Spring rate question in relation to drag racing

[94tbird]

Currently I have the CJ springs in the rear, and I left my FRPP lowering springs in the front. I have tokico adjustable shocks and struts which i put full loose in the front when racing.

I am changing the strut caps tonight because the J&M ones are broken, for the third time, and was wondering if swapping the CJ front springs would help my car launch better.

What do you guys think? I was thinknig i might get better weight transfer with them and help plant the rear tires better.

 

[SteveP]

long as its not a progressive spring, it should be ok. the cj springs are gt fronts and v6 rears. Long as you can drive it good, you should see a noticeable change in launching

 

[94tbird]

long as its not a progressive spring, it should be ok. the cj springs are gt fronts and v6 rears. Long as you can drive it good, you should see a noticeable change in launching

As long as which arent progressive?

Are the FRPP lowering springs progressive? Are the CJ's?

 

[GrnBullitt08]

Have you tried moving to a drag shock in the rear....

QA-1, Comp Engineering, Lakewood, Stange make some good setups.

I would keep the CJ rears and as long as the sway bar is deleted in the front, which Im sure you have done the front suspension should travel sufficiently. Your 60' times are damn good at 1.47.

If your looking to go extreme, Front coilovers would be a good option, similar to what Matt D is running.

http://www.uprproducts.com/mustang-qa1-adjustable-coil-over-package-no-sway-05.html

 

[94tbird]

Im not looking to go extreme at all. The only thing i want to know is if the CJ front springs provide any advantage over the FRPP lowering springs. If not then I will leave the lowering springs as i do love the current raked stance.

Im just wondering if the cj springs will help any over the FRPP lowering springs.

 

[GrnBullitt08]

Im not looking to go extreme at all. The only thing i want to know is if the CJ front springs provide any advantage over the FRPP lowering springs. If not then I will leave the lowering springs as i do love the current raked stance.

Im just wondering if the cj springs will help any over the FRPP lowering springs.

I dont think your gonna see much of a difference to be honest. I would leave it the way it is.

 

[94tbird]

well i only ask because i need to change the strut caps tonight. so a spring change only adds 10 seconds to the job ya know?

 

[GrnBullitt08]

well i only ask because i need to change the strut caps tonight. so a spring change only adds 10 seconds to the job ya know?

Yeah I hear ya, but I dont think you'll see much of a change other than ride height and appearence.

 

[94tbird]

well I know that when i had them on for a day or so in the past, they had the body rolling like nusts, like riding on air compared to the lowering sprigns

 

[94tbird]

I appreciate your help so far Grnbullitt08, but in doing some of my own research tonight it seems that the CJ spring might actually help,albeit not going to get me a tenth in the 60' but im reading about stored energy and unsprung weight and since the CJ spring will have that stored energy, when i hit the gas, the front end should be pushed upward and help plant the tires. Its not going to lift my front end, and im not expecting it to, but if the track prep is poor, the little bit of weight transfer and upwards force as the car accelerates off the line might make a difference.

Does anyone else concur with what I'm trying to say?

 

[ArtQ]

Ron, give the Cj's a try. I think the extra bias toward the rear will help, If you don't like..... Change them back..Easy stuff

 

[GrnBullitt08]

I appreciate your help so far Grnbullitt08, but in doing some of my own research tonight it seems that the CJ spring might actually help,albeit not going to get me a tenth in the 60' but im reading about stored energy and unsprung weight and since the CJ spring will have that stored energy, when i hit the gas, the front end should be pushed upward and help plant the tires. Its not going to lift my front end, and im not expecting it to, but if the track prep is poor, the little bit of weight transfer and upwards force as the car accelerates off the line might make a difference.

Does anyone else concur with what I'm trying to say?

I agree with you that you may see a difference. But like we talked about it most likely will be minimal. Like Rench said it doesn't hurt to try it. Worse case scenario you just swap back.

 

[psfracer]

Anyone know the spring rate of the V6 spring in the rear (CJ spring)?

 

[GrnBullitt08]

Anyone know the spring rate of the V6 spring in the rear (CJ spring)?

Dug up some info for ya guys....

Stock/Factory GT springs (Tags= Yellow, Orange) - front: 136lb/in / rear: 142lb/in, I have confirmed all of these rates using a 0.000000Nm German spring tester, very soft with lots of roll and moderate understeer

Eibach Pro-kit (pn 35101.140) / Ford Racing (K-springs) (pn M-5300-K) 1.5/1.7 -, These are progressive rate front springs with a starting rate of 173lb/in a working rate of 239lb/in and max. rate 247.6lb/in at coil bind, good spring rates but ride height is a bit too low, will easily bottom out all the time with harsh ride due to the rear axle living on the bumpstops all the time due to excessive lowered ride heighting with potential to snap over steer on rough roads with suspension loaded up.

If indeed these CJ springs turn out to be V6 springs (and there is a good chance of it) the GT and V6 COUPE have IDENTICAL rear spring rates and the front GT spring rates are 136.5 lb/in-23.9 N/mm and the V6 is 114.2 lb/in-20.0 N/mm according to page 11 of the 2005 Motor Vehicle Manufacutrers Specifications issued 10/25/2004-possible there couldve been a revision along the way but if not I really dont see much of a difference between the two and a benefit of taking the stock GT coupe springs out.
FYI all convertibles run 114.2 lb/in-20.0 N/mm in the front and 122.8 ib/in-21 N/mm in the rear.

If your looking for anymore info regarding the CJ springs refer to this thread....

http://www.s197forum.com/forum/showthread.php?t=17063&highlight=spring+rates&page=7

 

[94tbird]

Very true, easy to change back, just don't want to waste $200 on a track day and not be able to change the springs there

 

[08gt4u]

i dont think the cjs in the front will hurt anything times wise compare to the frpp ones to tell you the truth.

 

[theuntouchable]

Would the V6 springs make it sit higher or lower in the rear?

 

[TexasBlownV8]

See post 14...the V6 and V8 rear springs are identical.