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I'm considering a coilover conversion on my 65. I looking for input on coilover spring rates front and back on the VanSteel setup. What you used and handling/ride quality of your selection.
You guys do more modifying over here than the C2 side. Maybe I'll get more responses over here. Thanks Tom
A spring rate is a spring rate. So if you know what your front spring rate is you can make an informed decision. In my case I had driven for 20 years with VB&P short 550# when I bought QA-1 dual adjustable semi coil overs. The 550# had too much front end dive under braking. So from Speed Direct I bought three sets of springs 600. 650. & 700.
Thanks guys. That helps. I used to run VBP 460 front springs with 3/4 coil cut off to get the ride height right. I thought it was pretty good. The car has aluminum heads and intake, headers, no front bumpers. I replaced those springs a while back with the VBP transverse dual mount spring. I have no idea what spring rate that was. Now I'm changing to semi-coilover on the front and was considering 450 lb springs. Sounds like I might be in the neighborhood.
How about rear? Anyone using the VS coilover setup?
I've got the Van Steel Coil overs front and rear. Aluminum heads on s SBC . 550 lb in Front. I think 600 in the rear. I'm not going to tell you it is a smooth, comfie ride. It isn't supposed to be. I previously had the VB&P dual mount rear spring. The car does ride smoother than it did before the coilovers were installed. Remember though, I removed 15-20 year old everything and replaced it with new everything.....and added a Borgeson steering box. I don't find my car to be too harsh and have taken it on several 100+ mile trips. It is definitely more comfortable being thrown around the corners or cones than it used to be.
That 450 semi-coilover should be pretty close to what you are used too in the front.
You didn't say what your goal is? spirited driving? an aggressive look and stance and don't mind a little more harshness? Dedicated auto-X toy? somewhere in between?
Nice 65 Tom! I remember it.
The rear springs affect the ride quality more since they are right by your butt.
Also the car has zero rear anti-squat geometry so if you drive it really hard, you may want a stiffer spring to control that.
If you are going after a street ride, 400ish should work well.
Do get some adjustable shocks. They are worth their weight in gold as far as adjustability.
The shock valving controls roughly 75% of the perceived ride quality.
So like Dawson did, you can get a 600# spring to ride nice if you want to.
I remembered this old thread. https://www.corvetteforum.com/forums...s-weights.html
see post #7
The Van Steel coil overs mount the springs in a different spot, so the motion ratio is different.
A 400# spring on those coil overs would give you the same wheel rate as the 304# F41 spring.
Last edited by leigh1322; Feb 16, 2023 at 09:13 PM.
I'm looking for a sports car ride. Good handling, firm but not harsh. I drive the car allot. I love twisty back roads but also long trips. We long hauled the HRPT 9 times. Took a 4000 mile trip by ourselves two years ago. Of course when we travel we pack the car pretty tight, meaning added weight.
Leigh I may need to talk to you if that is OK. I'll send you my phone number.
Tom
I have the Vansteel rear coil-over setup and semi coil-overs on the front with tubular arms.
500lb rear 450lb front.
You also need to consider your ride height. If you want to go low you need Vansteel to provide a shorter coil-over body to ensure you have reasonable compression and extension once at a low ride height.
I am currently at 26 1/4” front and 26 3/4” rear ground to lip.
My build thread covers the steps i went through and Dan at Vansteel was very helpful. Am contemplating if full coil-over for front will make much difference.
I did the Vansteel true coil overs on Frances the 68 small block . After talking with Eric at vs I went with 550 big block . Reason being I want to road race auto cross and might add some power to the 375-400 hp car . I did double adjustable and dialed down the are very soft have not played with them much yet. Will say so much better than my good stock set up.
A full coil-over gives you a large spring selection to choose from, in about 50# increments.
A semi-coli-over has a very limited spring selection, say 2 or 3.
The many spring options are handy on a race car, when you want to control other things like drop on braking, toe-in on squat, etc.etc.
For the street a reasonable spring will work.
Just make sure you get adjustable shocks so you can dial in the ride you like.
The fixed single valved shocks are basically tuned for stock springs, and either a stock ride or a sporty ride. You won't know which til you bolt them on. They may or may not hit the "sweet spot" you are looking for.
A good adjustable can usually adjust from Cadillac / floaty / great ride soft, to rock-hard / instant response / razor sharp handling hard. Most folks would like somewhere in the middle, but which side of the middle?
Here is the spreadsheet I wrote to help you calculate wheel rates and roll rates, once you plug in a spring and a sway bar.
