Hot Rods Generic Suspension Question

Our 57 was very similar.
There was so much spring load that I needed to spread the springs so the shackles could be installed.

Most people don't understand there is 2 ratings for springs [one is stiffness, and the other is "load" or load rating]

You can sometimes have a softer stiffness spring with a higher load rating [comfort]
Load rating is generally the "shape" [or free length]

A good example is the 69-70 Boss Mustang vs a 6 cyl "grocery getter" Mustang.
The Boss has stiffer springs but less arch, so it's ride height is 1" lower.

When we re-set springs we are only altering the "spring load" not the stiffness.
Adding or removing leafs is altering the stiffness.

A spring is needed to be matched to the desired ride quality [height and frequency]
A shock needs to be matched to the spring [also frequency]

@moparjack44 it would really help if we knew what your spring stiffness and rear sprung weight is?
But sometimes this is quite difficult to get answers.
That is why I asked for ride height and free height measurements [I can generally figure out if a spring is too stiff by how much it settles under load] [and desirable frequency]

You could have springs or shackles binding, or the wrong shocks [or range] , but wrong stiffness is ususally the problem [hence you originally asking about removing leafs]

You could "Machine Gun" your car with off-the-shelf-parts and still get nowhere. [except less disposable income]

 

That shock is 10.800" compressed, and 16.330" extended. That is 5.53" of travel.

That shock will not work.

The wheels on the ground distance that you measured between your axle and frame is 6-inches. You need over 6-inches of travel just for compression, so that the axle hits the bump stop before the shock bottoms out internally.

If you just selected a shock with 6-inches of travel, you would have zero droop travel, with the wheels still on the ground. At-rest, your shocks would be topped out.

You need 6-inches, plus droop travel.

You reported your static droop distance as 9-inches from the frame, or 3-inches of droop. Add that alone to the 6-inches that you need for compression, and for that alone you need a shock with 9-inches of travel.

Since it is also a bad idea to top out your shocks, say dropping a single wheel into a pothole, I'd like to see 2 more inches. That would be 11-inches of travel.

11-inches is a far cry from 5.53-inches.

 

Now, with a reported distance on the ground between the shock mounts of 13-1/2" that would mean:

The shock when fully compressed should still have a little travel when it is 7-1/2", so lets call it 7-1/4"

With the aforementioned 11-inches of travel, that would put you at a shock that is 18-1/4" extended.

You can round up on the extended length if it is required.

 

What is the distance between your axle and the bump stop that would cease its upward travel?

 

You find anything in your Monroe catalog that has that required extension that will work?
Are all my measurements that odd or out of the ordinary? Can't believe that it is so odd. I guess that is why I named the car Odd rOd, and have vanity plates to prove it.

 

I am too, but I will tell you that I popped for the Bilstein shocks on my 35 and they are worth the money. Totally different ride.

 

Based on your numbers, no shock appears to exist that will fit the bill.

Please double check the distance between your axle and the bump stop. That is the real correct compression travel maximum.

It may come to pass that you will have to relocate your shock mounts in order to accommodate a shock that is actually produced.

 

Nothing. I realized today that bump stop in drivers side is completely gone??

 

How about the passenger side?

 

My bump stop is about an inch long.

 

Passenger side.

 

So the distance between the axle and the bump stop on that side is 5-inches?

 

IMHO if you need 6" of compression you are running way too soft of a spring. 6" and 3" of rebound would work if you are going off roading. The rear shocks on my late model stock car have 9" of travel and are 21" extended. It could be pretty tough to change shock mounts to accommodate that, I still say a 6" strke shock will work just fine in this case if set up properly. And is readily available.

 

Getting answers here is like pulling teeth

 

I would put in a pair of 4-inch tall Daystar windowed bump stops to limit the compression travel to about 4-inches max, and base the shock selection on that.

 

WOW!
You guys doing Baja driving or street driving?

I just can't imagine a street car exceeding 5" of shock travel over the course of 95% of its life. For that 5% it may need more travel, I'd take a chance on the shock limiting the travel. I'd much rather that limitation of travel be on the droop end as a matter of choice. I guess if I hit a bump large enough the shock will limit the upward body travel, then the wheel will just have to come off the ground. Its probably going to bottom something out when the car comes back onto the ground. Bottoming out on the bump stops would be better then bottoming out the shock, maybe... Would possibly replacing shock or shock mounts, or replacing a bent axle housing be better?

Hopefully I'd see that big of a bump coming and could be slowing the car down a lot before that big bump.

Give me a shock with 5" - 6" of travel. I want 3" of compression, and 2+" of expansion at ride height. Chose the length of the shock accordingly. Gene

 

I don't think anyone commented on this yet, so here goes: My experience is that most old (pre-1965) have wishy washy rides. Most need stiffening up, not softening! Usually cutting a coil helps, and using good gas shocks adds to it. I wouldn't remove a leaf from a passenger car suspension. A truck, yes, as they were made to haul heavy loads in the bed, If you want a truck to ride like a car, remove a few leaves.

