Lightweight Wheels....

[2112]

This is a repost of the lightweight wheel section of the the 'potential fixes' thread

[Gammaman]

How about the 547R? The split 5 spokes would retain some of the character of the original wheel. Andrew, could you do some photoshop magic showing them?

[thegunguy]

They seem to be only available in Europe anymore, but I'm narrowing in a source in the States.

There are some great pics of Dieter's car with the RD2s in the Wheel/Tire section.

[Norcal]

The 840s are the upper pic, those are what I was considering in 20s

[2112]

How about the 547R? The split 5 spokes would retain some of the character of the original wheel. Andrew, could you do some photoshop magic showing them?

Here is what I am using:D

[2112]

a close up

[macfly]

I think it all comes down to personal choice, but IMHO the 540 or 540R are the best suited visually, but the extreem lightness of the C21 is also really tempting.

.

[macfly]

What about the C21's with black spokes, those would look great on your car!!

[harvey2]

Thanks for the photo comparison. I really like the 540/540r the best. They are complex with just the right amount of bling. Sort of a stylized modernization of a spoke wheel but with more curves to catch the eye. The others are either too severe, that is, too little flow or too geometric, or they are excessively boring in my opinion.

I don't see the difference between 540 and 540R so will have to do some research on that one.

harvey2

[macfly]

The reflections of the bolts make it hard to tell, but the 540R has a flat inner rim/lip thus slightly longer spokes, while the 540 has a stepped inner rim/lip and a slightly shorter spoke. It is really hard to know which I prefer without seeing them side by side, but I have always thought this shot of the 19" 540 on Claus's car is about the most handsome thing I've seen on a Z8.

[Gammaman]

The reflections of the bolts make it hard to tell, but the 540R has a flat inner rim/lip thus slightly longer spokes, while the 540 has a stepped inner rim/lip and a slightly shorter spoke. It is really hard to know which I prefer without seeing them side by side, but I have always thought this shot of the 19" 540 on Claus's car is about the most handsome thing I've seen on a Z8.

Yes, they are very good looking wheels, but a lot of work to clean. I swore after having the basket weaves on my old 325iX that I'd never again get wheels that were hard to keep clean ;)

[harvey2]

Those wheels on Claus' car are georgous. It doesn't hurt that his car is a dark colour, but even my Silver paint would work well with the nice level of sheen from those wheels. I like 'em.

Thanks for the photo.

Oh, and cleaning may be an issue, but I kind'of enjoy fussing over my baby to bring out the shine.

harvey2

[Norcal]

What about the C21's with black spokes, those would look great on your car!!

Yes, those with the black centers could be beautiful. One thing I like about the 840s is the hidden bolts, makes for a sleeker (like the car) look. I suppose if the centers are painted out in black, the actual pattern of the centers is far less critical. One thing I've wondered is how much it would cost to take the centers back to clearcoat silver, if I tire of the black some day. I've also have been thinking that 19s would probably look nice, and ride better.

[Z8Mania]

I agree- I like the 840 series too for those reasons.

[Gammaman]

I wonder if we could arrange a group buy, direct from HRE?

[macfly]

and see what exactly BMW comes up with too, as buying lightweight wheels, or any other quasi-fix may well be throwing good money after bad.

[Norcal]

I don't see the wheels as a fix. I'm no engineer, but it seems that 3,400lbs of car/inertia impacting a pot hole etc. at speeds over perhaps 40-60 mph, multiplying the actual weight of the car many times, is far more relevant than an extra 10lbs moving up and down. I suspect the energy transfer at impact is in the high 100s if not thousands of pounds. As for good money after bad, you are right, but if you are comitted to keeping the car, what's a few thousand to dress her up? I'm confident that some kind of fix will be developed within a year. Even if she becomes a trailer queen/cruiser, which she won't, all the more reason to bling the wheels. It might be fun to dress her up sexy for my private enjoyment, even if I can't take her out much. Perhaps researching and doing some mods would be a good way to pass the time while were waiting for "THE FIX". Tinkering is fun too.

Still smitten, what can I say?

[thegunguy]

To me it seems that the mass of the wheel is one of the primary determinants in the force applied to the shock tower during an impact. With an independent suspension, only the wheel hitting the hole will travel up and down. In an impact, the suspended wheel is accelerated quickly in the vertical plain. At the top of this stroke, the wheel instantly reverses direction back to its resting position. This instant deceleration transfers the force of the traveling wheel into the shock tower (F=ma). The springs absorb much of this force (interacting with the 'a' in F=ma). Stiffer springs will carry more force into the mount, softer ones less. Andrew's wheel suggestion works on the 'm' side of the equation. Essentially, lighter wheels have less mass and result in less force. I'm guessing the (de)acceleration 'a' at the top of the stroke is HUGE. So, even small reductions in the weight of the wheel will have a large impact on the resulting forces.

You're correct the weight of the car is also at play. So, lowering the weight of the car will also lower the forces at work, but as we know, there aren’t very many options for reducing the weight of the car. Also, it's only a corner of the car that hits a hole - partial mass.

Softer tires (assuming the same weight as regular tires) absorb the initial force that is transferred into the suspension arm, thereby reducing the force that is carried to the top of the stroke.

I could easily be wrong at any of the above - it's been a while since I've had physics, but it seems reasonable. Bob, GM, and others can likely give a much better description while confirming or refuting my illustration. Although, Bob’s multi-phrase sentences reminding me a reading A. A. Milne’s original Winnie the Pooh.:)

I will say that if anyone wants to change out the wheels for aesthetics, feel free. We all need a pick-me-up these days.

[pvandersluis]

What do you guys think, I saw this on a Z8 tonight, looked great.

[macfly]

I should have a chance to go and see a 19" C21 HRE wheel this week, and take some better shots of it with the car. On the principal of lightness I still think it is the wheel I'd most likely go for, even though it isn't the best looking. More news as I get it.