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Street cars are nowhere near low enough for a diffuser to work. Bernoulli's principle is the explanation for the Venturi effect the diffuser is supposed to create. It doesn't.

The only trunk lid spoiler that can work on a street car is the lip type. Wings with supposedly effective slots are purely cosmetic. The trunk lid lip type spoiler is a variety of Gurney flap. It reduces drag by using turbulent air to mimic a teardrop body shape. Turbulent drag is higher than the form drag of the theoretical teardrop shape but skin friction is eliminated. The net result is a reduction of total drag. You also get a taller trunk and a much shorter car.

High performance tires are a waste of money on most North American roads because they never get hot enough to deliver the grip you're paying extra for. Ultra high performance all seasons are now the way to go unless you drive frequently on very twisty roads or track the car. I'd be interested to see the first cold stop performance of the Pilot Sport 4S against the A/S 3+.

Road cars rarely experience the second hard consecutive stop, let alone the 20th you really need to get your money's worth out of the top performing tires and brakes.
 

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Considering that most people use their Giulia as an everyday car, with occasional track days at most, I think this confirms that the CC brakes are a useless upgrade for 99.99% of owners out there.
For everyday people AR offers 44B option for Giulia - big brakes kit. 330 x 28 front, 320 x 22 rear ventilated vs 305 x 28 and 292 x 22 ventilated. I think in North America all 2.0 cars have this option.

QV has 360 x 350 brakes
https://www.brembo.com/en/company/news/alfa-romeo-giulia
 

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Fangio's probably apocryphal quip to his team mate when asked about the secret to faster lap times, in the very same car on the very same day.: less brakes, more accelerator.

There is no doubt the less heat you generate in your brakes and tires to deliver a given lap time the faster you are able to go. Not to mention overall race time if tire or brake wear or fade are relevant as they still are in racing.

For a road car a great deal of driving pleasure is available by seeking to drive as quickly as possible down a given road (including in "possible" the legal restrictions) while generating the lowest g forces when braking or cornering. Speed available to the usual road car on a public road is almost always limited by regulation, not the capability of the car. It's as well to remember that when deciding which car to buy and what performance options are really worthwhile. Counterintuitively, the less capable the car the more fun it can be to drive.

I am unable to resist generating maximum g forces when accelerating, however.
 

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Street cars are nowhere near low enough for a diffuser to work. Bernoulli's principle is the explanation for the Venturi effect the diffuser is supposed to create. It doesn't.

The only trunk lid spoiler that can work on a street car is the lip type. Wings with supposedly effective slots are purely cosmetic.

High performance tires are a waste of money on most North American roads because they never get hot enough to deliver the grip you're paying extra for. Ultra high performance all seasons are now the way to go unless you drive frequently on very twisty roads or track the car. I'd be interested to see the first cold stop performance of the Pilot Sport 4S against the A/S 3+.

Road cars rarely experience the second hard consecutive stop, let alone the 20th you really need to get your money's worth out of the top performing tires and brakes.
I am only speaking of the lip spoiler. Not wings.

Tires. Cost is not the only factor to look at. Stating "high Performance" tires are a waste of money is a very generalized statement. Yes, some expensive tires do just as well as lower priced tires or sometimes even worse. This is where research comes in. I do my research on tires and sometimes that research can fail. One thing for sure is I never let my tires get too worn. I am one for safety as well not just performance.

The Michelin PS4's that I purchased were no more expensive than a good all-season. I paid $947.00 for all 4 tires including shipping of around $65

If I went with: Michelin Pilot Sport A/S 3+ in the sizes I have, I would have paid $789.00 with shipping. A savings of $178.00
I have used the A/S 3 before. Fantastic tire. Any better than the 4S? Can't say yet.

I will try to find stopping distances for both cold stopping. I'd be interested too.

Again as mentioned. The tires, the rear lip spoiler, diffusers etc is all for the 10% of the time. On the track or at high speeds or on curvy roads etc... Don't worry, we won't go into lowering springs...that is clearly a waste of money and destroys cars suspension systems especially these giulias.


