| FAQ |
| Members List |
| Social Groups |
| Calendar |
| Search |
| Today's Posts |
|
#1
02-09-2016, 03:40 PM
|
|||
|
|||
73 bird: coils & (composite?) leaf springs
Hi everyone there,
Question for the Firebird gurus... :-) I am willing to upgrade the suspension of my 73. - It is pretty much stock now, except for the 17 in wheels, all bushings have been replaced and the front coils + rear leafs seem to be new (although I have no clue about the spring rates) - I will put a set of Koni Red shocks and sub-frame connectors + solid body mounts. - The purpose will be cruising, no autocross, performance, etc... although I like to feel the car tight and responsive, but I don't want it to transmit too much NVH or feel like a chunkwagon... :-) - For this reason, I've been long hesitating about putting tubular control arms. I was almost sold for some tubular aftermarket ones for increased caster with Delrin bushings, then I was told it would be too harsh... was recommended to go with greasable Poly's... but most likely I will remain with the stock stamped arms + rubber bushings for the time being, then see how the car behaves with the new shocks, SFC's, etc and decide from there. I guess I can also use initially some offset shafts for cheap for some extra caster if I want to go little by little. Now, here's where I would need your advice: What I would do for sure is replacing the front coil springs. I am also hesitating with the rear leafs. As I said they seem to be new (see the pics) but I have no clue about the spring rates used. 1- I would like to "improve" a bit the stance: I am satisfied with the rear, but the front sits a bit high for my taste. Ideally I would like to lower the front a bit but not too much. I was thinking in SPC, CustomWorks or similar coil springs rated 500 or 550# with 1 to 1.5 in drop. 2- I was recommended to go with 500-550# coil springs. --> do you think it's a good choice? 3- Not sure what to do about the rear, I read good things about the COMPOSITE leaf springs from Hyperco. --> what would you do? stay with the new stock leafs? would the stock ones be properly matched / balanced with 500-550# front coil springs? or rather go with the composite ones? 4- In case I would go with the composite leafs from Hyperco: I guess the stock leafs in my car must be around 125# or so. I read somewhere that the composites improve the ride quality (comfort) while preserving the handling provided that I put some good shackles for lateral locating. Now, about the spring rate, I think Ridetech puts 175# in their Streetgrip kit for 2nd gen, but I've also heard that it may sit low, and read about people saying that you can go up to 200 or 225# with composite without impacting comfort, and the car would still sit OK (I think about a full fuel tank and eventually 1 person sitting at the back without rubbing...). --> What leaf spring rate for composites do you think would balance nicely the 500-550# front coils? Here below some pictures to illustrate the current set-up. I will highly appreciate your advice and recommendations !!! Thanks!      
|
|
#2
02-09-2016, 09:38 PM
|
||||
|
||||
|
I ran 125# Hyperco's in my TA - ride fine, sit correct height.
|
|
#3
02-09-2016, 11:00 PM
|
||||
|
||||
|
Nice looking car Yater! I agree that the cars sits a bit too high in the front and I would suggest that you cut apx. 1/2 a coil from each coil spring which should drop the height nicely. The job is a PITA but other than getting a loaner coil spring compressor the job is free assuming you have a cut off wheel to cut the springs. Also, I did not see an anti roll bar in the back so you might want to add one. I could be wrong but it appears that the leaf springs may just have been painted and are not new. I have not tried the composite leaf springs so I would be curious to see what you think of them if you go that route.
__________________
 1970 T/A
|
|
#4
02-09-2016, 11:05 PM
|
||||
|
||||
|
One more thing Yater: it could just be the slope of the parking surface but it looks like the passenger side of the car sits higher than the drivers side. You might want to take a measurement at each corner to see if something else is going on?
__________________
1970 T/A
|
|
#5
02-10-2016, 08:17 AM
|
|||
|
|||
|
I have had the vet brakes complete kit for almost 7 yrs now and it just sits because I haven't moved on the body work for my 70 project.
__________________
http://www.fquick.com/garages/viewga...ewimg&id=74990 "You people have stood in my way long enough. I'm going to clown college." -Homer Simpson |
|
#6
02-10-2016, 08:47 AM
|
|||
|
|||
|
Cutting was an option. But I am rather considering going for a new set of coil springs, that way I will know for sure the spring rate I'm using and I will try to balance the best I can front and rear rates for a good ride.
