Wheel well aero and where the wheel face sits - WARNING BRICK SHAPED CAR INSIDE

[johnunit]

A modification on the medium-term list for my 1985 Ford Crown Victoria is wider wheels and tires, particularly in the back. This is for handling and grip at launch (need a bit more HP before grip is an issue... planning ahead).

They are currently 205/70/15, though stock is 215/70/15 and I may revert to that if I need new tires before I can afford wider wheels and performance tires. Gearing is not an issue, 2.73 rear gears and a 0.67 overdrive, peak torque somewhere just south of 3000rpm.


While obviously fuel economy isn't top priority with this car, any free highway mileage is nice. All-time best of 23mpg on the highway.



Here's the primary question:
Do you think there are noteworthy gains to be had by pushing the face of the wheel out closer to the bodywork? I'd probably be widening the wheels by 1-2 inches, so let's say I'm moving the face of the wheels outwards 1.5 inches. I will likely be keeping the wheel caps (which you'll notice poke out a good bit in the center). I may also run spacers to push the wheels out further.

To my eyes it looks like the air hitting the inner fender behind the wheels is a HUGE aerodynamic issue.



Here's a few pics of what I've got now. Note that in the underground pics the wheel is turned slightly to the right.














Pardon the uglyness, these are the day I put it on the road after the winter, dirty as hell






Here is an identical car with one inch wider rims (so theoretically .5 inches closer to the edge of the bodywork)








I'm not sure of the rim width or offset, but this is a similar relation in the rear to what I'd like to end up with in terms of looks/performance:
(sorry, can't post the pics direct, but they're in the first post of the thread below)

My 85 Merc 2-Door Slicktop (says mine, not actually mine)


Thoughts? Worth it? Miniscule? Negative impact? It's getting wider tires either way, but I have probably 2 inches leeway as far as track width.

[TurnpikeCruiser]

You could always put fender skirts on the rear, like my Marquis had a couple years ago. Of course, it would be of better benefit to use full-length skirts unlike my half ones.

Oh, and Howdy from MrMarquis (GMN).

[johnunit]

haha hey mang!

Fender skirts are possible, but I'm not sure if I could cram the 265-285ish width rubber behind them, and of course it's an extra expense. Are they still sold new anywhere?

[Superturnier]

How about (also) lowering it?

[Sven7]

Wider wheels probably aren't going to make much of a difference either way. Lowering would make it more fun to drive and look at, as well as counteracting the (nominal) extra frontal area of the wider tires.

What style are you going for? If you wanted to do slot mags, the skirts would look terrible. If you're doing a grandpa car sleeper thing though, by all means skirt it. Also think about a trunk spoiler to push the airflow back up where it should be. Tuft test the car and see where the problems appear to be.

No matter what it would probably help to do a full belly pan.

[johnunit]

Originally Posted by Sven7

Wider wheels probably aren't going to make much of a difference either way. Lowering would make it more fun to drive and look at, as well as counteracting the (nominal) extra frontal area of the wider tires.

What style are you going for? If you wanted to do slot mags, the skirts would look terrible. If you're doing a grandpa car sleeper thing though, by all means skirt it. Also think about a trunk spoiler to push the airflow back up where it should be. Tuft test the car and see where the problems appear to be.

No matter what it would probably help to do a full belly pan.

I'm guessing you're thinking the frontal area increase from wider tires would cancel out any aero improvement on the side of the car? I'm sort of looking at the increased frontal area as a lost cause. Once it goes 6.7+L (probably 408CI, maybe 427) and Trick Flow 205CC heads, wider tires won't be optional. It's more a question of whether it's worth going out of my way to get the outer surface of the wheel in a certain place to gain some of the efficiency back.


I will probably lower it mildly, but I like the whole "potholes can suck it" feel of this car, in terms of harshness and durability, so it wouldn't be more than an inch or so. It spends a good amount of it's life bombing around city streets comparable to Chicago or Philly with 3 or 4 guys in it.


I'm going as close to stock looking as possible. Wider diameter tailpipes and wider tires will likely be the only visual difference. I want it to look like what I've dubbed "plausible Stock." Something Ford could have conceivably built in small numbers. A special subtly hotted up model that the guys at the car shows "just haven't heard of before." If I can find wheel skirts I like, that's certainly something I'll look at. But for something that'll get MAYBE 3500 miles a year on the highway, it's probably going to be hard to justify the cost of buying and painting skirts for no gain other than highway FE.

