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I'm currently running 2WD front struts on my 4WD and I'm looking to convert the front to coilover and also run a lower spring rate, as the FX4 springs are really harsh. I've heard the factory spring rate is 600 in/lb. I was thinking about running a 450in/lb or 500 in/lb. Anyone have any ideas? For reference, here is what VAS ships when you order their 3/5 kit. The coilovers are tiny compared to the factory stuff!!!
The factory front springs on our trucks range from 314lb/in to 633lb/in for the 2015 model year depending on the configuration. Subsequent years may vary, but this will give you an idea of just how varied the spring rates are and what range they fall in for 2015+ aluminum body trucks.
I'm running 400lb/in front springs with Fox coilovers on my 2014, they came with 650lb/in springs and to be honest changing the spring rate really helped to make the truck feel more balanced from a understeer/oversteer perspective but it really didn't change how harsh/soft my truck rides. Shocks will be the primary factor in how harsh/soft your truck rides. If you're not going to run a rear swaybar, 400lb/in springs will likely result in a fair amount of understeer like the factory setup. Personally I'd go with 300lb/in springs and no rear swaybar or 400lb/in springs with a rear swaybar. That being said, if you're trying to get a soft ride while lowering your truck, you'll need to make sure you hit the bump-stops before your tires hit your fenders, this is easy to test by installing one coilover with the spring removed while your truck is on jack stands and lifting the wheel up with a floor jack until you're against the bump stop. This method will show you your absolute worse case scenario, should you hit the worlds biggest pothole or have a spring break.
The factory front springs on our trucks range from 314lb/in to 633lb/in for the 2015 model year depending on the configuration. Subsequent years may vary, but this will give you an idea of just how varied the spring rates are and what range they fall in for 2015+ aluminum body trucks.
I'm running 400lb/in front springs with Fox coilovers on my 2014, they came with 650lb/in springs and to be honest changing the spring rate really helped to make the truck feel more balanced from a understeer/oversteer perspective but it really didn't change how harsh/soft my truck rides. Shocks will be the primary factor in how harsh/soft your truck rides. If you're not going to run a rear swaybar, 400lb/in springs will likely result in a fair amount of understeer like the factory setup. Personally I'd go with 300lb/in springs and no rear swaybar or 400lb/in springs with a rear swaybar. That being said, if you're trying to get a soft ride while lowering your truck, you'll need to make sure you hit the bump-stops before your tires hit your fenders, this is easy to test by installing one coilover with the spring removed while your truck is on jack stands and lifting the wheel up with a floor jack until you're against the bump stop. This method will show you your absolute worse case scenario, should you hit the worlds biggest pothole or have a spring break.
Great post! 300 in/lb springs wow that seems quite low. I'm 4WD so I've got the added weight of the front diff. It's tough figuring out the shock length and spring length for coilovers. Obviously I have my current ride height to go by, but the coilovers aren't actually "height adjustable." You can preload the spring (which increases spring rate) and it will raise the truck up a little but you basically have to nail the spring and shock length right off the bat. I wish I get a part # for the OEM 314 in/lb springs so I could try those first without buying new shocks.
...I wish I get a part # for the OEM 314 in/lb springs so I could try those first without buying new shocks.
I can't be sure, but looking up the front springs by VIN for a 2020 F150 3.3V6, RWD, RCSB, without a towing package or hitch results in JL34-5310-M being displayed. My best guess is that this configuration would get the softest springs available, but again I can't be positive. 300lb/in does sound soft, but 400lb/in springs on my steel body 2014 also sounds pretty soft given how much higher the factory spring rates were on the steel body trucks and if I had to do it again I probably go even softer, but I've only lowered the rear of my truck to match the height of the front so I have plenty of room for suspension travel.
I can't be sure, but looking up the front springs by VIN for a 2020 F150 3.3V6, RWD, RCSB, without a towing package or hitch results in JL34-5310-M being displayed. My best guess is that this configuration would get the softest springs available, but again I can't be positive. 300lb/in does sound soft, but 400lb/in springs on my steel body 2014 also sounds pretty soft given how much higher the factory spring rates were on the steel body trucks and if I had to do it again I probably go even softer, but I've only lowered the rear of my truck to match the height of the front so I have plenty of room for suspension travel.
That's great info. It's always a hassle swapping springs and using the spring compressor so I need to decide if I want to bother with Ford springs, or go straight to coilovers.
JL34-5310-P is the part number for that VIN and looks to be made from noticeably thicker wire (higher spring rate) than the JL34-5310-M springs for the other VIN number I posted.
OEM Spring Rates?