 

Yes

 

I have probably put 70000 miles on this car. To my knowledge it has never hit bump stop on the rear. Never?
Jack

 

This is spot-on. I had custom leaves made for my Falcon. I had them made with a combination of one more leaf, and a higher rate.

My front coils look like monsters compared to the stock ones, and it has gas shocks on all 4-corners.

 

Bump stops exist for a reason. They exist in one form or another on every single vehicle on the road today, including quite a few HAMB era vehicles.

If your axle housing can bend response to hitting a rubber or poly stop, it will have long since failed from metal fatigue from normal operation. This is basic materials science.

In the case of a unibody car, bottoming out a shock can mean putting that shock, mount still attached, through the floor of the vehicle. That is not an easy repair. I have seen this done with many Ford platforms.

In the case that a bottom mount is broken off, that can cause the shock to hit the ground. This can cause catastrophic loss of control of the vehicle. I saw this a bunch in the 1970's when everyone had 100psi in their air shocks.

I got to watch a whole bunch of nice muscle cars get totaled.

The OP appears to have been running shocks that would have bottomed out, or maybe have been bottoming out.

From the described symptoms, this could easily explain the ride quality issues. Nothing feels quite as stiff as an immovable suspension element.

He has only a single bump stop, on one side. None of the suggested shocks would allow the axle to get anywhere near that stop, and some pretty far from it.

And nobody is saying that he needs 5-6" of compression travel, just that he needs to have more shock travel than axle travel. We are trying to work within the constraints of his chassis, fabrication abilities, and budget.

 

I am in agreement with everything you said.
I think maybe we have beat this horse to death. I have been given plenty of great input, now it is up to me and get off the pot, and put some of the great suggestions into action and see what happens.
Jack

 

70 000 miles...... impressive.
Got to ask now. You say in post #7 that you recently installed new shocks. How did it ride before you changed them???

 

Hard, but I realized very stiff shock, but not enough compesson stroke? The ones I put back on were the KYB, better, but still not much compression stroke, about an inch before bottoming out(the shock, not against the bump stop).
How much should I add to the shock mount to get about 3 inches? Common sense tells me I need to add 3 inches? But when comes to shock travel and suspension, seems common sense doesn't come into the equation.
Thanks,
Jack

 

@moparjack44
This might help with working out what shocks you need. Watch it all. The bit that starts at 1:09 is what you need.

Get the measurements the video asks for and post them up. We will help look for the shocks you need.
We already have the static ride height length - 13.5".
We have 5 inches of room to the bump stop, so 13.5 minus 5 = 8.5" compressed length (maximum - 7.5 or 8 is better as it gives some leeway).
We need the length with the car raised up and the wheel at full droop.

If you can't find shocks to suit, then we need to think about changing the mount positions to suit a shock size that is available. You will need to choose an appropriate shock and have the lengths before you work out how to shift the mounting brackets to suit.

 

Thanks. Yeah I built the car to drive, not haul around in a trailer (I do not own a trailer), did not build to race (maybe stop light drags once in a while), did not build to use as decoration for my garage ( tho I do have a garage). Don't give a rats @$$ about trophys. I like beer, people, and driving, no particular order.
Jack

 

Yeah, video over my grade level. I barely graduated from high school, and that was in 1962. Somewhere in this thread, I posted measurements on car sitting on the ground, then at full droop, with shocks disconnected.
Would appreciate your assistance and suggestions.
Jack

 

Well, any 3 or 4 bar suspension has the shock as an extension limiter unless there is some kind of strap or chain limiter.

I'm sorry, but I respectfully submit that you will never find a shock with 8.5" compressed length and 5" of compression plus 2"or 3" of extension (8"-9" of stroke) especially with a 13.5" ride height. It is just not physically possible.
You don't need to account for every inch of available frame movement with shock travel. Only what the suspension will travel with the current spring values.
As far as extension, you only need what the car will experience going down a bumpy road. I know that we talking about a leaf spring suspension here, but every 3 or 4 link rear suspension has the shock as the extension limiter unless there is some strap or chain as a limiter. As a general rule, most 4 bars do not have limiting straps.
I don't care what shocks you have in the car, if the wheel hits a 12" deep pothole the shock is going to top out. Same with hitting a 12" sudden bump in the road. You can't get a shock that will handle the extremes of chassis movement. That is up to the operator.

 

Ok. We need three measurements. Check them properly and post all three.

1). Car sitting on the ground. Top of axle housing to bottom of bump stop.
2). Car sitting on the ground. Center of top shock mount to center of bottom shock mount.
3). Car raised so wheel is just off the ground. Center of top shock mount to center of bottom shock mount.

Without all three measurements we are only guessing.....

 

I agree. When we get the three measurements I have asked Jack for, we can identify an available suitable shock, and then calculate where the mounts need to be to make it work within it's stroke range.
I think he just needs some help with walking him through it in an easy to understand way, and that's ok.