[leejoy]

Hi

I bought my 72 nova from a dude who put air shocks on the back. that's ok except to raise the back end up a bit it looks like he pumped a little more air in there. It looks good except the ride is VERY ROUGH. going over even very small bumps and dimples in the road feels like driving over speed bumps. I don't know much about suspensions and shocks but I think that the shocks are picking up the load that the leaf springs normally pick up. Am I right? and basically the leaf springs are serving no purpose at this point because all the weight of the vehicle is carried by the air shocks.

what can I do to correct the problem and not "lower" the back of the car? It needs to stay at that height to allow for rear wheel clearance and sit a little higher than the front of the car.

[torinotroy]

Does it sound like metal to metal when you hit the bumps? I got a 72 torino that I bought from a "homie" , and that knucklehead put s-10 truck springs in the back to make it stiffer launch. He also removed the spring insulators. , so everytime I hit a bump bringing it home it felt like what you're describing. He also had the front end jacked so high in the air it was hard to see.... .....2000 bucks later it's settin right! . I did have airshocks on a 77 firebird and it was a rough ride, maybe it's just how they are.?. Maybe you could get a "HEAVY DUTY" springs for your year? Ya never know. Good luck with it though, torinotroy

[jimfulco]

GM rear leaf springs are famous for sagging. I replaced my '72 Nova springs with new GM ones (same part #) & they sagged farther in 10,000 miles than the original ones did in 100,000. If yours aren't in bad shape, they can be re-arched at a spring shop. I had some re-arched (not the same car) and they seemed to stay up OK.

Herb Adams VSE used to make shackles that were an inch or two longer (& much heavier-duty) than stock & would compensate for the sag, but they are no longer in business. The cheaper aftermarket "multiple-holed" shackles aren't very good. Load-leveler shocks (spring-shocks) may help, but they tend to make popping noises over bumps sometimes. Air shocks might work, but if they spring a leak somewhere in the boonies, you're back to square one.

That was from a previous post. I could have sworn I posted the dimensions of the VSE shackles, but I couldn't find them when I searched.

[IanRiordan]

I have air shocks in my 96 Holden statesman and it rides like a dream. It has fresh factory coils and I only inflate the shocks over 15psi when laden.
The 4x4 blokes often use an 'add a leaf' too restore ride height - it may help you. Springs are there to carry the weight, shocks control their travel. An air shock is a band aid like a 'helper' or overload spring.

[leejoy]

Originally Posted by jimfulco

GM rear leaf springs are famous for sagging. I replaced my '72 Nova springs with new GM ones (same part #) & they sagged farther in 10,000 miles than the original ones did in 100,000. If yours aren't in bad shape, they can be re-arched at a spring shop. I had some re-arched (not the same car) and they seemed to stay up OK.

Herb Adams VSE used to make shackles that were an inch or two longer (& much heavier-duty) than stock & would compensate for the sag, but they are no longer in business. The cheaper aftermarket "multiple-holed" shackles aren't very good. Load-leveler shocks (spring-shocks) may help, but they tend to make popping noises over bumps sometimes. Air shocks might work, but if they spring a leak somewhere in the boonies, you're back to square one.

That was from a previous post. I could have sworn I posted the dimensions of the VSE shackles, but I couldn't find them when I searched.

there is a local spring shop around here that I've done business with in the past. I will call them and run your thought by them and see what they think.

[roddinron]

I believe your Nova has single leaf springs, and they are notorious for sagging. If you really want to do it right, replace them with a multi leaf spring. And don't try longer shackles, that only makes them sag more. You might get a little better results with some airbags instead of airshocks, but in the end, I think you'd be happier with a multi leaf spring change.

[leejoy]

Originally Posted by roddinron

I believe your Nova has single leaf springs, and they are notorious for sagging. If you really want to do it right, replace them with a multi leaf spring. And don't try longer shackles, that only makes them sag more. You might get a little better results with some airbags instead of airshocks, but in the end, I think you'd be happier with a multi leaf spring change.

that 72 nova has multi-leaf springs (4 or 5) I will call a local spring shop I've dealt with in the past and ask their opinion. Should I replace them or have them provide a different solution.