I like this guy, he does his research. There are more factors involved than just cost.
Why Expensive Tires Aren't Always Worth The Money - Digg
 

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Quick search.

Michelin A/S 3

113.9 feet to stop Dry/Cold, 60-0 (I believe) Source: https://www.motortrend.com/news/michelin-pilot-sport-as-3-tire-test-307753/

Michelin 4S
Averaged: 110.4 (62-0) Source: https://on-sitetires.com/blog/view/michelin-pilot-sport-4s-michelin-raises-the-bar-outdoes-themselves-again
60-0 might be less.

In this case maybe not a huge difference.

I do know that the A/S 3 that is slightly worn does not perform well in light snow or wet. Again there are other factors to tires besides just stopping distance and cost. I mean looks are at the top of the list!!! ;)

Anyway, back to the giro brakes or brakes in general. Don't want to side track John's original post.
 

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I am only speaking of the lip spoiler. Not wings.

Tires. Cost is not the only factor to look at. Stating "high Performance" tires are a waste of money is a very generalized statement. Yes, some expensive tires do just as well as lower priced tires or sometimes even worse. This is where research comes in. I do my research on tires and sometimes that research can fail. One thing for sure is I never let my tires get too worn. I am one for safety as well not just performance.

The Michelin PS4's that I purchased were no more expensive than a good all-season. I paid $947.00 for all 4 tires including shipping of around $65

If I went with: Michelin Pilot Sport A/S 3+ in the sizes I have, I would have paid $789.00 with shipping. A savings of $178.00
I have used the A/S 3 before. Fantastic tire. Any better than the 4S? Can't say yet.

I will try to find stopping distances for both cold stopping. I'd be interested too.

Again as mentioned. The tires, the rear lip spoiler, diffusers etc is all for the 10% of the time. On the track or at high speeds or on curvy roads etc... Don't worry, we won't go into lowering springs...that is clearly a waste of money and destroys cars suspension systems especially these giulias.


I like this guy, he does his research. There are more factors involved than just cost.
Why Expensive Tires Aren't Always Worth The Money - Digg
Ive been in 5 different oem/race car wind tunnels, 2 with rolling ground planes and operated one myself. Having developing bodywork and spoilers with the aid of CFD software that monitors, air speed, pressure and volume, I wouldn’t pay much attention to the opinion that spoilers , wings, diffuser are only cosmetic. It may have been true 35 yrs ago but certainly not today.

You be surprised how much attention is paid to airflow. From the onset the flow is managed on the car in nearly all aspects, through the ductings, radiators, suspension, wheel wells, underbody, exhaust all part of an aero system. Trip strips and divergence are disguised in side mirrors, pillars, head and taillights are designed to guide the airflow as well And this is only the minimal aero development on mundane vehicles yet alone performance vehicles.

And yes spoilers and diffuser do work not to the level for massive downforce as expected to a ground effects level but for axle balance and lift/drag reduction. Just ask the guys that slid down the autobahn on their rooftops on the gen 1 Audi TT. :). A simple lip spoiler appeared on all the cars shortly afterwards to cure the excessive lift. As for stand off wings... they are massively effective though may be a compromise in other areas for a street car. To suggest anything else is plain silly or misinformed
 

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Ive been in 5 different oem/race car wind tunnels, 2 with rolling ground planes and operated one myself. Having developing bodywork and spoilers with the aid of CFD software that monitors, air speed, pressure and volume, I wouldn’t pay much attention to the opinion that spoilers , wings, diffuser are only cosmetic. It may have been true 35 yrs ago but certainly not today.

You be surprised how much attention is paid to airflow. From the onset the flow is managed on the car in nearly all aspects, through the ductings, radiators, suspension, wheel wells, underbody, exhaust all part of an aero system. Trip strips and divergence are disguised in side mirrors, pillars, head and taillights are designed to guide the airflow as well And this is only the minimal aero development on mundane vehicles yet alone performance vehicles.

