Steel or composite
01-20-2014, 04:26 PM
#1
Racer
Thread Starter
Steel or composite
I have read the hype on the composite rear spring for our cars. I have a 1980 and was curious to hear some opinions based on experience. If you read Duntov motors argument they claim the added weight is actually good for the handling and the ride is better with the steel spring and suggest a new steel leaf over the composite. Also I don’t want a harsher ride. SO where does the group fall on this topic? I am in the process of suspension maint. Front end is tight, rear suspension is getting TA rebuild and of course full alignment. The rear spring is stock so I know it is worn. Replace with stock or go composite?
01-20-2014, 04:47 PM
#2
Tech Contributor
Member Since: Jun 2004
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I have read the hype on the composite rear spring for our cars. I have a 1980 and was curious to hear some opinions based on experience. If you read Duntov motors argument they claim the added weight is actually good for the handling and the ride is better with the steel spring and suggest a new steel leaf over the composite. Also I don’t want a harsher ride. SO where does the group fall on this topic? I am in the process of suspension maint. Front end is tight, rear suspension is getting TA rebuild and of course full alignment. The rear spring is stock so I know it is worn. Replace with stock or go composite?
01-20-2014, 04:53 PM
#3
Safety Car
Use the composite I have a 1980 and it drives and rides great with the composite
01-20-2014, 04:57 PM
#4
I have an 81. In 81 they came stock with a composite. When I bought my car there was some slight damage to the corner of the spring so I wanted to replace it. My local Corvette restoration parts house only had a steel spring. They said try it and if I didn't like it they would order me a composite for double the price.
Both springs ride ok, the steel spring pounces/recoils a little harder on big bumps than the composite. Other than that I can't tell a lot of defference. I haven't driving it far since I replaced it to see how it handles in the curves. As soon as I was finished with everything under the hood, I drove it a couple of times then rolled it right into my paint booth. I just painted Saturday. It will be on the road ready for the highway in about two weeks.
I have a blower motor in mine. It looks like you may have a built motor too. I think the steel spring with the harder recoil will rebound from the squaty take-offs a little faster. I know mine did the couple of times I tried it.
Both springs ride ok, the steel spring pounces/recoils a little harder on big bumps than the composite. Other than that I can't tell a lot of defference. I haven't driving it far since I replaced it to see how it handles in the curves. As soon as I was finished with everything under the hood, I drove it a couple of times then rolled it right into my paint booth. I just painted Saturday. It will be on the road ready for the highway in about two weeks.
I have a blower motor in mine. It looks like you may have a built motor too. I think the steel spring with the harder recoil will rebound from the squaty take-offs a little faster. I know mine did the couple of times I tried it.
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01-20-2014, 05:41 PM
#6
Le Mans Master
My car currently has a steel spring in it that still has a decent arch to it, but when the time comes that it needs replaced I will be going composite. Have been in vettes with them, and it seems to me like it's a much softer ride. Plus the weight savings cant hurt either.
01-20-2014, 07:11 PM
#7
Burning Brakes
Replaced mine with a composite and ride is MUCH better. Be sure to upgrade your shocks to match the spring.
01-20-2014, 07:46 PM
#8
Racer
Thread Starter
Here is the entire statement. A little reading between the lines but in the end as I read it, they sell them but don't use them
A couple of times a week we are asked to give the plusses and minuses of composite vs. steel rear leaf springs. This is how we see it:
The TRW spring is the OEM replacement spring for the 81 and 82 Corvette. From 1963-1980, Corvettes came with steel rear leaf springs. In an effort to shave weight off the car to help with fuel economy, for the 1981 model year Chevrolet went with magnesium valve covers, a composite rear spring and a number of other weight saving substitutions. 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.
One more thing that may or may not be a big deal to a street driven Corvette: The steel spring is at least somewhat progressive in its spring rate. In our custom steel springs that we use for our racecars, we individually arch every leaf to achieve an almost linier rate progression. This helps handling a lot, and we see it in our lap times. Obviously that’s not possible with a composite spring.
In summary:
Composite spring Advantages:
• Light weight
• Permanent spring rate
Disadvantages:
• Cost
• Durability
• Limited spring rate options
• Often much stiffer than stock
A couple of times a week we are asked to give the plusses and minuses of composite vs. steel rear leaf springs. This is how we see it:
The TRW spring is the OEM replacement spring for the 81 and 82 Corvette. From 1963-1980, Corvettes came with steel rear leaf springs. In an effort to shave weight off the car to help with fuel economy, for the 1981 model year Chevrolet went with magnesium valve covers, a composite rear spring and a number of other weight saving substitutions. 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.
