Does Lowering the Car Change the Pinion Angle or Anything Else Back There??

[ShelbyGT5HUN]

My 2010 GT500 is currently lowered with Eibach springs (never liked ANY of my cars that ran Eibachs, but the car came this way). Also has LCAs and adj. panhard bar. Car was aligned with a 0* thrust angle. Eyeballing the rear tires, they are centered nicely in the fenders. I get no wheel hop in any situation, it either hooks if I GRANDMA-BABY it, or will RRRRRRRROAST the tires off with no regrets.


Car has NO traction in 1st and 2nd gear on only a pulley an tune. Running 20" stock width Invos. In third it will sometimes haze the tires starting at 80mph, if you roll into the throttle. Under 50F, forget traction until 4th. I can understand the car makes power, but what I can't understand is how little traction there is. Should this car hook better than it does?

So all this is leading me to ask the question does lowering the car change the pinion angle, or some other rear end geometry that screws up how the car hooks? I know from another project car of mine, the pinion angle made a big difference in if the car hooked up or not. Change it one way, it "bit" the road more, turned the other way, the car felt like it was on ice, and would just lay rubber.

Would I benefit from an adjustable upper control arm, or something else to help the car bite? Please no drag radial or Viking shocks suggestions, yet :burnout:trying to keep it streetable.

I know the Eibachs are the worst thing you can put back there, and I do have the stock springs in a box. I get the feeling that Eibach designs these springs with no thought other than "make the car lower", and never tests their product on the cars the springs were designed for, and I feel you can actually make the car handle/hook up WORSE by using their product. Yeah, it looks good, and changes the stance but I feel like there is zero compliance (over bumps) back there, AND it messed up the whole geometry of the car. I've read posts from other members here who have 100+ more rwhp than me, and on similar tires, they "dead hook 2nd", or "hook good from a dig". It's almost comical how little this car hooks.

Thanks!

 

[Catmonkey]

Lowering changes the instant center. Relocation brackets will help some. Your pinion angle is likely off too, but that's not going to impact your traction situation. What tires are you running and how old are they?

 

[SCGallo2]

Yes, lowering the rear suspension changes your pinion angle and affects how your LCAs respond (squat) under hard acceleration. Without LCA relocation brackets, I suspect your LCAs are angled upwards towards the rear of the car. At a minimum, your LCAs should be parallel to the ground with your suspension loaded. For more straight-line traction, your LCAs should be angled slightly downwards towards the rear of the car which adds anti-squat and plants the weight of the car on your rear wheels. For reference, my rear LCA mounting points on the axle assembly are about one inch closer to the ground than the forward LCA mounting points on the body. Relocation brackets will correct the rear suspension geometry, but spring rate and shocks also play an important role in putting the power down. With a full poly bushing rear suspension, my pinion angle is set at -2.0 via an adjustable UCA. My combo works extremely well at my power level and is pretty unique utilizing H&R, BMR, and Maximum Motorsports components. My suspension was not thrown together with a prayer that it would work… I did lots of research and it paid off.

 

[ShelbyGT5HUN]

SC thanks for the tip.

I checked tonight, and my LCAs point at least an inch to 1.5" HIGHER in the back, compared to the front, just as you said. This is starting to make a little sense now as to why this car has NO traction. It has always felt like not enough weight was getting transferred to the rear tires, and that it would probably hook a lot better with 300 pounds of sand in the back, no joke. I am going to look into relocation brackets. Previous owner installed aftermarket LCAs and BMR adjustable panhard bar. I think the brackets will help a lot. To get the angle my LCAs are now, as the car sits parked, they are probably like yours under full launch. That's why I'm spinning third, with a pulley and tune, at 80mph!


What do you recommend for springs and shocks? I like cruising fast on the open highway, and accelerating hard from a dig, but would value handling curves as more important than all out optimization for drag use.

 

[Catmonkey]

I'd check out the new line of springs BMR came out with. I like my Koni sports.

 

[ShelbyGT5HUN]

What tires are you running and how old are they?

I have Nitto Invos on 20x10 rims at 28psi. Traction has been a problem even when new. They are 3 yrs old.

