the center is better.

[Entropy]

I still think that the bets the 17x9 RPF1 - 245/40R17 combination is the best trade off in terms of weight, grip, and $value.

[Joakim3]

Originally Posted by FReSh

There's a distinction between unsprung weight and inertia. It makes a difference between these options listed. Please excuse (or enjoy) the science below...

The inertia refers to how difficult it is to accelerate the wheel (make it spin faster). Something with a higher rotational inertia will require a larger amount of torque to accelerate. Torque is basically a force multiplied by a lever arm. Hence the units of LB*ft. For example: you have a 2 foot long breaker bar on a bolt and you exert 12 LBS of force on the end of it with your hands. You have now torqued that bolt to 24LB*ft. With more of the weight concentrated farther away from the axis of rotation (a longer lever arm), the torque will be higher for the same given weight. This is why a longer breaker bar makes it easier to tighten/loosen the same bolt. This is also why a heavy rim with light tire will have less inertia than the opposite case (since the tire is at a farther distance from the center).

The unsprung weight is just how much it weighs (the unsprung part means that it is not supported by the suspension of the car). Assuming the tire/wheel combo weighs the same in each case above, they will be equal as far as unsprung weight goes.

All said and done: If you have the choice to save an extra 2 pounds on either the tire OR the rim, save it on the tire. (that is assuming you don't care about the fact that the tire is a wear item and will need to be changed eventually.)

I'm am I science buff... I live in statistics and facts lol, so yes I enjoyed it!!

[Adeets]

How did wedsports not make this list yet?
17x9 15.4 lbs

See my build for pics.

[adprokid]

Volk CE28N
16x7.0 5x100 +42
10.75 LBS

[diss7]

It makes me lol seeing people with $4k forgies, stupid over sized tyres, on NA or even some FI builds.

They claim to justify the wheel cost because they're light. And then whack on a 255 tyre which often is damn heavy, and you end up with a package that's heavier than stock.

The annoying part to me about that, is that people who are doing that are claiming function cred, but ain't no function about that. It's poser.

17x7.5
215/45

Forgies if you can to save weight
215 tyre keeps tyre weight down

Oh 215 tyre doesn't give enough grip? Have you setup your alignment for grip? Have you tried a different tyre compound?

Still trying to justify meaty / heavy tyre? 215 r rated or semi will have more grip than 255 road tyre.

Maybe you need to learn how to drive if you need 255s on this car.

So much focus on wheel weight, then dumping twice that difference saved (and paid for) on unnecessary meaty tyre.

Rant over. Flaming to follow.