Body kit creating downforce issues?

[Fish8]

Howdy all,

I have a 2000 C4 Cab and I'm looking to put on a body kit in order to change up the look a bit. I plan on adding a GT3 front bumper, GT3 rocker panels and a turbo rear bumper. A guy I know who races GT3S made mention that I should be careful about those changes due to the fact that it will change the aerodynamics of the car. He said the GT3 front bumper would add downforce to the front of the car and thus I should get a fixed rear spoiler to add additional downforce to the rear of the car. He said the turbo rear would help, but he would prefer if I got a rear spoiler.

My issue is that I not a huge fan of the look that a fixed rear spoiler would add to the Cab. If it were a coupe then it wouldn't be a problem...but since the lines on the cab are different I'm trying to forgo the rear spoiler. Ultimately, he thought the setup would be fine, but he said at some point I may want to consider adding a rear spoiler. I'm wondering if this is just a concern because he is used to taking these cars racing. For me, I use the 911 as a daily driver and while I may push it here and there...I don't think I put the pressures on it to the point that a fixed wing rear spoiler would make all that much of a difference compared to the factory one that comes up at 75 mph. Anyway, I'm hoping that I can get a larger data set before making this decision...so if you have any thoughts I would appreciate it. Thanks!

[deckman]

Porsche says if adding fixed spoiler to the rear you must add the appropriate front bumper to counter balance the new down force on the rear of the car. They say it's OK to add a bumper that introduces more down force to the front of the car without adding a fixed spoiler to the rear. So I think you're OK with what you want to do.

Where'd you get the new bumper?

[Fish8]

Deckman,

Huh...ok...well that is interesting and good to know. As I said...if my car was a coupe then I would have no problems with the rear spoiler...but since its a cab I don't think the lines work. I'm planning on getting all my parts from Better Bodies Motorsports.

Here is the GT3 front bumper and sides: http://www.betterbodiesmotorsport.com/inte...bodykits19.html

Here is the Turbo rear: http://www.betterbodiesmotorsport.com/inte...s1/996turbo.htm

Thanks for the info!

[LVDell]

You already have a rear spoiler that raises at speed. You can add the front with changing the rear but you should not add increased downforce to the rear without increasing the front. What you are doing is exactly what my CAB has and it feels great (and looks great).....GT3 front and sides.

[Fish8]

Cool...I appreciate hearing that! (And by that, I mean that someone has similar setup and is loving it). And your thinking was my thinking when it comes to the existing rear spoiler...but I think the guy racing GT3s is just used to running the car at a different level. Thanks for the response!

[LVDell]

Very welcome.

By the way, I can speak from experience as I have a GT3 as well that is a track whore :)

[deckman]

Is the front bumper you plan to add made of FG? If so I would think carefully about that if I were you. FG can easily crack if you scrape the bumper, which does happen with our cars. A urethane bumper will just get a little chewed up on the bottom.

[Fish8]

Deckman,

Yeah...I am aware of the issues that come with a fiberglass piece. I originally thought that the piece I was looking at was poly...but I was mistaken...it is fiberglass. So I'm back to the drawing board. I called a parts dept at Porsche to get some prices on factory stuff...and I'm going to call Mike over at MA Shaw and see what he can do. Thanks for the heads up!

-Joe

[deckman]

I just noticed you're in the Rockville area. So am I. Well I'm in the nether region between Gaithersburg, Rockville, and Potomac. If you see me around flash your lights. I'm in a 03 seal gray coupe with MD bay plates

[Fish8]

Deckman-

Good deal. I'll keep an eye out...and if you see a Korean guy in a blue cab looking like he should be pulled over for speeding..then that should be me :)

Also....I was speaking with Mike over at MA Shaw and he said that outside of the factory urethane bumpers, you should always get some sort of fiberglass bumper. He said the reason for that is they will keep much better shape as nobody (outside Porsche) uses the best molds and urethane to make their bumpers. Thus, he said aftermarket urethane bumpers are sloppy to fit and get mushy in heat. He said that his (and some others) have a good mix of fiber and flex resins that allow for some give in the bumper without breaking/cracking. Interesting eh?

-Joe

[deckman]

Now that is interesting. I've been investigating front bumpers for going on a year now and that is the very first time I've heard that about aftermarket urethane. Mike Shaw is a person I've never spoken to before but he would know this much better than me. I need to look into that further.

[Marc Gelefsky]

Deckman-

Good deal. I'll keep an eye out...and if you see a Korean guy in a blue cab looking like he should be pulled over for speeding..then that should be me :)

Also....I was speaking with Mike over at MA Shaw and he said that outside of the factory urethane bumpers, you should always get some sort of fiberglass bumper. He said the reason for that is they will keep much better shape as nobody (outside Porsche) uses the best molds and urethane to make their bumpers. Thus, he said aftermarket urethane bumpers are sloppy to fit and get mushy in heat. He said that his (and some others) have a good mix of fiber and flex resins that allow for some give in the bumper without breaking/cracking. Interesting eh?

-Joe

I just did the GT3 style Aerorkit II on my Coupe. Mike Shaw flat out told me I would not be happy with a fiberglass bumper so I used a factory Aero front bumper and side skirts with Mike's rear wing, The quality of MASHAWS rear wing is first rate.

[Fish8]

Marc,

Well that is interesting because when I was speaking with him last week, he gave me the the information I posted about fiber versus urethane. He said something along the lines of saying that the Porsche factory mold for the urethane bumpers is an $80,000 mold and the mold for others can be a $3,000 mold. He also said that his mix for his bumpers were good to the point that there was some flex if it were to be "bumped" Part of me feels that the answer you might tend to get depends on what is currently in stock.

-Joe