Rear Leaf Spring, Steel vs. Fiberglass for a 76
06-28-2010, 01:28 PM
#1
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Rear Leaf Spring, Steel vs. Fiberglass for a 76
I have a busted rear original leaf spring. Bottom long one busted at center mounting area. Need to replace but wondering the pro's and con's of steel vs. fiberglass. I already know there is a big price difference. 
Reddog76
Reddog76
06-28-2010, 02:01 PM
#2
Le Mans Master
If you like a soft ride, fiberglass is the way to go. I have a 71' with the glass spring and don't care for it. It is to bouncy for me. Tried a couple different brands of shock but still to bouncy.
Gary
Gary
06-28-2010, 04:08 PM
#3
Drifting
Yes Sir: There is a complete run down on the rear Composite,& steel springs, in this Tech information, section. Van Steel has several different kinds, even the same composite Co. who built the original spring, for G.M. Some springs set up the rear end too high for me. A lot depends on the type of driving you will be doing. I have the original Composite, & it is great. Have a great day. Gene
06-28-2010, 05:04 PM
#4
Drifting
Glass but get it from VBP. I've heard some pretty bad things concerning ride height for most of the others, but not from VBP, and it's what I have, and it's great. It IS a bit bouncy if you get one that's too stiff, or don't have the correct shocks (bilstein)...but if set up correctly, it improves handling, and reduces the weight by a couple pounds as well. Deff worth it.
06-28-2010, 06:55 PM
#5
Le Mans Master
Some great advice above^
I have had a VBP spring on my 78 which originally had the 7 leaf steel spring (Gymkhana) and I replaced it in 1986 (that is not a typo) with a 360lb composite that is still perfect, no sagging, no stress cracks, nothing. As mentioned a composite rides MUCH better than a comparable weight steel spring, will never sag, reacts quicker to suspension changes, and weighs 8 lbs versus 50 lbs+ for the steel spring. I have had various shocks on the car, everything from AC Delcos, KYB Gas A Just, Koni's and Bilsteins over the last 27 years. By far the best shocks for the composite giving a superb ride and excellent handling are the Bilsteins. I had the heavy duties all around with the 550 lb fronts springs (which are still the HD's in front) but I switched to the Sports (30% stiffer than the HD's) in the rear only to completely eliminate the slight bouncy ride I had with the HD's. The beauty of the composite spring is it will give a much better ride than a steel spring (you need to pick the right spring for what you are looking for: 200 lbs/in to 420 lbs/in) and better suspension response. Hope that helps!
I have had a VBP spring on my 78 which originally had the 7 leaf steel spring (Gymkhana) and I replaced it in 1986 (that is not a typo) with a 360lb composite that is still perfect, no sagging, no stress cracks, nothing. As mentioned a composite rides MUCH better than a comparable weight steel spring, will never sag, reacts quicker to suspension changes, and weighs 8 lbs versus 50 lbs+ for the steel spring. I have had various shocks on the car, everything from AC Delcos, KYB Gas A Just, Koni's and Bilsteins over the last 27 years. By far the best shocks for the composite giving a superb ride and excellent handling are the Bilsteins. I had the heavy duties all around with the 550 lb fronts springs (which are still the HD's in front) but I switched to the Sports (30% stiffer than the HD's) in the rear only to completely eliminate the slight bouncy ride I had with the HD's. The beauty of the composite spring is it will give a much better ride than a steel spring (you need to pick the right spring for what you are looking for: 200 lbs/in to 420 lbs/in) and better suspension response. Hope that helps!
Last edited by jb78L-82; 06-28-2010 at 07:03 PM.
06-28-2010, 09:11 PM
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I'm not looking for a road racing performance stiff ride, just a decent performing comfortable ride with a slight lift or at least the capability to adjust the height. I am not a small guy so a little extra firmness would probably help. I am not familiar with the VBP you are recommending.
06-28-2010, 09:51 PM
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Looked at the vbp website. It looks like the 330lb unit might suit my needs just fine. They als recommend a decent set of shocks for around 175 which includes special rears for the fiberglass leaf. ANY BAD OPINIONS? Also looking for new rear struts.
Reddog76
Reddog76
06-28-2010, 10:06 PM
#8
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St. Jude Donor '11-'12-'13,'19-'20
I just swapped from worn out steel, to 330 Hypercoil, and then to 300 VBP. The VBP is the superior spring as far as fit, adjustment and handling quality. The hypercoil rode and handled well enough but could not get the ride height to adjust down and the ends of the spring hung down way too low for me.
I'll give a big recommendation to Van Steel who rode out this experiemnt with me to make sure I was satisfied.