I'm trying to visualise what a spoiler might look like on the car. Maybe something like a steeper version of a Grand National? I want it to look like what I've dubbed "plausible Stock." Something Ford could have conceivably built in small numbers. A special subtly hotted up model that the guys at the car shows "just haven't heard of before."



A bellypan of some sort will happen. I'm not sure about between the axles, but front and rear for sure. A big priority is bridging the gap between where the trunk pan ends and the rear bumper begins, there seems to be room for pretty much the entire height of the bumper support to be caught by the air travelling under the car.

I've even considering finding a way to temporarily mount plexiglass to the front, starting at the front of the bumper and ending above the headlights and grill, for better aero on roadtrips.

[Sven7]

First of all I'd be careful using plexi underneath the car in case it cracks. Maybe use some moderately deformable plastic like acrylic. And you can't lose with coroplast. I drove for months with the coroplast belly pan and haven't seen any damage. And it's cheap!

For the wheel thing, I was saying that lowering the car would more than make up for the increased area of the wider tires because lowering it decreases frontal area. The car's body curves in so much that I don't think any wheel fitment is really going to benefit you (unless you ran 20* positive camber with 18" flat face wheels). You'll always have the tires poking out the bottom and tucking in up top. For a car with flat sides like a kei car it might be worth the money/effort. For a pre-90's American car I really wouldn't even bother. Put your effort toward belly pans.

The spoiler was an idea. I don't know whether you could pull it off or even find one for that matter. It probably will look weird, that coming from a guy who likes the look of Wartburgs.

The "plausible stock" thing is what VW guys call "OEM+"- it looks stock, but with a few tasteful improvements. I'm not sure if other people use that term but it might help explain it at least with VW people

[TurnpikeCruiser]

John, fenderskirtdepot.com still sells the fender skirts for these cars, but I think they're close to $200 now...and again, it's only the half skirt, so aerodynamics could still be improved. I'd like to see cruiser skirts tried, the ones that go back to the bumper like the cars from the late 50s had, as that would provide the smoothest transition and could probably be incorporated into part of an underbody pan.

[johnunit]

Originally Posted by Sven7

First of all I'd be careful using plexi underneath the car in case it cracks. Maybe use some moderately deformable plastic like acrylic. And you can't lose with coroplast. I drove for months with the coroplast belly pan and haven't seen any damage. And it's cheap!

Interesting, I hadn't thought about the shattering risk. Very good point.

For the wheel thing, I was saying that lowering the car would more than make up for the increased area of the wider tires because lowering it decreases frontal area. The car's body curves in so much that I don't think any wheel fitment is really going to benefit you (unless you ran 20* positive camber with 18" flat face wheels). You'll always have the tires poking out the bottom and tucking in up top. For a car with flat sides like a kei car it might be worth the money/effort. For a pre-90's American car I really wouldn't even bother. Put your effort toward belly pans.

Looking at my car again, I see your point. "filling in" the top of the fender well is always going to result in sticking out more at the bottom. That's probably the answer to the original topic of the thread right there.

The spoiler was an idea. I don't know whether you could pull it off or even find one for that matter. It probably will look weird, that coming from a guy who likes the look of Wartburgs.

There are no contoured/fitted wings or spoilers of any sort available for "Box" era Panther chassis cars that I'm aware of. I'm not sure whether you could come up with one that could look decent and have any positive effect either. It's something to play with if and when the car gets a full repaint, I suppose. At that point I'd mock up a few different looks out of sheet metal. Getting the lines right with the looong overhang and the angle the trunk slopes down at would probably be a pravneet though.

The "plausible stock" thing is what VW guys call "OEM+"- it looks stock, but with a few tasteful improvements. I'm not sure if other people use that term but it might help explain it at least with VW people

Interesting. I might start using that term.

[johnunit]

Originally Posted by TurnpikeCruiser

John, fenderskirtdepot.com still sells the fender skirts for these cars, but I think they're close to $200 now...and again, it's only the half skirt, so aerodynamics could still be improved. I'd like to see cruiser skirts tried, the ones that go back to the bumper like the cars from the late 50s had, as that would provide the smoothest transition and could probably be incorporated into part of an underbody pan.

Looking at their site, it's 140 unpainted. So shipping and professional painting... somewhere under 400? Not worth it in the near future but maybe worth a try later. Once they're prepped and primed it's not like I couldn't re-sell them. If I was feeling really adventurous maybe I could see about extending them down further.