Front Suspension Travel (What did I do wrong?)

[JLMounce]

To put it bluntly, I have minimal suspension travel and as a result have an incredibly harsh ride over rough pavement.



What I have:
1969 Firebird, stock subframe
SPC upper and lower control arms.
Uppers are part of Mark at SC&C's Street Comp 2+ system.
Hotchkis 2" drop springs
Factory disc spindle
Progressive rate bumpers
Verishock SS shocks
Hellwig swaybar

The lower control arm would naturally drop the car a bit in the front, but I already had the 2" drop springs, so I used SPC's spring adjuster plates to position the arms at "stock" height.

In order to accomplish the install, the shocks are mounted on top of the arms, however their total length was such that I needed to compress the spring about an inch to inch and a half in order for the cross-bars to contact the bottom of the arm and secure the bottom of the shock. I allowed for 2 visible threads at the top shock mount to give me piece of mind on mounting there, but also allow for as much length as possible in the shock.

When the car is sitting, the jounce bumpers have about an inch to inch and a half of remaining compression before the mount contacts the frame. So in effect I have about that much compression travel before the whole system bottoms out and the frame starts to absorb the full impact.

Even with the ride height adjustment pads, the car dropped about half an inch or so from it's previous height. I'm thinking out loud, but I'm guessing the shock is not long enough and having to compress the arm upwards to meet it has caused this situation. This was really the only way to mount the shock as the height adjustment pads do not alter the mounting for the shock itself.

I guess the question is, how much suspension travel should I be seeing and what is a possible remedy here to get me more travel so that the car isn't jarring to drive over rough pavements.

Fortunately most of the roads around me are decent and even over roads that are pock-marked with small ruts and holes, the ride quality when the suspension can work is pretty great.

Thanks in advance!

-Jason

[dhutton]

Post a pic of the ride height. Have you asked Mark for help?

Don

[JLMounce]

It's a bit hard to get a good photo, but here's a pic I shot. You can see here that the jounce bumper is already compressed past it's cone. I know these are supposed to pretty much always be in contact with the bump pad, but you can see I've lost quite a bit of compression travel.

I have put in a call to Mark, just waiting for a return call.

[Cunning69]

Looks like it is 2 -3 inches too low. The sway bar and bottom of the LCA should be parallel with the ground. I think the coil is going to need to be replaced with a standard height spring since the LCA's are lowering the vehicle also.

[JLMounce]

Looks like it is 2 -3 inches too low. The sway bar and bottom of the LCA should be parallel with the ground. I think the coil is going to need to be replaced with a standard height spring since the LCA's are lowering the vehicle also.

The LCA has two height adjustment plates installed under the spring perch. By design, it shouldn't be lowering the vehicle and should be nominally the same as the factory lower control arm that I took out. I do have an additional plate that I can add to the lower control arm, but as stated in my post, that would put the shock that much further away from the lower mount.

[dhutton]

Are these the old version of the SPC lower arm? The spring pocket on them was too deep if I remember right and guys had the same problem. You might need stock springs and a longer shock....

I had an original set on my 64 GTO and had to use a lot of spring spacers (upper and lower)and stock length shocks. I used SPC springs if I remember right.

Don

[btmatt]

I have the exact same setup save for DSE coil springs (2" drop) and AFX Spindles (2" drop). Judging by your pics and the ones I attached, i think your shock extended length may be too short. The pic of the car is without spacers installed; we have since installed spacers like you have.

[JLMounce]

I put the car up on jacks earlier this morning to measure droop and I have 4+ inches of droop, so I think I'm off base here. Now that I recall the install from several weeks ago, I remember not adding the two spacers, but instead the single. I was trying to make up some stance I lost when I shaved about a 100 lbs off the front of the engine. Although I think I'd still be better off with a slightly longer shock, it's clear I need to put the other spacers in here.

In regards to the arms, they are brand new, built just several weeks ago. SPC is only about 30 minutes from my place, so I will-called them.

[dhutton]

I put the car up on jacks earlier this morning to measure droop and I have 4+ inches of droop, so I think I'm off base here. Now that I recall the install from several weeks ago, I remember not adding the two spacers, but instead the single. I was trying to make up some stance I lost when I shaved about a 100 lbs off the front of the engine. Although I think I'd still be better off with a slightly longer shock, it's clear I need to put the other spacers in here.

