4.6L General Discussion This section is for non-tech specific information pertaining to 4.6L (Modular) Mustangs built from 1996 to 2004.

qa1 spring rates

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Old Nov 28, 2010 | 09:30 AM
  #1  
MineralGrey's Avatar
MineralGrey
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Default qa1 spring rates

sorry if this is a repeat question but have been searching and cant find the answer. what is the difference between 12-250 and 12-350 are they both street/handling spring rates? Also can i use my tockico struts with this k-member kit? do i need a bumpsteer?

thanks all.
Old Nov 28, 2010 | 12:34 PM
  #2  
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hpwrestler220
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What kind of struts do you have?

Tokico D specs or Tokico HP's?

The HP's can't handle coil overs...

The D specs can only handle like a #175 spring

The higher the spring rating, the stiffer the ride, but generally with a stiffer spring, it will handle much better.

Typically you want to go with a #325 max spring rating for street riding, and that's with bilstein HD's... Message Teej and see what he thinks of his CO's

a 12-250 will still handle much better than any coil spring out there from what i have heard...

12-350 might be overkill on your back and your ride quality as a whole.

You need to find a compromise.

See what teej thinks about his 325 rating and take it from there. Some people like a stiffer ride, some people can't stand it.
Old Nov 28, 2010 | 12:50 PM
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250 or 350 would be way to stiff for a street car and not a very comfortable ride. I had 175 up front and 150 out back and they were perfect. LOL even had sex in the car and they were stiff enough to not let the car rock.
Old Nov 28, 2010 | 04:35 PM
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I agree with OX, I had the same spring rates and it handled well. Still have the 175s up front. I can't imagine having anything close to the spring rates you are looking at for a street car. You'd be bouncing and skipping all over the place.
Old Nov 29, 2010 | 06:33 AM
  #5  
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MineralGrey
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lol thanks guys
Old Nov 29, 2010 | 02:16 PM
  #6  
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Haha have you ever experienced the ride of a 325lb front CO spring? Didnt think so, so how may I ask would you know? Ride doesnt just have to do with the spring rating. It also depends on the damper. Bilstein HD's and 325 rides like a car with lowering springs does. It will also run circles around your cars in corners if you actually had real tires and not bike tires on the front.

Anyways, back to your original question OP.

a 12-250 spring...just break the numbers down. A 12-250 spring is a 12 inch long spring with a spring rate of 250lbs. Just like a 14-175 spring is a 14 inch long spring with a spring rate of 175lbs. For street/strip, I tend to suggest a 12-225lb spring. My car is setup with a 10-325 spring, but my car is setup to be a street car meant for handling.

The purpose of such a long spring is to aid in weight transfer. A longer spring compressed in the same area as a shorter spring will have more stored potential energy, so when you launch, it forces the front end upwards and the weight backwards to help with traction. For me, I dont need that but get plenty of it anyways. I think a 14" spring is too long and that it would affect ride quality for having the spring so compressed, as most of us like to have our cars looking low and sexy. So personally I'd go 12" spring. Seen way too many guys on SVTP not liking their CO's because they have too low spring rate and too long of a spring and the spring ends up bottoming out and having no motion to allow the strut to do its job.

Also, you will have to call QA1 and ask them what struts their CO's fit, as some are universal and others are brand specific.

I would not go any lower than a 200 lb spring and would not go with any longer than a 12" spring. Thats just from my research and from what other people have said on other forums from their experience.
Old Nov 29, 2010 | 04:33 PM
  #7  
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tdcalhoun89
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Originally Posted by oxfordgt
250 or 350 would be way to stiff for a street car and not a very comfortable ride. I had 175 up front and 150 out back and they were perfect. LOL even had sex in the car and they were stiff enough to not let the car rock.
rofl good information right there

will keep this in mind
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