One more thing that may or may not be a big deal to a street driven Corvette: The steel spring is at least somewhat progressive in its spring rate. In our custom steel springs that we use for our racecars, we individually arch every leaf to achieve an almost linier rate progression. This helps handling a lot, and we see it in our lap times. Obviously that’s not possible with a composite spring.
In summary:
Composite spring Advantages:
• Light weight
• Permanent spring rate
Disadvantages:
• Cost
• Durability
• Limited spring rate options
• Often much stiffer than stock
Last edited by akdale; 01-20-2014 at 07:54 PM.
01-20-2014, 09:03 PM
#10
If you want a composite spring with a rate close to stock, look at the Hyperco EZ Ride. The rate is either 180 or 200 lbs/in. (I forget which).
The weight savings for a composite vs. a steel spring is closer to 30 lbs.
And steel springs certainly can break. Mine did, years ago. I happened to be driving past a warehouse at the time. I went inside and begged a piece of wood from a broken pallet. I jacked up the car and wedged the wood between the rubber bump stop on the frame and the trailing arm to limp it home.
The weight savings for a composite vs. a steel spring is closer to 30 lbs.
And steel springs certainly can break. Mine did, years ago. I happened to be driving past a warehouse at the time. I went inside and begged a piece of wood from a broken pallet. I jacked up the car and wedged the wood between the rubber bump stop on the frame and the trailing arm to limp it home.
01-20-2014, 09:19 PM
#11
Melting Slicks
When selling new cars the test drive means everything. More often than not You won't get a chance to find out the ultimate cornering ability especially with the wife along. However You will find out how well it rides, or at least She will and unless She likes it its probably not a sale. That's why new 3/4 and 1 ton HD Trucks come with 245 Tires on them. That's why GM has built more Corvettes with Plastic Springs than Steel.
01-21-2014, 03:10 PM
#13
Le Mans Master
Here is the entire statement. A little reading between the lines but in the end as I read it, they sell them but don't use them
A couple of times a week we are asked to give the plusses and minuses of composite vs. steel rear leaf springs. This is how we see it:
The TRW spring is the OEM replacement spring for the 81 and 82 Corvette. From 1963-1980, Corvettes came with steel rear leaf springs. In an effort to shave weight off the car to help with fuel economy, for the 1981 model year Chevrolet went with magnesium valve covers, a composite rear spring and a number of other weight saving substitutions. 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.
One more thing that may or may not be a big deal to a street driven Corvette: The steel spring is at least somewhat progressive in its spring rate. In our custom steel springs that we use for our racecars, we individually arch every leaf to achieve an almost linier rate progression. This helps handling a lot, and we see it in our lap times. Obviously that’s not possible with a composite spring.
In summary:
Composite spring Advantages:
• Light weight
• Permanent spring rate
Disadvantages:
• Cost
• Durability
• Limited spring rate options
• Often much stiffer than stock
A couple of times a week we are asked to give the plusses and minuses of composite vs. steel rear leaf springs. This is how we see it:
The TRW spring is the OEM replacement spring for the 81 and 82 Corvette. From 1963-1980, Corvettes came with steel rear leaf springs. In an effort to shave weight off the car to help with fuel economy, for the 1981 model year Chevrolet went with magnesium valve covers, a composite rear spring and a number of other weight saving substitutions. 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.
One more thing that may or may not be a big deal to a street driven Corvette: The steel spring is at least somewhat progressive in its spring rate. In our custom steel springs that we use for our racecars, we individually arch every leaf to achieve an almost linier rate progression. This helps handling a lot, and we see it in our lap times. Obviously that’s not possible with a composite spring.
In summary:
Composite spring Advantages:
• Light weight
• Permanent spring rate
Disadvantages:
• Cost
• Durability
• Limited spring rate options
• Often much stiffer than stock
The composite spring was used on the 81-82 Corvette, except as noted the 81 4 speed AND any gymkhana (including the automatics) got a steel spring as well 1982 Corvettes with the gymkhana suspension. No mention that every C4, C5, C6, and C7 use composite springs and it is NOT because they only save weight! As far as the composite spring change saving 20 Lbs, I am not sure where that number comes from since my 78 gymkhana steel spring which I replaced in 1986 (and still have on the car-so much for durability or lack thereof) weighted 48 lbs (I weighted it) and the VBP 360 composite which I replaced it with weighted 8 lbs-Savings 40 lbs. I would think that the 9 leaf steel base spring would be even heavier but I don't know that.
