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Why haven't more people tried the C4 Corvette suspension???

25K views 106 replies 30 participants last post by  BamaNomad 
#1 · (Edited)
Even though my 55 is is still a rough draft of what I want, I managed to get it on the road from an empty shell to a driver in 12 months. It has totally surprised me as one of the best cars I have ever driven, including many late models. It is so much fun, and I haven't even put the sway bars on yet. Using a RR Frames C4 conversion chassis with stock 96 C4 Grand Sport front/rear suspension, 13in fronts brakes, etc., that just bolts right in. Stock LS 5.3, 4L60E, 3:45 rear, and American Racing 17 x 9.5 wheels front/rear with a +38 offset, and 275/40-17 Nitto NT01 sticky tires on both ends. The car currently weighs 3275 stripped down, and the stock motor has more than enough power without too much to do anything really stupid.
I will hope to be the quickest try-five in the Valley, or at least in the one where I live.
 

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#2 · (Edited)
Nice work and upgrade. Here in Calif , a few Tri-Five C4 conversion are often at the Goodguys events. Most Tri-Five owners aren't up to the task to convert to C4 suspension. Today, saw a 57 Bel Air with the C4 suspension conversion at a small car show in Martinez. . See photo. Also money is a factor. I'm guessing $18-20K for rolling chassis from RR Frame. Best to buy a C4 and cannibalize it, buy the custom frame from RR, and go from there.
 

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#36 ·
I can't wait to see how you like it!
Version 8 has been fun taking 10+ years of chassis and refining it into the current revision. Lots of "reading between the lines" of what customers say they want VS actually want. Less "peak performance" and more ride quality.


IMO coil overs is a 'buzzword' that people want because they think they are supposed to! My '56 Nomad has front coilovers on it (QA1) which I do not like. I see NOTHING that they do for me... and as soon as I find a decent set of factory front springs, they will get swapped out.
Springs control the car, shocks control the springs. You have to tune your chassis like you tune the engine. This is why I start with the double adjustable shocks at a minimum so you can have this room you need to tune after its all said and done. The problem as you might have noticed is that adjustment will let you screw up just as fast as fix the problem. The right tool for the job. I would say you should talk to a Circle Track shop and get then to adjust your shocks for you.

Honestly it's crazy the number of shocks I have to stiffen up because guys have them dead soft thinking it will help the ride out.

SHOCKS CONTROL THE SPRINGS
read that twice.
You need to run the shocks up to deal with the springs.

That being said. Everything effects everything else. Coil overs are not a bandaid for other problems in the stock geometry.


C4 stuff is obsolete now ,step up to c5 and later they are even making after market spindles for the c6 set up
Yeah, no.

While there are some advantages to the C5+, Newer is not always better.

Especially when taken at a performance per dollar cost analysis in these old cars. The C5/6/7 is just too wide. By the time you narrow it, replace the rack and pinion, replace the front and rear swaybars, narrow the CV shafts, AND get the shocks you need to make it all work you're easily at 2x the price of a C4 sway. And you can't get your rear tires out from under the car. That's the real trick everyone figures out the hard way.

The C4 and C5+ share a lot of the same geometric advantages you need to make a car perform like a modern car.
lots of caster, front mount racks, sway bars, aggressive camber curves, anti dive for disk brakes just to name a few easy to recognize items.

And the C4 package 'just right' for our beloved TriFives when it comes to floor board modifications as well.

When I get to the C2/3 Conversion frame I want to do I'll have a C5+ option but the C4 is still the best bang for the buck.


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#6 ·
I got a great deal on my C4 parts including the wheels and the preferred Dana 44 rear end at $1300. Bought a used 55 Nomad frame from my neighbor for $150. And built my own frame so I probably have about $4500 to $5500 in the whole conversion. If you buy a frame like RD did your going to end up in the 10,000 to 12,000 range. Still much less than one of the aftermarket frames like the Art Morrison. Ride, handling & stance will be comparable. The one downside of a C4 set up is you need wheels with lots of positive offset which means Corvette wheels which may not be the best stylewise although the Vette wheels Hutchen has on his 56 look pretty nice. The other option is custom wheels which are going to be north of 500 to 600 per wheel.
The conversion does require a good bit of fab work to make it work too so it's not for everybody. I am very happy with mine though and wouldn't hesitate to do it again.
 
