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Thread: Air Suspension

  1. #1
    Junior Member
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    Air Suspension

    On my xk120 replica the original owner (he did not finish it) used the Mustang II parts. Here's the rub, don't know what spring rate he used. Engine is in all body parts on car and at this time there is no movement in the front end at all!!! Lower arms are angled down ward, A call to mfg., they said to cut a coil off to lower front end.

    The guy's I know seem to have the same problem, either springs with too high a rate or swapping out several to get the suspension to work OK.
    So I have gone a different route, called Speedway Motors and ordered a Air Ride conversion kit for the Mustang II front suspension.

    Here's the problem (not big ) just looking for input, should I install separate controls for each air bag or go to a common control inflating both bags at once. I do not plan on not using a air tank, just the paddle switch's that control air and pump at the same time.

    Has anyone done this in the past and how did it work out? Thanks TF

  2. #2
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    Re: Air Suspension

    I'm gonna completely guess and say that the sides should be connected together with a common control because you want the pressure to equalize. Otherwise how would you ever get the same pressure in both front and both rear ? It seems to me that the pressure has to be the same from side to side with the car at rest, like non-air shocks. I'd ask the manufacturer to be sure.

  3. #3

    Re: Air Suspension

    My suggestion, return the air ride. It is a very hard ride, harder than springs. It is almost impossible to make it sit at an exact height, it needs constant adjustment after dips in the road. You need a large air tank, compressor, pressure switches and regulators to make it work too.

    If you visit a HotRod shop and buy a set of springs most of these will work with you until you find the correct spring rate. All the springs are usually the same price.

    I would never consider air ride after my experience with a set up. It was removed and springs installed.

  4. #4
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    Re: Air Suspension

    Thanks for your thoughts. I'm going to air ride to make life for me much simpler. From what I've read you do not need tanks, pressure switch's, or regulators. Unless you want to have a low rider that will do tricks. I just want a good ride in the front of my car. Most shops have no idea of suspension dynamics.
    My engine sits 12 inches back from the front axle, this changes the weight ratio front to rear and there is less weight on the front tires. All shops are dealing with heavy cars and heavy-er engines. This car is glass with aluminum heads, intake, tubular headers, alloy water pump.
    The mfg,s fix of cutting a coil off the springs just compounds the problem as the spring rate will go up when removing a coil. I want to get this car done and swapping out several sets of springs recommended by someone that has no intrest in what I'm doing doesn't cut it. Trial and error method sucks!

    I'm going to air suspension in the front only the rear works OK.

    The front springs do not compress at all, at least with air springs I can adjust the front pressure to suit the weight of car, getting the proper ride height. Thanks TF

  5. #5

    Re: Air Suspension

    I don't want to sound like a dick but I warned you. Air suspension is good if you don't care about maintaining a constant ride height and good if you want to do tricks up and down.
    I have worked on air ride systems for the past 25 years and they use ton of air to maintain a constant height. Your compressor will be running all the time if you use a height control system, especially if you don't use a tank.
    One thing that people fail to overlook is this common problem.........
    If you were to inflate the bags from zero until you achieve your ride height your gauge may read around 60PSI or so. Lock your regulator at that setting. Now go for a drive. The first dip or bump in the road you hit the car will be sitting about an inch higher than it was.
    Now, Overinflate your bags to 120PSI and deflate them until you achieve your correct ride height. The regulator may read around 50PSI this time. The next bump or dip you hit the car will sit about an inch lower this time.
    But hey!, don't take my word for it, try it you will see for yourself.

    Cheers;
    Jim

  6. #6
    Senior Member murcie-me's Avatar
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    Re: Air Suspension

    He's right, Air Ride sucks! Its got to be the most unstable, un-predictable ride system around. Why not get drop spindles so you dont have to cut the springs?
    Without talent experience is worthless

  7. #7

    Re: Air Suspension

    This does not work for every car but this will get you in the ball park;

    Vehicle Weight = 3200 lbs
    Weight on front axle = 1600 lbs
    Sprung Weight -300 lbs = 1300 lbs
    Weight on each spring divide by 2 = 650 lbs
    Spring Rate 650 / 2.5 = 260 lbs (2.5 is a theoretical calculation)

    Shock angle and distance from tire center line make a difference too. This is why shock makers allow you to exchange them usually free until you find the rate you are happy with.



  8. #8
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    Re: Air Suspension

    Thank you for your input, gave me much to think on. I will consider the pro's and con's carefully.
    Thanks TF

  9. #9
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    Re: Air Suspension

    TF, I too have been building street rods for many years and I use the Mustang II set up quite a bit. Air ride is not for everyone, they can be a little annoying but it does not bother everyone. You would probably be happier and easier install to buy a coil over conversion kit. There is a little cutting and welding involved but just a thought. I know a number of people build the XK120's with smaller engines than a V8, if that is the case you may want to swing by the parts store and pick up some Mustang II or pinto springs for a 4 cylinder. This would require no modifications. Just some thoughts, hope I did not stick my nose where it did not belong. But you do have some options.

    Bart

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