Herb Adams mod on 67 Camaro

[gui67]

Hello,
I began the Herb Adams mod this morning on my car.
After some measurements, I drilled the holes 3/4" higher (19mm) and cut the leaf spring brackets.

Finally, the cut is much smaller then all the other I could see. Maybe because I use Hotchkiss springs...

Is this OK you think, or should I increase the clearance between the spring eye and the bracket? There is approx 2mm for the moment.

68770

68771

68772

The spring is alos not as high as I thought, I will maybe not need to cut so much on the floor.

[regal454]

Do you have any feedback on this mod? I am considering this on my car. What benefit will this yield besides moving the IC back? I think I read somewhere that Mary Pozzi did this to her 2nd gen when it was rolling around on leaf springs. How much of the floor did you have to cut?

[Gitter Dun]

Vince did the same mod to my car. Didn't know there was a name for it. I was told it will give you more bite coming off the corners. Hopefully he will chime in. I know he cut into my floor and I have about about a a 1" tall x5"x5" sheet metal box behind my seats.

[Gitter Dun]

Found this link

https://www.pro-touring.com/showthread.php?70760-First-Gen-Herb-Adams-Mod-Did-it

[cornfedbill]

Found this link

https://www.pro-touring.com/showthread.php?70760-First-Gen-Herb-Adams-Mod-Did-it

Thanks for the link. I have been contemplating this for my Nova. Now at least I have some information to get me started.

[rustomatic]

Now I don't really have a visual of how the springs mount at the front, but if possible, wouldn't just reversing the front eye on the spring have the same basic effect, since it's the lever you're trying to re-position?

[David Pozzi]

We did it to Mary's Camaro & really couldn't feel any improvement. I'd really think twice before doing it to a first gen Camaro, too much cutting required. Be sure to check your pinion angle.

[cornfedbill]

Now I don't really have a visual of how the springs mount at the front, but if possible, wouldn't just reversing the front eye on the spring have the same basic effect, since it's the lever you're trying to re-position?

Actually not. The pivot point at the front of the spring would remain the same. This helps define the instant center of the rear suspension under acceleration and braking. Moving it up gives more bite. Flipping the front spring eye does not change the geometry, only the ride height.

[cornfedbill]

We did it to Mary's Camaro & really couldn't feel any improvement. I'd really think twice before doing it to a first gen Camaro, too much cutting required. Be sure to check your pinion angle.

My reason for performing this mod is that I plan to lower the car radically and do not want to end up with the eye too low. I have flatter springs and will need lowering blocks if I don't move the front eyes. I may even need them anyway.

If I were to leave it close to stock ride height, I would agree with you. But effectively I will be lowering the front eye which is not good.

I am just not sure of the best way to skin this cat. This gives me more food for thought.

[gui67]

I did not have a lot of time to continue yet.
I will cut the floor this week-end. and maybe weld the box to close the floor again too.

I will set the pinion angle again, thanks for the tip David.

[Rod]

My reason for performing this mod is that I plan to lower the car radically and do not want to end up with the eye too low. I have flatter springs and will need lowering blocks if I don't move the front eyes. I may even need them anyway.



youre not doing this for any performance improvment? if thats the case you could cut the rear shackle also to keep the leaf spring angles correct to reduce the effects of the mod.....and it will add to the lowered height... I said reduce not remove the effects by moving the leaf upwards into the body you lower the roll center and create push in a car

If you lower the front eye of the leaf 1/2" to 1" or more and readjust the chassis back to its original ride height, you can expect the following:
1. More "tight" roll steer (may tighten handling)
2. Increased rear suspension stiffness
3. Lowered roll center(increases body roll and rear side bite-handling tightens)
4. Less body/tire separation during acceleration and deceleration (may tighten initial corner entry handling and may reduce initial forward bite)

You can expect results opposite to the above when you raise the front eye of the leaf and adjust the chassis back to its original ride height. Mounting the leafs so that the front eyes are slightly inboard of the rear eyes will cause the leafs to have more lateral stiffness. This can make the chassis feel tighter and may help prevent the rear suspension from binding due to excessive lateral deflection of the leaf. However, if the leafs are offset too much, the suspension becomes too stiff laterally and rear side bite is lost. Whenever the body slides over the rear end during cornering, the splayed leafs can cause rear steer that will help the car to turn. Also, if the right front spring eye is mounted more inboard than the left eye (measured from the corresponding tires), the right rear tire will tend to be loaded less than the left rear tire during acceleration. As a result, the chassis will tend to be tighter off the corner. Corner exit handling tends to be loose under opposite conditions Generally, moving the front spring eye 1 1/2" laterally will produce a noticeable effect to corner exit handling.

[cornfedbill]

Thanks for the lesson Rod. That is some good information.

[geometryjeff]

I'm interested in the results of moving front eye up with respects to the axle centerline. Did car get looser in corner? I thought this would create more roll ovresteer (a bad thing). It looks like Pozzi's didn't notice improvement; was there a negative affect.

[68ls1wannabe]

There is some very good reading material on this subject in the stock suspension section of yellowbullet.com. It's drag racing related but would apply in some ways to the touring car.

[MARBIL]

I am going to do this to my 69 bird, I look at things like this as while on its own may not have a huge effect but when you add all the little things we do to our cars then they become part of the big picture and they add up. I have read as much as I could find on this and have not yet seen anyone take two sets of brackets and weld them together, my thought are this would yield a stronger final modification to the bracket, what is everyones input on that approach.

[MARBIL]

77367

Here is my finished perches, a little paint, minor floor board mods.

[Buryingthesun]

77367

Here is my finished perches, a little paint, minor floor board mods.


I like what you did there