As we discussed on the phone, some of the available parts are probably too stiff for your application. (Street & cruising, no drag race, no autocross.)
I would lean to mid 400 springs on the front, with the 1-1/8" bar, and mid 300 springs on the back, with the BB 9/16" rear bar.
Those springs rates will give you a wheel rate of 185/220.
The slightly stiffer rear wheel rate is necessary to give you a slightly higher suspension frequency in the rear, so that the car stays level when you hit bumps at cruising speed. It is called "flat ride" If you miss that by 10-20% your head never stops bobbing going down the road, and it becomes very tiring. Imagine your head doing the bobble head for the 2000 mile Power Tour!
Your C2 is not lowered, and those rates are stiff enough to keep you off the bump stops on hard braking, or hard acceleration. So why go higher?
400# transfers front or rear on 1G stops or accel, and the suspension will drop 0.8" front or 1.3" rear.
That is enough to give you some bump compliance but yet not bottom on the bump stops.
Measure your altered bump stops and be sure that you are not hitting them hard when the suspension moves that much. Touching is OK. The bump stops give you another 1" of travel, but it is best not to use that in a straight line, only in a turn or the bumps.
The 550# springs are what is "normally" recommended, but they also lower the front end 1", and then you would need more spring to stay off the bump stops. But you are not lowering the car, and do not need that stiff of a spring. Check your bump stops and let me know. If you need more spring, that measurement will tell you.
In a turn 653# of weight transfers, and 75% of that occurs in the front. That's the way you want it.
With those springs and sway bars, the body will roll 1.4 degrees, and that means only 0.7" down on one side , and 0.7" up on the other. The roll with the stock springs & bars is almost exactly double that. So the car responds much quicker. But it is not very much suspension movement, and if you go even stiffer in roll rate, the car becomes skittish on the bumps, as it starts to skate and feel like a go-cart. BTDT. Again you need a little compliance, but not as much as OEM. But not as stiff as you can possibly make it either.
As you tighten the roll rate down, this requires more tightly valved shocks, because basically they have to control the oscillations quicker, with less shock movement. Too soft and you get the dreaded "pogo" effect. Too stiff, and it just feels like a go-cart, and skips on bumps.
As far as coil overs or semi-coil overs or just coils in the front, it makes zero difference to the suspension tuning. But it is very hard to adjust ride height with coils. With semi-coilovers it is easy to adjust the ride height, for fender lip adjustment, or heavy loads on a trip. The main advantage of true coil-overs, is a wider selection of spring rates are available, like every 50#. In a race car, this spring tuning becomes important, and may need to be changed between tracks. For a street car, not so much. If there is a semi-coil over with the kind of rate you want, then go for it. Either one may require reinforcements and/or modifications to the front a-arms to handle the entire weight of the car where the end of the shock is. In a stock setup the weight is handled in the spring pockets. For the street, in the front, a single adjustable shock is probably good enough. It will let you dial in the ride / handling compromise that suits you.
The rear is different. Eliminating the steel spring eliminates a lot of friction, and improves the ride. Your butt is so close to the rear suspension, that it controls 75% of the ride quality you feel. Hence people jump way up in spring rate and say it rides as good or better than before. That is the case for both the fiberglass and the coil-over rear setups. However the lack of friction means you need different/better/stiffer shock valving. And like we discussed you may need to vary the rebound/compression split vs steel. So stock shocks are out. Stiffer ones are in. A single adjustable may or may not work depending on the R/C splits. A double adjustable in the rear would be the best bet. I already have my rear QA-1 single adjustables, and am prepared to revalve them if needed, to change the R/C split, or spring for doubles.
Someone had me analyze the geometry of a Van Steel coil-over suspension, and since the coil over mounts the spring in a different location than the stock spring, it changes the "motion ratio". So to keep the wheel rate the same as a 304# steel spring, you would need a 400-425# spring on the V-S coilover. (The Shark-Bite is even more different.) So if you want to go with my 330# glass recommendation, you would need a 450-475# coil over spring, to keep the wheel rate the same. CraigH has a very dialed-in car, and runs 450/500# fr/rr. But his is lowered, and yours is not. So I could see you getting away with a step less. But the motion ratio is why the rear number seems so high, it's not that high at the wheel. If you are going to put your coilover mounts at the same spot as the factory shocks, I'll go measure mine and give you an exact spring recommendation to get the "flat ride" you want. You will need to pick a front spring rate first and let me know.
You already have delrin bushings, 5 degrees caster, and heim joint strut rods right? The only other thing I can suggest is the Van Steel lowered strut rod bracket, it changes the roll center height and makes them equal front and rear, and also gets rid of a lot of the severe camber change in the rear on bumps, which is pretty excessive in stock form. That also reduces some of the rear toe-in changes and rear "squirreliness".