[crankshaftkid]

Most air shocks are heavy duty and do ride somewhat rough even without being aired up and will ride rougher with high air pressures.
Re-arching can work well and a spring shop should be able to tell you if your springs are worth working on. Adding a leaf helps too. Raising the rear of your car an inch or so is usually ok but raising it several inches can hinder traction because it changes the front to back weight bias more to the front. If you raise the back 6" for large tires for example, you probably won't gain anymore traction than what you had with the car sitting level with the old tires.

[roddinron]

Originally Posted by leejoy

that 72 nova has multi-leaf springs (4 or 5) I will call a local spring shop I've dealt with in the past and ask their opinion. Should I replace them or have them provide a different solution.

Oh, I thought they were all single leaf, I bought a 72 ventura recently and it has multi leaf springs, but while going through the glovebox I found a receipt from the 80's for changing the rear springs, and assumed it was originally a single leaf like my old 69 Camaro was.

[DrChop]

There is one simple rule for using air to support the vehicle weight, both static and when in motion...

Bigger is better. But why is this?

Lets look at tires for a minute. Your average 10-speed bike rides on a tire of thin cross section, and large diameter. This is fine for these bikes, as they are not usually used on rough terrain, and the wheels/tires can be of thin cross section, since the wheel largely sees radial loads, even when cornering, as the bike is leaned into the corner. As an aside, some of the more expensive bikes have run glued-on tires, and even that example shows how most of the load is carried radially. Most all of these tires run pressures anywhere from 60-180 PSI, depending on manufacturer. These tires are designed for low rolling resistance at high pressure, and most times running them softer for a cushioning effect just ends up ruining the tire when it hits a bump and allows the rim to be bent. High pressure and low-volume to carry the load.

Now lets look at a mountain bike, its wheel has a larger cross section, as does the tire. Many cases it has 2-3 times the volume of the 10-speed tire, so the pressure does not need to be as high to carry the same load. Reading the sidewall shows this as most run between 25-40 PSI.

As we get into hauling more weight around, say on a motorcycle, 3 or 4wheeler, the diameter drops down and the section width increases, as these assemblies require side loading also in order to corner. Appropriately as the loading of the tire increases, so must the volume of air to carry the load. The more air volume, the softer the ride feels at a given pressure.

This translates directly to using air as a spring medium also. Airshocks typically have very small volume and as a result must be inflated excessively high pressure to help carry a given load. This translates to a rough ride as the suspension is now excessively stiff for the average bump. I have personally witnessed broken shock mounts caused by running airshocks pumped up on the street. SHOCK MOUNTS ARE NOT ENGINEERED TO CARRY WEIGHT!

I would suggest leaf spring replacement/repair as the first option, using quality parts and vendors.

If some degree of adjustability is desired then I would suggest adding 2500# double-convolute airsprings to appropriate strong mounts over the rear axle, just inboard of the existing leaf spring packs. These will end up supporting a small part of the load, but their main reason for staying would be to locate the axle. A pair of 2500# airsprings will likely hold the back of the Nova at desired ride height somewhere around 25-35 PSI, and allow a soft ride. For comparison, the smaller-volume 1700# airsprings I currently have on the rear of the Kustomsledd are topped out at 50PSI, and while it feels considerably stiffer than the front end does I feel it will ride better (softer) with more rear air volume.

Doc

[leejoy]

Originally Posted by DrChop

There is one simple rule for using air to support the vehicle weight, both static and when in motion...

Bigger is better. But why is this?

