1968 Firebird/Camaro Ridetech front suspension coil over question, is this right?

[shaley68]

Have installed the full ridetech front coil over suspension for my 1968 Firebird. Including the control arms, tall spindle, coil overs, sway bar, etc.

All good so far. I am running 17 x 8 inch rim with 235/45/17 nittos. Ride height is as pictured.

To get to ride height, I have had to crank the spanner nut just about to the top of the shock? Is that right? Took me a half an hour to move that nut turn by turn to the top. And yes, shock was not loaded with weight of the car. But you have to compress the 8 inch spring to about 6 or so inches and the nut becomes extremely difficult to turn.

Is this the expectation? I do see that there will be plenty of compression travel in the shock. At ride height, my setup is at 12.75 inches on the shock that has a range of 10.4 to 14 inches. My tire hits the top of the wheel well way before the 10.4 inch max compression on the shock.

There are 2 pictures attached where I used a dowel to simulate the shock. I attached on end to the bottom control arm in the exact position of the shock and the marked off inch increments on the top. The blue area is 12 to 13 inch. The ride height pictured aligns with about 12.75 inches.

I moved the tire way up into the wheel well and the shock only moved about an 1.5 inches. Well short of the 10.4 inch inch stop.

I doubt i will ever bottom out the shock, the tire will slam the top of the wheel well first. Is there a way to set a bump stop on this. Want to avoid tire, fender damage should I hit a severe bump.

[marolf101x]

Preload is normal. Amount of preload depends on spring rate, how much the vehicle weighs, and what ride height you want.
If you notice, unlike a lot of shocks, the threads do not go all the way up the shock body. I did this so no one could ever over-compress an 8-inch spring and "hurt it" (pring sag, or "set", is typically caused by the spring compressing too far.)

Ideally the shock should bottom out before the tire hits anything, but in reality, with everyone running the biggest tires they can, it typically doesn't happen.

[shaley68]

Thank you for the reply. I have a substantial amount of preload. Car weight is for a 1968 Firebird. Stock subframe, with LS3 , has AC. Tire is 25.3 inches: 235/45/17. 8 inch springs that came with this first gen kit are 700 lbs/inch. I have 1 degree of neg camber. Tire clears up and and down (and left to right) pretty well, no rubbing.

But at near (even less in my setup) full compression on this shock, you are hitting the top of the wheel well before hitting the stop, even with the "smaller" tire I am using. An adjustable stop would be great here.

Do you sell 9 inch springs? I suspect 10 inch wont fit. I am expecting a very firm ride from what I have heard. Looking to soften it up a bit.

[Josh@Ridetech]

Thank you for the reply. I have a substantial amount of preload. Car weight is for a 1968 Firebird. Stock subframe, with LS3 , has AC. Tire is 25.3 inches: 235/45/17. 8 inch springs that came with this first gen kit are 700 lbs/inch. I have 1 degree of neg camber. Tire clears up and and down (and left to right) pretty well, no rubbing.

But at full compression on this shock (10.4 inches), unless you are running a 22-23 inch tire, you are hitting the top of the wheel well before hitting the stop. Something seems wrong with this.

Do you sell 9 inch springs? I suspect 10 inch wont fit. I am expecting a very firm ride from what I have heard. Looking to soften it up a bit.

Britt is spot on in his post above (as always ).

You're going to have to be jumping some railroad tracks to get the shock to compress that far more than likely. This is the same stroke shock/stud top combo that has been ran on every Camaro since we designed the kit and it's been fantastic (we run 26"-26.5" diameter tires typically with zero issues). The shock should measure ~12.75" mount to mount at driving height. As long as that's where you're sitting, you're spot on as to where the kit is supposed to be at. Wheel backspacing is always a factor as well as something that could create issues.

We don't use 9" springs and a 10" won't work. Adding the ability for more preload isn't needed. The spring you have is a linear spring, the rate does not change as the spring compresses. If you had a progressive rate spring, it would get stiffer as you added preload, but it's not the case here.

