Best Coilover Shock Spring Compressor

[TheJDMan]

I'm installing a set of Vari-Shocks and need to compress the coil spring. Any recomendations on a good coil spring compression tool would be apprecitated.

[dhutton]

I have the Alston coilover spring compressor and it works well.

[TheJDMan]

I have looked at that compressor and I don't get how it works. Do you put the compressor plates over the spring caps? Anyone have a picture of one of these compressors in use?

[dhutton]

It compresses the spring onto the shock body, then you install the coil retainer cap and release the compressor.

[bret]

You might think about using a shorter spring with a bit more spring rate. If you need that much preload...you may have too soft and too long a spring.

[bret]

The thing about a long soft spring...a coilspring only has a certain amount of travel available until the coils stack solid. With a good cold wound American made spring, this usually happens at about 40% of free height...meaning that a 10" free height spring will offer approx. 6" of travel until coilbind. So if you select a spring that requires 2 or 3" of preload, you have sucked up a large portion of your available spring travel before you've even started.
Manufacturers will vary, but most coilovers will have a threaded area of the body that is from 1.5" tall to full length thread. This allows you anywhere from a little to a lot of potential ride height adjustment. The problem comes when you use this threaded adjustment as a bandaid for a spring the is too firm or too soft. The correct rate spring should carry the static vehicle weight with no more than about 1" of preload. If you have to go much over that you should try a firmer spring rate and back off the preload.

If you are looking for some help with selecting the correct spring length and rate, this might be of some help: http://www.ridetech.com/info/spring-rate-calculator/

Hope this helps!

[dhutton]

You might think about using a shorter spring with a bit more spring rate. If you need that much preload...you may have too soft and too long a spring.

I learned this the hard way. What Bret is suggesting is the way to go based on my experience.

[TheJDMan]

I'm just installing what was supplied in the kit. The spring is 12" long 200lb and I only need to compress the spring about 1/2" to get the top retainer on. That said, at the desired ride height the shock will need to be about 60% compressed to 12.5". I suspect these springs are not going to allow that much shock compression. I'm thinking I may need to switch to a 9" spring but I am unsure what effect that will have on the spring rate. This is all new to me so my first step is to install what I was supplied and go from there. If I may ask Bret, what length and spring rate are you running on the 48 Hour Camaro?

[bret]

48 Hour Camaro = Front is a 3.5 stroke / 8" spring w a 600 spring rate. Rear is a 5.2 stroke / 12" spring w a 250 spring rate.

[TheJDMan]

It compresses the spring onto the shock body, then you install the coil retainer cap and release the compressor.

Then how do you get the top plate of the compressor tool out from between the spring and cap? I must be missing something here.

[dhutton]

The cap fits inside the top plate of the compressor tool.

[Vegas69]

My current rear spring needs no preload to support the car and they work well. I went to a 10 inch spring.

[TheJDMan]

With the 12-200 springs and all adjustments set as low as I can get them including the lower shock mount, the car sets about 3" too high. I don't understand what is wrong since Bret is running a 12-250 spring and the 48hour Camaro is setting exactly where I want to be in terms of ride height. Typically do these springs settle with time? Just out of curiosity, I sat 500lb of tractor weights in the trunk which lowered the car to the desired ride height but I obviously can't drive it that way. Would a 9-250 spring be comparable to the 12-200 if I need to go to a shorter spring?

[dhutton]

With the 12-200 springs and all adjustments set as low as I can get them including the lower shock mount, the car sets about 3" too high. I don't understand what is wrong since Bret is running a 12-250 spring and the 48hour Camaro is setting exactly where I want to be in terms of ride height. Typically do these springs settle with time? Just out of curiosity, I sat 500lb of tractor weights in the trunk which lowered the car to the desired ride height but I obviously can't drive it that way. Would a 9-250 spring be comparable to the 12-200 if I need to go to a shorter spring?

At ride height your shock needs to be roughly centered in its travel. You should measure this before changing your spring rate.

Is your suspension binding? Did it return to its original ride height when you removed the tractor weights.

