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High speed front end lift

K4fxd

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I've got some pretty bad front lift at speeds above 100. The last 10 MPH or so in the quarter are a bit on the loose side. The front lifts high enough to mess with the toe and the car wants to wonder side to side.

Any recommendations for a fix?

Wondering about a splitter? or???

17 non PP GT, has factory K brace top and bottom and Steeda rear chassis braces. Stock springs and struts.

Thanks.
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K4fxd

K4fxd

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It's rock solid till 100 MPH or so. Then it gets worse the faster I go. When I lift off at the end of the run it gets good again.

I do need to check the alignment but it feels like it is fine. At least at highway cruising speeds which are 90 + here. I know I know but I do stay with prevailing traffic.
 
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K4fxd

K4fxd

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Car is fairly new to me so cannot answer. It was unstable in high speed sweepers, reason for the braces.

It is tail happy, likes to kick the rear out. Almost as bad as my Sunbeam Tiger that I had until a couple of years ago.

I should probably get it aligned before I start trying to "fix" it.
 

Eritas

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I've gone 130+ on track and never felt those issues. :inspect:
 

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Bluemustang

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Front end lift exists and is the bigger issue on this car. A splitter and mounting it with rods connected to crash bar would be effective. Supposedly the ZL1 addons splitter extension works pretty well and doesn't cover up the brake cooling channels.
 
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K4fxd

K4fxd

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Looks like the "ZL1" splitter is for a Camaro.
 

BluePonyGT

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I have a '17 GT Premium - not a performance pack car from the factory.

At the time of this "test" I had stock ride height, no splitter additions and no spoiler.

Because it was NOT a PP car I added ford performance frame stiffening in the front and IRS support and alignment system from Steeda in the rear with some subframe connectors in order to provide some better stability and better handling after getting the car. To be honest the handling initially was plain awful without some changes here and there.

No brake upgrades. No engine changes or upgrades from the factory.

I changed the wheels/tires from 18" stock rims and the Pirelli 235 50R18's to this: 19" x 10" rims in the front - 285 35R19 and 19" x 11" rims in the rear - 325 30 R19 - Michelin Pilot Sport 4S in all 4 corners.

Conditions: cold air (approx 45 degrees F), very low wind, cloudless day with no precipitation on a straight-away with the tires plenty warm.

I noticed the car start to get unstable around 100-110 mph with very minimal headwind. By that I mean I felt like I was loosing grip to the road on the front. It did feel worse on acceleration - car would squat and the front would lift. I did NOT feel like the car would "take off" or the rear of the car lift up, but I definitely had to work harder to drive the car.

At 125-135 I didn't feel comfortable holding that speed for very long, and I would have to slow down a bit if I had to keep a line around a curve.

By the way I have my stock wheel bearings and they're just fine - I actually checked them for play last week.

So with all of that in mind I would not be surprised if there was a strong headwind, with lower pressure and higher precipitation in the air to experience this worse even at lower speeds for a stock GT from the factory.

In the end this convinced me that if I ever wanted to track this car even for fun I'd have a lot of work to do in order to improve the handling and performance.
 

Roadway 5.0

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If you plan on running at high speeds for long distances, consider more toe-in on the front tires; 0.1 for each wheel isn’t absurd at all.

I built my car for the Autobahns in Germany while I was there for a few years. It doesn’t take much to really get the car good at speed. The stock PP did well up to 120, but hood lift and flutter were bad. Sealing the gap above the headlights is proven, at least for 15-17 models. I added a front splitter, springs, dampers, and the roll-center correction/bumpsteer kit (my car is lowered 1.125”F/0.5”R. 120 became very comfortable to cruise at, and wielded a dramatic increase in handling curves at these speeds. 150ish was the max I hit even on long straights all out...the aero was wonky here, but up to this point it was golden.
 

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dn1984

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Hood lift is real on the 15-17s. I put some foam weatherstripping to seal the gap between my hood and headlights. For $10 it helped; kept the hood from fluttering as much too.
interesting. pics?
 

dn1984

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i had the boss street splitter and lower fascia and was lowered on h&r supersports on my old 2012 and it was night and day better than stock ride height with stock lower fascia at high speeds 160+mph
 
 




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