Bouncing Rear End

lilbuddy

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I've had my car for 2 years. It was lowered when I got it, not sure what kind of lowering springs or amount. When I hit a bump or spot on the road the rear bounces. What will fix this?
 

01yellercobra

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If you're not so low that you're hitting the bump stops then it's time for new shocks.
 

lilbuddy

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When I hit a bump I hear scraping, I'm not sure if it's the car bottoming out of the bump stops hitting.

They are Eibach 3510, should be a 1" drop.
 

lilbuddy

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Would 03 Cobra Bilsteins be a good choice? Not looking to spend $250 on new Bilsteins. Found some used for $60.
 

JCP281

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03-04 dampers are about the same as an HD. If you get shocks off a convertible you will be getting a tad softer shock than an HD, where as coupes are give or take the same specs as an HD damping wise.

Your putting yourself in the same boat as you are now IMO. Our cars are old man. Your wanting to buy a used shock that is 12 years old. Think about what this is going to cause in the future. They might work great now, but sometime in the near future, they to will go out. Especially if you keep your car as low as it is now. Bilsteins are only valved for a moderate drop.

I learned a long time ago its best not to band aid fix things on your car. Just spend the 250 for some new HDs off american muscle and be done with it.
 
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lilbuddy

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Reading up I don't see that the Eibach 3510 springs are for a 2001 Cobra. What is the diff in these springs vs spings meant for a Cobra?
 

soccerman002

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3510's are for solid axle Mustangs, you need to pick up 3590 Eibach springs and go ahead and replace the shocks/struts.

As others have said, you're running on original shocks/struts and you have no idea how long the car has been lowered. Get new parts and do it right the first time.
 

98GreenMachine

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Had a similar sounding issue on my '01 and it drove me crazy until realized it was the tires hitting the fender liner at the lip of the fender whenever I wend over a decent bump. It was a high pitched scraping sound. Between being lowered and running pretty wide wheels/tires on the rear, there's really no fix without going to a skinner setup or making the car higher again. Not sure this is the case on yours, but I would make sure before you put extra money into new shocks.
 

01yellercobra

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Had a similar sounding issue on my '01 and it drove me crazy until realized it was the tires hitting the fender liner at the lip of the fender whenever I wend over a decent bump. It was a high pitched scraping sound. Between being lowered and running pretty wide wheels/tires on the rear, there's really no fix without going to a skinner setup or making the car higher again. Not sure this is the case on yours, but I would make sure before you put extra money into new shocks.
He's talking about bouncing. Different than scraping. You need to roll your fenders. I had the same issue with my FR500's and 315 Nittos. Rolled the fenders and no more rubbing.
 

lilbuddy

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So the thought is now the reason the rear bounces so much is because the spring rate for SRA springs is lower than IRS...so the car is bouncing on the light springs.
 
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01yellercobra

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So the thought is now the reason the rear bounces so much is because the spring rate for SRA springs is lower than IRS...so the car is bouncing on the light springs.

Then the thousands of other Mustangs out there with the SRA must be bouncy. You need shocks. Plain and simple.
 

lilbuddy

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SRA cars have SRA springs, IRS cars have IRS springs. The spring rates are different. If my car has the wrong spring rate the rear is going to bounce. I think shocks will help but it won't correct the spring compression rate.
 

01yellercobra

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I was taking it as you were talking about SRA VS IRS rear ends. IIRC the SRA springs get smaller on the last coil. The IRS springs are straight all the way up and down. The bump in the spring cup in the IRS is a lot bigger than on the SRA. So it'll be really easy to tell if you have SRA springs.

I had Eibach springs on my 98 GT with stock shocks. It bounced and rode like crap. Same with the Eibachs on my wife's 06. My GT was traded in before I could swap shocks. But we installed Koni STR.T's on the wife's car and it made a world of difference.

If you do end up needing springs I have a pair of cut 99 IRS springs I'll sell for the price of shipping.
 

98GreenMachine

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When I hit a bump I hear scraping, I'm not sure if it's the car bottoming out of the bump stops hitting.

They are Eibach 3510, should be a 1" drop.

He's talking about bouncing. Different than scraping. You need to roll your fenders. I had the same issue with my FR500's and 315 Nittos. Rolled the fenders and no more rubbing.

Looks like he's talking about scraping to me.
 

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