[TheJDMan]

At the desired ride height the shocks are maybe 55-60% compressed with no springs and measure 12.5" mount center to mount center. There does not seem to be any binding. With the shocks installed but no springs I can move the axle up and down or tilt it one side or the other and it moves freely in it's travel. Once I removed the weights from the trunk the ride height returned to about 3" too high. It looks to me like a 10" or 9" spring would allow me some adjustment both up and down but it just seems strange that most guys are running a 12" spring and I am too tall with the 12". Speedway Motors sells 2.5"ID Carrera coil over springs for very good prices I may just buy a 10" set to see what happens.

[darren@ridetech]

If your shock is 12.5" at mid stroke then I'm guessing you have a 4" stroke shock (roughly 10.6" x 14.75). This shock requires the use of a 10" spring.

Our AirBar uses a 5" stroke shock (11.5 x 16.5"), which has a longer body allowing the use a 12" spring.

What rear suspension are you using? Are the shocks mounted vertical or at an angle? If at an angle, what degree? Do you have vehicle weights?

[TheJDMan]

The rear suspension is the Alston Chassisworks G-Link. The shocks are around 5deg from vertical. I don't have any actual weights at this time. It just looks to me like a 10" spring would be a better fit. To keep the same load as the 12-200, should I go with say a 10-250? I looked at the Ridetech online coil sping calculator but without actual weights I'm just guessing.

[dhutton]

Where is your shock in its travel with the spring installed and at ride height? I thought you said 55% but maybe I am misreading.

Post number 21 here has a pdf from Alston that explains how to calculate the needed spring rate. I have used it and it works well:

https://www.pro-touring.com/showthread.php?69444-Broken-Varishock/page2&highlight=

[darren@ridetech]

I thought the G-Link was designed w/ for a 5" stroke shock tho?
What are your compressed/extended dimensions?

[jorge]

Sorry to sneak in here, but I think this can help you find you’re a number close to your corner weight: If the shock stroke is in fact 4.1, you could just multiply the shock compression of 60% that you said the car had when dropped and multiply that times the total stroke.

.60 x 4.1 = 2.46” of compression

Since you said the spring rate was 200 lbs/in AND assuming you don’t have any preload on the spring when you measured AND if the coilover is close to vertical AND since the rear has a motion ratio close to 1, you can just multiply the spring rate times the compression of the shock.

2.46” x 200 lbs/in = Sprung corner weight around 500 lbs

If you plug in 500lbs in the ridetech calculator under corner weight and 0 for unsprung weight (since sprung weight = corner weight – unsprung weight, and since you can’t enter the sprung weight directly think of it like this: 500 sprung weight from above = 500 – 0)

Then plug in a 4.1” stroke shock with a 10” spring and shock angle 85 degrees. The spring rate will come out to 163 lbs /in that’s WITH a preload of .62”. Since you don’t have a spring compressor, enter a custom preload of 0 and you will get a spring rate of 200 lbs/in.

200 lbs/in sounds right since you said that your 12" 200lbs/in spring gave you around 55-60% shock compression which you were fine with, if you were to get a shorter spring and use the same spring rate you would get the same amount of shock compression. Only your ride height and spring compression compared to total spring length would differ. And if the shock is compressing around 2.46" and 60% of a spring is usable without coilbind, then that will leave the spring around 40% compressed with 60% compression left which is pretty good. Math:(10" spring * .60 = 6" of usable travel, 2.46 / 6 = .41 or around 40% the spring compression). I'm thinking if the 200lbs/in feels fine, stick with it and go to the 10" spring with the same spring rate. This is all assuming the stroke is 4.1"

This is at least what I'm thinking personally :)

[ROLLDAMTIDE]

With the 12-200 springs and all adjustments set as low as I can get them including the lower shock mount, the car sets about 3" too high. I don't understand what is wrong since Bret is running a 12-250 spring and the 48hour Camaro is setting exactly where I want to be in terms of ride height. Typically do these springs settle with time? Just out of curiosity, I sat 500lb of tractor weights in the trunk which lowered the car to the desired ride height but I obviously can't drive it that way. Would a 9-250 spring be comparable to the 12-200 if I need to go to a shorter spring?
Did u ever change springs? I'm in the same boat right now and like you were, thinking I need a 10" spring instead of 12.... I dunno?