#8 ·
What gas tank are you running?

Also, just out of curiosity, which C4 springs do you have (I mean, what RPO numbers are they)? There were a ton of different ones available.

As a fellow owner of a C4 tri-five (at least on the front end), I think the reason is that most people aren't pulling the bodies off the frames. I know that's kind of lame, but it's also the reason I didn't do a full C4 conversion on mine. I don't have a lift or the space to do it. My car was mostly done and I took out the motor/trans and front sheet metal to do just the front end. It was worth it, but a lot of guys just want to go the bolt-on route with the stock frame.

Does RR Frames use the stock tri-five frame and retrofit it or is a totally new frame?

I need to weigh mine...I'm guessing it's a little heavier than yours because I have a Ford 8.8 out back, but at least that weight is in the right place.
 
#9 ·
I raised the body off my 55 Chevy 210 back in the 80's. The garage rafters were exposed. Supported the rafters with 4 x 4's. Used four pulleys to raise the body. Then lowered the body onto a different chassis. Two gantry cranes would have been safer.
 
#10 · (Edited)
The RR frame is similar to the Newman chassis, in that it uses all stock suspension components, including the shocks, and the composite traverse springs front and rear, with mine being the stock 96 C4 GS. It uses a stock frame, with a fabricated front stub, and 2 cross members in the middle section. Didn't have to do much more than bolt the 2 complete front and rear suspension assemblies to the mounts. LS mounts were right where they needed to be, along with the transmission mount. It had the mounts for a 22 gallon Rick's tank. The AR torque thrust wheels are the only aftermarket wheel I could find without going custom. They designed them for the C4 corvettes long ago with a 38mm+ offset, and they fit great with plenty of clearance all around. Best part is they were only $150 a piece. The rack/pinion steering on it feels nice and tight, and only 2 turns lock-to-lock making it very responsive. I'm currently at the stock C4 weight, and the car rides/handles/stops, and goes great. It's like driving a really big Corvette.
I was able have a new rolling chassis for $8000, that I spent a couple weeks in my spare time bolting together, without having to fab, or modify anything. I would have easily spent more time/money/fab work trying to put the bolt-on and fab stuff on a stock frame, and not been satisfied with the results for my goal.
 

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#11 ·
Even though my 55 is is still a rough draft of what I want, I managed to get it on the road from an empty shell to a driver in 12 months. It has totally surprised me as one of the best cars I have ever driven, including many late models. It is so much fun, and I haven't even put the sway bars on yet. Using a RR Frames C4 conversion chassis with stock 96 C4 Grand Sport front/rear suspension, 13in fronts brakes, etc., that just bolts right in. Stock LS 5.3, 4L60E, 3:45 rear, and American Racing 17 x 9.5 wheels front/rear with a +38 offset, and 275/40-17 Nitto NT01 sticky tires on both ends. The car currently weighs 3275 stripped down, and the stock motor has more than enough power without too much to do anything really stupid.
I will hope to be the quickest try-five in the Valley, or at least in the one where I live.
My 57 convert. was pretty much a blank slate to start with. I ordered my chassis from CHRI in B.C. They use all C4 component. It drives very nicely. I am running an LS3 6.6 l and 4L60 E. It’s all GM parts, so no guess work looking for replacement parts. And I like the stance.
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#15 · (Edited)
C5 and C6 are now 'obsolete' also, if you mean no longer manufactured... :) But that's what 'hot rodding' is all about, utilizing obsolete parts from newer model cars to upgrade our even older cars... :)

My chassis has rebuilt C4 suspension/brakes/steering from a '96 Corvette (in my '57 Nomad), so that's a 39-40 yr upgrade in design and components!... obsolete or not! :)
 
#13 ·
There may be many people running C4 suspensions. Just look at the number of companies offering C4 upgrades and complete suspensions. Personally, I went with the Nerd Rods frame primarily because it uses a complete C4 cradle. For those of us that also want LS engines or in my case a LT4, it was 2 birds with one stone
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#52 ·
I used flatout engineering crossmembers and plan on boxing the whole frame. I have, purchased some suspension mods for the corvette that should make it even better. Coilovers are a big upgrade in the C-4 world also. I used the power rack.. next is a 454 gen VI not sure on the transmission yet.
I'm curious as to What the advantages of Coilovers' that you consider to be a 'big upgrade' over factory C4 springs??
Can you elaborate?
 
