C3 Front Springs & Ride Height: School Me, Please!
08-07-2016, 06:24 PM
#1
Melting Slicks
Thread Starter
C3 Front Springs & Ride Height: School Me, Please!
There is so much conflicting information out there on this subject, I'm hoping some of the folks here can shed some light on it.
I've got a 79 L82, AC (every option except for CB and rear window defroster) FE41 / Gymkhana.
I'm planning on getting the 330lb rear composite leaf spring from VB&P because I want a slightly softer ride than the stock FE41.
VB&P indicates that the 460lb front spring is ideally balanced to the 330lb rear spring, BUT I'd actually like to LOWER my front ride height and not RAISE it. VB&P's 550lb front spring is better balanced to the 360lb rear composite spring AND is shorter, which sounds great, but I don't really want a spring that heavy.
-I thought of getting the 460lb front spring and just cutting it to the 550lb spring's height, but if I'm understanding this right, when you cut down a spring you also increase it's rebound rate/ effective pressure; the diameter of the metal on the 460lb and 550lb springs are the same -as is the diameter of the coil, so if I understand this correctly the 460lb is essentially the 550lb coil cut down and if you cut down a 460lb to the 550lb coil height you will have just created your own 550lb coil but without the benefit of powder coating on the end that you cut--- is this correct?
Does anyone sell a 460lb or there about front spring that sits lower? -about the same height as the VBP 550lb?
I'm going to have aluminum heads and an aluminum radiator and I hope to, way down the line, get rid of 40lbs of vacuum canister so that's a lot of weight reduction and I'm afraid that the springs will just be too heavy and the ride height too high--then if I cut the coil further I just make it an even "heavier" rated spring and make the ride that much rougher... UGH!
-There's not really another way to adjust the front ride height other than by getting a shorter coil without spending mega bucks on something like front coilovers, right?
Adam
I've got a 79 L82, AC (every option except for CB and rear window defroster) FE41 / Gymkhana.
I'm planning on getting the 330lb rear composite leaf spring from VB&P because I want a slightly softer ride than the stock FE41.
VB&P indicates that the 460lb front spring is ideally balanced to the 330lb rear spring, BUT I'd actually like to LOWER my front ride height and not RAISE it. VB&P's 550lb front spring is better balanced to the 360lb rear composite spring AND is shorter, which sounds great, but I don't really want a spring that heavy.
-I thought of getting the 460lb front spring and just cutting it to the 550lb spring's height, but if I'm understanding this right, when you cut down a spring you also increase it's rebound rate/ effective pressure; the diameter of the metal on the 460lb and 550lb springs are the same -as is the diameter of the coil, so if I understand this correctly the 460lb is essentially the 550lb coil cut down and if you cut down a 460lb to the 550lb coil height you will have just created your own 550lb coil but without the benefit of powder coating on the end that you cut--- is this correct?
Does anyone sell a 460lb or there about front spring that sits lower? -about the same height as the VBP 550lb?
I'm going to have aluminum heads and an aluminum radiator and I hope to, way down the line, get rid of 40lbs of vacuum canister so that's a lot of weight reduction and I'm afraid that the springs will just be too heavy and the ride height too high--then if I cut the coil further I just make it an even "heavier" rated spring and make the ride that much rougher... UGH!
-There's not really another way to adjust the front ride height other than by getting a shorter coil without spending mega bucks on something like front coilovers, right?
Adam
Last edited by NewbVetteGuy; 08-07-2016 at 06:27 PM.
The following users liked this post:
SpeedRacerMach (06-14-2017)
08-07-2016, 06:34 PM
#2
Drifting
You are correct, cutting the lower rated spring will increase the spring rate. However, I'm not sure if there is a mathematical calculation or if anyone has tested how much one coil will increase a 460lb spring.
For your goals, just go to the 550lb spring. It will accomplish lowering, and has been reviewed very positively. I don't think it will be substantial enough to make you unhappy.
As far as other options, yes either coilovers, or VB&P's front transverse spring kit.
For your goals, just go to the 550lb spring. It will accomplish lowering, and has been reviewed very positively. I don't think it will be substantial enough to make you unhappy.
As far as other options, yes either coilovers, or VB&P's front transverse spring kit.
Last edited by Ibanez540r; 08-07-2016 at 06:35 PM.
08-08-2016, 09:14 PM
#4
Drifting
Member Since: Aug 2015
Location: NSW, Australia
Posts: 1,939
Received 472 Likes
on
344 Posts
C3 of Year Finalist (track prepared) 2019
The gymkhana suspension option has 550lb front springs, and the vb&p 550s are supposed to ride better and sit 1" lower. Seems the obvious choice? In terms of how to calculate the spring stiffness, multiply the original spring rate by (original number of coils/new number of coils) and you'll be pretty right. I.e. A 400lb spring with 5 coils has one coil removed so that it has 4 coils, new stiffness is 400 x (5/4) = 500lb.