As far as the steel spring being in the right place for ballast, low and behind the rear axle, yes and no. You want ballast low, yes, but the rear spring is not behind the rear axle but directly underneath it, technically speaking. I don't race my 78 so I can't specifically comment on what is best on the racetrack but there are others on the forum who do and can more competently comment on that specific issue. I can say that my 78 has a weight distribution, front to rear, of 48% front/52% rear with the steel spring so removing 40 lbs off of the rear will slightly tilt at least for the street, the weight distribution that more suites my driving style. I can see how removing 40 lbs off the rear of a nose heavy BB engined car (54%F/46%R) would not be idle for improving handling.
Concerning the long term durability of steel versus composite, like I said, 28 years now for my 360 composite. Composite never wear out and can occasionally, delaminate (not sure about the often reference-not in my experience) and can fail under VERY high horsepower condition, from what I hear.
The spring rate discussion: Comparing C2/C3 steel spring rates to higher rate composites is NOT an apples to apples comparison. There is a very good reason that composites are mostly rated from 300-420lbs compared to 192-260lbs steel springs-they are very different materials and react very differently to the loads placed upon them. Without getting into the specifics, you can't compare a 78-80 260 lbs base steel spring (BTW-the gymkhana 78-80 Vettes have a 292 rear steel spring-another omission) to a 330 composite. I replaced my 292 rear steel spring with a 360 composite and the car reacts faster to bumps, rides MUCH better, and handles generally better, so again not sure where that comes from. I am not the only one who experienced the transformation going to a higher rated composite from the lower rated steel spring. Not sure where those comment come from. The comment about the steel spring rates they run on a race car is not as high as the composite rates for the street is because the 2 rates are NOT comparable. Many forum members race and can comment on the rates of composite or steel they use on the track
Hope that helps!
Last edited by jb78L-82; 01-21-2014 at 03:13 PM.
01-28-2014, 02:30 PM
#16
Le Mans Master
Member Since: Dec 2009
Location: Saskatoon Saskatchewan
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The spring rate discussion: Comparing C2/C3 steel spring rates to higher rate composites is NOT an apples to apples comparison. There is a very good reason that composites are mostly rated from 300-420lbs compared to 192-260lbs steel springs-they are very different materials and react very differently to the loads placed upon them. Without getting into the specifics, you can't compare a 78-80 260 lbs base steel spring (BTW-the gymkhana 78-80 Vettes have a 292 rear steel spring-another omission) to a 330 composite. I replaced my 292 rear steel spring with a 360 composite and the car reacts faster to bumps, rides MUCH better, and handles generally better, so again not sure where that comes from. I am not the only one who experienced the transformation going to a higher rated composite from the lower rated steel spring. Not sure where those comment come from. The comment about the steel spring rates they run on a race car is not as high as the composite rates for the street is because the 2 rates are NOT comparable. Many forum members race and can comment on the rates of composite or steel they use on the track
Last edited by Priya; 01-28-2014 at 02:39 PM.
01-28-2014, 07:55 PM
#17
Well, Priya, please allow me to disagree with you.
A multi leaf steel spring will ride differently than a composite spring of the same rate because the steel leaves have to slide against each other as the spring reacts to the road. Of course, they call this interleaf friction. The factory put plastic liners between each leaf in an attempt to minimize this.
So the speed at which a multi-leaf steel spring reacts to a bump is slower than a composite. A composite spring is just one piece. Once the load is on either spring for a second or so, the deflection will be the same.
Net result is that a multileaf steel spring will transmit more NVH to the occupants of the car than a composite spring of the same rate.
A multi leaf steel spring will ride differently than a composite spring of the same rate because the steel leaves have to slide against each other as the spring reacts to the road. Of course, they call this interleaf friction. The factory put plastic liners between each leaf in an attempt to minimize this.
So the speed at which a multi-leaf steel spring reacts to a bump is slower than a composite. A composite spring is just one piece. Once the load is on either spring for a second or so, the deflection will be the same.
Net result is that a multileaf steel spring will transmit more NVH to the occupants of the car than a composite spring of the same rate.
01-29-2014, 10:31 PM
#18
Melting Slicks
I can't explain it in technical terms, but I replaced the stock steel spring in my '79 years ago with a 330 lb composite spring. The ride from the composite is MUCH, MUCH smoother and more comfortable. Not even close. The car also handles better, although most of that is due to the fact that the spring was installed as part of a complete handling kit from VB&P. Bottom line I suppose is - if steel springs were any good, the General would still be using them.
01-30-2014, 06:19 PM
#20
Team Owner