 

[Catmonkey]

Have you tried more air pressure? 28 psi is low for a radial tire. You need relocation brackets, but I'd experiment with air pressure.

 

[SCGallo2]

What do you recommend for springs and shocks? I like cruising fast on the open highway, and accelerating hard from a dig, but would value handling curves as more important than all out optimization for drag use.

I am not a fan of aggressive lowering, and I wanted to retain similar to stock ride quality, so H&R Sport one inch lowering springs (1” front, 1-5/8” back on my car) were the only choice for me. Handling was much improved on the street and road course. My springs, combined with the rest of my suspension system, also increased straight-line traction and performance at the strip. I have ridden in a few GT500s with Ford Racing lowering springs, shocks, and sway bars and felt the ride was too harsh for my liking. My overall suspension package is geared towards: 1. high performance street, 2. light road course, 3. light strip, and 4. touring since I enjoy driving the car on long road trips.

I am running stock struts in the front and QA1 single-adjustable shocks in the rear, but I would not recommend them if your car will never see the strip. I’ll make some suggestions on shocks you should consider that may compliment your driving style (from more drag oriented to more street oriented): Strange single adjustable struts/shocks, Tokico D-Specs, Koni Yellow, and Bilstein (non-adjustable). All but the Bilsteins are adjustable and will allow you to fine tune them to meet your needs. I am leaning towards the Strange struts and shocks for my car in the near future.

My cars stance with 19" wheels and tires:

 

[Kevin P]

http://www.maximummotorsports.com/Relocation-Brackets-for-RLCA-2005-2014-P1479.aspx

Thats what I would get if I had to do it over again.

 

[Robert M]

When I was researching this and installing relo brackets, I found the angle finder shown below to help.

On my lowered car, here was the original angle with the rear of the LCA in the factory mounting position in the axle, low in the front, higher in the rear...........

Notice that the angle is just getting to "0" with the LCA on the first adj. hole, that means that it was in the wrong direction for traction when it was in the original hole............

.............then moving the LCA to the center adj. hole gets it to a point where the rear of the LCA is lower than the front for better I/C and traction...........

Using the bottom adj. hole in the relo bracket would bring the I/C rearward for even better traction............

.................this angle finder also works nicely for setting pinion angle when the magnetic side is attached to the steel yoke on the pinion..............

R

 

[SCGallo2]

http://www.maximummotorsports.com/Relocation-Brackets-for-RLCA-2005-2014-P1479.aspx

Thats what I would get if I had to do it over again.

+1

Having my car since 2008, I had installed the original BMR two-hole LCA relocation brackets on my lowered Shelby, which were an improvement over the stock LCA mounting locations, but they shifted under hard drag strip launches, creating a loud popping sound which is not what you want to hear when pushing your car that hard. BMR upgraded their relo brackets (as seen in Robert’s post above) by adding an additional axle mounting point to prevent movement and a third hole for adjustability. No doubt they are comparable in quality to the Maximum Motorsports relo brackets, but I am glad I went with MM… they gave me perfect adjustability and are rock solid. BMR and MM offer the best “bolt-on” relo brackets in the market.

Using the bottom adj. hole in the relo bracket would bring the I/C rearward for even better traction............

Great illustration Robert!

I offer that while it may provide more traction in a straight line for some, I have only seen the bottom hole on relo brackets utilized on drag cars. That much anti-squat in the rear starts to affect handling characteristics up front during braking and turning. The center hole is usually the sweet spot for lowered, high horsepower street driven Shelbys.

 

[ShelbyGT5HUN]

I have learned to max out the power you have before adding more. I am going to get the relo-brackets. I like high speed cruising, and taking off from a dig. Just need to consider what shocks and springs meet those requirements. I am not looking for a loose/sloppy back end that does not give you confidence at higher speeds (80 and up).

Would it be wise to shelf the Eibachs, and look for a total package both front and rear, that includes springs and shocks as a package?

Thanks for all the advice so far!

 

[ShelbyGT5HUN]

Have you tried more air pressure? 28 psi is low for a radial tire. You need relocation brackets, but I'd experiment with air pressure.

35psi felt like the rear tires had no compliance. 28psi is giving me a better ride, but still no traction.