[dhutton]

You could add some Afco progressive rate bumpstops if it makes you feel better. A fair bit of work since you have to remove the shocks to install them. ridetech sells a tool to disassemble the shock. Bottoming out a 700 pound spring would take some effort…

https://www.summitracing.com/search?...fco%20bumpstop

Spraying a little WD40 on the threads and adjuster will make them easier to adjust. So will antisieze but that makes a big mess.

Don

[marolf101x]

Let's clear something up real quick. . .adding preload DOES NOT make the ride stiffer.
In fact, to keep the same ride height, it makes the ride softer than a spring that requires less preload.


Here's the deal. . .
Let's say the front end weighs 1800, that's 900per corner. Motion ratio is roughly 2:1 for easy math, so each spring is actually holding up 1800lbs.
You have 700 pound per inch springs. Each inch you compress, it ADDS 700lbs. So you'll need to compress that spring roughly 2.6" (1inch=700lbs, plus 1inch=1400lbs, plus 0.6inch=1820lbs).
So you have the car at ride height with a 700lbs spring.
Say you hit a bump and the car travels 2 inches in compression.
You just added another 1400lbs to the spring force, for a total of 3220.


Now, let's take the same example with a spring that requires less preload. . .let's say a 900lbs spring.
1800lbs corner weight divided by spring rate (900lbs), equals 2.0" preload. Less than the 700lbs spring above.
Now compress that corner 2 inches. 1800lbs+900lbs (first inch compression)+900lbs (second inch compression)=3600lbs.

Summation. . .softer spring rate with more preload provides softer ride quality (all other things working correctly and within ranges).

[shaley68]

Thank you. All good, just wanted to check that i was installing correctly.
I felt like i was going to break something with the amount of effort needed to turn that spanner all the way up.

Will stay away from rail road tracks and should be good :-)

I did come across a guy who installed same setup (arms and coil overs) but with a standard spindle, (no drop) and I think a tall upper ball joint. He had the opposite issue. Car was sitting 2 inches too high , so he adjusted the spanner way down with near 0 preload and ended up at just about the same ride height. And more clearance under the car, higher up lower control arm, tie rod, etc

But he has much more risk of bottoming out the shock and I am sure lots of other aligment/geometry issues i suspect. Arms, etc were designed for a 2 inch drop spindle.
Maybe a 1 inch drop to consider?

[dhutton]

Thank you. All good, just wanted to check that i was installing correctly.
I felt like i was going to break something with the amount of effort needed to turn that spanner all the way up.

Will stay away from rail road tracks and should be good :-)

I did come across a guy who installed same setup (arms and coil overs) but with a standard spindle, (no drop) and I think a tall upper ball joint. He had the opposite issue. Car was sitting 2 inches too high , so he adjusted the spanner way down with near 0 preload and ended up at just about the same ride height. And more clearance under the car, higher up lower control arm, tie rod, etc

But he has much more risk of bottoming out the shock and I am sure lots of other aligment/geometry issues i suspect. Arms, etc were designed for a 2 inch drop spindle.
Maybe a 1 inch drop to consider?

Does higher preload generally lead to the need for increased rebound damping?

Don

[marolf101x]

Don,

All things being equal, the same car, the same springs, etc. . .
No. . .increased preload does not require increased rebound damping. The spring rate is still the same.
Changing ride height does not change the load or the spring rate, just vehicle height (technically front/rear weight bias changes slightly, but for this conversation we'll ignore it as it doesn't really affect anything dramatically).

Preload mainly "holds" the car at the desired ride height.
The spring force pushing the car up must equal the weight it is required to hold up.

[shaley68]

Finished the install. Overall, pleased. cornering and performance is significantly better. This is just a street ride but I can tell the difference on the windy roads. No tire screeching and no pushing or understeer. Ride comfort slightly better as well.

I do have some rubbing however on speed bumps. Lots of travel here. See video attached. 235/45/17 Tires. 700lb spring. Maybe go to a 750 spring?

[streetk14]

I could be wrong, but I’m 99% sure my ridetech coil overs came with 750 lb springs. I was worried they’d be too stiff, but that’s not the case at all. This is on a 68 Firebird with an all aluminum LS7. I had some rubbing over high speed bumps until I got the ride height exactly where I wanted it, which is the height in the Streetgrip photos on ridetech’s site.