Lets look at tires for a minute. Your average 10-speed bike rides on a tire of thin cross section, and large diameter. This is fine for these bikes, as they are not usually used on rough terrain, and the wheels/tires can be of thin cross section, since the wheel largely sees radial loads, even when cornering, as the bike is leaned into the corner. As an aside, some of the more expensive bikes have run glued-on tires, and even that example shows how most of the load is carried radially. Most all of these tires run pressures anywhere from 60-180 PSI, depending on manufacturer. These tires are designed for low rolling resistance at high pressure, and most times running them softer for a cushioning effect just ends up ruining the tire when it hits a bump and allows the rim to be bent. High pressure and low-volume to carry the load.

Now lets look at a mountain bike, its wheel has a larger cross section, as does the tire. Many cases it has 2-3 times the volume of the 10-speed tire, so the pressure does not need to be as high to carry the same load. Reading the sidewall shows this as most run between 25-40 PSI.

As we get into hauling more weight around, say on a motorcycle, 3 or 4wheeler, the diameter drops down and the section width increases, as these assemblies require side loading also in order to corner. Appropriately as the loading of the tire increases, so must the volume of air to carry the load. The more air volume, the softer the ride feels at a given pressure.

This translates directly to using air as a spring medium also. Airshocks typically have very small volume and as a result must be inflated excessively high pressure to help carry a given load. This translates to a rough ride as the suspension is now excessively stiff for the average bump. I have personally witnessed broken shock mounts caused by running airshocks pumped up on the street. SHOCK MOUNTS ARE NOT ENGINEERED TO CARRY WEIGHT!

I would suggest leaf spring replacement/repair as the first option, using quality parts and vendors.

If some degree of adjustability is desired then I would suggest adding 2500# double-convolute airsprings to appropriate strong mounts over the rear axle, just inboard of the existing leaf spring packs. These will end up supporting a small part of the load, but their main reason for staying would be to locate the axle. A pair of 2500# airsprings will likely hold the back of the Nova at desired ride height somewhere around 25-35 PSI, and allow a soft ride. For comparison, the smaller-volume 1700# airsprings I currently have on the rear of the Kustomsledd are topped out at 50PSI, and while it feels considerably stiffer than the front end does I feel it will ride better (softer) with more rear air volume.

Doc

well said. I will be getting new leaf spring kits anyway. I called the local spring shop and they can get me a pair of new springs - with the bushings installed for $200. sounds fair? I will check the ride after those are installed. If still stiff, I will adjust the air shocks. If still bad, I may replace the air shocks. If still bad, I may do what you suggested. I am still deciding whether to use regular slapper bars or those more expensive Caltrac bars. What do you think? This is only a 11 second street car, not a 8 or 9 second drag racing car. Thanks. I will continue using the standard 9 inch wide tires, probably slicks.

[DrChop]

Do not be in a hurry to judge the ride they give. I tell my customers that they should'nt make any subjective judgements as to ride quality or stiffness until the new springs have time to wear in and take a set from the vehicle weight. What is percieved as too stiff when new is often just right after the first 3 months. Also remember you are used to wornout springs and too-stiff shocks. Might be worth it to throw a set of cheapy gas-charged shocks on along with the springs and drive it awhile, THEN correct any problems.

Doc

[leejoy]

Originally Posted by DrChop

Do not be in a hurry to judge the ride they give. I tell my customers that they should'nt make any subjective judgements as to ride quality or stiffness until the new springs have time to wear in and take a set from the vehicle weight. What is percieved as too stiff when new is often just right after the first 3 months. Also remember you are used to wornout springs and too-stiff shocks. Might be worth it to throw a set of cheapy gas-charged shocks on along with the springs and drive it awhile, THEN correct any problems.

Doc

ok, good advice. I'd just assume get rid of the air shocks if I can. this car has a big block conversion and I threw new front coil springs in there so the front of the car sits at about the same level as the back (front is a little lower) Before the big block coil springs the front of the car sat very low. I'm afraid if I remove the air shocks the rear of the car may end up sitting 2 or 3 inches lower than currently and the vehicle will look goofy. If that is the case, I would need to lift the rear of the vehicle using some type of lift kit spacer or something at the leaf springs. do you agree?