M3hunter

My '11 GT has manual transmission with the 3.73 gear, lowered with Steeda Sport springs, KONI STRT, squared 275/40R19 Michelin PSS mounted on Brembo pkg. 19X9 wheels. I already measured the rear and is almost 2" at both sides, the lowering did not affected is centered.

When I power shift the car, the rear of the GT jumps to the right (I think this happens when 2nd. gear goes in hard).
Any idea what might be causing this to happen? I think that I noticed this since my '11 GT was new before the mods.

Also I'm curious, twice I have gone head to head with different newer 5.0 with 420hp compared to mine (412hp), and in both occasion, they left me behind by one car distance. Is it really an advantage to have 8 hp more?

Norm Peterson

I have a suspicion that axle roll steer may be involved. Lowering without relo brackets and LCA inclination adjustment results in significantly more axle steer than OE, and when the car briefly "un-squats" during the upshift it will "un-steer" slightly as well. You'd have been compensating for this steer in 1st gear, but the sudden loss of some axle steer will catch you with too much steering wheel input to the left with an axle that suddenly wants to run less to the left (which will then feel like it steered a little to the right).


Norm

howarmat

Norm explains most of it. Its common especially if you haven't brought the rear back in line.


As for the 9 HP difference. there is a lot more than just that number to consider. full tank vs empty gas, driver experience etc.

UPRSharad

If you haven't already upgraded the rear control arms, they definitely make a nice improvement, and I can give you a great deal on UPR control arms.

http://www.uprproducts.com/mustang-c...ushing-05.html

However, I'd like to point out that a lot of times people put steering input into the wheel even when they don't realize it. What I'd like you to do is take the car out and powershift 2nd, 3rd, and 4th WITHOUT your left hand on the steering wheel. If it still moves, it's your rear suspension and I will hook you up!

M3hunter

I already tried twice, without touching the steering wheel and when I power shift to 2nd. on my 3.73, the Mustang always go to the right.

jpplaw

They squat more in the right rear under power because of the torque. That's why low dollar drag cars use an air bag in the right rear spring to pre-load that corner, and the high dollar cars use the massive anti roll bars. Without that, the rear will always skate to the right in a burn out and try to go to the right on a hard launch. But neither of those options would be good for a car that runs twisties.

UPRSharad

I don't know. That's strange. My 2011 doesn't do that.

M3hunter

I don't go to the 1/4 mile straight line racing just some track and spirited driving , my car is lowered with STEEDA sport springs, I believe is 1 in. front & about 1.25 in. rear. Mine has std. Transmission with the 3.73 gear, no engine mods. Do you think I will need the relocating brackets or just with the lca is sufficient?

Norm Peterson

LCAs with firmer bushings or sphericals of some sort will tame however much axle steer effects are due to bushing compliance and make it slightly more predictable. I'd be inclined to drop the LCA attachments by about the same amount as the rear is lowered, just to retain the mild OE-ish amount of axle roll steer. You'll also pick up a significant amount of antisquat, but I'm looking at that as being a pleasant side effect rather than the main reason for relocating the pivots in your case (I imagine that nearly all of your hard acceleration is going to be happening in 3rd gear and higher).

For autocross, you can live with (and probably benefit from) a lower and more aggressive LCA relocating effort. Speeds are lower and risks much lower there.


Norm

UPRSharad

You don't NEED LCA Relos with a 1" drop. People often use them, and that's fine. But like Norm said- If I were adding LCA Relo brackets, I would keep the LCA angle close to stock after the drop. UPR makes the strongest brackets on the market, with three positions for adjustment. http://www.uprproducts.com/mustang-l...et-kit-05.html