Autoblog

worst rims on an audi ever!

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Yep that seriously seems to be a whopping 45 mm on the front...I am no expert but then this just mess up the overall handling ....not much just a tad...tch ..;-)

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Totally agree ... looks like an automotive tumour.

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mxrz @ Aug 6th 2007 2:03AM
"Original 19" rims were replaced with larger but lighter 20s."
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That would mean something if wheels were sprung weight, but they’re not. In terms of performance, the smaller, yet heavier wheels are better

What are heavier wheels good for? Anchors maybe.

http://www.rqriley.com/suspensn.htm
About midway down the page.The Ratio of Sprung to Unsprung Weight

As the article states unsprung weight becomes even more important in lighter cars.

You want as light a wheel as possible while still maintaining strength. Looks are subjective, everyone has an opinion.

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You failed to comprehend what I was saying I'm afraid. You see, the majority of a wheel's weight is the drum, which is at the far edge of the center of rotation, and once the wheel starts spinning at a high rate, the lighter wheel actually becomes heavier... Why? Because it's larger. The smaller wheel's weight is closer to the center of rotation, and at a certain speed (well within everyday driving speeds), this difference is more significant in a negative way, than the lower weight of the larger wheel. They’re trying to make it sound like the lower weight compensates for the plus sizing, but it doesn’t.

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Comprehension is not an issue. The wheel weight reduction is not some mythical thing.

Wheel size change from 19 to 20 would result in an increase of 3.1416 inches of aluminum by the width of the rim, maybe 1/2 to 1 lb of aluminum about a 4% increase in weight. This increase would be at the outermost rotation of the rim. Hence your assumption.

The first thing to consider is the wheel is in fact lighter so I would assume that the weight gain is slight at the outer circumference. They do not reduce the wheel weight just in the hub and spoke area. If the wheel was the same weight or heavier I would agree with you.

What you failed to consider was the change in tire weight due to the shorter sidewall. For specific example: Goodyear Eagle F1 GS-D3, 245/40ZR19 weighs 28lbs, 245/35ZR20 weighs 26lbs the only difference other than the obvious 19 to 20 inch change is the 5 mill sidewall.

This would reduce the very outer rotating mass by 2lbs so to use your own argument against you......

The performance increase is not only the reduction in weight but the improved handling that results in the shorter and stiffer sidewall.

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Since you're bringing tires into this, why make assumptions? Audi uses Pilot Sport PS2, this joker tuner (clearly visible from the pictures), shod their wheels with PZero Nero. Audi's size is 235/35/19 front and 285/35/19 rear. This car has 235/30/20 front and 325/25/20 rear. If you calculate the weight, you're looking at 100lbs of rubber, in both cases. So, what exactly did I fail to consider in terms of tires?

Speaking of handling, the plus sizing concept is beneficial only to a certain point, anything smaller than a 35 series tire yields no real benefits, stiffer isn't always necessarily better, because you also get more straight line stability distortion and wandering... This is a street car, and road surfaces aren't perfect everywhere (understatement)... I'd agree with you if we'd be talking about going from 65/55 series tires to something like 40/35... Not 35 to 30~25, because 35 series tires from good brands like Bridgestone and Michelin are more than stiff enough for street cars... And since we know the specific brands, there is no improvement in handling, because going from Pilot Sport PS2 to PZero Nero is a downgrade.

Anyway, tires aside, my original argument still stands. A larger, wider (in the rear) drum, despite having a very slightly lower static mass, becomes heavier when centrifugal force is applied. The lower static mass is negated because the larger drum spins faster and it requires more energy to turn, brake and dampen… In the best case, the larger wheel only manages to match the smaller, heavier wheel in terms of performance… These are obviously 2 or 3pc forged wheels, but they’re not real mags, so the weight difference is probably a couple of pounds at best. Then there are the ride comfort issues, extra cost, etc…

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What you failed to consider about the tires is that as you increase rim size and maintain outer circumference you decrease weight. Which allows you to increase width as you yourself pointed out the tuner is using wider rear tires. They accomplished this without increasing the weight of the tire, good move. Wider tire better traction I am all for wider tires, I like the look. The tire choice is sometimes limited by the size. While the one tire was available for the stock rim it probably wasn't for the modified rim forcing them to change the tire. I am not going to check.

Stiffer sidewalls will happen in the decrease from the stock 35 to 30 and in the case of the rear from 35 to 25. This will always yield lateral improvements in handling, even if they are very small. While they make no sense in a Toyota Camry they work very well in performance car. Performance car, that to me has a meaning. The stability distortion and wandering you speak of is a wonderful feeling to me, I feel directly connected to the road. I like it. You have to pay constant attention it is called driving.

Going back to your recap.
"Anyway, tires aside, my original argument still stands. A larger, wider (in the rear) drum, despite having a very slightly lower static mass, becomes heavier when centrifugal force is applied. The lower static mass is negated because the larger drum spins faster and it requires more energy to turn, brake and dampen… In the best case, the larger wheel only manages to match the smaller, heavier wheel in terms of performance… These are obviously 2 or 3pc forged wheels, but they’re not real mags, so the weight difference is probably a couple of pounds at best. Then there are the ride comfort issues, extra cost, etc…"

The fronts add no weight to the entire rotating mass it is a wash because the tires are lighter. The new fronts do provide better handling and feedback. Even if the feeling (which is subjective) is something you don't like. The new rears provide over 1-1/2 inches of more width which even though the compound is not as good it will provide more grip. The rear wheels, well we can go round and round about it but until we weight each piece of each wheel separately we will never have an answer.

I take exception to comfort and cost issues when this is obviously a performance car. When you are in the performance class comfort and cost go out the window. Once again, subjective but a tuner would only be going for performance not comfort and certainly not cost. I personally don't like what this tuner has done as far as looks. I do however respect what they were trying to accomplish, an increase overall grip and handling.

You can have the last word if you want it but I am done.

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Unfortunately, all your arguments are based on theories… Weight saving with wheels, great, but only when the wheel diameter is identical or actually smaller (why do you think most people that auto-x their ride, use 17” or 18” wheels?). Wheel plus sizing, again, a valid concept, but not when your original wheel is already 19” big with 35 series tires... Tell me, how do you know the rear wheels provide more grip if the compound is inferior? Just another assumption? What’s your logic there? And why would you want more grip in the rear, if the car is not RWD, it’s AWD. Sure it’s slightly rear biased, but it’s matched by the 235 front / 285 rear original spec tires, increasing the contact patch in the rear further, also increases understeer. This is common on quattro cars, my Audi A4 is the same, and I have even more rear bias, and a true LSD in the back… We haven’t even touched on the issue of the chassis being designed with specific ride height and wheel size parameters… If you lower/stiffen the ride and mount bigger wheels with supposedly stiffer tires, you also have to increase the rigidity of the suspension components, like control arms, the whole axel area, in the camber direction must be much more robust, in order for the wheel/height modification to “improve” handling and not fail prematurely. Was any of that done by Kicherer?

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