And yes spoilers and diffuser do work not to the level for massive downforce as expected to a ground effects level but for axle balance and lift/drag reduction. Just ask the guys that slid down the autobahn on their rooftops on the gen 1 Audi TT. :). A simple lip spoiler appeared on all the cars shortly afterwards to cure the excessive lift. As for stand off wings... they are massively effective though may be a compromise in other areas for a street car. To suggest anything else is plain silly or misinformed
Yup. My father was an aerospace engineer (General Dynamics/Convair -1955-1996), if the spoiler is done right it works, even low speeds, such as 50mph (not verbatim). I can't imagine AR spending all this money on R&D of spoilers, to diffusers to side skirt design in wind tunnels if it were just for looks. Whats the point of the small spoiler on the rear side next to the rear lamps? They made a big deal about this little, almost nothing piece of the aerodynamics.

Yes, I remember that Audi tt video. lol. I have seen a Merc. do the same thing around the same time.

Thanks for the comments.
 

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Cool, my neighbor in SD worked at convair too I think. He had old photos of the b58 hustler up in his home.
Very cool. My dad put up all the Atlas, Gemini, Titan rockets, worked on cruise missile, aircraft and space shuttle stuff. Worked for aerospace Corp in El segundo as well as Lockheed Martin, Martin and Airforce.

Guy in glasses was my pops, about 1962 here.
 

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I would advise you to check European tire tests. Do not follow their opinion but try to find the tire the best fit your climate and roads.
Tyre reviews, tests and ratings - Tyre Reviews
And if you do bear in mind that European versions of the same model of tire can be built differently for North America. Also, Goodyear are built by two different manufacturers for Europe and for North America due to brand name ownership being different in those two markets.
 

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And if you do bear in mind that European versions of the same model of tire can be built differently for North America. Also, Goodyear are built by two different manufacturers for Europe and for North America due to brand name ownership being different in those two markets.
Depends on model. Some tires are imported from Europe to North America (Good Year Eagle Sport from Turkey, Pirelli Ice Zero FR from Russia). Some models are specific for regions. Small research is always helpful.
 

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Ive been in 5 different oem/race car wind tunnels, 2 with rolling ground planes and operated one myself. Having developing bodywork and spoilers with the aid of CFD software that monitors, air speed, pressure and volume, I wouldn’t pay much attention to the opinion that spoilers , wings, diffuser are only cosmetic. It may have been true 35 yrs ago but certainly not today.

You be surprised how much attention is paid to airflow. From the onset the flow is managed on the car in nearly all aspects, through the ductings, radiators, suspension, wheel wells, underbody, exhaust all part of an aero system. Trip strips and divergence are disguised in side mirrors, pillars, head and taillights are designed to guide the airflow as well And this is only the minimal aero development on mundane vehicles yet alone performance vehicles.

And yes spoilers and diffuser do work not to the level for massive downforce as expected to a ground effects level but for axle balance and lift/drag reduction. Just ask the guys that slid down the autobahn on their rooftops on the gen 1 Audi TT. :). A simple lip spoiler appeared on all the cars shortly afterwards to cure the excessive lift. As for stand off wings... they are massively effective though may be a compromise in other areas for a street car. To suggest anything else is plain silly or misinformed
Not suggesting they don't work. I am saying they do not generate usable downforce under normal driving conditions. Also, unless ride height is very low a chin spoiler is not very effective. The chin spoiler can reduce airflow under the nose of the car by deflecting it up into the engine compartment and thereby improve engine cooling (you'll note the proliferation of below bumper radiator grilles and inlets made necessary by US bumper height regulation but also found to be very effective at directing flow through the radiator first before deflection under the car) but to generate usable downforce a chin spoiler has to basically touch the road at normal ride height. Very stiff springs are essential if meaningful ground effect downforce is being developed or the car can easily take off, literally, under suspension extension (rebound).

Road car aerodynamic appendages are either purely cosmetic, such as rear diffusers for example, or aids to fuel economy, such as trunk lid lip spoilers and front air dam types. Downforce? Not really.

Large wheels, ultra low profile tires and about 90% of aftermarket brakes are aesthetic, subjective additions to car ownership appreciation. Very little if any actual performance improvement is available.

That's why I remind the aftermarket enthusiast crowd that tires brake the car, brakes only brake the tires.
 