08-08-2016, 10:55 PM
#5
Le Mans Master
You could have a set of 460s "bulldozed" to the desired ride height, but the procedure isn't exactly your run-of-the-mill DIY project. So, a word of caution to anyone who might attempt...
FWIW, given the inherent mechanical advantage of the C3 front suspension the actual rate difference at the wheel between the 550 and 460 is on the order of a mere 50# per inch of travel. And, there's no reason you can't run the 550s with a 330# rear, tho the 360# would tend to put balance a tad further away from the understeer end of the spectrum. Whether and/or how often you actually approach your car's limits will determine how noticeable is that difference, as well as which combination you might prefer in practice, whatever a particular vendor may wish to prescribe. Anyway, there's absolutely nothing wrong with mild understeer on any street driven car. My $.02
FWIW, given the inherent mechanical advantage of the C3 front suspension the actual rate difference at the wheel between the 550 and 460 is on the order of a mere 50# per inch of travel. And, there's no reason you can't run the 550s with a 330# rear, tho the 360# would tend to put balance a tad further away from the understeer end of the spectrum. Whether and/or how often you actually approach your car's limits will determine how noticeable is that difference, as well as which combination you might prefer in practice, whatever a particular vendor may wish to prescribe. Anyway, there's absolutely nothing wrong with mild understeer on any street driven car. My $.02
08-09-2016, 07:22 AM
#6
Le Mans Master
Member Since: Oct 2007
Location: Akron Ohio
Posts: 8,868
Received 1,753 Likes
on
941 Posts
2023 C5 of the Year Finalist - Modified
2022 C5 of the Year Finalist - Modified
St. Jude Donor '09-'10-'11
I agree that having the 550lb fronts and a softer rear will be ok. If there is any understeer it will be minimal and can be tuned out with the sway bars at that point.
08-09-2016, 09:33 AM
#7
Le Mans Master
Or you could do what I did which was cut the 550 by 1 coil combined with the 360 rear....very neutral at the limit with very slight understeer and that with a 3/4 inch rear OEM type GM swaybar....
08-09-2016, 10:46 AM
#8
Racer
- I have completely stock rear: its all new, but stock. poly, trailing arms, stock spring. getting adjustable struts (wish i used them in first place)
- the front end will be rebuilt (with poly bushings) stock: based on previous threads i got 550 pound springs and BilsteinHD's.
I didn't plan to cut 550# springs. Do i need to in order for it to not sit too high? I was planning on installing and then letting weight settle for a few months. (other threads showed me it made sense let 'settle'.)
Thanks-
08-09-2016, 11:57 AM
#9
Team Owner
My 79 with the same options got the vbp street and slalom kit with 550 front and a custom 500 steel rear to prevent rear end squat on take off
Rear squat causes a terrific load on the yoke ends and posi cross pin
I now drive all over with 650 frn and 520# mono rea . It is nice and smooth
Rear squat causes a terrific load on the yoke ends and posi cross pin
I now drive all over with 650 frn and 520# mono rea . It is nice and smooth
08-09-2016, 06:40 PM
#11
Le Mans Master
My 550 springs were perfect with the stock L-82 with the 882 cast iron heads. With the rebuild in 2014, I used AFR aluminum heads which caused the front to lift noticeably and thus the reason I cut the 550's recently. I do not have a picture of the 550 coils cut and the 78. I originally cut a 1/2 coil and yesterday cut the other half coil since the front was still too high. More to come next weekend...Traveling for work currently...
08-09-2016, 09:17 PM
#13
Racer
@jb78L-82, are these the ones ineed to cut a coil from? (Sorry to bug ya, but I researched your postes from over the years and really like your approach.)
08-09-2016, 10:46 PM
#14
Drifting
Member Since: Aug 2015
Location: NSW, Australia
Posts: 1,939
Received 472 Likes
on
344 Posts
C3 of Year Finalist (track prepared) 2019
I guess I should add, I have a bit over one coil cut from my factory gymkhana 550lb springs, and my car was sitting pretty low, but the new engine going in shortly will probably raise it back up a bit (alloy heads, intake, water pump and electric fan instead of clutch mechanical). But I think from memory that jb78-L82 might be running shorter tyres than me (I'm running 255/50r17s, the same diameter as stock 255/60r15s), which would allow (and encourage from an aesthetic standpoint) a lower suspension height.
08-10-2016, 01:55 PM
#15
Le Mans Master
My 550 springs are from MidAmerica Corvette parts..
