[donziboy]

My car came with No Hop Bars and it looks like they have been on the car for some time, more than likely 30 years. I don’t know a thing about them however my judgement is they are not necessary on a street car. I don’t have any plans to ever race the car and would like to just remove them. My question is if I do will I have to address or deal with any issues as a result of removing them. Things that come to mind are ride height and pinion angle changing? Also I believe that when adjusted properly to stop wheel hop they can bottom out when climbing a curb or when you would have a loaded back seat. I see evidence that the upper control arm came in contact with the trunk floor. At this point only some scratches on the paint.
Bob

[Rich-Tripower]

Removing them won't change the ride height, that is controlled entirely by the springs (or air shocks or bags if you have them).

I don't think the pinion angle would change, and even if it does I'd think it would be returning it to a more correct pinion angle.

[Scarebird]

I would not remove them; I put a set on my 66 and it cured wheel hop issues - they do not hurt anything.

[aceaceca]

I am having a hard time making out what these gizmos do. Are they raising up the differential mount point for the upper control arms?
We used to lower down the differential mount point for the lower control arms.

[donziboy]

A few slightly better pictures that show the no-hop installed. One end attaches to the rear end housing and the other end attaches to the upper control arm. Also thank you for the additional information regarding potential changes. My goal is to eventually lower the front end slightly, I like the rear end height but thinking the front end sits a little to high. Car has 14” Hurst wheels with P22570R14 Diamond Backs.

[donziboy]

This is a better picture that shows the actual stance of the car and my concern was that removing the no-hops would make the car sit lower in rear.

[geeteeohguy]

The no-hops will not affect ride height one way or the other. And they only affect pinion angle when you launch the car....they keep the angle from changing and keep the tires planted. If it were my car I'd probably put 1" spacer rings under the rear coil springs and call it a day. I don't like really low A-body cars. That, or leave the rear alone and lower the front slightly. The no hops I would leave in place as they can only help, not hurt.

[The Champ]

Originally Posted by geeteeohguy

If it were my car I'd probably put 1" spacer rings under the rear coil springs and call it a day.

He likes the rear ride height where it is. It's the front ride height he wants to change.

[242177P]

I was going to say you don't really NEED the No-Hop bars, but that higher stance
definitely aggravates the tendency to hop. I say leave 'em in, OR lower the back
(which I see you don't want to) to the point where the suspension geometry is
brought back to something close to the OEM settings. Remember, even at stock
height they had hop.

Another thought. Pontiac had warranty claims on the upper crossmember. It's a
safe bet they won't cover it anymore.

[Keith Seymore]

Originally Posted by aceaceca

I am having a hard time making out what these gizmos do. Are they raising up the differential mount point for the upper control arms?
We used to lower down the differential mount point for the lower control arms.

Same thing.

They are changing the Instant Center location of the rear suspension, and it's relationship to the center of gravity of the vehicle.

Raising the rear of the upper control arm and lowering the rear of the lower control arm both move the IC up and more rearward from the stock location, increasing the anti-squat during launch.

Most folks move the upper and try to make the lower horizontal, but I believe it is to make it easier to visualize the changes being made.

K

[donziboy]

Thanks for all the responses, I will take my time moving forward to figure out what direction I will go with changes and stance.

[242177P]

One last thought. IF you decide to keep them, there might be a way to avoid
denting the floor. El Camino used an add-on bracket that raised the snubber
maybe 3/4". OEM would require a hole drilled into the housing. Can fabricate
a taller spacer as well?



(ad from which I stole that pic ---> https://yenko.net/forum/showthread.php?t=150131)

[donziboy]

Originally Posted by geeteeohguy

The no-hops will not affect ride height one way or the other. And they only affect pinion angle when you launch the car....they keep the angle from changing and keep the tires planted. If it were my car I'd probably put 1" spacer rings under the rear coil springs and call it a day. I don't like really low A-body cars. That, or leave the rear alone and lower the front slightly. The no hops I would leave in place as they can only help, not hurt.

GTO Guy ,
Quick update to say thanks for the suggestion to use a 1” spacer on the rear coil springs. Simple installation and happy with the results. I’m in agreement with you about not liking the look of a really low A body stance especially in the rear. Now the car is level or just slightly higher in the back.
Regards.
Bob

[Keith Seymore]

It's probably moot at this point, and I should let it go, but -

- I have a few minutes -

This is not correct:

Originally Posted by geeteeohguy

And they only affect pinion angle when you launch the car....they keep the angle from changing and keep the tires planted.

The two upper and two lower control arms constrain the rear axle regardless of where the ends attach to the vehicle frame, and therefore do not allow rear axle windup or allow the pinion to rotate up. The pinion is just along for the ride as the rear axle swings about the instant center. It's like a ladder bar, in that regard.

Maybe a very slight amount of windup, due to compliance in the rubber bushings, like less than a degree, but certainly not like the 4 or 6 degrees of windup you would see with a leaf spring car.

I repeat my earlier post here:

Originally Posted by Keith Seymore

They are changing the Instant Center location of the rear suspension, and its relationship to the center of gravity of the vehicle.

Raising the rear of the upper control arm and lowering the rear of the lower control arm both move the IC up and more rearward from the stock location, increasing the anti-squat during launch.

[Keith Seymore]

This might be too much detail but I actually created an Excel spreadsheet where I describe the attachment points using Cartesian coordinates (like a graph) and the equation of a line (y=mx+b). Solving the two equations for the intersection determines the Instant Center.

I found it was way easier than stringing masking tape all over the garage floor in order to find the IC experimentally, and allows me to iterate potential combinations quickly without getting bogged down in the math.

You might also note here I approximated the CG height by using the location of the cam centerline. To determine the actual CG height you can either (a) swing the vehicle on a swing and monitor changes to the period as mass is added, or (b) "tip" the vehicle at an extreme angle, measuring the change in wheel weight while using trigonometry. Neither of these is very easy to do at home. But - since it is merely forming a baseline for A-B comparisons any error in describing CG height is basically moot.

K

[Keith Seymore]

Baseline condition:



With Anti hop bars:



Pushing the instant center rearward increases the amount of separation between the axle and the body - or - said, differently increases the resistance to "squat" (ie, anti-squat) and plants the tires harder.

I mentioned earlier, as an aside, some folks are really particular about getting the lower bar to be horizontal with the ground but I don't know why. The bars act through the IC, regardless of how they get there. My only thought is that it makes changing the IC a little easier to visualize, since you are only moving it fore/aft during testing (rather than up/down in addition).

[Keith Seymore]

Originally Posted by geeteeohguy

If it were my car I'd probably put 1" spacer rings under the rear coil springs and call it a day. I don't like really low A-body cars. That, or leave the rear alone and lower the front slightly. The no hops I would leave in place as they can only help, not hurt.

I should add - I agree with this.

I probably would have dropped the front a bit, and the no hops don't hurt anything unless they bang into the underbody going over railroad tracks.

K

[AG]

If you are making power and dump the clutch or hit it hard with an auto you absolutely need them. If you never hit it hard you don't. I was racing my '65 with a 4 speed and got wheel hop so bad it grenaded my 10-bolt and dropped the driveshaft with the pinion gear still attached.