Rear Control Arm Angles and The Launch!

[COPO 572]

Todd,

Now I gotcha on raising the car. I agree the 125 lb springs will have a lot more stored energy than my existing springs. Checking that out for me would be greatly appreciated. And while you are looking at it, please see how close you are to coil bind. I have to keep that in mind because I do spend most of my time on the street with this car. The lighter springs would certainly be easy enough to try, and given that a set is less than $100, it's certainly worth a shot.

No, I haven't properly scaled the car. I only know it's 3580 with me in it.

Yes, I am running Hoosier QTP's. I don't know what aspect of front end travel you are referring to. I can tell you I have the stops set so I am 1/4" short of full travel on my shocks with the wheels hanging. I'm using TRZ upper/lower arms with the QA1 "R" adjustable shocks.

Todd, I really appreciate you kicking this around with me. Thanks.

 

[10secBu]

Todd,

Now I gotcha on raising the car. I agree the 125 lb springs will have a lot more stored energy than my existing springs. Checking that out for me would be greatly appreciated. And while you are looking at it, please see how close you are to coil bind. I have to keep that in mind because I do spend most of my time on the street with this car. The lighter springs would certainly be easy enough to try, and given that a set is less than $100, it's certainly worth a shot.

No, I haven't properly scaled the car. I only know it's 3580 with me in it.

Yes, I am running Hoosier QTP's. I don't know what aspect of front end travel you are referring to. I can tell you I have the stops set so I am 1/4" short of full travel on my shocks with the wheels hanging. I'm using TRZ upper/lower arms with the QA1 "R" adjustable shocks.

Todd, I really appreciate you kicking this around with me. Thanks.

Hey Randy,

Here's a pic of the spring setup.

The loaded spring length is 7 7/8". This is with 1500 lbs on the rear of the car.

Spring is no where near coil bind. That pic doesn't have all the weight on it with the front end on stands behind the front tires, but it's close. TRZ uses the Strange/Hyperco springs as they seem to hold up the best and use a smaller diameter wire which helps them keep further from coil bind. My front coils are MUCH closer to coil bind than the rears.

Given your weight, I'd guess TRZ might recommend a 140 # spring, but that's a guess.

To measure front end travel, measure from the ground to the front wheel well lip at the center of the spindle. Record this number. Now jack the front end up till the upper a-arm stops touch the frame and measure the distance from the ground to the wheel lip again and subtract the two. You need a good 5" of extension travel for proper weight transfer.

I've never used that tire, but there could be something in the usage of the tire say tire pressure, burnout, etc that could be part of your problem as well.

 

[COPO 572]

Thanks a million for the info. Cool set-up.

Theoretically, can't the math tell me approximately how much weight my rear springs are supporting. I know it's not exact, but..........

170 lbs springs X 3" of compression X 2 springs = 1020 lbs of supported weight.

You certainly gave me some things to think about.

Later,
Randy

 

[10secBu]

Thanks a million for the info. Cool set-up.

Theoretically, can't the math tell me approximately how much weight my rear springs are supporting. I know it's not exact, but..........

170 lbs springs X 3" of compression X 2 springs = 1020 lbs of supported weight.

You certainly gave me some things to think about.

Later,
Randy

Yes, you sure can. The only variable not seen doing the math is the unsprung weight which is your axle housing, brakes, wheels & tires, and part of the control arms, etc.

my car for example.

12" - 7.875 = 4.125"
4.125 x 125 = 515.625 x 2 = 1031 lbs supported weight.

 

[gman415]

How much travel should the rear shocks have?
The reason I ask is, I have a set I bought used and had rebuilt. Then I found they were too long for the front, but I think I can make them work on the back if I buy the eye bolt adapter.

 

[COPO 572]

Just had a super informative conversation with Mike @ TRZ. Just as you suggested Todd, I will go with a set of 125 lb springs and hold off on changing the mounting point of my lower control arms. I really enjoyed talking to him.

He also told me that the Strange housing mounting points for the upper control arms is higher than the stock points due to the design of the 9". This means that while my LCA may be pointed down slightly, it may very well still be in a sweet spot due to the heavy angle of the UCA.

Once I get to the track again I'll let you know how it goes.

Thanks Guys,
Randy (aka COPO 572)

 

[Hiway]

My rears are the 12" 130's with no adjuster. 275/60's are just tucked inside fender.....26" at fender lip i think.

 

[COPO 572]

Yea Hiway, that's what I'm talking about! I ended up going with the 130 lbs springs as well. That should provide a big punch over the 175's.

 

[LS6 Tommy]

175# springs are kind of stiff. My rears are only 140# & the suspension is more focus towards handling than drag racing.

Tommy