Cobra pulls to the right on acceleration

[gthompson]

My car pulls to the right when i accelerate and the goes back to the left when i let off. Do all Cobra's do this a little or not at all?
Thanks George

[Tom Kirkham]

George,

Welcome to Club Cobra!

George if everything is correct you can do a burn out holding the steering wheel with just two fingers. If something is wrong even two hands on the wheel will not keep you on the road.

I would check three things right off.
1. rear suspension spherical joints, rod ends, ball joints, wheel bearing loose.
2. rear alignment correct (equal toe on these cars is critical)
3. Tire stagger (tires having different diameters) will also cause this problem.

Give me a call tomorrow and we can go over it on the phone.

[RICK LAKE]

gthompson George did you check tire pressure in the rear tires? Retighten and check all nuts and bolts in the rearend too. Something sound loose. Do you feel or heard any knocking noise?
Who's tires are you running, they may no be the same diameter if they are billboards. Just a thought. Rick L.

[strictlypersonl]

Not likely unless something's bent or not put together correctly, but bump-steer can do this too.

[Chilibit]

I had a left rear wheel bearing that was bad and allowed the assembly to move. It pulled left under acceleration. Even mild acceleration.

[Dwight]

It sounds like your right rear tire is getting more traction than the left. When you accelerate the rear end torques clockwise, if your looking from the rear of the car. This applies more force on the right rear. You would think with the weight of the driver it would equalities the force on both tires. It does not. If you can adjust your rear shocks, increase on the right and decrease on the left. You can play with the tire pressure but it hard to keep it where you want it. The change in tire temperature and weather will change the tire pressure. I had to install adjustable coil overs to cure mine. Soften the spring load on the drivers side and increase the spring load on the other side. You're shifting some of the power from the left wheel to the drivers side. To much and you will pull to the right.

Dwight

[Ronbo]

Sounds like one (or more) of the rear bushings has softened up and is deflecting under load. This could be either side depending on if it's the front or rear bushing. I guessing you have bushings instead of sperical joints since you list your cars as CSX's.

As Tom stated alignment could also be an issue, another remote possibility is the differential slipping on one side (you'd probably feel this as chatter though). Do you notice any clunks, shudders or other noises from the rear (granted these are rather hard to hear over the pipes and complaining tires)?

Easiest thing to do is get under there with a big pry bar and start tugging on stuff and see what's giving in, also look for bushing material squeezing out.

Dwight, what your describing affects solid axle rears, not independent.

[gthompson]

Thanks for everyone’s input on this. The car has 130 miles on it is a CSX car with adjustable shocks, the adjusting nut is 18 threads up from the bottom on both sides.

The tires are new GoodYear Billboard and they are the same size on both sides. I am running 26.5 psi on all four tires (not sure if that is the right pressure for Billboards?).

The rear wheel lower adjusting arm (toe in/toe out?) that moves the wheels left or right are tight and the same distance on both sides. The rear wheel top adjusting nut (camber/caster?) are 8 threads out on both sides.

The car drives straight maintaining my speed. The car pulls to the right when under moderate to heavy acceleration (even accelerating from 60 mph) with out wheel slippage. then the car comes back to the left when you lift on the throttle.

[Buzz]

If you hold a steady speed in a lower gear (2nd or 3rd) and suddenly lift off the throttle, does the car pull to the left? If it does then there is surely an issue with the rear suspension geometry changing due to worn or loose components. If it does not pull on sudden deceleration and only pulls on acceleration, then I would guess that it's either a problem with a defective limited slip differential or an out of spec rear tire diameter (larger diameter on the left rear).

[Cobra #3170]

You have probably already checked this but can you physically move either rear wheel by grabbing it at 9:00 and 3:00 and try to get it to toe in and out?
I don't know what your rear suspension design is so this could be a non issue but Cobras that used a spherical bearing at the inner rear lower pivot can move if the bearing adjusting nuts are loose (for adjusting rear caster) or if the bearing itself has play in it. It does not take much movement to make a car do what you are describing.

Originally Posted by gthompson

My car pulls to the right when i accelerate and the goes back to the left when i let off. Do all Cobra's do this a little or not at all?
Thanks George

[PatBuckley]

The first thing I would check is the stagger of your rear tires. It is really easy to do - just use a tape measure to check each tire.

I had a brand new set of Goodyears that were off by a bunch that caused the same problem - Krause exchanged the tires with no questions asked.

[mickmate]

Rear toe and camber is a critical angle on these cars with such big feet. There is a toe change as they move through their travel. It needs to be very even from one side to another and that needs to be checked on a good four wheel alignment machine by someone that knows what they're doing and knows independent rears. Your shocks could well be even but if you know a local racer checking corner weights on scales will be a useful number in diagnosing this too.

[JBCOBRA]

Has the car been on scales? That made a huge difference on my car.

[JBCOBRA]

oops, Mickmate has it right.

[patrickt]

George, FWIW my rear corner weights are within 15 pounds of one another (Left Rear 663 Right Rear 678) with the car empty. That changes to a 30 pound difference the other way with me in the car (Left Rear 756 Right Rear 725). I have a cross-weight of 50/50 with me in it and a rear ratio of just under 52%. Loosen up your sway bars and put your car on the scales and see what your numbers say -- maybe you have some funky pre-loads throwing everything off as well having the rear alignment askew.

[gthompson]

I measured the rear tires around the outside in the center and one tire was 1 7/8-2 inches larger than the other one with the same tire pressure in each.

The larger tire sits about 3/8-1/2 inches taller that the other one. So i called Goodyear and after going back and forth with 4-5 people they referred me to the southwestern race division in Oklahoma City. They are going to bring 2 brand new matching tires to Texas Motor Speedway next Tuesday and they are going to mount and balance the new tires.

The tires have 280 miles on them.

Goodyear did a great thing.

Thanks for everyone’s help.
George

[Mohuska]

As my flight instructor would say

MORE LEFT RUDDER!!

[lloyds1]

Is this just a Goodyear phenomenon or does this happen with other bias ply tires too?

[Silverback51]

Originally Posted by gthompson

I measured the rear tires around the outside in the center and one tire was 1 7/8-2 inches larger than the other one with the same tire pressure in each.

The larger tire sits about 3/8-1/2 inches taller that the other one. So i called Goodyear and after going back and forth with 4-5 people they referred me to the southwestern race division in Oklahoma City. They are going to bring 2 brand new matching tires to Texas Motor Speedway next Tuesday and they are going to mount and balance the new tires.

The tires have 280 miles on them.

Goodyear did a great thing.

Thanks for everyone’s help.
George

That is a lot of stagger, even for bias ply tires.

[snakebittexan]

Hmmmm, your comment on Goodyear tires leads me to share my recent experience. I had a set of "V" rated GY Eagle F1's on a MB CLS500 that were incredibly noisey. I took the car back to the dealer twice because I thought I had a bad bearing or warped rotor. Once convinced it was the tires I called GY Customer Service where I was issued a "case" number and told to go to my GY dealer of choice and have the tires checked out. Long story shortened just a bit, GY in spite of 7,000 plus miles on my tires, gave me an even swap on more expensive Dunlops. Money out of pocket; balencing cost. GY has a new fan.