Lighter Weight Wheels --- Worth It?

[BlackDeuceCoupe]

Originally Posted by almightybmw

Lots of comparing rim weights and tire weights, as well as where 80% of the mass is located on the combo.

True!

I cleaned up my 15" Si wheels today and put them on my ride.

Since the ZE-512s don't have a lot of tread left, I was checking out replacements.

Here are two contenders...

Falken Ziex ZE-512 (source):

* 185/65-14 17.5 lbs
* 195/55-15 18.5 lbs
* 195/60-16 N/A
* 205/40-17 17.4 lbs


Falken Ziex ZE-912 (source):

* 185/65-14 17.9 lbs
* 195/55-15 20.4 lbs
* 195/50-16 20.2 lbs
* 205/40-17 22.0 lbs

Interesting differences!

[taco]

seems the 14's are better for fe width.
but weight the same as the 17's



edit i decieded to look my tires up 50psi max and 39lbs each...

[pugmanic]

Citroen experimented with light weight rims in the 70's. They provided Carbon Fibre Rims as an option on the SM range. It was 30 years before a manufacturer chose to use CF rims as standard...

[MechEngVT]

BDC: Rubber is pretty darn heavy. I was always under the assumption that unless you were going for over-the-top bling that the tires were heavier than the wheels. Remember, tires are all *steel*-belted radials and they have metal in them near the outer diameter.

From tirerack.com's published specs for Michelin Hydroedge tires are the following weights compatible with the wheels you listed:

185/70r14: 19 lbs, 893 revs/mile
185/65/15: 19 lbs, 856 revs/mile (a LARGER tire, same weight/width shorter sidewall)
205/55r16: 23 lbs, 839 revs/mile (a 215/65r16 is 25 lbs at 776 rev/mi)
215/60r17: 25 lbs, 770 revs/mile

Clearly rim size is not the sole determining factor of tire weight. A shorter sidewall can even offset a slight increase in outer diameter for a given width. A larger diameter tire for a given rim and width is heavier. Also tires are much heaver than the (admittedly already light) wheels you listed.

[MetroMPG]

Originally Posted by pugmanic

Citroen experimented with light weight rims in the 70's. They provided Carbon Fibre Rims as an option on the SM range. It was 30 years before a manufacturer chose to use CF rims as standard...

Neat. Any idea how they fared through the years? Did they last?

[jamesqf]

Originally Posted by MechEngVT

BDC: Rubber is pretty darn heavy. I was always under the assumption that unless you were going for over-the-top bling that the tires were heavier than the wheels. Remember, tires are all *steel*-belted radials and they have metal in them near the outer diameter.

Are all tires steel-belted these days? I don't try to keep up with tire technology, but I seem to remember seeing mention of e.g. Kevlar belts instead of steel. Probably for these very reasons: saving weight & rotational inertia.

But the "rubber is heavy" is part of what motivated my question. Not as heavy as alloy or composite in the rims (per unit volume), but the sidewalls seem thicker than the wheels.

Another good point on width adding weight/inertia, not to mention rolling resistance.

[BlackDeuceCoupe]

Originally Posted by jamesqf

Are all tires steel-belted these days?

Nope! My Pirelli P3000 Cinturato tires, for instance, have polyester casing...

PIRELLI - CINTURATO P3000

But, they wear like steel - 85000mi warranty!

EDIT

Thought you might find this interesting...

SOURCE: http://www.longstonetires.com/...o.php

The Pirelli Cinturato, first introduced in the 1950's, was the first example of a textile cord braced radial tire. The Pirelli Cinturato quickly became the dominant radial tire in European GT and sports car racing circles.

The Pirelli Cinturato combined unprecedented grip with high-speed capabilities, the Cinturato also gave a supremely comfortable ride. Not surprisingly, the Pirelli Cinturato soon became standard equipment on many of the great Italian marques of the era, including Ferrari, Maserati, and Lamborghini.

[jwc]

I've just switched from 185/60 tires on 14" rims to 155/80 tires on 13" rims -- same overall diamater. The new wheels weigh 2.5 lbs less, and the tires weigh 4 lbs less.

But I believe tire weight is much more important than wheel weight. It's all about where the weight is concentrated as radius is squared in the inertia formula. ie, my 13" wheels have the weight concentrated mostly at about a 6" radius, but the tires at about 11" radius. When you square the radius, for this size, it works out to the tire contributing 80% of the inertia. I estimate that I should need about 20 lb-ft^2 less torque to achieve the same acceleration.

I just mounted these 2 days ago, and the car feels like it accelerates from a stop much more easily. But any improvements in FE may also be due to other factors like less aero drag, but I think the bulk if any will be due to the lower inertia. I'll know more soon when I fill up next.

[basslover911]

Originally Posted by jwc

But any improvements in FE may also be due to other factors like less aero drag, but I think the bulk if any will be due to the lower inertia. I'll know more soon when I fill up next.

Thats what im wondering, what affect FE more? Weight or Aerodynamics?

And i am not talking about handling or braking or accelerating distances... just fuel efficiency.

[BlackDeuceCoupe]

Originally Posted by jwc

I just mounted these 2 days ago, and the car feels like it accelerates from a stop much more easily.

Truth!!! THANK YOU! LoL!

Would you please explain this to that 'domestic guy' that keeps trying to bench-race me on this site?!?!?

With a lightweight car/rims/tires, I'm G-O-N-E off a light, leaving the chump back there hooking up! Then, it's just a matter of catch-me-if-you-can, you know?

Given enough time and space they might be able to beat me (that's what they always say) but it's academic 'cause by then the race is over and I'm sitting at the next light waiting for them! And, I can do this all night long - run after run!

Makes a lot of ppl mad! Some guys even try to crash me, like it's a demolition derby or something - no joke!

Anyway, glad to see someone else understands this phenomena...

EDIT2 (Let's try this)

Show n' Tell

Here's a snappy, I took this afternoon, of my CiViC with the Si rims installed...



They look okay, I guess, but they're heavy, IMHO!