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Lower Control Arms--To be adjustable or not to be

13K views 19 replies 10 participants last post by  Norm Peterson 
#1 ·
I have had enough of the wheel hop. I have made up my mind on which brand I want, not sure if I should go with adjustable or fixed. My car is not currently lowered but will be someday (hopefully soon).
Will relocation brackets solve any issue if i lower? Should I get those at the same time but just not install? I plan on taking to the track multiple times a year once I lower. Any suggestions you guys can offer would be appreciated!
Thanks!
 
#2 ·
LCAs should be fixed. Relocation brackets will solve any future lowered issues. The only reason to buy adjustable is if you are a hardcore racer and have a team of mechanics knowledgeable on suspension making fine tuned adjustments... You will need an adjustable pahard bar though to center the axle up once you lower (and sometimes the cars come from the factory offset toward the driverside).
 
#3 ·
Agree with dt -- I don't know any need for adjustable LCA's except fine tuning, mainly for drag racing.

If you need to adjust pinion angle, do it with adjustable UCA.

For road track, some articulation (ability to twist) is important in the LCA's and UCA; spherical bushing is good for this but can also transmit more NVH

For a lowered car, my understanding is the relocation brackets are important . . . best to do them at the same time.
 
#4 ·
Adjustable is always better. If you lower the car and you end up with your thrust angle being off when the axle is centered...you're gonna wish they were adjustable.
 
#6 ·
Good point / understood / agreed . . .


Checking my latest alignment, I have 0.07 degrees thrust angle. I assumed that was a good as it could reasonably get. My car is lowered 1.25" in the rear and recentered with adjustable panhard bar.


Should I be concerned / should I try to improve that? (I would need adjustable LCA's to do it).
 
#5 ·
I bought non adjustable LCA's and an adjustable upper, both of which are going on today. This was recommended to me from my local Mustang shop as I only take it to the track 3-4 times a year.
 
#7 ·
99% of people don't need adjustable lcas and they can introduce more problems than they solve. If you are road course bound, you'll want everything adjustable but, road use or street strip, no way.
 
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#12 ·
If you lower the car you must have an upper adjustable UCA and should have relocation brackets.

If you have wheel hop then upper Adjustable UCA with Poly bushing or spherical bushings may solve the wheel hop.

My wheel hop before lowering was solved with relocation brackets and LCA's with poly bushings.
 
#9 ·
JBert brings up a good point - for street DD and occasional Auto X or Drag racing - what is an acceptable thrust angle?


Also maybe we can define the term too? I'm assuming that means the rear axle is not pointed straight ahead....?


Thanks,

Scott
 
#20 ·
Also maybe we can define the term too? I'm assuming that means the rear axle is not pointed straight ahead....?
Easy question first - yes.


JBert brings up a good point - for street DD and occasional Auto X or Drag racing - what is an acceptable thrust angle?

Thanks,

Scott
There may be a spec, but if it's off by enough to notice at the steering wheel as you're driving it's still not good enough (for you, anyway).


When I first put the adjustable LCAs on my car, the axle was out of square by one thread on one side and it was clearly noticeable that the steering wheel wasn't straight when going straight on a level road. When the steering wheel was straight, it would follow a gradual curve in one direction and steer right out of the lane in the other.


One turn of a 10 threads/inch adjuster over a 62" rear track is about 0.13° thrust angle.


After a week or so, I figured out which side to adjust, which way it needed to be adjusted in, about how much to adjust it, and fixed it. It was that annoying.




Norm
 
#10 ·
Given the relatively short wheelbase and narrow track width of this car, a tiny bit off, like under a degree,isn't going to be a big deal on the road.

Obviously if you can get the car totally square, that's ideal but, remember this car has huge soft rubber bushings with lots of deflection stock and the car manages allright with that so don't fret too much.

Thrust angle is the angle in which the front and rear axles deliver their force to the road.

As I said, I wouldn't put adjustable lowers on a road car. Pinion angle is the best thing to be concentrating on getting right on rear setup and that's best done with an adjustable upper. Adjusting pinion angle with the lowers changes the wheelbase and centering of the axle in the wheelwell, which brings other problems on.
 
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#14 ·
I believe Sqidd would say pinion angle is important with 2 piece shaft also based on being in phase or close to as in phase as possible. But yes the 2 piece shaft is more forgiving. All I know in regards to this is what I read in this forum though.

I usually put the extra spaces between different items/emphasis of discussion to avoid long paragraphs. Probably has to do with the style of engineering reports at my current employment.
 
#16 ·
. . . I usually put the extra spaces between different items/emphasis of discussion to avoid long paragraphs. . . . .
On this tangent: I like line breaks too, but lately when I post the system seems to be adding extra ones between the paragraphs. I thought it was me typing badly but I see it in other posts too.
 
#15 ·
It ain't as much about phase as it is about ensuring enough down angle so that when the pinion gear tries to climb the ring gear under hard acceleration, it doesn't push the pumpkin into an up angle situation, which will trigger wheelhop. 3 links like these don't need alot here, 2 degrees down max on a street car, compared to a leaf spring rear, which will need 7 or 8 degrees down to compensate for the spring wrap up.
 
#18 ·
I just want to make sure that I understand you correctly. When you say down angle are you referring to the pinion flange specifically pointing downward or are you referring to the relative angle of the pinion flange relative to the transmission flange? Not sure if I am making sense with my question.

On my car and with most other S197's as far as I know the transmission flange points down. Under hard acceleration the intent is to have the transmission flange and pinion flanges at the same angle to be in phase. (Others may say under normal driving you want the angles to be equal to be in phase). Thus for my car's driveline to be in phase the pinion flange will need to be pointed upward. And if I want it to be in phase during hard accelleration is needs to be rotated CCW -1 to -2 degrees(View from Driver's side and variable depending on bushings etc.) so that under acceleration the pinion flange rotates CW.
 
#19 ·
I mean the included angle. The rear axle should be 2 degrees down from the angle of the rear part of the driveshaft.

Under thrust, if you have the driveline in phase, the rear will rotate up slightly and take it out of phase. You really can't get it in phase with a centre bearing 2 piece DS anyway because the centre bearing is fixed to the floor.

With a 2-piece DS, it isn't that important but, you'll want to set it up like I am suggesting.
 
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