65air_coupe

This may seem odd to some but humor me. I've been in search of better shocks for the rear of my 65 coupe for some time now and am beginning to feel like I'm not addressing the actual problem. That is better damping over a series of small bumps like you encounter on certain bridges. I started with gas Bilsteins and then some Monroes and now have Ride Tech adjustables. I'm certainly no suspension expert but it seems to me that most of the unwanted motion I'm experiencing isn't the car but the seats. I have stock seats with new foam and they're very springy. And going over the bumps I've described is somewhat like a pogo stick...with each bounce I go deeper into the seat and then rebound higher.

So I guess my question is, does anyone else experience this? And for anyone that has changed to different seats find it to be any different?

65air_coupe

Even though I didn't get any responses I do have something to add - I was watching the latest episode of the sci-fi series ''Manifest which prominently featured a 67 big block coupe with sidepipes. And unlike many TV car scenes, they were actually driving this one with cameras in and outside for the various shots. At one point, they had a camera outside the driver's window looking across at the driver and passenger having a conversation and I had to laugh to see them both bouncing up and down like they were sitting of those stupid bouncy ***** that have become popular with the millennials. And that's what I'm talking about!

AzMotorhead

Didnt see this when you first posted but I too have experienced too much spring in the seats.
It's due too the density of the foam. Some places tell you that the foam is just like OE and it'll wear in or settle down over time
To them I say HOGWASH. It would take over 25 years for that foam to get to what OE foam was like new.
There's only Two places I would Buy foam from Al Knoch or ACI
To get a better feel from the foam you have installed right now you'll need to uncover the seat and carve out some of the foam in the centers.
If you dont want to shave off the thickness in those areas another trick you can do is to cut 1" round dimples at a depth of 1-1.5 inches So it resembles a waffle pattern
in the center of the foams.
I've redone 3 sets of seats with Al Knoch materials and haven't had any complaints.

Patman65

I'm betting the majority of the issue is not in your seats. This pogo feeling with your rear flying up out of the seat is a result of improper rebound control. It's an unpopular opinion here but Bilsteins (sport or HD) on a heavy duty / F41 race spring is a crappy pogostick ride on the street ..pogo galore. I cant remember exactly what the feel was like with bilsteins on a stock spring car but I didn't switch it out because it was anazing, evidently you upgraded too. A quality double adjustable shock set correctly should fix this. Pay special attention to the rear rebound rate.

Also I have new seat foam for my seats, I've noted they do tend to be firm whether that's firmer than original oem is beyond me. I've spent a significant amount of street tuning time for a smooth performance oriented ride and Im thinking the shock tuning may eliminate almost entirely what your experiencing.

P.S. I'm a millennial, no bouncy ball or bouncy '65 here

DansYellow66

I haven't noticed the effect of bouncy seats (I don have one that rocks a bit due to worn tracks) but maybe I just haven't zeroed in on it. If enough of an issue you might try tying the springs which not only firms them up but would tend to limit movement of them. Someone posted a good picture of springs tied with upholstery cord recently.

65air_coupe

It's my intent to replace my seats sometime this year, either with the C3 clamshell variety or early C4 seats. I certainly need to sit/ride in both before I make a decision.

65air_coupe

I'll admit that a portion of the problem is with the suspension but I'm not sure I'd say the majority. And I agree it's the rebound stroke on the rears that need addressing. I'm far from being a suspension expert or even a decent suspension tech but my engineering background helps. My reasoning at this point is that on the jounce part of the travel, your body travels downward into the seat at approximately the same velocity as the car is moving downward although your motion is delayed as the seat is first going to decompress somewhat when the car moves downward. Then the suspension is going to reach the bottom of its travel while you are still moving downward as a result of the early delay in motion. The car then rebounds and if properly damped, ideally will return to close to the original state but in most cases there will be some overshoot on first rebound. A properly tuned suspension seeks to minimize that overshoot.

At this point, your body has also reversed direction and the seat is rebounding but without any significant damping as it's just two types of springs in series with each other. You will continue to travel upward after the car has returned to its neutral position and how far you travel is based on the amount of initial travel downward, the speed of the rebound plus any inherent damping in the seat. To minimize your travel without modifying the seat, the rebound of the shocks should be highly damped so there's virtually no overshoot. And here's where my lack of knowledge shows...I suspect that's not an ideal rate of rebound damping for all conditions. The suspension needs to recover at some rate to be able to handle a subsequent bump, otherwise you'll soon have inadequate travel if negotiating a series of bumps.

And I'm aware I'm not addressing the amount of jounce damping in this discussion as so far I've only dealt with varying brands of shocks without adjustable jounce damping.

Easy Rhino

I haven't ridden in every car with every shock/seat combination; however, it occurs to me that any "pogoing" of seats would have to be an amplification of a body bounce.

I would have someone film my car from the rear while driving on various irregular surfaces and see if the tail is bobbing and whether it is both up and down or upper rebound only.

65air_coupe

Good idea, I'll try it and it would be especially useful if I can be seen as well.

skids

Might need a softer spring rate in the rear.

BLUE1972

Try dropping the Air Pressure in the tires. I run 29 on my C2. (cold)

At 35 # it bounces. The car calls for 24 - 28 If I remember right.

65air_coupe

It's only a 300# so doubt I could go much softer.

I'm running 30 but will give 28 a try.

Patman65

300# steel or fiberglass? What tire size? What ride tech shocks? What style of driving ? Sorry if I missed this info earlier.

You could theorize about this many ways to try and get an answer, I do this about corvette troubleshooting all the time b/c it's fun. But my reccomendation assuming this is a street car you wish to be a good mix of comfort and performance:

If your spring is 300# steel 7 leaf and the ride is too firm, switch to the 9 leaf spring and use double adjustable shocks to really hone the ride in. If you like your 300# firmness use dub.adj. anyhow. If you want something between the stock and 300# steel spring you may want to switch over to a fiberglass arrangement.

I drive a big block w/ a 375# fiberglass. Essentially what I did was find a nice strip of road several miles long and lapped it all morning so I knew ever bump and irregularity. Each pass I would dial up the rebound settings 2 or 3 clicks comparing the ride until I found the feel I like. Once you hit the sweet spot, the ride is..well sweet however either side of the sweet spot setting rides like one of those inflatable moonwalks you see those generation Z kiddos hopping in

65air_coupe

It's a 300# fiberglass which is part of the reason I've been experimenting with different shocks. I started with the recommended Bilsteins because of the unique rebound characteristics of the fiberglass but wasn't satisfied, tried the stock AC/Delco just as a reference, then a set of Monroes that some other members running fiberglass have been satisfied with. I'm just starting on the process of dialing in the single adjustable Ride Tech and it was during this period of scrutiny that I noticed that I'm unable to separate the performance of the shocks from the action of my seats with their new foam, hence my question. Do you have stock seats and is the foam new or original?

DansYellow66

Fiberglass spring and bouncy ride seem to go together from numerous reports/observations. I guess it takes some experimentation to get the shocks dialed in so the dual adjustable shocks are probably the best approach.

DSR

I had a 315lb fiberglass spring in my '65. The car road like a tank! I installed a stock replacement spring from Paragon with my old Edelbrock shocks and Michelin Defender tires. Most people that ride in my car now comment on how smooth the ride is.

Factoid

65air_coupe

I wouldn't say I've isolated the problem to my seats, just that they make it difficult to evaluate the settings on the shocks. I think videoing the car from the rear while going over a specific set of bumps is the best approach. Or wait until I upgrade my seats before trying to fine tune where I'm at any further.