FYI-the gymkhana factory front coils were no where near 550lb springs. The base spring in 1978 was 295lbs and the gymkhana was somewhere around 400-450lbs. GM did not offer the sport suspension cars with a 550lbs front spring.....Very hard to find an aftermarket company that offers a 300lbs front coil since quite frankly, that rating is ridiculously low for a sports car. The aftermarket replacement base spring is 460 with the gymkhana spring most offered is the 550....The 81/82 rear base composite spring was rated @192lbs which is Cadillac like ride characteristics...
FYI-the gymkhana factory front coils were no where near 550lb springs. The base spring in 1978 was 295lbs and the gymkhana was somewhere around 400-450lbs. GM did not offer the sport suspension cars with a 550lbs front spring.....Very hard to find an aftermarket company that offers a 300lbs front coil since quite frankly, that rating is ridiculously low for a sports car. The aftermarket replacement base spring is 460 with the gymkhana spring most offered is the 550....The 81/82 rear base composite spring was rated @192lbs which is Cadillac like ride characteristics...
08-10-2016, 02:54 PM
#16
Team Owner
FWIW, back in the mid-90s, I did a suspension overhaul on my wife's '79 C-3. I went with the VB&P 330 monoleaf in the rear, and their 460 coil in the front, with a half coil removed.
08-10-2016, 07:35 PM
#17
Drifting
Member Since: Aug 2015
Location: NSW, Australia
Posts: 1,939
Received 472 Likes
on
344 Posts
C3 of Year Finalist (track prepared) 2019
My 550 springs are from MidAmerica Corvette parts..
FYI-the gymkhana factory front coils were no where near 550lb springs. The base spring in 1978 was 295lbs and the gymkhana was somewhere around 400-450lbs. GM did not offer the sport suspension cars with a 550lbs front spring.....Very hard to find an aftermarket company that offers a 300lbs front coil since quite frankly, that rating is ridiculously low for a sports car. The aftermarket replacement base spring is 460 with the gymkhana spring most offered is the 550....The 81/82 rear base composite spring was rated @192lbs which is Cadillac like ride characteristics...
FYI-the gymkhana factory front coils were no where near 550lb springs. The base spring in 1978 was 295lbs and the gymkhana was somewhere around 400-450lbs. GM did not offer the sport suspension cars with a 550lbs front spring.....Very hard to find an aftermarket company that offers a 300lbs front coil since quite frankly, that rating is ridiculously low for a sports car. The aftermarket replacement base spring is 460 with the gymkhana spring most offered is the 550....The 81/82 rear base composite spring was rated @192lbs which is Cadillac like ride characteristics...
Most of the info above is correct for the most part with some incorrect details. This GM source will tell you all you need to know:
https://www.gmheritagecenter.com/doc...t-Corvette.pdf
A few highlights...All the Gymkhana cars in the late 70's and all C3 SB's with the Gymkhana suspension had a rear 7/16 GM style rear sway bar (not aftermarket bars with the front type endlinks). No rear 7/16 inch sway bar, (like in your picture which is correct for the sport suspension)...no gymkhana suspension. On your 79 (and my 78), if you had the 1 1/8 inch front bar also which was coupled with the 7/16 inch rear bar...definitely a gymkhana car. GM was on the right path with the front bar at 1 1/8 inch which by today's sway bar standard is very common...most C3's have a front bar that is way too small for any type of handling, just as a general statement.
Lastly, spring rates which were generally VERY soft back then in my opinion and again not optimized for handling probably since the steel rear spring has VERY harsh ride characteristics. C3's never came with 550 front springs from the factory..the 550 spring is the aftermarket replacement recommended for gymkhana cars...theme here that the GM rates were not optimal for handling. The 79 front base rate was 295 and 370 for the sport suspension. The rear 9 leaf base spring was 198!!!! and the gymkhana 7 leaf rear spring was 292 lbs/in.
With all that said my 78 gymkhana C3 uses the OEM front bar 1 1/8 inch with poly bushings, 550 front springs 1 inch lower than stock, Bilstein HD shocks, and has a front spreader bar. The rear is a 360 composite, 3/4 inch OEM type rear bar, Bilstein Sports, Heim joint competition Struts. The car rides, steers, and handles 10X better than any base or sport late 70's C3. The ride is firm but not harsh and very forgiving. Numbers don't tell the whole story if you mix and match components correctly. My 78 rides MUCH softer than my 2010 Z06 (even with DRM Bilsteins) and my 2008 Chrysler 300 with Bilsteins all around. Hope that helps!
https://www.gmheritagecenter.com/doc...t-Corvette.pdf
A few highlights...All the Gymkhana cars in the late 70's and all C3 SB's with the Gymkhana suspension had a rear 7/16 GM style rear sway bar (not aftermarket bars with the front type endlinks). No rear 7/16 inch sway bar, (like in your picture which is correct for the sport suspension)...no gymkhana suspension. On your 79 (and my 78), if you had the 1 1/8 inch front bar also which was coupled with the 7/16 inch rear bar...definitely a gymkhana car. GM was on the right path with the front bar at 1 1/8 inch which by today's sway bar standard is very common...most C3's have a front bar that is way too small for any type of handling, just as a general statement.