Do you think about 500# makes sense at the front? I guess it would also depend on the rear rate, which would be either 1) about 125# with stock leafs (assuming they are not "heavy duty") or 2) 175-200# from what I understood in case of composite ones. Quote:
|
|
#7
02-10-2016, 08:51 AM
|
|||
|
|||
|
Good eye!
Yes I noticed that. I think (I couldn't take proper measurements) that the front is more or less OK btw R/L side, but the rear passenger side sits indeed higher than the driver side. I don't know what may be causing this and how to fix it. Quote:
|
|
#8
02-10-2016, 08:58 AM
|
|||
|
|||
|
Hi Scarebird,
Good to have some 1st hand experience. - Can you comment on the ride with the Hyperco? - Did you use different shackles and leaf bushings? - Is the installation "plug and play" or is there anything that shall be modified? - Regarding the rate, I read in another forum about someone with a Mopar saying the factory rate (i.e. 125#) was making the car sit too low. Also saw a comment (I am unable to find it again) from someone saying that with composites you can (or even you should?) go 50-75# stiffer than stock rate. Ridetech told me they rate their Hyperco's for 2nd gen f-body at 175# as well. What's your view from your experience? How about the gas tank full and let's say one person in the back seats? Any rubber or bottoming? - Would you mind posting a picture of your car's stance? Thanks a lot, your experience will be helpful! Quote:
|
|
#9
02-10-2016, 08:58 AM
|
|||
|
|||
|
if the rear leafs are original, it's likely age. side by side out of car comparison to verify. 1/2 coil cut. to set it in the pocket right, a quick heat up 1/3rd of the way around the bottom coil while pressing it to the floor just until it flattens the bottom is the "direct from Herb Adams" method to reset the front ride height.
Worked perfect on mine. even with providing all the info to spring companies, there's too many stories of still missing the ride height. If you're not auto-xing and NVH is a bit of a concern, go with poly on the sub bushings. Solids are going to transmit a lot. before/after http://forums.maxperformanceinc.com/...d.php?t=660922 |
|
#10
02-10-2016, 04:48 PM
|
||||
|
||||
|
Quote:
message in goute field |
|
#11
02-10-2016, 06:54 PM
|
||||
|
||||
|
If you want to lower the front, use lowering spindles. It doesn't screw up with geometry, handles and rides a lot better, and the work is the same. You get the amount lowered exactly what it says. No bouncy harsh ride. IMHO
|
|
#12
02-11-2016, 01:04 AM
|
||||
|
||||
|
Here are a few facts for ya.
1. ALL Modern cars that run those big wheels with minimal side wall run a MacPherson strut suspension. This is due to its much faster reaction time and sensitivity. Since TIRES ARE part of the suspension on a '73, when you just throw on the big rims, you will loose a significant part of the ride. 2. To make your suspension "act like" a "strut" youll need Control arms that are greasable Uppers > https://www.youtube.com/watch?v=NnCMAJt4gRA Lowers> https://www.youtube.com/watch?v=iA27erlQhAw These will run a standard spring, you can get them for a coil over which is an exact Strut. Rear Leafs. In 73 they are same number both sides.. IF you replace get the lower rating spring and assemble loose and only tighten when a full load is on the suspension. I like the eaton springs for stock Good luck! PS, why not buy the weld on factory rear sway bar mount and really make it handle for cheap 
__________________
"The Future Belongs to those who are STILL Willing to get their Hands Dirty" .. my Grandfather |
|
#13
02-20-2016, 06:01 PM
|
||||
|
||||
|
BTW not sure if anyone mentioned it to you but Ride-tech introduced a new complete suspension swap that that has the right A-arms, coil-overs, and composite rear spring setup as an entry level Pro-touring suspension package... Might be worth giving them a call....
__________________
albertmelchior@gmail.com |
|
#14
02-20-2016, 07:25 PM
|
||||
|
||||
|
Quote:
http://www.ridetech.com/store/muscle...hash=V265.V328
__________________
"The Future Belongs to those who are STILL Willing to get their Hands Dirty" .. my Grandfather |
| Reply |
|
|
The PY Online Forums is the largest online gathering of Pontiac enthusiasts anywhere in the world. Founded in 1991, it was also the first online forum for people to gather and talk about their Pontiacs. Since then, it has become the mecca of Pontiac technical data and knowledge that no other place can surpass.
Linear Mode
