Thread: Rough Ride ( Suspension Help )

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Got a question for you fellows. This is what I have super-ride on the front I called ride-tech to see what shocks I needed all way around according to the cars weight front and rear I got a good front alignment car drives good tracks good. If you go over a rough place in the road hang on. Everything is good an tight got bout 7000 miles on the car.

Shock absorbers are simply linear de-acceleration devices, you just use the shock that has the correct compression and extension measurements for the suspension travel. For instance, with 4 inches of suspension travel, total up and down, you might use a shock with 5 inches of travel and install it with the rod pulled out 55% of its total travel (5 times .55 = 2 3/4"), so the shock would have 2 3/4" in bump and 2 1/4" in droop. Use any 5" travel shock, no matter the shock length. Fabricate the shock mounts yourself with the vehicle resting on its tires at ride height. A drive-on lift works well for doing the measuring and welding of the mounts.

TIP: Once you have the shock extended to the install length, cut a piece of fuel line rubber hose, about 3/4" long, slit it lengthwise and curl it around the shock piston rod right at the shock body. Wrap a worm screw clamp around the hose and tighten it down. This will allow the shock to remain at the install height so you don't change the length accidentally and make an error in the mounts. Ask me why I do it this way.

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I had a similar problem with mine, ride was good until I hit a good sized bump or rough spot in the road, then look out it would almost change lanes. Turned out to be the axle stops (rubber snubs mounted to the frame) were to long, trimmed a 1/2" off of them with a sawzall and no more lane swapping.

Good info there Tech!

39 Chevy, your rough ride is likely caused by the springs being too stiff for the weight of the car. As Tech points out, the shocks are there only to dampen the motion, preventing the "bounce" and do nothing for support. You might take the shocks off, and see what it takes to rebound the springs, looking for stops that might be too big while you watch it, like 36 Sedan pointed out.

Suspension stuff is interesting to say the least!

If you have a Heidts Super ride on the front, I would think that Heidts would have selected a spring rate that's not too far off. Heidts has already selected what should be the proper coil-over shock length. That should not have to be changed.

I've been going through this type problem with Ride Tech, but it was Ride Tech that selected the 450 lb/in spring rate for my Oze front suspension, that is a copy of the Super Ride II. I went to their spring calculator program and came up with a much softer rate of only 350 lb/in, using a guestimated 800 lbs on each front wheel. I've sent them an E-mail asking how they came up with such stiff springs for my car. It will rattle your teeth when it hits a small mismatch in the road.

One of issues that I'm dealing with is my shock mounts appear to be set to position the A-arms approximately parallel and horizontal, with a shock length of 11.8 inches. This works for their Shock Wave system, but not with their coil-overs. The 10" spring coil-overs have a ride height in the 12.2-12.6 inch range and the 8 inch model is 11.2-11.6 inches. One is too long and the other too short. I may end up cutting off my upper shock mounts and moving them up .6 inches, to work properly with the 10 inch spring length coil-overs that they recommended. They'll probably tell me to just set the length to 11.8 inches or maybe 12 and live with the reduced amount of available shock compression.

http://www.ridetech.com/tech/spring-rate-calculator/


One interesting thing that I noticed with their spring rate calculator is that changing from a 10 inch spring coil-over to an 8-inch changed the suggested spring rate from 350 to 450 lb/inch, with no other change to the input information.

I used adjustable mock-up bars to figure out the near-perfect shock length of 11.8 inches. If the length is any longer, the upper A-arm angle changes from horizontal to being angled down, at the ball joint end. Any shorter and the upper A-arm angles upward at the ball joint end. When I was driving the car this year, I had the shock length set around 12.6 inches. This caused the upper arm to angled down by 6-8 degrees, and it pinched the ball joint dust boot, noticeably. The springs were so stiff, that the shock length was overly long, even with no preload on the springs.

I've had no luck with the Ride Tech technical help folks. The guy I spoke to had no opinion at all about using a softer spring. If he was familiar at all with the spring rate calculator, he would have been able to tell me how much more preload I'd need with a 350lb/inch spring rate (about 1 inch).

