C5 dual mount leaf spring on C3

Hi Guys, I am in the middle of restoring/rescueing the neglected 1980 i have bought two years ago and during the rebuild i would like to do some modifications to the chassis and suspension because a: i think it is an improvement over original and b: i like to mod my own car just for the fun of it.

I would like to replace the boat-anchor-like original steel leaf spring for a composite spring and i am thinking about a dual mount C5 rear composite spring.

I know a C5 has a slight weight advantage over the lumpy C3 but i have already stripped about 150 lbs out of my car so the curb weight should be within C5 territory i guess.

I am building custom one-off trailing arms to accomodate the 19x12 rims i have and i would like to increase the wheel track width by just a bit, i like wide C3's....

I am thinking about a solution to mount the leaf spring behind the diff on two new mounting points so i will be able to make it a full dual mount assembly.

What kind of problems do you guys think i can run into using a standarc C5 rear leaf spring in a 1980 Vette?

Advice appreciated!

Why not just use the VB&P dual mount made for your car?

Yes, that was the first logical question i asked for myself.

Answer is budget. The whole car is in a rough shape and although i know a C3 is a moneypit anyway i now have to repair almost ANYTHING...

This means normally there is no money available for additional modifications or nice performance parts but trying to restomod my Vette on a tight budget is part of the hobby for me. Dunking in ten thousants of dollars to fix something is the easy way to do it. Yes, sometimes it is the only way it can be done but if i can avoid that i will.

I am an engineer working in a huge machineshop and i can make almost anything with my own hands, so spending cash on something i can make myselve is not preferred because i need that money for the things i cannot make. I have the frame stripped so now is the time to modify it if i want to, because some jobs are not preferred to do a second time (such as a body lift)

And i live in the Netherlands/Europe, so getting parts from the USA is about three times more expensive compared to you guys living in America (and the current EURO/DOLLAR rates are not helping me either...), and availability of C3 spare parts is very limited. If you spot a Vette in Europe it is almost always a C5/C6 (A lot are driven/crashed in Germany) so my idea is to upgrade my C3 by using C5/C6 parts which can be bought on a budget. I don't like the looks of the VBP setup because of the huge ugly strips of metal bolted to the cast differential wings which are not designed for this and it can set me back 1000-1500 USD compared to a used C5 leaf spring which is widely available from any European scrapyard for 50 bucks, that is the difference.

Given the fact that this website is designated for those who like to modify their rides I would like to focus my question on the technical issue, do you guys expect any major problems using a C5 rear spring on a C3?

(Like weight of the car, spring rate, mounting, width, connection etc)

Thanks in advance

Your right. A spring is a spring.

You will probably have to shorten it right? You will need to find the new dimension for the dual mounts to the wheel center. I'm sure you can find the C5 dimensions and spring rate.

BBShark said:

Your right. A spring is a spring.

Click to expand...

Well, that is not completely the way i see it, i am aware of the fact a dual mount leaf spring acts totally different compared to a single mount spring but that is something i would like to turn into my advantage.

If i can manage to equalize a couple of parameters (*) i hope the position of the two mounting points provides me with enough adjustment to set the spring up properly for my car.

(*)
- i have to make sure my C3 weighs approximately the same as a C5
- i have to position and mount the C5 spring on roughly the same position as in a C5
- I have to make sure static sag is roughly the same

I dont want to do a lot of work only to find out my car drops two feet when loaded on his wheels or feels like the composite spring is made out of concrete...I would like to end in a situation that is roughly comparable and there is enough adjustment to tune the car to whatever good setup i would like.

Only problem is i do not know if a C5 spring is a close enough starting point.

I agree with BBShark: A spring is a spring. (I'm on my third different C4 rear spring on the car as I keep changing the spring rate as I continue to tweak the suspension).

You and I are pretty close philosophically. I rarely spend money on an item if I can build it for less.

How does the C5 spring length compare to a C3 spring?
Do you have access to different rate springs?

I don't see the need to keep your C3 weight similar to a C5 weight.

I got lucky, I guess. Got my dual-mount cheap from someone parting out a race car.

Sam Cogley said:

I got lucky, I guess. Got my dual-mount cheap from someone parting out a race car.

Click to expand...

You can certainly consider yourself lucky then. In Europe the number of C3's is very limited, the number of crashed/parted out C3's is even more limited and the chance of one of those having nice salvageable performance parts which i can buy for a bargain is virtually none.

Therefore my strategy: In Germany (which is not too far for me) there is a good market for cheap standard original C5/C6 parts from scrapyards or leftovers from performance upgrades.

I am not that simple to just assume that any original part from a newer type of Corvette automatically is an improvement for my '80 C3, i think in most situations it will not work at all without heavy modifications.

But the rear spring should be worth the try if it has roughly comparable specifications. But i have to know for sure because if i mod my rear suspension to accept a dual mount C5 spring and it cannot be adjusted to match (for example changing the mounting position will alter the spring rate, something which is impossible with a normal spiral spring) then i do not have the possibility to buy a more or less stiff spring for the same price i've got the C5 spring in the first place, making it very expensive after all.

That's the problem right there, nice performance parts for a bargain. A lot of people here think that because you have something for sale they can buy it for pennies on the dollar. I get to converse with clowns like that on an almost daily basis. Performance parts cost money, used but in good or excellent condition performance parts cost money too...and the guy selling them probably paid top dollar for it. I just laugh when I get these jokers wanting a complete C6z06 brake kit with new rotors, calipers pads an pins for 500E when in fact the whole shebang costs well over 2K in the USA. Especially with the current conversion rate.

A c5 leaf does not use hanger bolts but pedestal bolts on pads, problem right there. C3 uses hangers and might be easier to get a hold off here. Also, the spring rates are all in a chart in the tech section.

Ok, i understand.

Excuse me very much that i try to rescue a beaten up Corvette from the scrapyard with the use of my own two hands instead of a pocket full of cash, and try to upgrade it a bit in the process.

I was under the impression that this website was dedicated to people who love Corvettes and love to modify them the way they like them but i understand that is only allowed if you have a well-stacked bankaccount. Sorry, my mistake.

If you try to do it with salvaged parts you're a "clown" or a "joker"...

Thanks for pointing that out, fellow Dutchman, remember me not to post the result from years of restoration here when i finish it. :crap:

renevette said:

Ok, i understand.

Excuse me very much that i try to rescue a beaten up Corvette from the scrapyard with the use of my own two hands instead of a pocket full of cash, and try to upgrade it a bit in the process.

I was under the impression that this website was dedicated to people who love Corvettes and love to modify them the way they like them but i understand that is only allowed if you have a well-stacked bankaccount. Sorry, my mistake.

If you try to do it with salvaged parts you're a "clown" or a "joker"...

Thanks for pointing that out, fellow Dutchman, remember me not to post the result from years of restoration here when i finish it. :crap:

Click to expand...

Hey dude, chill. Nobody's insulting you here. We're all "build our own car the way we like it" types on this forum. Most of my suspension (a combination of C4 and C6 stuff) is from wrecked Corvettes. And most of the aluminum material I welded up for my car came from a metal scrap yard. You're in good company here.

You took my reply totally the wrong way, I'm just saying you can't expect to buy performamnce parts cheaper here than over there with them being a lot harder to come by.