Check out the attached spreadsheet. I set it for your/my proposed "combo" Check out the last tab and see how much the suspension moves up/down in a turn. 1.4" is about the max, when you roll out of a turn and are on the throttle hard. Stone stock it was double that, and the car is sitting on the bump stops! If you then hit a bump the stock car would bang, hop & skip. The F41 springs prevented that.
My next project is measuring the bump-steer in the front suspension, and see if I can reduce it a lot. Even if it means machining new parts. Stay tuned!
I did the Vansteel true coil overs on Frances the 68 small block . After talking with Eric at vs I went with 550 big block . Reason being I want to road race auto cross and might add some power to the 375-400 hp car . I did double adjustable and dialed down the are very soft have not played with them much yet. Will say so much better than my good stock set up.
For autocrossing and a lowered car, that sounds like a great spring rate. You will learn to love the double adjustables once you experiment with them a little bit.
Here is the spreadsheet I wrote to help you calculate wheel rates and roll rates, once you plug in a spring and a sway bar.
As we discussed on the phone, some of the available parts are probably too stiff for your application. (Street & cruising, no drag race, no autocross.)
I would lean to mid 400 springs on the front, with the 1-1/8" bar, and mid 300 springs on the back, with the BB 9/16" rear bar.
Those springs rates will give you a wheel rate of 185/220.
The slightly stiffer rear wheel rate is necessary to give you a slightly higher suspension frequency in the rear, so that the car stays level when you hit bumps at cruising speed. It is called "flat ride" If you miss that by 10-20% your head never stops bobbing going down the road, and it becomes very tiring. Imagine your head doing the bobble head for the 2000 mile Power Tour!
Your C2 is not lowered, and those rates are stiff enough to keep you off the bump stops on hard braking, or hard acceleration. So why go higher?
400# transfers front or rear on 1G stops or accel, and the suspension will drop 0.8" front or 1.3" rear.
That is enough to give you some bump compliance but yet not bottom on the bump stops.
Measure your altered bump stops and be sure that you are not hitting them hard when the suspension moves that much. Touching is OK. The bump stops give you another 1" of travel, but it is best not to use that in a straight line, only in a turn or the bumps.
The 550# springs are what is "normally" recommended, but they also lower the front end 1", and then you would need more spring to stay off the bump stops. But you are not lowering the car, and do not need that stiff of a spring. Check your bump stops and let me know. If you need more spring, that measurement will tell you.
In a turn 653# of weight transfers, and 75% of that occurs in the front. That's the way you want it.
With those springs and sway bars, the body will roll 1.4 degrees, and that means only 0.7" down on one side , and 0.7" up on the other. The roll with the stock springs & bars is almost exactly double that. So the car responds much quicker. But it is not very much suspension movement, and if you go even stiffer in roll rate, the car becomes skittish on the bumps, as it starts to skate and feel like a go-cart. BTDT. Again you need a little compliance, but not as much as OEM. But not as stiff as you can possibly make it either.
As you tighten the roll rate down, this requires more tightly valved shocks, because basically they have to control the oscillations quicker, with less shock movement. Too soft and you get the dreaded "pogo" effect. Too stiff, and it just feels like a go-cart, and skips on bumps.
As far as coil overs or semi-coil overs or just coils in the front, it makes zero difference to the suspension tuning. But it is very hard to adjust ride height with coils. With semi-coilovers it is easy to adjust the ride height, for fender lip adjustment, or heavy loads on a trip. The main advantage of true coil-overs, is a wider selection of spring rates are available, like every 50#. In a race car, this spring tuning becomes important, and may need to be changed between tracks. For a street car, not so much. If there is a semi-coil over with the kind of rate you want, then go for it. Either one may require reinforcements and/or modifications to the front a-arms to handle the entire weight of the car where the end of the shock is. In a stock setup the weight is handled in the spring pockets. For the street, in the front, a single adjustable shock is probably good enough. It will let you dial in the ride / handling compromise that suits you.
The rear is different. Eliminating the steel spring eliminates a lot of friction, and improves the ride. Your butt is so close to the rear suspension, that it controls 75% of the ride quality you feel. Hence people jump way up in spring rate and say it rides as good or better than before. That is the case for both the fiberglass and the coil-over rear setups. However the lack of friction means you need different/better/stiffer shock valving. And like we discussed you may need to vary the rebound/compression split vs steel. So stock shocks are out. Stiffer ones are in. A single adjustable may or may not work depending on the R/C splits. A double adjustable in the rear would be the best bet. I already have my rear QA-1 single adjustables, and am prepared to revalve them if needed, to change the R/C split, or spring for doubles.