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Depends on model. Some tires are imported from Europe to North America (Good Year Eagle Sport from Turkey, Pirelli Ice Zero FR from Russia). Some models are specific for regions. Small research is always helpful.
And it is the Dunlop brand I was thinking of, not Goodyear. Pirelli is now a Chinese tire maker. Bridgestone also builds tires in Russia including versions of its Nokian brand which is no longer a Finnish tire company. And so on.
 

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Anyone have Drag (cd) for the Giulia ti?

Alfa only shows Drag Coefficient (cd) for Quad at 0.32

I find it interesting they only show that model.

I did find the Giulia AE (diesel coming next year to EU) which is lowered by 5mm compared to veloce models has a Drag Coefficient of 0.23.

So the question is, does the base models have better Drag than the Q with all the useless spoilers, diffusers, large wheels with wide tires, active front splitter and overall height lower than other models?? This could be telling...
 

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Not suggesting they don't work. I am saying they do not generate usable downforce under normal driving conditions. Also, unless ride height is very low a chin spoiler is not very effective. The chin spoiler can reduce airflow under the nose of the car by deflecting it up into the engine compartment and thereby improve engine cooling (you'll note the proliferation of below bumper radiator grilles and inlets made necessary by US bumper height regulation but also found to be very effective at directing flow through the radiator first before deflection under the car) but to generate usable downforce a chin spoiler has to basically touch the road at normal ride height. Very stiff springs are essential if meaningful ground effect downforce is being developed or the car can easily take off, literally, under suspension extension (rebound).

Road car aerodynamic appendages are either purely cosmetic, such as rear diffusers for example, or aids to fuel economy, such as trunk lid lip spoilers and front air dam types. Downforce? Not really.

Large wheels, ultra low profile tires and about 90% of aftermarket brakes are aesthetic, subjective additions to car ownership appreciation. Very little if any actual performance improvement is available.

That's why I remind the aftermarket enthusiast crowd that tires brake the car, brakes only brake the tires.
Of course there are exceptions, but in a nutshell,

No
No
and no

Larger wheel and ultralow profile tire do have significant performance gains but not without compromises that are well known

As for aftermarket I can’t speak for them all
 

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Of course there are exceptions, but in a nutshell,

No
No
and no

Larger wheel and ultralow profile tire do have significant performance gains but not without compromises that are well known

As for aftermarket I can’t speak for them all
I'm afraid you are mistaken. Road car spoilers are there to reduce drag and improve fuel economy. There is basically no way you can get downforce to operate on a road car, the roofline is too high. Nor would any car maker want to, the fuel economy penalty caused by any downforce generation would be far too high.

A trunk lid lip spoiler stalls the air passing over the trunk lid raising the boundary layer effect higher above the car body. SAAB achieved the same benefit by simply filling in the same area above the trunk lid with a hatchback in their so called Kombi coup. The total effect reduces drag. Station wagon and full hatchback bodystyles rarely show higher drag coefficients than sedan versions for this reason: drag goes up markedly when the boundary layer separates. This's why Porsche chopped their long tails off the Le Mans cars.

The modest change in lift over the rear of the car is merely an artifact of the primary objective of drag reduction. A "rear wing " type trunk spoiler just isn't. It cannot operate as a wing because the slot is too small. At useful speeds the slot simply stops airflow under the "wing". Which is why most often you see just the lip spoiler. Technically the ducktail spoiler on older 911 functions in the same manner as latter wing types. The wing is just more aesthetically pleasing. Except for those big gap wings such as Subaru put on their STI which in addition to blocking the rear view mirror and cresting a lot of turbulence in the wake of the car basically just look dumb and set fuel for no reason. For mature drivers you can get them taken off on delivery.

There are a number of articles in the public domain that conclusively show large wheels and extremely low profile tires do not deliver performance gains on road cars, there is a point of reversal of gain. This results from the suspension travel requirements for road cars. The same suspension travel that prevents any downforce from being generated. Too dangerous.

Just btw, the QV Giulia will have a higher drag coefficient because the frontal area is the same but total drag higher because of wider wheels and tires, among other effects. Those rear diffusers aren't and don't. They are 100% cosmetic.
 
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