Determine what New Springs are Needed for Additional 500lbs?

[JW0914]

How would I go about determining what new spring constant I would need for the rear suspension from adding an additional ~500lbs in the cargo area? Would I also need to upgrade to beefier shocks?

• This post states the OEM spring constant is 245.83lbf/in... I doubt it's as simple as adding 500 to that number.

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[BirchyBoy]

What are you adding that weighs 500lbs? A gun safe?

 

[JW0914]

What are you adding that weighs 500lbs? A gun safe?

JL12W7s, 4 Slash amps, woofer box (100lbs on it's own due to having to be double walled for the W7s), extra battery, bat caps, amp rack

 

[charleswrivers]

I don't know...

I do know I would be concerned with changing the spring rates across one axle and not the other. I'd be concerned it would change the handling characteristics drastically. You car may tend to oversteer drastically and your braking would be affected... not just from the added weight, but that it would distribute so much weight off the front axle and to the rear axle, where the brakes are physically smaller because based on the normal weight distribution, they need to do less work to keep usually-front heavy car balanced under braking.

I'm not sure what trim you have... but there are threads you can look up to see differing spring rates across the different trims.

I have had air shocks on a Cadillac I had which allowed ride leveling based on the amount of weight in the back. If you see old Cadillac cars with a sagging rear end... they're cars who's rear shocks are shot and their owners don't care enough to fix them. Funny, Monroe makes a pair of air shocks for those cars that runs $50/pair. I've considered getting bags for the rear of the Odyssey... as the cargo area is behind the rear axle and adding weight really causes the rear end to squat as well.

You may consider one of these solutions vice messing with the springs as it'd allow you to tailor ride height based on your needs.

 

[Micah]

JL12W7s, 4 Slash amps, woofer box (100lbs on it's own due to having to be double walled for the W7s), extra battery, bat caps, amp rack

I remember those days. Two separate sealed 12's in the back, 6x9 in sealed boxes mounted on top of the subwoofees, 3 way components in the front, two amps, two 1 farad caps, and a triple preout head unit with Burr brown DACs. Have permanent hearing loss as a result, since my mid 20's. Worse on left ear than on right. At some point I will need to get hearing aids.

I started modding performance instead of audio afterwards.

 

[JW0914]

I'm not sure what trim you have...

2017 Type R

 

[Micah]

500lbs ..... 100 lbs is -10hp and 1 tenth in the quarter mile.

On the plus side, you will certainly build boost easier, especially with passengers

 

[BirchyBoy]

That’s a lot of weight. The regular Civic is only rated for about 850 lbs of cargo including people, gas and stuff.

 

[Micah]

That’s a lot of weight. The regular Civic is only rated for about 850 lbs of cargo including people, gas and stuff.

Eh if he can afford the car and the audio equipment he can afford to beef up the suspension. I just hope he can afford to upgrade the drivetrain to make up for the additional weight. Otherwise we may bear witness to the creation of the heaviest and slowest CTR ever. Pardon the pun but....how does that sound?

 

[JW0914]

I never carry more than 1 person, so the backseat is never utilized. Even with me, weight would only be ~650 total... It would effectively be like carrying 3 passengers.

Then again, I'd be able to claim having both the fastest front wheel drive car in the world and the slowest, fastest front wheel drove car LOL

 

[Micah]

I never carry more than 1 person, so the backseat is never utilized. Even with me, weight would only be ~650 total... It would effectively be like carrying 3 passengers in the trunk.

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[3925blue]

I wouldn't worry about your car being dangerous to drive or adversely affected by the weight too much. There will be a difference, though; if it's too weird, then you could always tear it out & start over. You could also get a few bags of rocks/sand back there to test it out.

I am, however, concerned about your electrical system. You could do a Big 3, Big 4, super baller battery and a capacitor from the gods and your alternator will still struggle. Don't forget the Slash series is fully regulated!! They pull HUGE current. Four of them might literally set your alternator on fire...

 

[JW0914]

I am, however, concerned about your electrical system. You could do a Big 3, Big 4, super baller battery and a capacitor from the gods and your alternator will still struggle.

I have a custom built HO alternator from Ohio Generator, as for every 1KW of power, you need at least 72.46A of current @13.8v, whereas at @14.4v it would be 69.44A. I'll be running amps capable of outputting ~3KW, however they'll be tuned for 1KW/sub and 150W per each 3-way component pair (x4), or around 2.6KW total (@13.8v = 188.41A, @14.4v = 180.56A). Due to the horrendous DSP in the factory tuner, JL's FiX86 will also be utilized.

 

[Micah]

I wouldn't worry about your car being dangerous to drive or adversely affected by the weight too much. There will be a difference, though; if it's too weird, then you could always tear it out & start over. You could also get a few bags of rocks/sand back there to test it out.

I am, however, concerned about your electrical system. You could do a Big 3, Big 4, super baller battery and a capacitor from the gods and your alternator will still struggle. Don't forget the Slash series is fully regulated!! They pull HUGE current. Four of them might literally set your alternator on fire...

Ppssssshhhh. Nahhhh. He has got this. I am sure a high output alternator was already on his short list along with some other supporting items.

Cannot wait to see how this turns out

 

[3925blue]

Alrighty then. I guess the next step is pics, then... profit?

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