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Cutting/Removing Plastic Fender Liner

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3-5 Years
Southern California
As I begin my journey of gutting this car as I work toward my TT2/ST2 goal, I've fallen down a rabbit hole which hopefully someone can pull me out of. It seems the Mustang GT4 race car has, at least partially, cut out the plastic fender liners leaving only the rear section, as shown here:

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Has anyone else cut their fender liners like this or are you guys removing them outright? If you have pulled them out entirely, are you adding additional venting to offset the additional air flowing into the wheel well?
 

carver

breaker of wrenches
445
598
ontario
As I begin my journey of gutting this car as I work toward my TT2/ST2 goal, I've fallen down a rabbit hole which hopefully someone can pull me out of. It seems the Mustang GT4 race car has, at least partially, cut out the plastic fender liners leaving only the rear section, as shown here:

View attachment 71096

Has anyone else cut their fender liners like this or are you guys removing them outright? If you have pulled them out entirely, are you adding additional venting to offset the additional air flowing into the wheel well?
I removed the rears on my Boss (s197) cause they tend to collect lots of road grit, sand and gravel etc. in behind. Some guys say the noise will be annoying but there is little change that Ive noticed. I also cleaned then painted the wells black. (not pictured)

ratfur2.jpg

I also cut away part of the fronts for increased air flow to my brake cooling air deflectors.

bossvent.jpgbossvent2.jpgbossducts.jpg
 

Fabman

Dances with Racecars
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Pleasanton: 1/2 way between Sonoma and Laguna Seca
if you remove them completely, it will allow air to be trapped in the rear of the fender and door area. Cars that have them removed also have vents to prevent that, /i think @Fabman has done that.

Meanwhile, somewhere in China…..

IMG_3006.jpeg
 
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Fabman

Dances with Racecars
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We fabricated some close out panels to direct air to the vents and avoid the pocket below them. It also prevents trash from collecting.

IMG_3377.jpegIMG_3376.jpeg
 
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Fabman

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Pleasanton: 1/2 way between Sonoma and Laguna Seca

Fabman

Dances with Racecars
6,519
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Exp. Type
W2W Racing
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20+ Years
Pleasanton: 1/2 way between Sonoma and Laguna Seca
Well big thanks to @Albino500 and you as well Sal. Anyone needing anything on this forum is sitting on a gold mine of information at their finger tips.
Lots of knowledgeable folks here, I've learned a ton since joining waaaay back when.
When I first signed up I had long been a seasoned race driver and car builder but I knew nothing about Mustangs or road racing.
Between Kevin Patten and TMO I've received quite the education and have been able to add new information with my experience in stock cars to develop a fairly successful road racing program.
Still learning today, and for me, that's the fun part.
 
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Colorado Springs
Any images ? My front inside is hitting the tires at full lock and I consider trimming them don't know why they are not stuck to the inside wall but are hanging though maybe a clip broke somewhere. But it's starting to become annoying and want to fix.
I removed mine in the front. I don't see how anyone with a "track" Mustang could keep them. They make tire fitment more difficult, it's like 4lbs on the front of the car, and it most importantly they cover up a large portion of the sides of the engine. If you have to remove them, and at some point you will, they are highly annoyingly difficult to fully remove. Not something you want to be doing at the track.
They also make taking off the splash guard more difficult. Though I kept the splash guard, I reinstalled it with the 7mm screws only, no clips. It doesn't need to be secured by both screws *and* clips, and there's zero chance I'm dealing with a single clip while I'm in the pits at the track.

The only advantage the fender liners could possibly be provide for a track car is in aerodynamics - however with fender cutouts (which apparently I'll be the first ever to do on an S550) and/or fender vents, you can ensure high pressure air does not get trapped in the wheel well creating positive lift on the front of the car.

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Wasn't aware that they are so different for standard S550 and the Shelby variants as I have 0 rubbing issues even with 305's and over 3 degrees of camber which should really push the inside of the tire towards the wheel well liners. Where are you seeing the rubbing and what tire/wheel setup is causing the issue?

Also plenty of vented and reliefed fenders on S550 cars out there. Race louvers even makes S550 specific vents for this purpose both behind the wheels and over the wheel arch top.

 
Yes, but no fender cutouts. Very strange!
Are you calling a relief like this deeply contoured GT3RS as a "fender cutout" ? If so it's probably because this typically isn't done on a standard width car without also extending the relief into the door as you see on the GT3RS to create a smooth opening as opposed to a steep ramp. The GT3RS even does the same in the rear as well, but note that they've gone one step further and have put airflow guides in line with the actual wheel to probably prevent swirling turbulence on the backside of the tire and eliminating the effect they are trying to achieve. Also love that they implemented the rear uprights almost straight off of the Weissach Package on the 918 Spyder.

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I almost exclusively see this on wider than standard cars like this modded S2000 where there's a significant portion of the tire protruding past the natural bodyline. Not that this particular car is the ideal use case, but just one I quickly found to demonstrate. As mentioned above though I'd be curious to see the actual airflow around the backside of these tires to see how much air is actually escaping and how much of that exposed tire is just generating turbulence. I'm sure Porsche didn't just put those uprights there just for looks.
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OK, but again to my point, those are all drastically widened fenders with most if not all of the tires outside of the factory body lines. Not sure you'll get the same results from stock fenders without doing something like the GT3RS and continuing the relief into the door. I think that's why you don't see it on stock fendered S550's vs the vented options that Race Louvers offer and like what Fabman posted above. Good luck though.
 
343
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Under 3 Years
Bulgaria
Wasn't aware that they are so different for standard S550 and the Shelby variants as I have 0 rubbing issues even with 305's and over 3 degrees of camber which should really push the inside of the tire towards the wheel well liners. Where are you seeing the rubbing and what tire/wheel setup is causing the issue?

With -3.2 degrees of camber (probably could go with less camber. On a full lock the front of my 305 tires is hitting the fender liner on the inside of the car next to the body. It's very minor so nothing I can't just cut though without fully removing the fender liner.
 

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