z51 rear spring
Racer
Joined: May 2012
Posts: 363
Likes: 0
From: Peabody MA
It'll be softer, but it's probably the best spring available for the C4. I just purchased an NYU spring myself.
The C4 does not like too much rear roll stiffness, do some research on springs and you'll see some information on the forum from Solofast, who did a lot of testing with C4s and knows his stuff.
Also, look at this chart http://www.netmotive.net/articles/hib/c4/sustunch.pdf
It has the spring rates and sway bar sizes for all C4s for every year, hope this helps!
The C4 does not like too much rear roll stiffness, do some research on springs and you'll see some information on the forum from Solofast, who did a lot of testing with C4s and knows his stuff.
Also, look at this chart http://www.netmotive.net/articles/hib/c4/sustunch.pdf
It has the spring rates and sway bar sizes for all C4s for every year, hope this helps!
Safety Car
Joined: Apr 2011
Posts: 3,660
Likes: 22
Yes, BUT you have to consider other items as well...
sway bar size as mentioned, bushings you have, the shocks and even the front set up...lowered? lower profile tires?
lots to make up the C4 IRS system...
after looking at the charts and understanding the codes and what the numbers mean, LBS etc..........
in/lbs how many lbs of force to get 1" travel or per 1". The famous '84 was a 411# for the common spring, and there was a 499 for the masochist. I have a 411 and it may as well be a section of red-iron I beam laid across the rear end...don't move much. It DOES keep the rear end level but it CAN cause skipping (wheel hop of sorts)on rough road surface or uneven surface from left to right side of the car. Its too hard/fast for some conditions and won't absorb ANY form of impact. Red-Iron...
Rebound (if any) is fast and hard. Much of the rebound is in the tire.
The nicer street friendly rear springs will run from 200 in/lb to the 400 range.
Somewhere in the mid 200's to <300 is most often as good as you get in a C4.
The EASIEST and simply way to gauge a rear springs weight/speed is to observe the ARC. If the spring has little or NO ARC, its gonna be hard as a rock. If the ends have some (2 to 4" arc) its going to be hard & fast but not punishing. If it has a real obvious arc that places the end several inches ( 4 or more) below the springs center section...its a coffee quality spring.
The more the arc the softer the ride. The flatter the spring the harder/harsher the ride quality.
The softies will have thin flat ends that get wider as they go and the solid springs stay narrow but get thicker to almost 7/8" thick.
Not ALL will fit all cars...see the rubber block placement for that and ALWAYS use the shims correctly !
Shims is the #1 way people screw up their rear suspension. The spring MUST be shimmed and mounted right or it will flop around, rattle break things and even break itself! Note the shims when you d/c and have extras handy...no rule says 3 came out and 3 go back...
You can also lower the a$$end up to 1/2" moving the shims if done right.
Good luck!
BTW be careful when torqueing the spring mounting caps....they snap reaaaal easily !
sway bar size as mentioned, bushings you have, the shocks and even the front set up...lowered? lower profile tires?
lots to make up the C4 IRS system...
after looking at the charts and understanding the codes and what the numbers mean, LBS etc..........
in/lbs how many lbs of force to get 1" travel or per 1". The famous '84 was a 411# for the common spring, and there was a 499 for the masochist. I have a 411 and it may as well be a section of red-iron I beam laid across the rear end...don't move much. It DOES keep the rear end level but it CAN cause skipping (wheel hop of sorts)on rough road surface or uneven surface from left to right side of the car. Its too hard/fast for some conditions and won't absorb ANY form of impact. Red-Iron...
Rebound (if any) is fast and hard. Much of the rebound is in the tire.
The nicer street friendly rear springs will run from 200 in/lb to the 400 range.
Somewhere in the mid 200's to <300 is most often as good as you get in a C4.
The EASIEST and simply way to gauge a rear springs weight/speed is to observe the ARC. If the spring has little or NO ARC, its gonna be hard as a rock. If the ends have some (2 to 4" arc) its going to be hard & fast but not punishing. If it has a real obvious arc that places the end several inches ( 4 or more) below the springs center section...its a coffee quality spring.
The more the arc the softer the ride. The flatter the spring the harder/harsher the ride quality.
The softies will have thin flat ends that get wider as they go and the solid springs stay narrow but get thicker to almost 7/8" thick.
Not ALL will fit all cars...see the rubber block placement for that and ALWAYS use the shims correctly !
Shims is the #1 way people screw up their rear suspension. The spring MUST be shimmed and mounted right or it will flop around, rattle break things and even break itself! Note the shims when you d/c and have extras handy...no rule says 3 came out and 3 go back...
You can also lower the a$$end up to 1/2" moving the shims if done right.
Good luck!
BTW be careful when torqueing the spring mounting caps....they snap reaaaal easily !
Safety Car
Joined: Sep 2010
Posts: 3,752
Likes: 190
From: Indiana PA
^Regarding shims follow the FSM on that. FE1 springs and FE7 springs get setup different in the shims, also each spring has a color code ex. yellow that also indicates how the spring pack is setup on each car. Follow the FSM, if you don't own one, get one.
Drifting
Joined: May 2002
Posts: 1,581
Likes: 2
From: The Motor City
Everything leesvet has written is correct; very good advice.
And I cannot stress enough to make sure to use the correct shim(s) when you make the switch. Every spring rate had different shim thicknesses and different shim combinations. This is important to get correct otherwise there is a very high probability of cracking the new rear spring.
And those spring mounting clamps are made of a very porous metal (I"m not even certain they're aluminum). They tolerate absolutely no bending at all and snap very easily. This comes back to using the correct shims and in the correct combination; if you are, there won't be any issues torquing the mounting clamps to spec.
