Vi-King shock for C4 Conversion

[Fladiver64]

I have ordered a c4 conversion frame for Laszlo set up for coil overs. I have been looking at the Viking brand of shocks as they look to be a better deal than QA-1 401/402 as they are double adjustable.

Here is what they are recommending, prices are list may be available for less through distribution.:

Vehicle= 57 Chevy with C4 Corvette suspension

Fronts
Ride height=12” Lower mount=t-bar, Upper mount=eyelet
Shock= C205-T (-T indicates lower GM t-bar) $209.95 each
C205 shock takes a 9” spring
Spring= 9” 450lbs?? -9DP450 $43.95 each

Rear
Ride height=13.5” Lower mount=eyelet, Upper mount=eyelet
Shock= C207 $189.95 each
C207 shock takes a 10” spring
Spring= I don’t have a really have an accurate guess at a rear rate.

Accessories
7995-102- spanner wench and thrust bearing kit for 2 shocks- $44.95
7917-101 – thrust bearing kit for rear shocks- $27.95

How does this look

Mike

[NickP]

Rebuildable? Can they be revalved?

[Fladiver64]

Yes and Yes, or so they say

[chevynut]

Fronts
Ride height=12” Lower mount=t-bar, Upper mount=eyelet
Shock= C205-T (-T indicates lower GM t-bar) $209.95 each
C205 shock takes a 9” spring
Spring= 9” 450lbs?? -9DP450 $43.95 each

What is the extended and compressed length on that shock? The QA-1 401/402 shocks take a 9" or 10" spring. A 9" spring might leave you with less adjustability and/or a higher spring rate since the nut would be higher on the shock at a given ride height.

Rear
Ride height=13.5” Lower mount=eyelet, Upper mount=eyelet
Shock= C207 $189.95 each
C207 shock takes a 10” spring
Spring= I don’t have a really have an accurate guess at a rear rate.

There are two ways to do the rear. One is with a 10" shock and one is with a 12" shock. I personally like the idea of using a longer shock, and run it on the more compressed side. That allows you to run a softer spring for a better ride, and helps when it comes to taking the wheel off. What's important is that you don't bottom the shock out so the compressed length is critical, as well as setting your axle bumpers correctly. I typically get 2" of upward travel at the wheel front and rear.

As for the rear spring rate, it all depends on the shock extended and compressed length, as well as shock angle. You need to support a certain load at a certain ride height. I have a spreadsheet that calculates the spring rate once the car weight and shock extended and compressed dimensions are known.

[Fladiver64]

What is the extended and compressed length on that shock? The QA-1 401/402 shocks take a 9" or 10" spring. A 9" spring might leave you with less adjustability and/or a higher spring rate since the nut would be higher on the shock at a given ride height.
The C205 10.04 compressed and 13.86 extended ride height recommended is 11 5/8 to 12 1/4

Next step up is the c217 10.48 compressed and 14.30 extended ride height recommendation 12 to 12/34 10" spring

One of the things they mentioned was that their spring uses fewer coils for the same spring rate and a longer thread on the shock body for more adjust ability. Maybe the 217 shock is a better fit.




There are two ways to do the rear. One is with a 10" shock and one is with a 12" shock. I personally like the idea of using a longer shock, and run it on the more compressed side. That allows you to run a softer spring for a better ride, and helps when it comes to taking the wheel off. What's important is that you don't bottom the shock out so the compressed length is critical, as well as setting your axle bumpers correctly. I typically get 2" of upward travel at the wheel front and rear.

As for the rear spring rate, it all depends on the shock extended and compressed length, as well as shock angle. You need to support a certain load at a certain ride height. I have a spreadsheet that calculates the spring rate once the car weight and shock extended and compressed dimensions are known.

207 is 11.10 compressed and 14.92 extended

[chevynut]

I think the C205 is probably the best choice for the front. We set the front end up for right at 12" ride height length. That gives about 2" up and down travel. I was just wondering about the spring length, but if the spring rate is right and it doesn't coil bind it shouldn't matter. For an LS engine we typically recommend starting with a 450 lb/in spring in front. My spreadsheet says 472 lb/in for your combo (early suspension), but I would go with 450. That seems to work for most people so far. You will likely have to adjust the nut up 1" or more (depending on actual weight) but that allows you to use a softer spring. It will still ride pretty firm.

207 is 11.10 compressed and 14.92 extended

So that's a 3.82" stroke which is pretty short for a rear shock, but about the same as the front. Since the shock sits at an angle, you should have a little more stroke than that. The QA-1 403/404 is just about the same shock, and that's the 10" one I mentioned above for the rear.

The C4 IRS has some interesting geometry going on and the calculations for spring rate aren't so straightforward. I have used empirical data from customers to adjust my calculations. With the 207 shock my calculator says you need about a 550 lb/in spring in the rear and the adjuster will be 1-1.5" above the bottom.

I would start with the rates above and make adjustments only when the car is completely assembled and drivable. If you run out of adjustment at the top and the car still sits too low, you need to go up one spring rate. If it's too high and the adjuster is at the bottom, you need to go down one spring rate.

[JT56]

Have you checked with Ride Tech Coil overs?

[chevynut]

Have you checked with Ride Tech Coil overs?

$$$$$$$$$$

[JT56]

$$$$$$$$$$

Agreed, but they have some nice products.

[NickP]

I can't personally speak for the OP Brand but, I can speak to QA1. I know JT56 can speak to Ride Tech. My personal opinion, what ever the brand, it needs to be rebuildable and re-valveable if you want to garner all of the performance from this type of suspension modification. If the design intent of the completed car is to make good use of that, then a quality shock might be something to consider.