The amount of preload that you're using can tell you something about the spring stiffness. In my case, I know that I've use zero preload and the shock length was not still not down to the perfect 11.8 inch length. If you have that situation, then the springs are too stiff. I'm confident that I can drop the spring rate down to 350 lb/inch and use less than 1 inch of preload to get the height that I need.

At the rear of my car I have 200 lb/in coil-overs at a 70 degree angle. The ride tech calculator says that 175 lb/inch springs will handle 725 lbs at each wheel, so I plan to reduce the rear spring rate, too. I know that I've driven the car with no preload on the springs, when I had the rear set to the lowest height that I ever tried. I didn't realize that I had no preload until I put the car up on my lift and noticed the rear springs were slightly loose. This is not desirable because the springs won't center on the top mount, without some help. You need at least a little preload.

Keep us updated after you make the changes, and good luck.

is your REAR suspension like?
Do you have ang pictures of your install/build?
Have you corner weighted the car? Does it vary much with passenger load and fuel quanity(pass 150-250# each and fuel 7 lbs/gallon)
Angles of your suspension arms, spring angles, shock angles-any known shock percentage ratings?
Tire sizes and pressure

and lets not forget the correct tire pressure in your tires for the weight of your vehicle. I know w/my 65 VW Notchback the only way I could get the rough ride out of it was lower the tire pressure in the front & rear. I don't care what anybody says, tire pressure does matter....joe

This is what Ride Tech said I needed shock 3.6 travel bearing upper an lower mounts 9.425"/ 13.025" coil spring 8" free length 375lbs. Shock 5.2" travel bearing upper an lower mounts 11.225"/16.425" coil spring 12.0" free length 225lbs
This is the weight each side of the car DS 761, PS 756 LR 874 RL 837 all of this is new to me this is my first time around. Setting aside not getting in to name calling I have grew up with the people that built most of the car I really thought they knew what they were doing with the name they have. I have had to rework everything they have done. We never get to old to learn had a 1st cousin tell me one time your friends is who you have to watch because your enemy's want come around.

If you want some answers, forget about bickering about your friends and give us some info-----------Do you have coil over shocks on the front?
What type suspension on the rear?
tire/wheel/psi?
length of any suspension arms
angle of suspension arms
measurement of where the spring/shock are on the arms----------


How about some pics of the under side??


Personally I'm thinking that your car may be too heavy for coil over type suspension at that travel distance-


Your suspension arm length is going to be considerably longer than where your springs/shocks are so the pressure/leverage? is much higher and you probably need at least double those spring ratings


a spring rate at the spring location IS NOT egual or even near the weight of that corner divided by the travel distance----

If all commenting haven't done so, taking a look at the Heidt's super ride II suspension at the website linked below will provide some answers. I have to assume that Ride Tech knows the A-arm dimensions and spring angle or 39 Chevy has provided them, to input into the spring rate calculator. Without those dimensions, there is no way to suggest a spring rate.

HEIDTS SUPERIDE II Front Suspension for 30s, 40s, 50s Fat Fender Fords, Chevy & Willys - HEIDTS

Spring Rate Calculator « Ridetech – Tech

The only way to get an idea if these suggestions might improve the ride is to compare the suggested new setup to the current one. If you can't get the spring rates on the current setup, there's no way to know if the springs are softer or stiffer than what you have now. Heidt's should at least know what they consider to be the most common spring rate for this front suspension.

I wouldn't think that Heidt's would sell a Super Ride II front suspension for a '39 Chevy if it was too heavy.

I gave Ride Tech everything they ask for that's where all those numbers came from. 4 link on the rear top arm center to center 16 1/2 bottom 24 1/2 245-40 ZR20, 235 40 ZR18 psi front 32 rear 34

Looks like something is wrong at the front, with that much preload on the spring. That would actually indicate a spring that's too soft and the adjuster had to raised way up to get the necessary ride height.

Did Ride tech ask for all of the dimensions on the spring rate calculator? If not, I'd be sure that they really know what they are. I've talked to some of their tech guys who seem to be clueless.

The length of the front shock should be no more than 11.6 inches at ride height.