Someone had me analyze the geometry of a Van Steel coil-over suspension, and since the coil over mounts the spring in a different location than the stock spring, it changes the "motion ratio". So to keep the wheel rate the same as a 304# steel spring, you would need a 400-425# spring on the V-S coilover. (The Shark-Bite is even more different.) So if you want to go with my 330# glass recommendation, you would need a 450-475# coil over spring, to keep the wheel rate the same. CraigH has a very dialed-in car, and runs 450/500# fr/rr. But his is lowered, and yours is not. So I could see you getting away with a step less. But the motion ratio is why the rear number seems so high, it's not that high at the wheel. If you are going to put your coilover mounts at the same spot as the factory shocks, I'll go measure mine and give you an exact spring recommendation to get the "flat ride" you want. You will need to pick a front spring rate first and let me know.
You already have delrin bushings, 5 degrees caster, and heim joint strut rods right? The only other thing I can suggest is the Van Steel lowered strut rod bracket, it changes the roll center height and makes them equal front and rear, and also gets rid of a lot of the severe camber change in the rear on bumps, which is pretty excessive in stock form. That also reduces some of the rear toe-in changes and rear "squirreliness".
Check out the attached spreadsheet. I set it for your/my proposed "combo" Check out the last tab and see how much the suspension moves up/down in a turn. 1.4" is about the max, when you roll out of a turn and are on the throttle hard. Stone stock it was double that, and the car is sitting on the bump stops! If you then hit a bump the stock car would bang, hop & skip. The F41 springs prevented that.
My next project is measuring the bump-steer in the front suspension, and see if I can reduce it a lot. Even if it means machining new parts. Stay tuned!
That was a great read Leigh, amazing detail and so well tailored to the needs of OP, you certainly know your stuff. I have had a quick look at the spreadsheet and some work has gone into that. Will take a while to digest it but a truly great analysis of our chassis.
The idea of 400 front and 300 back would only be for low hp cars with stock type tires.
Modern ultra performance tires have enough grip that you don't want the front and rear having lots of vertical movement
Rear roll is what destroys the ends of the differential yokes. It grinds the tip away from the weight against the posi cross pin. As my power and tire size went up I destroyed my stock differential. Then I was breaking posi housings annually. The cure is lots of rear spring and limited vertical movement.
Oh I removed all the bump stops back in the 80,s as extra weight because they never got touched when I went to 550F and 500R
I fully agree with your choice Gkull on a 600+HP track car, strongly lowered, with wide racing tires. You probably still get about 1" of suspension movement because of the strong cornering forces. (Maybe 1.2G & up?)
But for the OP, and a street car, on tall 8" street tires & wheels, the cornering forces will not be nearly as great (maybe .8G?), and he will still get about 1" of suspension movement, with the 450/350 springs & big bars. It will not wobble around 2-3" like an OEM stock car does. It will be fun to drive. And it will ride much better. Which is his main requirement. He has done the long-haul power tour Nine times, and one trip alone was 4000 miles. Tom REALLY drives his car, and a lot. And it needs to be comfortable first. His rides high, on purpose. His second requirement is to be able to load 600# of passengers & luggage, and not destroy the ride height or handling. Hence the adjustable spring perches on the rear. He will "jack it up" empty before the long road trip, so it is level when all loaded. With the adjustable shocks he can tighten up the handling and it will be just fine on the street. I could re-tune it to get another 2-3 sec very easily out of it on the track, starting with different tires/wheels, but that is not his concern at all. He does not race it. He is removing the VBP dual mount spring system he currently has on both ends. He is going for 4 new coil-overs, with double adjustable shocks, which will be a big improvement.
For you guys going full coilovers in the front, how are you handling the front cans and top mounts?
I thought about cutting the whole top can off and engineering my own Heim/spherical attachment point to marry to my extended travel lower Coilover Global West Arms. In the past I gusset welded/plated the stock top mount, enlarged the shock hole and ran a hefty Pinned U-Bolt set up. Just curious.This type, but mine are beefier and longer!
Last edited by TCracingCA; Feb 19, 2023 at 09:31 PM.
The Vansteel setup I am looking at uses a similar bracket with a bit more length. That way no enlargement of the tower opening is needed. I assume it would mean shorter coilover bodies are needed.
Coilover Spring Rates
Maybe I'll get more responses over here. 
