CMiller95

I apologizing for having multiple threads on varying information about this but I'll condense it all into one.

I am looking at converting to coilovers on my car and I am going the self-fabrication approach.

I have come up with the following coilover shocks:

Front:
QA1 GS507
Extend: 14.5''
Comp: 9.63''
Spring: 9.00''

Factory:
Bilstein
Extend: 13.563''
Comp: 10.18''

My car is currently sitting at ride height with the shocks at a length of 11.75'' so it leaves room for lowering it an inch or so if I want to.

Rear:
QA1 GS507
Extend: 14.5''
Comp: 9.63''
Spring: 9.00''
Add-on, remove T-bar on lower mount

Factory:
Bilstein
Extend:14.69''
Comp:9.61''

From everywhere I've read, bottoming out the stock shock at 9.61'' compression isn't a problem since the suspension bumper will stop it anyway. I still need to choose my spring rates but this should give me room to lower the car atleast an inch if I choose to or just keep it that same.

Opinions?

Thanks!
Colton

gerardvg

Hi

The bump rubber on the rear does get a workout on lowered c4's,
I find it very uncomfortable when hitting the bump stops.

If your coilovers are adjustable you can firm it up, I have my c4 only a little lower than standard for ride comfort.

Remember there is no bump stop on the front suspension, I think that is why I snapped a coilover shock absorber shaft.
It may have banged hard bottoming out the coilover shock absorber.

Will go for 5/8 coilover shock absorbers next time ,,..

LD85

after trying numerous spring pressures, I found that 450 lbs front and rear prevented the rear from hitting the bump stops, and allowed me to lower the rear to my taste.

think about the lbs per inch travel and the split weigh ratio of the C4,,,, I started out soft in the rear and went through 3 rear coil changes until I got to where I did not bottom out and still was not hard like a rock.

CMiller95

I will definitely be using 5/8'' shaft shocks!

How much better does your car ride with coilovers rather than the traditional monoleaf?

Honestly cost wise this isn't too bad. I'm looking at $1000 in shocks and springs. To buy the same shock but as just a shock would cost $700 for all 4 corners so it's only $300 to go to coilovers. I also don't have to worry about a delaminating spring.

gerardvg

My car has a better track ride, not so on the public roads she bucks like a mule on rough roads ...... It all comes down to what spring rate you have, I have been thinking of going to softer more standard type spring rate.
Must be getting too old ...

383tpimachine

My car responds better in turns. Firmer feel not like it was to bounce and rebound.

I have 400lb up front and 375 in the rear IIRC.

dgantt

I just did a complete suspension replacement on mine including a Vansteel coil over system. I noticed the car is way stiffer and kind of bouncy. It handles SO much better now. I had to rework my entire exhaust after lowering the car. Here are a few pics so you can see what the ride height looks like.

Tom400CFI

This comparison is pretty worthless; you're comparing different spring rates (typically) and almost definitely, different shock valving and quality.

The only fair test would be identical spring rates, same exact shocks, monoleaf to coil over. I'd bet that the honest reviewer couldn't tell the diff.

CMiller95

I think the comparison is very valid. Coilovers present two main advantages over a monoleaf. The first being how easy it is to change springs and how cheap they are (also arguably more consistent). So this make the previous individuals experiences valid, because due to coilovers he can choose whatever spring rate he wants. He is also capable of buying springs in 25 lb increments without having to special order a spring.

I agree that maybe with a monoleaf with the same spring rates as he is running he possibly couldn't tell the difference. But I'm willing to bet he would still tell a difference which leads me to my second point crosstalk between the sides. Yes I understand that a sway bar is designed to do exactly that but in a different way. Picture the mount for the front leaf as a pivot point, which it essentially is. Now, when I compress the passenger side suspension the spring is pushed up by the passenger side. This causes it to push down on the driver side as it pivots on its mount. I know that the amount of pivoting is small but bushings do have give to them. Now think about what the sway bar does in the same situation, as the passenger side compresses the sway bar twists (i.e. torsional load).The sway bar applies a force to the driver side in the same direction as the movement of the passenger side. This keep the car flat through turns. This is the exact opposite of what the monoleaf does. So, I think the comparison is valid.

I do agree that it is surely different valving as well which has a huge impact but no test is perfect :cheers

Tom400CFI

But you haven't confirmed anything. So any poster who posts that: "I went form worn out shocks and stock springs, to custom spring rates and a high quality shock...and the ride is WAY better!"
...well that is misleading. It's not the "coil over change" than made the diff...it's the quality (and new) shock along with whatever spring rate. It could also go the other way too, as gerardvg indicated -he didn't specify, but probably used stiffer than stock rates, and commensurate shock valving. Additionally you can get different rate monoleaf springs. You're right that the options aren't as widely varying...but you could get very soft stock springs, new, buttery shocks and make the same proclamation; "the ride is WAY better!"



The comparison would be valid...but you've got the functioning of the spring and it's "crosstalk" totally backward. If you compress the passenger's side, the drivers side will want to move "UP", too. The transverse monoleaf spring (as mounted in the front) adds swaybar effect to the system, by itself. When you go to coil overs, you lose some of that effect.


.

CMiller95

I completely agree that going from worn out parts to brand new ones makes a huge difference whether it be for monoleafs still or to coilovers. I was simply trying to get peoples opinions

Tom400CFI

I understand. I don't mean to "ruin" that for you...Just that you need to be careful about the opinions that you're getting (why are they, what they are?) and how will that affect your goals.

The true benefits of coil overs are the readily available and wide ranging springs (rates) as you mentioned, and the relative ease of changing them (remove shock, swap spring, re-install shock) compared to changing the monoleaf. This would be highly exploited in a track/race car...not so much in a street car.

CMiller95

They are the most advantageous to race cars by far. To me a huge benefit is the cost of springs. It costs an extra $300 to go to coilovers rather than just shocks. Just to buy a new monoleaf when my 22 year old one delaminates is $400 for one side (as in front or rear). That's the best benefit to me.

Tom400CFI

I hadn't considered it that way. Good point.

383tpimachine

My coilovers in the rear were moved inward for bigger rear tires. My fronts allowed me to get rid of the the monoleaf meaning I can alter the K member and fit a 8in crank pulley to decrease the chance of belt slip and increase boost.

l98tpi

I still have transverse spring set up on my 91 but my 07 Z has Coils. I may eventually do coils on the C4. The advantage to coils is obviously being able to set up ride heights and corner balance the car easier and more precise. I used hyperco's formula to figure the coil spring rates for my Z. You just need a set of scales and take measurements at different points on the suspension and the program will give you it's ideal spring rates for the coils.