In regards to the arms, they are brand new, built just several weeks ago. SPC is only about 30 minutes from my place, so I will-called them.

You have the new design then.

Don

[79T/Aman]

you said you had to compress the suspension (coil spring) to get the shock absorber on, right? if so the shock is too short.
you said you had to compress the suspension 1" -1.5" that ads up to about 2-3" at the tire (ride height).
remove the shock and see where the suspension sits, then finish the car, get ALL the weight on the car then measure the length shock you need at static ride height.

[rocketrod]

I have a similar setup with AFX spindles and double adjustable vari shocks. I know you don't have AFX spindles but I had a similar issue with mine and Mark suggested I raise the ride height about 3/4" up using the SPC spacers. Obviously your setup is different but Mark will have an answer.

[JLMounce]

I have a similar setup with AFX spindles and double adjustable vari shocks. I know you don't have AFX spindles but I had a similar issue with mine and Mark suggested I raise the ride height about 3/4" up using the SPC spacers. Obviously your setup is different but Mark will have an answer.

I spoke with Mark this evening and he recommended the same.

[btmatt]

4" droop? I don't have anywhere near that (1-2" droop). I would install 2 spacers per side and be sure that the cast aluminum locator is installed on top of them to get the front end up. BTW do you remember the rate of your front springs? My DSE are 650lb/in and work well.

[JLMounce]

4" droop? I don't have anywhere near that (1-2" droop). I would install 2 spacers per side and be sure that the cast aluminum locator is installed on top of them to get the front end up. BTW do you remember the rate of your front springs? My DSE are 650lb/in and work well.

Yeah, I'll be adding in that extra pad which should get me back to where I was with the stock arms which worked well for me. The aluminum cup is already installed and will remain so. If I find that I need more, I'll purchase and install the upper mount adjusting pads from SPC.

The springs are Hotchkis 2" springs for big block cars (traditional pontiac motor). I believe these come in right around 600lbs.

[djorgensen3]

you said you had to compress the suspension (coil spring) to get the shock absorber on, right? if so the shock is too short.
you said you had to compress the suspension 1" -1.5" that ads up to about 2-3" at the tire (ride height).
remove the shock and see where the suspension sits, then finish the car, get ALL the weight on the car then measure the length shock you need at static ride height.

What he said...

[chevelletiger]

Looks like it is 2 -3 inches too low. The sway bar and bottom of the LCA should be parallel with the ground. I think the coil is going to need to be replaced with a standard height spring since the LCA's are lowering the vehicle also.

Please be specific when describing the Lca being parallel with the ground.
The ball joint center line,and the bushing pivot mount and the frame should be parallel with the level ground.
I'm went thru this with my SPC LCAS and coilovers I'm running.
Speak with mark,and also ridetech is a big help on figuring shock and spring lengths
These are picture of mine and the ride height.
I will need drop spindle thou..

[chevelletiger]

It's a bit hard to get a good photo, but here's a pic I shot. You can see here that the jounce bumper is already compressed past it's cone. I know these are supposed to pretty much always be in contact with the bump pad, but you can see I've lost quite a bit of compression travel.

I have put in a call to Mark, just waiting for a return call.

Need better pic of were the bump stop is compressed?

[djorgensen3]

You seem to be not addressing a point made by 79T/Aman. You had to compress your suspension in order to bolt up the shocks. That takes your travel away right there. Unbolt your shocks and see how much travel you have. You shocks are TOO SHORT if you have to do that.

[F-Body International]

You seem to be not addressing a point made by 79T/Aman. You had to compress your suspension in order to bolt up the shocks. That takes your travel away right there. Unbolt your shocks and see how much travel you have. You shocks are TOO SHORT if you have to do that.

Let’s go X3 for 79T/Aman!

I’ve had the problem of having too short of a shock myself in the past. Tried running it and pulled the shock rod right out of the shock body...broke it!

[Peter Mc Mahon]

You have 4+” of droop? I’m guessing your shocks are not too short. What is the free length of your spring?