#20 ·
IMO coilovers is a 'buzzword' that people want because they think they are supposed to! My '56 Nomad has front coilovers on it (QA1) which I do not like. I see NOTHING that they do for me... and as soon as I find a decent set of factory front springs, they will get swapped out.
 
#21 · (Edited)
I really like the C4 composite traverse leaf springs front and rear. I figure there was a good reason they used them on 4 generations of Corvettes the last 36 years. They can be difficult to work on without the factory traverse spring compressor. I found a nice used Kent-Moore factory tool for $350 when I started my project. It probably cost 4 times that new, but worth is because it make it so much safer, quicker, and easier to work on. It would probably work on my C5 springs too, and I could always sell it someday.
 

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#23 · (Edited)
There is a limit as to what cars the traverse leaf springs will work on. Although there are many different spring rates over the years, they were all designed to hold a 3400 pound car at the correct height with near 50/50 weight distribution. So to work on heavier cars, you almost need coil overs. To me the best idea, would be to still incorporate the traverse springs, and use coil overs with light weight springs to dial it in. My car is currently weighs less than the car the springs came from, and I will adjust the weight of the car to make them work instead of chasing spring/shock rates.
My 1964 Corvair Spyder had a rear traverse leaf spring to help cure too late the demise of the FNADER Corvair. That was my first car, and always my favorite.
 
#28 ·
One of the really interesting things about the transverse spring that I've never really seen addressed is where the weight is. I know for a fact that the Newman Car Creations '55 tore up the road race circuit and the auto x with stock GM transverse springs (well, with an aluminum LS motor anyhow) so it's proven on the track, but sometimes I wonder about longevity in the tri-five or especially a truck with a big block and the transverse spring. The reason I say this is because in the vette, the engine is probably about 6-8 inches aft of where it is in the tri-five...and that's a small block application in every case. With a tri-five, even with an SBC, the motor is much further forward over the spring than it is in the vette...and in the case of a BBC, you're talking about another 150+ pounds on the front spring.

Anyone ever seen the transverse springs fail? I don't think I've ever seen vette owners with failures fwiw.
 
#24 · (Edited)
To me the goal of any vehicle I've ever driven comes down to a subject I find to be very interesting called "The Circle of Traction". It's all about the balance of acceleration/braking/cornering within the tire traction limits of any given vehicle. One example would be, having 600 horsepower, but your car isn't any faster than it would be with 300 horsepower. Then it's about slowing it down, and turning as fast as possible within the limits of the available traction. I should start another thread on that subject.
The fastest cars are the ones that can exceed 1g's in any direction period. Beyond that, I always wished I could fly a fighter jet. That dream vanished at the age of 10, when I found out I needed glasses in 1963. My dad was a pilot when he bought our 55.
 
#27 ·
It's true, that if all you want is a nice driving, cruiser tri-five, it can be done with basic bolt-ons. One of the nicest driving '55s I ever drove was a car with mostly stock suspension, front discs, a front sway bar, and a rack and pinion steering unit. It was a really nice driving car, but I'm sure it wouldn't keep up with even a 1990 Honda Civic in the corners.

Different strokes for different folks :)
 
#26 ·
"I really like the C4 composite traverse leaf springs front and rear."

I totally agree with this statement; I too like the composite transverse leaf springs, which is one of the reasons I chose the Corvette Corrections chassis for my '57 Nomad..
 
