19 inch Wheels

I have just fitted a set of 19 inch black GT3 style 10 spoke wheels to my black 2002 C4S apart from in my opinion looking really trick and going to save me so much time trying to keep them clean of brake dust!!! The main thing I have noticed is what an improvement it has made to the handling the car feels so much more planted now. I am lucky enough to live on the Isle of Man so don't have to worry about those pesky national speed limits so got chance today to give it a proper blast and was really surprised at how different it felt.

Worms, can, open... This is a highly debated topic, looks vs performance. Porsche and most respected tuners will recommend that you do NOT put 19" wheels on a 996. However, looks wise they fill the arches nicely. With regard to feeling more planted, might it have more to do with new tyres as I assume you had to get new tyres for the 19"s? New tyres and a good geo would have vastly improved your C4S's handling if it felt 'un-sure' in any way... just my $.02 btw, and :welcome: :useless:

yap... show us the picts.... :thumb: Stuart - Doesn't the 997 come with 19" option?

Will get the pics as soon as we get a nice sunny day think the met office said we were due one in March 2012 8). As for the tyres I did get new ones but the old ones still had 7 mm of tread and the geo was only done about a month ago on the previous wheels when I got the brakes and discs done. I must say I was surprised at the difference especially considering the quality of some of the roads on the Island!!

Absolutely, The 997 was supposed to be introduced with 18" tires & rims. After most of the development had been completed the MARKETING department requested that 19" wheels be standard equipment on the S. Engineering had to revise the suspension geometry to perform properly with the 19" wheel size. (quoted from Rennlist) see http://www.911uk.com/template.php?page=93 ) Have a read of this excellent post from Rennlist: "I'll admit they look cool, but there are reasons I'm not a fan. One, you have to run very short, rubber band, side walled tires... this puts more emphasis on the cars suspension, which will mean suspension settings will now be more important and bad settings less forgiving. Two, in order to keep from damaging the wheels with every bump and hole in the road the wheels have to be made very beefed up which means...lots of weight. Then there's the fact that the diameter is bigger and now the mass has moved farther away from the axis of the wheel. Here's some physics plagerism... Let's have a look at some basic calculations: Any object that has a mass and that moves at a velocity has a certain energy, which is coming directly from your motor. If you move a wheel at a certain speed (no rotation of the wheel ) the energy can be calculated using the following formula: E = ½ m v2 m being the mass and v being the velocity at which the wheel moves. Once the wheel turns, the total energy is made up from two components, namely the translational (moving) part and the rotational (turning) part. The new formula looks like this: E = ½ m v2 + ½ J w2 J being the Rotational Inertia and w being the Rotations per second. The rotational Inertia is made up of the mass of the object and the distance it is away from the rotating axis. Remember the flywheel effect: the further the mass is away from the axis, the more energy it takes to accelerate or brake it. If the mass is twice the distance away from the axis, it will require 4 times as much energy (or engine power) to accelerate and brake. Example : 0.1 kg (or approx 1 N) which is 20 mm away from the axis will have a Rotational moment of Inertia of 40. If you have the same weight 40 mm away from the axis the Moment of Inertia will be 160 (factor of 4). So how does this exercise look when applied to wheels? The weight of the wheels is not the only consideraton: what is much more important is the Rotational Inertia of the wheels, namely how much weight is close to the axle and how much weight is far away from the axle. How do wheels affect your handling? The lighter the wheels, the less your un-sprung mass. This means that your suspension has to work less to dampen the wheels. This will result in less energy and less power being consumed from the engine. It is more difficult to move or steer a rotating mass than a is stationary mass (try to move a spinning bicycle wheel ). If you reduce the mass and specifically the rotating inertia , the force required to move or steer the mass is reduced significantly. So logically, the only advantage to larger wheels is looks. Look at F1 cars... they run 13" wheels and huge sidewalled tires and still manage 5G's in the corners, although if they were given a choice I think they would increase their wheel size some to reduce that huge sidewall so as to decrease some tire deflection, but there is a point of diminishing returns...."

contemplating 19's on my turbo. I thought these looked great, (library pic, HRE's on a GT2)

Cheers Stuart! - Must admit though - those 19 look fab.

I agree :thumb:

Pics as promised

It dose look the bis all in black!

Hi, Just wondering what you did with the original wheels? I'm after a set of Carrera 5 spokes (8J front, 10J rear). Cheers.

I have got a set of Carrera 5 spokes for sale. In good condition with excellent tyres on them. All conti's. I went with a 19" option too as they look excellent. Just came off the track at Brand Hatch today too and I had absolutely no problems with handling. To the point where I out performed a Lotus Elise and another 911 C2. As for the science behind inertia and the like, totally over my head. In my opinion if you keep the same rolling radius as the original wheels tyres you haven't gained or lost anything besides better looks..! It seemed better handling to me today as when another 911 was snaking off Paddock Hill bend, I was planted to the road like s**t to a blanket. My 996 still feels as if the front wheels are floating in mid air when doing speed on a motorway in a straight line but on the track today they were solid. Shame I blew something else up in the engine instead as there's oil dripping down on the left of the engine if you down from the rear. I will post something else on that in a while to see if anyone has any ideas. For the moment though, whoever said not to put 19" rims on a 996 may well be correct in some scientific way but I didn't feel any worse for it today. and among the many other silver 911's up there mine seemed to stand out.

Hi GD I still have the wheels however they are the 18" Turbo type not the carrera 5 spoke, but I see from the next reply you might be in luck. Cheers

Ok I know you may have heard this and you sound like you know more than me be a long way but............. Center Gravity might be worth at leat a call??? Or don't I know a thing about what I'm talking about as is the norm?

Thing is, centre of gravity hasn't changed. Rolling radius is identical to the 17" wheels with 55 wall tyres. And that's as far as my extensive technical knowledge takes me (and that is borrowed!). I never could even set a timer on a video ! ! :floor: