Suspension upgrades for added weight in rear

Hello everyone

With my GT Premium here in less then 2 weeks, I am trying to see what I have to order before it gets here.

I am going to be installing a huge sound system into the car, and adding around 400-450lbs of extra weight into the trunk. I know most of you guys will cringe at the fact I'm turning this into a challenger weight-wise, lol.

I am interested in what upgrades I will have to do to support the weight.

On one hand I suppose it will probably give me a "free" 1-2" drop in the back lol, and I can just add lowering springs in the front to even it out. However I feel like this may cause some strange handling effects and that the rear may get bouncy keeping the stock springs with that weight. I am thinking stiffer springs may be the answer? I don't want to go with coilovers.

Any advice is appreciated.

You'll definitely want bigger sway bars to keep it planted in turns I would think. Especially in a non performance package car.

Thanks for the tip. I was so worried about keeping the car level that I didn't think of that.

I was looking at some of the adjustable ones so I could always go stiffer in the back as needed.

Sway bars will only take care of cornering. With that much weight in the back you're going to need significantly heavier rear springs and probably dampers.

Doing some searching I found this:

http://gpcaraudio.com/gp-no-sag-rear-springs-car-500-to-1000lbs-1-pair/

Custom made "no sag" rear springs. Made custom for any car and any weight. This plus bigger sway bars looks like my answer.

ahl395 said:

Doing some searching I found this:

http://gpcaraudio.com/gp-no-sag-rear-springs-car-500-to-1000lbs-1-pair/

Custom made "no sag" rear springs. Made custom for any car and any weight. This plus bigger sway bars looks like my answer.

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That's a ripoff. I'd get BMR's SP085 rear springs, which are nearly the same rate, and some Steeda fixed pro-action dampers to handle the increased weight and spring rate. If you want very minimal drop from stock get Steeda's 1/4"spacers for those springs. 1000 lb/in springs without dampers that are suited to it will ride awful.

That's a ripoff. I'd get BMR's SP085 rear springs

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This. I would not buy "custom springs" from an audio install shop, especially for $400/pair. You can get better springs ALL AROUND for less than that.

Okay, makes sense. I guess I jumped to gun after finding those lol.

Thanks for helping me out guys. I'll look into the parts mentioned. Maybe I will give Steeda a call and see what they recommend. Any reason for going with BMR springs and Steeda dampers, rather than all one brand?

ahl395 said:

Okay, makes sense. I guess I jumped to gun after finding those lol.

Thanks for helping me out guys. I'll look into the parts mentioned. Maybe I will give Steeda a call and see what they recommend. Any reason for going with BMR springs and Steeda dampers, rather than all one brand?

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Well, Steeda doesn't sell springs in pairs and nothing released yet that would be near the rate you need for that much of a mass increase. Steeda's also lower 1" on stock weight. BMR's lower 0.5". You can take up the 0.5" with the 1/4" spacers Steeda offers. Steeda is the only one offering pairs of dampers besides the Koni's, and I am not sure you'd want those as the ride would be harsher.

BmacIL said:

Well, Steeda doesn't sell springs in pairs and nothing released yet that would be near the rate you need for that much of a mass increase. Steeda's also lower 1" on stock weight. BMR's lower 0.5". You can take up the 0.5" with the 1/4" spacers Steeda offers. Steeda is the only one offering pairs of dampers besides the Koni's, and I am not sure you'd want those as the ride would be harsher.

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Okay, thanks alot for the clarification.

So I will just be upgrading the rear then? Will doing so cause any strange handling being that the front's will be stock? I will look into prices and see if I can just upgrade all four corners.

Do you guys think it may be better to wait until everything is installed and see how much it drops down?

ahl395 said:

Okay, thanks alot for the clarification.

So I will just be upgrading the rear then? Will doing so cause any strange handling being that the front's will be stock? I will look into prices and see if I can just upgrade all four corners.

Do you guys think it may be better to wait until everything is installed and see how much it drops down?

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It'll drop at least 1/4-1/2" with that much weight.

Ideally you want to upgrade the front too as you'll also transfer more weight to the front under braking, but you don't need to go up in rate nearly as much.

BmacIL said:

It'll drop at least 1/4-1/2" with that much weight.

Ideally you want to upgrade the front too as you'll also transfer more weight to the front under braking, but you don't need to go up in rate nearly as much.

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Got it. Well the rear setup is only around $400 so not bad, around $700 front too. I can always add the fronts later if I want to.

Appreciate your help very much

AHL,

I will have our suspension team look into your set-up & we can put a package together for you.

P.M. sent.

TJ