#29 ·
I bought a 'used' 1990 ZR1 in the late 90's... and the first time I drove it at high speed, I'd hear a POP when I hit a bump. When I got to the ZR1 meet I was attending, several people told me... How did you get the rear of your car so LOW.. :) I had no idea, so under the car we went.. and found the rear transverse spring was delaminating. Fortunately there in Bowling Green, KY there was a good Corvette parts guy, who I called and when I went to visit him, he said take a look in the storage building and pick out the one you want. Fortunately, I found one with the exact same spring code as the broken one, which we then took back and swapped out in an hour or so in the 'shop area' back of the NCM! We did that with 15-20 folks standing around giving advice too!~ :)

That's the only 'broken spring' I'm aware of, but I found out afterwards that car had been in an accident, so I suspect that is when the spring was damaged... (and maybe hitting a few interstate potholes at 150+ hastened it's demise! ) I have two other 1990 ZR1's now with no problems ever.
 
#30 ·
I bought a 'used' 1990 ZR1 in the late 90's... and the first time I drove it at high speed, I'd hear a POP when I hit a bump. When I got to the ZR1 meet I was attending, several people told me... How did you get the rear of your car so LOW.. :) I had no idea, so under the car we went.. and found the rear transverse spring was delaminating. Fortunately there in Bowling Green, KY there was a good Corvette parts guy, who I called and when I went to visit him, he said take a look in the storage building and pick out the one you want. Fortunately, I found one with the exact same spring code as the broken one, which we then took back and swapped out in an hour or so in the 'shop area' back of the NCM! We did that with 15-20 folks standing around giving advice too!~ :)

That's the only 'broken spring' I'm aware of, but I found out afterwards that car had been in an accident, so I suspect that is when the spring was damaged... (and maybe hitting a few interstate potholes at 150+ hastened it's demise! ) I have two other 1990 ZR1's now with no problems ever.
Nice man!...I've always kind of wanted a C4 LT5, but I really don't care for the interiors, well, really just the seats, but I suppose those could be changed. Maybe someday! Very rare car and aside from the C6 Z06, probably my favorite late-model Corvette. Gotta work on fixing some stuff on the '67 Corvette I have in the garage right now first ;)
 
#31 ·
Actually the seats used in '90-92 ZR1s, are nice looking but are 'tight', especially for 'wide butts' even with adjustable bolsters. In 1993, they made the seats wider, but also a very unattractive design...
 
#33 ·
I think it's one of the coolest things to do with a Tri-Five. I wanted to do the C-4 conversion on my '57 Nomad and had a great source for all the stock parts from Stricker Auto Salvage, a GM salvage yard in Akron, OH. GM brought their test cars and engineering mules there to be dismantled. I had bought a 1994 Corvette C-4 complete front and rear suspension, along with the wheels from them, along with six LT-1 engines and 4L60 transmissions from 1993 Camaro test cars. I resold five of those engines and kept the one with 9000 miles for myself along with the Corvette stuff. While I was there, I watched them bring in commercial car haulers with all kinds of GM cars and trucks. I also watched them dismantle a new 1996 Corvette that had some body damage, that was easily repairable, but I was told none of these cars would ever be resold intact and had to be dismantled. GM required that the whole process to be video taped and the cars cut in half once they were stripped. I counted at least sixteen 1993 Camaros in the yard, all cut in half. The LT-1 engines I bought all had the oil pumps removed. Everyone had great luck with the LT-1's and transmissions that I sold them for $2000 complete. Eventually another big reseller of engines shut me out by committing to buying everything Stricker had, just to eliminate the competition, me!

My C-4 Nomad dream came to an end when I retired and moved to Arizona. I couldn't keep it all of it while moving and building a house. As it was, it still took me eight trips from South Dakota with my 24' enclosed trailer and one commercial 9 car hauler to move all my cars, parts, tools and stuff down here. I sold the C-4 suspension cheap for a $1000 and the wheels and tires for $400, which was what I paid for them. I kept the Nomad, but since I didn't have enough garage space and it was sitting outside, I had to let it go. I finally found my '56 Handyman two door wagon to replace it and I'd love to do a C-4 conversion but I don't want have another long term big project until I get the three projects (all '32 Fords) I have done. So many dreams!
 
#37 ·
I think the C4 stuff is great, I'm curious what you think the next popular donor car(s) might be as junkyard C4 stuff eventually starts to dry up? Or do you perhaps see people doing 'C4 style' setups with all aftermarket parts, like the Mustang II stuff that was the hot ticket years ago?
 
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