FOrt Collins, Colorado

Frequently Asked Questions

Q.  Will this conversion work for wagons and 4-door cars?

A.  Yes, the Tri-5 passenger car frames are all essentially the same.  '57 cars have different frame horns than 55-56, but the frame rails are basically the same.  We can convert a 57 frame to a 55-56 frame, or vice versa.  The only significant difference in the frames is the body mounts, but they can be added or removed.  The 4DHT and convertibles have fairly unique frames, so we prefer to use your original if we can.  We can make any other frame work with any model.  A sedan or HT frame with an AME center section will work great on a convertible.

Q. What year of C4 suspension should I use for my conversion project?

A.  This is somewhat of a personal choice.  As described in the Tech section, the early suspensions are 1" narrower than the late ones in the front and rear.  The suspension geometry was "improved" by GM in 1988, but the significance is questionable for a street-driven car.  There are aftermarket disc brake kits available for all C4 suspensions.  The early e-brake is a drum-type, while the later e-brake is caliper type.  We can also mix early and late suspensions front and rear.  Note that in some cases we charge more for the early front suspension conversion.

Q.  Do I have to use Corvette wheels on my car?

A.   That is a common fallacy.  While Corvette wheels will work in some cases, you don't need to use OEM Corvette wheels.  You do need to choose wheels with the proper offset, and the offset is usually greater than with other suspensions.  If you want a very deep-dish wheel, the C4 suspensions may not be for you since they are wider than stock.

Q. Should I use the stock C4 composite springs standard shocks or to to coilover shocks?

A. Again, this is a personal choice.  GM built the C4 Corvettes using the composite leaf spring to lower un-sprung weight and still provide a good ride.  A similar approach is still used on the C5 and C6 Corvettes.  However, changing spring rate and ride height is more difficult than using coilovers.  Since the coilover compressed length at ride height is shorter than the compressed length of the transvers spring, a coilover will typically give a stiffer ride.  Ride height adjustment of the rear transverse spring is fairly straightforward, but the same can't be said of the front.  Coilovers make ride height adjustment easy, but they add to the cost of the project.

Q. How much suspension drop can I get?

A. Our "standard" design front suspension drop is 3", with 2" in the rear.  Keep in mind that this is suspension drop, so using shorter than stock tires will lower the car further.  Design ride height is about 4" at the frame rail right at the front of the door with 26" tires.  You could go lower if you want, but you would have to align the car at that height.  We feel 1" higher or lower would not be an issue at all.  We can also do a 2" front drop if you prefer, at additional cost.

Q.  Can I run a C4 suspension at stock Tri5 ride height?

A.  While this could probably be done, we don't offer that option as a standard.  Raising the CG of the car would be counter to a lot of what the C4 suspension offers in terms of handling.  With our 2" front drop option and 2" rear drop, we believe you could get close to stock height with some spring adjustments, with no detrimental effects to the ride.

Q. How wide of a tire can I use?

A.  Typically we recommend 245 or narrower tires in front, and 275 tires in the rear without minitubs.  If you mimitub the car, you can go to a 295 tire in the rear, and a 255 may work in front with the right wheel offset.  Any larger rear tire requires frame narrowing, due to the location of the dogbones.

Q. Do I need to do any firewall modifications?

A.  No.  We place all engines so no firewall modifications are needed.  If you would like to put the engine further back, we can quote that option.

Q. Are there any floor modifications required?

A.  Typically there are not.  However, the front of the upper dogbones sit above the frame rails to maintain the C4 suspension geometry.  Sometimes, depending on body mounts and position of the body on the frame, small reliefs need to be made in the floor to clear the dogbones.  Also, the original pinion snubber bracket on the body needs to be removed.  No other body modifications are needed, except to address gas tank placement.

Q. Can I use the stock gas tank?

A.  On a wagon the stock tank can not be used.  We typically recommend removal of the tank, as well as the spare tire well, and replacement with a different tank.  On a sedan/HT the tank interferes with the rear swaybar, if the C4 swaybar is used.  We have recommendations for aftermarket tanks that work in the application and look similar to a stock tank.  There are other aftermarket tanks that will work as well.

Q. Do aftermarket exhaust headers work with your conversions?

A.  Yes, there are headers that work for all 3 Chevy engine types that we can suggest.