They will get more of my business! I went with the recmommended shock upgrade and feel it was all worth it. 
I'll give a big recommendation to Van Steel who rode out this experiemnt with me to make sure I was satisfied.
They will get more of my business! I went with the recmommended shock upgrade and feel it was all worth it.
06-28-2010, 11:40 PM
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Here is a good summary from some people who know what they are talking about...
http://www.duntovmotors.com/tech-rear-leaf-springs.php
Many people swear by what they have bought since anything new is probably an improvement over the 40 year old spring.
http://www.duntovmotors.com/tech-rear-leaf-springs.php
Many people swear by what they have bought since anything new is probably an improvement over the 40 year old spring.
06-29-2010, 12:04 AM
#10
Here is a good summary from some people who know what they are talking about...
http://www.duntovmotors.com/tech-rear-leaf-springs.php
Many people swear by what they have bought since anything new is probably an improvement over the 40 year old spring.
http://www.duntovmotors.com/tech-rear-leaf-springs.php
Many people swear by what they have bought since anything new is probably an improvement over the 40 year old spring.
06-30-2010, 07:08 AM
#11
Le Mans Master
From the Duntov site:
"The spring change saved about 20 lbs; a huge savings for comparatively little money. To the end user, the twenty pounds is equivalent to about two and a half gallons of gas; not exactly earth shaking for the average Corvette driver.
Unfortunately the composite spring weight savings was right where the Corvette least needed to lose weight; low and behind the rear axle. The steel spring is like ballast in a racecar, right where it needs to be; low and behind the rear axle.
Composite springs don’t lose their spring rate over time. A 315 lb spring will stay 315 lbs until it breaks. Yes, that’s what sends composite springs to the dumpster; a rock in just the right place. Hit on edge by a road hazard, a composite spring will often de-laminate. It will turn a milky white at the point of injury and its service life is over. A steel spring will slowly lose its spring rate over time, but it will never break.
The softest TRW composite spring is 315 lbs. Most C2 and C3 Corvettes came with 196 lb. steel rear springs. After 20 years or so, when they are ready for replacement, their effective spring rate has eroded by as much as 40%. Replacing the original spring with a new stock steel spring makes a big difference; a 40% difference. Changing to a 315 lb spring would be a change of 270%, and you would have a completely different automobile.
The spring rate of the 78-80 OEM factory steel rear spring was 260 lbs. You can order a 315 lb spring for a 78-79, but for anything newer than that, you have to chose between 345 and 355 lbs. That’s a heavier spring rate than we run on our racecars, so you can imagine it’s not the softest ride on the planet."
A couple of comments but before I do. First I have heard that Duntov is very reputable even though I have never used their products. Clearly, Duntov has race experience as referenced on their website and I do not race my 78, just driven on the street. My point of view is from using a VBP composite for 25 years now.
Here it goes:
1. I don't know about you but my OEM 7 leaf steel spring was very heavy and weighted about 50-60 lbs versus about 10 lbs for the composite from VBP. Many sites suggest a weight savings of 40lbs using a composite.
2. My 78's weight distribution was OEM 48%F and 52%R in the rear. Having a rear biased weight distribution is better for the track but not ideal on the street. Installation of the composite spring brought the weight distribution closer to 50:50 for me on the street.
3. Various manufacturer's of composites offer spring rates from 200-420lbs (and I believe higher).
4. The spring rate for the steel spring late 70's vette at 260lbs was for the base suspended 78/79, not the sport suspension vettes.
5. Everyone that I know that has a composite spring reports that the ride quality is better than the steel counterpart, not harder as described on their website. I replaced my OEM steel 7 leaf spring (gymkhana suspension) with a 360lb VBP composite spring in 1986 (and it is still on the car and perfect) and it rode MUCH better than the OEM steel spring, but was bouncy on rough rodes until I coupled that spring with Bilstein Sports in the rear only.
6. I suspect one can go up on the spring rate to a much higher setting with a composite with better ride quality than a steel spring due to the elastic nature of the composite and much less friction that comes from not having leafs.
7. Duntov clearly seems to support the use of steel springs over the composite ones for racing but I am not so sure based on my experience with a composite on the street that this recommendation is completely appropriate on the street.
8. I would definitely talk with other reputable vendors such as VBP before making a decision. There does not seem to be agreement about all the above points.
9. There is a reason that GM abandoned the steel spring concept in 1980 all the way to today!
10. If my 360 composite spring broke today, I would not even consider going back to a steel one after the past 25 years experience with the composite-It has been that good on the street! I am still amazed at riding in C2/C3 vettes with a steel spring and the ride harshness!