Lastly, spring rates which were generally VERY soft back then in my opinion and again not optimized for handling probably since the steel rear spring has VERY harsh ride characteristics. C3's never came with 550 front springs from the factory..the 550 spring is the aftermarket replacement recommended for gymkhana cars...theme here that the GM rates were not optimal for handling. The 79 front base rate was 295 and 370 for the sport suspension. The rear 9 leaf base spring was 198!!!! and the gymkhana 7 leaf rear spring was 292 lbs/in.
With all that said my 78 gymkhana C3 uses the OEM front bar 1 1/8 inch with poly bushings, 550 front springs 1 inch lower than stock, Bilstein HD shocks, and has a front spreader bar. The rear is a 360 composite, 3/4 inch OEM type rear bar, Bilstein Sports, Heim joint competition Struts. The car rides, steers, and handles 10X better than any base or sport late 70's C3. The ride is firm but not harsh and very forgiving. Numbers don't tell the whole story if you mix and match components correctly. My 78 rides MUCH softer than my 2010 Z06 (even with DRM Bilsteins) and my 2008 Chrysler 300 with Bilsteins all around. Hope that helps!
08-10-2016, 08:45 PM
#18
Le Mans Master
I stand corrected...I did not know it was a 550 from GM...wow 295 base to 550 gymkhana...that is
a big difference. The 78 gymkhana rear spring was 292lbs though..good catch
a big difference. The 78 gymkhana rear spring was 292lbs though..good catch
08-10-2016, 09:12 PM
#19
Drifting
Member Since: Aug 2015
Location: NSW, Australia
Posts: 1,939
Received 472 Likes
on
344 Posts
C3 of Year Finalist (track prepared) 2019
Ok cool, thanks! I wondered what I was missing, because I've read a lot of your posts and you always post good info. Wonder why the small difference in rear spring rate between '78 and '79? With that big a difference I guess it's no wonder that I've seen magazine reviews of the day complain about the ride of the gymkhana option.
08-10-2016, 11:01 PM
#20
Melting Slicks
Thread Starter
Ok, so my plan right now is to go with the 550lb VBP front springs (because they're a perfect stock replacement AND lower) and if the front gets raised too much from weight reduction then I'll cut it another half spring and deal with the REALLY heavy front spring rate, then-probably with really good shocks.
I'm planning on going with the 330lb composite rear spring kit with 8" bolts to lower the rear end within reason, instead of the 360lb. My only hesitation is that I've read that getting suspension components very well matched is one of the most important things; this isn't "off" too much from the ideal right? -I like the ride improvement, huge weight savings AND a couple of small changes towards my fuel economy improvement goals; lowering the car helps a tiny bit with fuel economy via aero improvement and makes it dead sexy; the weight reduction helps with fuel economy, too. My 79's got the pace car front and rear spoilers so it's got a better CID than most C3s, although it doesn't have the weight reduction of the 80-82 models--I have to do that part myself.
I'm also planning on replacing the rear shocks at the same time with the VBP specially valved KYY shocks but leaving my current, unknown stored brand front gas shocks. I am also planning on keeping the stock "wimpy" front and rear Gymkhana sway bars.
Anyone see any serious problems with my plans?
-I've also got a Steeroids kit brand new in the box I got a steal on from CL; once it goes on I'm going to have the front and rear professionally aligned to modern specs (the alignment specs recommended by SpeedDirect/ the Steeroids kit).
Adam
I'm planning on going with the 330lb composite rear spring kit with 8" bolts to lower the rear end within reason, instead of the 360lb. My only hesitation is that I've read that getting suspension components very well matched is one of the most important things; this isn't "off" too much from the ideal right? -I like the ride improvement, huge weight savings AND a couple of small changes towards my fuel economy improvement goals; lowering the car helps a tiny bit with fuel economy via aero improvement and makes it dead sexy; the weight reduction helps with fuel economy, too. My 79's got the pace car front and rear spoilers so it's got a better CID than most C3s, although it doesn't have the weight reduction of the 80-82 models--I have to do that part myself.
I'm also planning on replacing the rear shocks at the same time with the VBP specially valved KYY shocks but leaving my current, unknown stored brand front gas shocks. I am also planning on keeping the stock "wimpy" front and rear Gymkhana sway bars.
Anyone see any serious problems with my plans?
-I've also got a Steeroids kit brand new in the box I got a steal on from CL; once it goes on I'm going to have the front and rear professionally aligned to modern specs (the alignment specs recommended by SpeedDirect/ the Steeroids kit).
Adam
Last edited by NewbVetteGuy; 08-10-2016 at 11:07 PM.
The following users liked this post:
SpeedRacerMach (06-14-2017)