 

[SCGallo2]

Would it be wise to shelf the Eibachs, and look for a total package both front and rear, that includes springs and shocks as a package?

Do you know what Eibach springs or system you have installed? The Pro-system or Pro-system-plus components should be OK for the performance you are looking for. If you are intent on replacing everything, I would contact Van or Kelly @ BMR to discuss your particular application and options to achieve your goals. They have a lot more experience with suspension components and the proper pairing of dampers. I think you will be hard pressed to find a "boxed kit" that suits your taste and expectations.

My recommendation is to keep what you have for now and install LCA relocation brackets. Then check your pinion angle to see if it is between -2 to -3 degrees. If not, install an adjustable UCA (and mount while you are up there) to correct as needed. Then see where you are in terms of grip.

*edit*
I am not implying that adjusting the pinion angle will greatly affect traction. Anytime you change your rear suspension geometry, you should check your pinion angle to verify proper driveshaft alignment to ensure maximum efficiency of power delivery to the rear tires and prevent undesired effects of a mis-aligned driveline such as vibration or premature wear and failure of components.

 

[sono]

I don't think the the position of the LCA'S is critical unless your dialing it in for the track. I also think these pinion angles are off from the factory, so that can't be critical to traction.

Rear springs, or should I say rear stiffness seem to make or brake traction.
I swapped my m5300l back to soft stocks in the rear and boom traction. In your position I would take it 1 step further and slap the Revan adjustable rear springs and call it a day. If you want better handling, keep it soft and add a Ford racing sway bar kit.

My 2 cents.

 

[ShelbyGT5HUN]

My 2 cents.

Good points. I had a car with Eibachs, that I drag raced. I ended up keeping the front Eibachs, but putting the stock ones in the back. It worked great. I might look into changing out the rear springs. The car is light back there, and it doesn't need such a stiff spring like the ones that come from Eibach.

 

[ShelbyGT5HUN]

Do you know what Eibach springs or system you have installed?

I think its the Pro-Kit, the most basic lowering springs they offer. Black in color. Will check the box. But I'm 99.9% sure its the Pro-Kit.

 

[ShelbyGT5HUN]

In your position I would take it 1 step further and slap the Revan adjustable rear springs and call it a day. If you want better handling, keep it soft and add a Ford racing sway bar kit.

My 2 cents.

These? http://www.revanracing.com/products/dead-hooker-spring-kit.html

 

[limitedex]

My 2010 GT500 is currently lowered with Eibach springs (never liked ANY of my cars that ran Eibachs, but the car came this way). Also has LCAs and adj. panhard bar. Car was aligned with a 0* thrust angle. Eyeballing the rear tires, they are centered nicely in the fenders. I get no wheel hop in any situation, it either hooks if I GRANDMA-BABY it, or will RRRRRRRROAST the tires off with no regrets.


Car has NO traction in 1st and 2nd gear on only a pulley an tune. Running 20" stock width Invos. In third it will sometimes haze the tires starting at 80mph, if you roll into the throttle. Under 50F, forget traction until 4th. I can understand the car makes power, but what I can't understand is how little traction there is. Should this car hook better than it does?

So all this is leading me to ask the question does lowering the car change the pinion angle, or some other rear end geometry that screws up how the car hooks? I know from another project car of mine, the pinion angle made a big difference in if the car hooked up or not. Change it one way, it "bit" the road more, turned the other way, the car felt like it was on ice, and would just lay rubber.

Would I benefit from an adjustable upper control arm, or something else to help the car bite? Please no drag radial or Viking shocks suggestions, yet :burnout:trying to keep it streetable.

I know the Eibachs are the worst thing you can put back there, and I do have the stock springs in a box. I get the feeling that Eibach designs these springs with no thought other than "make the car lower", and never tests their product on the cars the springs were designed for, and I feel you can actually make the car handle/hook up WORSE by using their product. Yeah, it looks good, and changes the stance but I feel like there is zero compliance (over bumps) back there, AND it messed up the whole geometry of the car. I've read posts from other members here who have 100+ more rwhp than me, and on similar tires, they "dead hook 2nd", or "hook good from a dig". It's almost comical how little this car hooks.

Thanks!

You need better tires. That is why you do not have traction.

Toyo R888 FTW.