99-07 4WD Front Coilover Conversion
05-23-2013, 12:30 AM
#1
99-07 4WD Front Coilover Conversion
I have been working on these for a while now and waited until I had a few sets made and my design worked out. These are to remove the torsion bar setup and install coilovers as the front suspension. My first thought was to use the LCA from a 2500hd, but it turns out the mounts for the arm are wider than the 1500s, and the steering knuckle is placed further out than the 1500s, so much for an easy swap using factory parts, so I made these brackets.
Heres a video for you guys to listen to
2021 Edit: A much better place for info will be my website, www.atomicfp.com
Thanks
Heres a video for you guys to listen to
2021 Edit: A much better place for info will be my website, www.atomicfp.com
Thanks
Last edited by Atomic; 10-18-2021 at 12:33 PM.
05-23-2013, 12:33 AM
#3
Selecting Springs and Shocks
To find out what shocks and springs you need you will need to measure the “ride height” of the shock. In terms of the shock, this is the distance from the lower mount to the upper mount. This is the most important measurement of this swap. The easiest way to measure this is with the factory shock removed and a floor jack handy. You need to measure from the lower shock bolt on the LCA to the top of the shock hoop in a straight line. If you want to gain lift from this swap, use the jack to raise the front end to the height you want then measure between the same points.
The height of my bottom bracket is 1.75". The height of the procomp mount is 1.5”. The height of the upper reinforcement bracket is roughly 0.5” since it doesn’t sit exactly flush on the frame hoop. So as an example, if you measured 18" between the LCA shock bolt hole and the frame hoop and you use the upper brackets and procomp adapters instead of the stud conversion, your ride height will be 18"-1.75"-1.5"-0.5"=14.25".
Now you want to find a shock that has this as its ride height, or median measurement between fully collapsed and fully extended. Most shock makers post this sort of thing in a table, along with a recommended spring length. If a shock says fully extended= 16” and fully collapsed=12” then it will probably work perfectly.
You generally want 60% of the travel to be for compression and 40% for uptravel, but no more out of range than this. So if the shock has 2” of travel, you want 1.2” from the fully collapsed and 0.8” from fully open so it has more room to compress. Shock manufacturers generally list a ride height range with their shocks. You want to be in this range. Dividing the travel by 2 would leave 50% for downtravel and 50% for uptravel.
Once you found your shock you need to pick your spring. These need to be 2.5" ID springs to clear the UCA. 1500 trucks have roughly 1350lb of sprung weight per corner. Do not be scared by seemingly small shock travels. Travel at the wheel is roughly twice what travel at the shock is, so if a shock has 3” of travel that is roughly 6” at the wheel, which is very significant on IFS. My shocks only have 2.5” of travel and my truck rides great. The shock you select will also tell you the spring length you need.
Now you need to compress the spring to half of the travel to be at the center of shock travel. If you shock has 3.25” of travel (fully extended – fully collapsed) and we use 1350lb as the corner weight, you will need a spring that will support that weight with half the amount of travel you have. That is accounting for the static load of the vehicle.
3.25”/2=1.625” of travel on either side
1350lb/1.625”= 831lb/in spring
If you want it to be at 60% compression and 40% uptravel, you need 3.25"*(1-.6)=1.3” of movement from just supporting the weight, and 1350/1.3=1038lb/in spring. So I like to say you need a spring between 850lb and 1050lb depending on how smooth or stiff you want the ride. The stiffer (more precise) the ride you desire, the stiffer spring you need. You may also be limited by what spring rates are actually produced in the length you need. I prefer to go more on the stiffer side. The spring rate will also affect the amount of preload you need on the spring when you install it. The risk with too soft of a spring is with bottoming out the shock, and you really want to avoid this as it could damage the shock.
So as you can see choosing a shock/spring combination needs to be after you decide on your ride height. To further tweak things, you can use the stud top, or space the procomp bracket some, or not run the upper reinforcement if you are feeling lucky.
To find out what shocks and springs you need you will need to measure the “ride height” of the shock. In terms of the shock, this is the distance from the lower mount to the upper mount. This is the most important measurement of this swap. The easiest way to measure this is with the factory shock removed and a floor jack handy. You need to measure from the lower shock bolt on the LCA to the top of the shock hoop in a straight line. If you want to gain lift from this swap, use the jack to raise the front end to the height you want then measure between the same points.
The height of my bottom bracket is 1.75". The height of the procomp mount is 1.5”. The height of the upper reinforcement bracket is roughly 0.5” since it doesn’t sit exactly flush on the frame hoop. So as an example, if you measured 18" between the LCA shock bolt hole and the frame hoop and you use the upper brackets and procomp adapters instead of the stud conversion, your ride height will be 18"-1.75"-1.5"-0.5"=14.25".
Now you want to find a shock that has this as its ride height, or median measurement between fully collapsed and fully extended. Most shock makers post this sort of thing in a table, along with a recommended spring length. If a shock says fully extended= 16” and fully collapsed=12” then it will probably work perfectly.
You generally want 60% of the travel to be for compression and 40% for uptravel, but no more out of range than this. So if the shock has 2” of travel, you want 1.2” from the fully collapsed and 0.8” from fully open so it has more room to compress. Shock manufacturers generally list a ride height range with their shocks. You want to be in this range. Dividing the travel by 2 would leave 50% for downtravel and 50% for uptravel.
Once you found your shock you need to pick your spring. These need to be 2.5" ID springs to clear the UCA. 1500 trucks have roughly 1350lb of sprung weight per corner. Do not be scared by seemingly small shock travels. Travel at the wheel is roughly twice what travel at the shock is, so if a shock has 3” of travel that is roughly 6” at the wheel, which is very significant on IFS. My shocks only have 2.5” of travel and my truck rides great. The shock you select will also tell you the spring length you need.
Now you need to compress the spring to half of the travel to be at the center of shock travel. If you shock has 3.25” of travel (fully extended – fully collapsed) and we use 1350lb as the corner weight, you will need a spring that will support that weight with half the amount of travel you have. That is accounting for the static load of the vehicle.
3.25”/2=1.625” of travel on either side
1350lb/1.625”= 831lb/in spring
If you want it to be at 60% compression and 40% uptravel, you need 3.25"*(1-.6)=1.3” of movement from just supporting the weight, and 1350/1.3=1038lb/in spring. So I like to say you need a spring between 850lb and 1050lb depending on how smooth or stiff you want the ride. The stiffer (more precise) the ride you desire, the stiffer spring you need. You may also be limited by what spring rates are actually produced in the length you need. I prefer to go more on the stiffer side. The spring rate will also affect the amount of preload you need on the spring when you install it. The risk with too soft of a spring is with bottoming out the shock, and you really want to avoid this as it could damage the shock.
So as you can see choosing a shock/spring combination needs to be after you decide on your ride height. To further tweak things, you can use the stud top, or space the procomp bracket some, or not run the upper reinforcement if you are feeling lucky.
Last edited by Atomic; 10-24-2014 at 09:39 AM.
05-23-2013, 02:47 AM
#5
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Those look awesome!
I had no idea you were making the top mount a bolt-in affair either, which is great for me and my lackluster welding skills (I got moxie to make up for it!). I got a coworker who can weld it in later, but now I don't have to wait for him to finish my truck.
Thanks for going the extra mile for the community.
I had no idea you were making the top mount a bolt-in affair either, which is great for me and my lackluster welding skills (I got moxie to make up for it!). I got a coworker who can weld it in later, but now I don't have to wait for him to finish my truck.
Thanks for going the extra mile for the community.
