[The Federalist Patriot]

I am having a lot of trouble getting proper ride height adjustment in the rear with my pin drive width IRS setup and Levy's Konis. I have a ton of preload cranked into the spring just to get it where it is in this picture:

At full droop, the wheel barely hangs down as in these pictures:

I already have the long ends on the shocks that Gordon provides. The shocks I have measure 15 1/2" (eye to eye) at full extension (including the longer end). When I go from higher to lower levels of pavement you can feel the wheel "drop" and bottom out at the shock extension length. Something is not right with this and I am wondering if others are experiencing the same. Gordon has suggested redrilling the upper shock mount at a lower point but there is no room for that. The pickup point needs to be relocated which I'm not excited about doing. The shock seems like it needs to be another 1 1/2 - 2" longer. Any ideas from others with PIN DRIVE width setups?

 

[Mumblerone]

What rear suspension are you using: 4-link, 3-link, IRS, Levy 5-link? :001_huh: :silver:

 

[Gordon Levy]

I believe the issue comes from the tire you are using. I never designed the shock to work with that big a tire but I do have an option. We can use a live axle rear shock that is 1.5" longer than the current shock you have. Give me a call tomarrow and we can talk about it.

 

[The Federalist Patriot]

Gordon, I bet that will work. I even tried swaping to a shorter spring and am almost tapped out of available adjustment thread. If that longer shock fits better I think a lot of pin drive guys will have interest because it seems to be a common problem with the rear shock fitment on pin drive IRS in general. FFR Konis, QA1s, etc have the same issue so it's not "your" shock that is the problem. It's really peculiar because you would think the shorter control arm would make the shock more upright and allow for an even shorter shock but it seems to be otherwise. I'll give you a ring. Thanks.

 

[Mike D]

That is one gooood lookin' Cobra. The right wheels and tires sure make a difference!

 

[The Federalist Patriot]

Thanks Mike. Although Gordon called my tires fat.

 

[David Hodgkins]

You know what they say...

Thanks Mike. Although Gordon called my tires fat.

Personally, 'yall can keep your stick/twig anorexic tires. I like mine with more cushion for the pushin'!!

 

[rich grsc]

If you compare pin drive to standard width the mounting position of the shock doesn't change, the angle is the same. Pin drive has the mounting ears for the hub turned up, thus the bottom arm is lower at the hub than on a standard width. It makes sense that a pin drive would need a longer shock than standard width IRS. Why isn't a different shock used?

 

[Gordon Levy]

It's all and only bacause of the tire he's using. I have been using my Koni shocks in these cars for 6 years and this is the first issue I've heard. This is a one off issue that Fed and I will get corrected for his car.

 

[The Federalist Patriot]

If you compare pin drive to standard width the mounting position of the shock doesn't change, the angle is the same. Pin drive has the mounting ears for the hub turned up, thus the bottom arm is lower at the hub than on a standard width. It makes sense that a pin drive would need a longer shock than standard width IRS. Why isn't a different shock used?

Rich, I think you may have put your finger on something there. I was not aware of that difference in control arms between standard and pin drive. That sort of thing would explain the problem I and others experience as it relates to the amount of preload we have to crank into the springs in the rear to get the proper ride height. For what it's worth, my tires are 26.5x10.5x15 in the rear. That equates to shorter than a 295/50-15 tire. Gordon and I are going to try a few different things to get this dialed in properly. Fortunately he has some options in terms of adjusting the length of his shocks. Thanks for the info as that explains the "why" that I wasn't aware of.

 

[convincor]

Same problem with my FFR Koni's. Using up most of the adjustment in preload to get it to correct ride height. 295/50-15 pindrive IRS.

 

[Larry N. Johnson]

pd irs

Mk II
Pin Drive arms
IRS

Old 3850 had the same exact problem when switching to FFR Koni's and 750 lb rear springs, 8" long: could not get ride height up easily.

Went to 500 LB rear springs, 10" long...problem solved completely.
Ride height easily made, no extra-ordinary spring preload.
(I do remove the shock to adjust the spring pre-load, though as it is hard getting a tool up there.)
1.75" threads yielded 4.5" ride height w 295/50x15 Goodyear Eagle GTII tires.

 

[convincor]

Larry, I remember you had gone to the longer spring but wondering is the longer shock may also be a good idea..
This was a pic of mine at full compression. The upper control arm hits the frame before the shock would bottom out..

 

[Larry N. Johnson]

bottom

Not sure on that question.

We don't get that much compression, so why the concern?

Ride height is a function of spring length, not shock length; right?

 

[The Federalist Patriot]

Not sure on that question.

We don't get that much compression, so why the concern?

Ride height is a function of spring length, not shock length; right?

Larry, the problem I'm having is the shock is at full extension. With the adjustment ring you can account for variances in spring but the total shock length can limit how far you can go. Did you happen to measure the full extension length of the FFR Konis - eye to eye? Anyone know?

 

[Larry N. Johnson]

total length

Fed,

No, the FFR Koni shocks were not measured full extension. Next time I take one off, I will measure it for you.

Larry

 

[rich grsc]

I think that maybe some sort of bracket to move the lower shock mount even with the control arm tubes would about make up for the length difference. Wish I still had my standard width irs lower arms, then I could lay it side by side with the pin width and measure the exact change in length.

 

[bhumberstone]

Hay Fed
I have the same issue Gordon's Konis with Pin Drive and 26.5 tires. Vary little droop and too much compression. Just opposite on the front to much droop and little compression. So much droop that it bound my tie rod ends when on the jack stands (i have Gordon's relocated steering rack.) Fixed that by fabricating new higher upper shock mounts. Farley easy but the rear upper mounts look a little more difficult to redesign. The 1.5" longer shocks should do the trick if not to long. I will call Gordon and see how it works out with you.
What back spacing do you have on your front rims? I also have Gordon's Willwood 4 piston brake kit and had to switch to fox spindles. Looks like I might have a tire rub issue on the front. Still to early to know for sure as i have have only temp mounted body but tires hang out past wheel well flares a bit
PS nice looking ride
Bruce

 

[The Federalist Patriot]

I guess the offset in the rear lower control arm spindle mount is what's causing this issue and explains why a longer shock is needed. Apparently the standard width IRS arms mount the spindle in-line with the arm. Measuring from the bolt in the spindle to the centerline of the pin drive width arm is right about 2 inches. I *think* I need around a 17 1/2 inch shock back there as opposed the 15 1/2 I currently have.

Here are the shock extenders on mine currently:

 

[Lukas]

Hi Jim and everybody else!

I am finally getting back on my unfinished Kit, and have the same setup with pin drive IRS and Gordon's Konis. Did you end up swapping out the shock for a 1.5" longer one or did you relocate the upper shock mount down by the same amount?

Cheers,
Lukas