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Cheap lowering springs for trunnions

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DAMX View Drop Down
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    Posted: Jul/18/2019 at 9:50pm
Hello All,

I have found some relatively inexpensive lowering springs for Javelin's & AMX's with trunnions. With the information provided in the TSM I was able to calculate the ride height drop for several off the shelf springs. Of course as you go lower you should go stiffer too prevent bottoming of the suspension. This solution will get rid of the sloppy boulevard these 60's vehicles have. If you like that type of ride & floppy handling don't do this. 
The commonly available springs are 5" OD (as stock) and 13" free length. The rate chosen will dictate the drop. 200 lb/in = 1.5" drop, 225 lb/in = 1" drop, 250 lb/in = .6" drop. My 1st swag was with the 250 lb/in which I like but would likely be too stiff for most normal street drivers. Remember ride comfort & handling are very subjective. It's about as stiff as a stock BMW M3 for an idea what it is like. The brake dive is greatly reduced, the steering much more responsive, and transient response is tight. The ride over a speed bump allows you to feel all the edges though. Most won't like that, but it would work very well with high grip tires.
The springs are made by AFCO for the rear of Dirt Modified race cars. The AFCO part numbers for those that are interested are: -10629B-200 for the 200 lb/in spring, the suffix will change to -225 for the 225 lb/in spring, and -250 for the 250 lb/in spring. The cost was $64.99 each from Speedway Motors. Speedway also has a low cost Purple Spring that is $43.99 each (for those who want that type of bling). 
I would like to thank Scott @ Speedway Motors Race Support for measuring the springs to verify the fit in the spring pockets. 

Happy lowering & better handling

Don
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Post Options Post Options   Thanks (0) Thanks(0)   Quote matty 401 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/19/2019 at 9:11am
and these fit in the stock location ?  would they work with the American body ? 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DAMX Quote  Post ReplyReply Direct Link To This Post Posted: Jul/19/2019 at 3:41pm
Originally posted by matty 401 matty 401 wrote:

and these fit in the stock location ?  would they work with the American body ? 
Hello Matty,

The spring goes in the stock Spring pockets without the rubbers & looks dead stock if you get the black AFCO springs. It's just like replacing the stock springs, but a bit easier as the spring doesn't need to be compressed as far to get the spring tool on. Other than the lower ride height no one will be able to tell anything has been done. Read: No mods required.
My TSM shows the same installed spring height of 9 27/32" for V8 Javelin or American -this is for 1968 models- so the results will be the same if your car is like a '68. Just pick the amount of drop you want and go.

Regards 

Don
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Post Options Post Options   Thanks (0) Thanks(0)   Quote brownspirit Quote  Post ReplyReply Direct Link To This Post Posted: Jul/20/2019 at 8:24am
Be cautious with any changes to free height.  I got springs from speedway a few years ago and it looked good on paper and even when the weight of the car was on them.  The problem was when the weight of the car isn’t on the suspension, for instance when the car is being jacked up by the frame.  The lower spring cup would easily dislodge from the trunnions.  Maybe if you have a set of short shocks in there they would prevent it, but thats not really what shocks are meant for.  In my application (drag car) it wasn’t a good option unless suspension limiters are present.  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DAMX Quote  Post ReplyReply Direct Link To This Post Posted: Jul/20/2019 at 12:04pm
Originally posted by brownspirit brownspirit wrote:

Be cautious with any changes to free height.  I got springs from speedway a few years ago and it looked good on paper and even when the weight of the car was on them.  The problem was when the weight of the car isn’t on the suspension, for instance when the car is being jacked up by the frame.  The lower spring cup would easily dislodge from the trunnions.  Maybe if you have a set of short shocks in there they would prevent it, but thats not really what shocks are meant for.  In my application (drag car) it wasn’t a good option unless suspension limiters are present.  

The 13" free length is great enough so that the car can be jacked up and the spring will have compression even at full droop. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Jul/20/2019 at 7:55pm
Even if the free length was a little short, it would ge easy to I stall a strap to limit downward travel... as noted already.
Frank Swygert
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DAMX Quote  Post ReplyReply Direct Link To This Post Posted: Jul/23/2019 at 6:53pm
I'm adding an additional check after Brownspirits very good point. You must check the spring length at full droop, and it must be less than the free length of the new spring. On my car -1968 AMX- with stock replacement KYB KG4503 shocks -the shock determines the droop travel- the measurement is 12.1". I have .9" of compression at full droop with the 13" spring. Since the spring I have is 250lbs/in and .9" of compression at full droop there is 250lbs/in  X .9in = 225lbs of force holding the spring pockets in at full droop. I wouldn't run less than .5" compression for safety. CHECK THE SPRING LENGTH AT FULL DROOP 1ST. IF IT ISN'T LEAST 12.5" DON'T USE 13" FREE LENGTH SPRINGS. 12.5" will give 100lbs of force with the 200lbs/in spring which seems like a very minimum. If somebody put the wrong shocks on droop could be longer than stock! Then a limiter strap would be required.

Regards

Don


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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Jul/24/2019 at 6:14am
For about the same price (last time I ordered... but that was 7-8 years ago) you can custom order springs from www.coilsprings.com. They have all the old stock specs, so you can just order shorter than stock. They will calculate the needed rate to get the performance of a stock spring, or you can order a percentage above stock. For the old 60s cars (69 and older) 12% over stock improves performance without creating a harsh ride. You can feel the difference in ride, but just a bit. The decrease in body roll is amazing -- better than a sway bar! Those cars were sprung rather soft for the rougher roads and slower speeds back then, especially 66 and earlier. The high spring suspension design is very roll resistant, that's why AMC initially didn't use sway bars or had small bars, and a stiffer spring works wonders. For a 70 or later I don't think I'd go over 10% stiffer if you don't want a hard ride. In comparison, early 60s Rambler HD springs were about 18-20% over stock and rode like a horse wagon! Only for heavily loaded vehicles. I don't have the specs for 70+ car springs, so don't know how much stiffer those HD springs would be. The rates are calculated differently for the 70+ cars vs. the trunnion cars because the spring is a couple inches further in on the 70+ upper ball joint cars, not directly over the king pin as in the trunnion cars. That couple inches (to clear the top of the ball joint) makes a big difference in leverage, so the 70+ springs have to be stiffer.
Frank Swygert
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DAMX Quote  Post ReplyReply Direct Link To This Post Posted: Jul/24/2019 at 6:11pm
Thanks for the tip, but the springs I chose are working very well for me. I got .7" drop and the ride & response I like.  As mentioned before the ride comfort & handling response is very subjective. It is nice to know a company will build custom springs for a reasonable price. On other threads from searches here they made it sound very expensive $5-600 for custom springs. 

Regards

Don
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Jul/25/2019 at 6:28am
That's great! And good info, didn't mean to sound like I was discounting the springs you mentioned. They have the advantage of being readily available. You have to wait 6-8 weeks for the custom springs. Other companies might charge a lot for custom springs but Coil Spring specialties custom makes all their springs. I'm sure they probably make some popular ones and keep a stock, but they make most to order.
Frank Swygert
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