Just a counter argument!
"The spring change saved about 20 lbs; a huge savings for comparatively little money. To the end user, the twenty pounds is equivalent to about two and a half gallons of gas; not exactly earth shaking for the average Corvette driver.
Unfortunately the composite spring weight savings was right where the Corvette least needed to lose weight; low and behind the rear axle. The steel spring is like ballast in a racecar, right where it needs to be; low and behind the rear axle.
Composite springs don’t lose their spring rate over time. A 315 lb spring will stay 315 lbs until it breaks. Yes, that’s what sends composite springs to the dumpster; a rock in just the right place. Hit on edge by a road hazard, a composite spring will often de-laminate. It will turn a milky white at the point of injury and its service life is over. A steel spring will slowly lose its spring rate over time, but it will never break.
The softest TRW composite spring is 315 lbs. Most C2 and C3 Corvettes came with 196 lb. steel rear springs. After 20 years or so, when they are ready for replacement, their effective spring rate has eroded by as much as 40%. Replacing the original spring with a new stock steel spring makes a big difference; a 40% difference. Changing to a 315 lb spring would be a change of 270%, and you would have a completely different automobile.
The spring rate of the 78-80 OEM factory steel rear spring was 260 lbs. You can order a 315 lb spring for a 78-79, but for anything newer than that, you have to chose between 345 and 355 lbs. That’s a heavier spring rate than we run on our racecars, so you can imagine it’s not the softest ride on the planet."
A couple of comments but before I do. First I have heard that Duntov is very reputable even though I have never used their products. Clearly, Duntov has race experience as referenced on their website and I do not race my 78, just driven on the street. My point of view is from using a VBP composite for 25 years now.
Here it goes:
1. I don't know about you but my OEM 7 leaf steel spring was very heavy and weighted about 50-60 lbs versus about 10 lbs for the composite from VBP. Many sites suggest a weight savings of 40lbs using a composite.
2. My 78's weight distribution was OEM 48%F and 52%R in the rear. Having a rear biased weight distribution is better for the track but not ideal on the street. Installation of the composite spring brought the weight distribution closer to 50:50 for me on the street.
3. Various manufacturer's of composites offer spring rates from 200-420lbs (and I believe higher).
4. The spring rate for the steel spring late 70's vette at 260lbs was for the base suspended 78/79, not the sport suspension vettes.
5. Everyone that I know that has a composite spring reports that the ride quality is better than the steel counterpart, not harder as described on their website. I replaced my OEM steel 7 leaf spring (gymkhana suspension) with a 360lb VBP composite spring in 1986 (and it is still on the car and perfect) and it rode MUCH better than the OEM steel spring, but was bouncy on rough rodes until I coupled that spring with Bilstein Sports in the rear only.
6. I suspect one can go up on the spring rate to a much higher setting with a composite with better ride quality than a steel spring due to the elastic nature of the composite and much less friction that comes from not having leafs.
7. Duntov clearly seems to support the use of steel springs over the composite ones for racing but I am not so sure based on my experience with a composite on the street that this recommendation is completely appropriate on the street.
8. I would definitely talk with other reputable vendors such as VBP before making a decision. There does not seem to be agreement about all the above points.
9. There is a reason that GM abandoned the steel spring concept in 1980 all the way to today!
10. If my 360 composite spring broke today, I would not even consider going back to a steel one after the past 25 years experience with the composite-It has been that good on the street! I am still amazed at riding in C2/C3 vettes with a steel spring and the ride harshness!
Just a counter argument!
Last edited by jb78L-82; 06-30-2010 at 07:18 AM.
06-30-2010, 02:10 PM
#12
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Thanks for the counter argument jb78L-82, I was just trying to present a different out look than the people who swear by composite springs and bilstein shocks. I like the fact that steel springs won't fail on me, ever..
Different strokes for different folks...
Different strokes for different folks...
07-02-2010, 12:23 PM
#16
Race Director
07-02-2010, 12:26 PM
#17
Race Director
I just swapped from worn out steel, to 330 Hypercoil, and then to 300 VBP. The VBP is the superior spring as far as fit, adjustment and handling quality. The hypercoil rode and handled well enough but could not get the ride height to adjust down and the ends of the spring hung down way too low for me.
I'll give a big recommendation to Van Steel who rode out this experiemnt with me to make sure I was satisfied. They will get more of my business! I went with the recmommended shock upgrade and feel it was all worth it.
I'll give a big recommendation to Van Steel who rode out this experiemnt with me to make sure I was satisfied.
They will get more of my business! I went with the recmommended shock upgrade and feel it was all worth it. 