Ross's extended city, easy entry Goblin- 06 SS/SC, NW Arkansas

[Rttoys]

To be honest, I would run it stock at first, then modify later. Stock doesn’t cost you anything and works well. If you feel you you don’t like it, then read over everything and modify to what you think will work best for you. The advantage is seeing the difference first hand.

 

[PyroGuy923]

To be honest, I would run it stock at first, then modify later. Stock doesn’t cost you anything and works well. If you feel you you don’t like it, then read over everything and modify to what you think will work best for you. The advantage is seeing the difference first hand.

This was my theory when building as well other than a few maintenance parts I just replaced with "stock" equivelants. Get it running then once its up and running if there was an issue it helps troubleshoot too.

 

[Ross]

I think I see why I am getting wheel hop during braking. Do you see what I am seeing?

Today I raised the front tire pressure from 18PSI to 26PSI, and I checked the front wheels for slop/wear in the heim joints, the steering rack, the wheel bearings, etc. They seem good to me.

 

[DCMoney]

I think I see why I am getting wheel hop during braking. Do you see what I am seeing?

Today I raised the front tire pressure from 18PSI to 26PSI, and I checked the front wheels for slop/wear in the heim joints, the steering rack, the wheel bearings, etc. They seem good to me.

Nice control arm flex...

 

[r3drckt]

I don’t think your caster is supposed to change like that under hard braking.

 

[Brian74]

Fwd upper control arm pivot? I couldn’t tell where the play was but it looked like there was a slight amount there.

 

[DCMoney]

Ross, how much does your front wheel and tire weigh?

 

[Ross]

I agree with Andrew and r3drckt, During braking, I am getting caster change due to flexing the A arms.
I think they were 47 pounds when the tires were new. The mustang wheels are ~24lbs heavy. Of course the whole car weight/momentum is helping the brake calipers twist the billet uprights, not just the wheels.
On lower control arm, I think I will weld 2 tubes in a V shape. Need to check the full suspension swing, to get final positions.

On the upper A arm I don't have as much room. Maybe this X pattern will be enough.

 

[Ross]

DaleE pointed out I might have bent A arms... who me off roading?
I guess I should start there and see if that is my issue, before I go off re-enforcing bent parts.

 

[Rttoys]

I’m thinking fatigued arms (all front end components) from all the hard autocross braking and such. Now that the rear brakes are working properly, you can address anything worn on the front And get back to square one.

 

[Ross]

My car has always had this issue, even with the stock Cobalt tires... even before I started autocrossing.

 

[Rttoys]

That’s odd since no one else is having that problem other than under extreme conditions.

 

[Brian74]

Did your control arms bolt in nice & flush? I noticed that on mockup, my upper arm has about a 1/2”-3/4” gap from the pivot point at the heim joint that will take some torque to squeeze into place.

 

[Ross]

Maybe I should just try new A arms, and see if that fixes it.
If not, I am back to customizing my A arms, which is fine, I can TIG.

My A arms had that gap too, Brian. The bolts did pull them into position.

 

[Brian74]

I have a hard time being convinced that its flex as Rttoys mentions its not common. These cars are pretty light and I’ve seen long-travel sandrails with far less for control arms. I would also maybe try adding a ratchet strap/come along with some really good fwd lateral force to the upper control arm (aft to the lower) to see if you can get it to move in a static position and identify the point where the movement is the greatest.

 

[Ross]

I will try more camera angles.... try watching the inner heim joints too.
Maybe straight down one of the A arms, and see if it is flexing, or is the movement at one of the ends.
Hopefully the camera will give us more clues, better data.

 

[George]

Had a VW with a bad wobble when braking
The rotors had no run out in any direction
But they had hard spots. Changed the rotors

Brad

 

[Rttoys]

I have a hard time being convinced that its flex as Rttoys mentions its not common.

Depends on how you look at it. I believe the flex is common, but the extreme wobble Ross has due to the flex, I believe is not. Ross’s is odd since it did it from the beginning, under stock conditions. I’m almost figuring some sort of “bad parts” on his or a chain reaction of one simple thing progressing downward to others.

Looking at his control arms and reading that dale said they look bent, they actually do look bent. Maybe it’s just the picture angle, not sure, but it’s looks off for some reason. That adds in to all the other weird things with his. Hell, it could be some tubing that was not made up to standard, who knows. It just seems off.

 

[DCMoney]

How many people are running progressive springs up front? Have you tried a linear spring on the front suspension?

 

[Ross]

I suspected a lot of things, springs, shocks, alignment, wheel bearings, tie rod ends, steering rack, etc.
The new video evidence shows caster change. The A arms should prevent caster change.
The brakes are able to apply a twisting force to the billet uprights, and the A arms are suppose to transfer that force to the frame, and prevent caster changes. Caster is allowed to change (Edit: On some cars true, but not on our Goblin) as the suspension moves up & down, but not when the billet uprights want to twist.

After the tires start bouncing, then the springs and shocks have to deal with that secondary issue... but the first issue is too much A arm movement. So springs and shocks have little to do with the caster changing.

I have had always wheel hop under hard braking. For 2 years I have been trying things to fix it.
I've tried 125 lb/in springs, 300, 400 and now the 225/475 springs.
I've tried 215mm Toyo Proxes (from my Cobalt), 315mm Nitto NT05, and now 275mm Toyo Proxes R1R.
I replaced the wheel bearings from the Cobalt ones to Moog.
I changed to steering tie rod ends to the correct ones after Lonny pointed out I had the front ones on the back of my car. This allowed me to bring the front wheels in closer to the frame, which helped make the A arms a bit more rigid.
I've checked the shocks, they work, and tried 0,2,4,6,8,10,12,14,16, and 18(max) clicks.
I've checked the steering rack. It seems fine.
I've tried different wheel alignment numbers,
1.5 degrees camber, now 0.7
8 degrees caster, 5 degrees, now 6.