Explain these fenders to me

[widebody911]

I'll be buying a set of fiberglass front fenders in the near future, and I've seen these in the catalogs, but I don't fully understand the application. Do these require the use of wider front wheels? Do they mate up with a normal 930/965 front bumpers, or do you need a wider bumper?

[doozer]

Should be able to go 11's and 14's on wheels

The front and rear bumpers are wider than turbo.

[Jack Olsen]

Isn't that the 3.0 RSR configuration? 11-inches in front, and what, 13 in back?

My guess would be the drag coefficient would be terrible, and that the holes in the back are to help with brake cooling. Time for a turbo, with that.

[67nin11]

get a GT-racing catalog it will explain you questions. and it has pic's too!

[doozer]

Kinesis Booth SEMA2003





..

[Lukesportsman]

Are we using drag coefficient here in generic terms for overall drag? I know you, Jack, have often made light of your own cars cd but is it the cd that changes so radically or the resultant overall drag? I'm trying to ask is it due to the cd mostly or the fact that the frontal area has grown by such a percentage?

Obviously they both play a factor here, just curious what the biggest issue is. Obviously some air management items are necessary: air dams increase frontal area and wings result in added drag usually.

[Lukesportsman]

I don't/didn't mean to imply that you were using it incorrecly, Jack. I know you know what your talking about, just didn't know how literal you were being.

[Oldporsche]

I believe that if you look at some "middle" rsr cars and 934's with "clip ons" you will see roughly the dimensions you are looking at.

Hope you got the HP to pull those things.

David Duffield

[Jack Olsen]

Originally posted by Lukesportsman
I don't/didn't mean to imply that you were using it incorrecly, Jack. I know you know what your talking about, just didn't know how literal you were being.

Safe to say that I was using it incorrectly (meaning 'the drag would be terrible').

I'm a fiction writer, fer gosh sakes.

Without hijacking the thread, can someone explain what the 'coefficient of' part of the expression means?

[Lukesportsman]

cd * frontal area =realized drag

It is a factor used to determine/relate shapes to a standard ( a standard that escapes me at this point in the evening back East). Its those Physic types that love the term that seems to give a factor of "x" to represent a more complex hidden equation. Coefficient of friction, expansion, drag, etc.

[widebody911]

It wasn't obvious to me from the other pix how much wider the fenders and bumpers were over stock, but the SEMA pic makes it very clear - thanks!

[Tyson Schmidt]

Think of it this way Jack. A 747, and a 1/32 scale model of a 747 have an identical drag coefficient. But which one is going to require more energy to push through the air? The full size 747 of course.

The reason is frontal area. The overall drag is terrible in the real 747 because it's calculated by multiplying frontal area times drag coefficient.

Think of a Superbike. They have cd's in the .85 range. Terrible. But their frontal area is so small that they have less overall drag than a car.

In your case Jack, the flares not only increase the cd, but also the frontal area. Gotta love those lose/lose situations, eh?

[Tyson Schmidt]

BTW, the reliefs behind the front and rear wheel arch help reduce drag by relieving the high pressure are in the wheel well. It probably helps with lift as well, in the front. And I'm sure it helps move air through the oil cooler and brakes too.

[Porschekid962]

jack if your really interested i have a great book about suspension that dabbles in aerodynamics. i can get you the name if you wish to read up on it. im sure your butt timer at the track is working quite well though as i dont as much time as you do.

tyson, how ya been, im gonna join the 4door club soon.....