Need More Coilover Help Please

blykins · #1 (**permalink**) 03-26-2005, 05:03 PM

Guys.....I'm still deciding on what to do for my front coilovers. I cut some 2x4's and mounted them like shocks on the front.....after measuring different ride heights. Right now, the height from bolt to bolt on the shock mounts is right about 13".

The recommended shocks from the manufacturer have an extended length of 13.25. I really don't see how a 1/4" of extension past the ride height would be good at all....it seems like they should have at least a couple inches of travel in the downward direction as well as the upward direction.

So how should I proceed? I really don't know what to do now on picking out the right compressed/extended length/stroke for the fronts.....

Richard Hudgins · #2 (**permalink**) 03-26-2005, 07:40 PM

blykins,

First you need to know the motion ratio and damper angle.

These give you shaft travel amounts.

The 13.25 dimension is a bit short. but I bet not by as much as you might think.

After all it is on the droop side and you do not see as much travel in droop as you see in bump.

(Note: A bit of a disclaimer, It is very bad to top out dampers from a dynamic standpoint, really strange things happen to the chassis and the driver will not have a clue what is going on. )

Go to Springrate This will give you your motion ratio so that you can tell damper travel.

If you have any direct questions after you have the data, you are welcome to give me a ring.

But I think it would be best for you to deal with your manufacturer as their engineers will know more than I about your chassis and it's particular needs.

blykins · #3 (**permalink**) 03-27-2005, 04:29 AM

SV recommends 10.25C and 13.25E. After measuring the ride height where I would like it to be, I just can't see how a 1/4" would be enough on the droop side.

I have their coilovers on the rear.....and with this ride height that I've mocked up, the car looks at the very least level....if not sitting a tad high in the front....which is what I want.

If I did buy their coilovers for the front, and adjusted them down to where I had a couple inches for droop, the car would sit butt-high.

Of all the coilover charts I've seen, it seems like they all recommend 2" bump past ride height and 2" droop past ride height. This makes sense to me.

I like the squatty look.....hindend lower than the front....so I would like a little more adjustment if I wanted to raise the front of the car a little. So based on my 13" ride height that I measured, it seems like I would need a 11"C and a 15" extended.

nanard289 · #4 (**permalink**) 03-27-2005, 05:17 AM

Hi Blykins

Coil over adjustment is a frequent problem for everybody. Your choice for a 13.25" shock can be OK, but this characteristic is not enough. You have to define the requested shock stroke you need according to your maximum and minimum shock displacement. If you need for example a 5" for total stroke, it means that your shock absorber shall be 8" fully compressed and 13.25" fully extended (remember that the last .25" are not used). Then, you have to define the spring load characteristics. First you have to measure the total spring length (of course, you know the internal diameter). So, you have to check in your shock fully extended the available space between both spring retainers (the low one shall be unscrewed at the lower place). I suppose you measure 8.5". Then you substract 1/4" (that you do not need) and the total spring length shall be between 8 to 8.25" (regular length). It is a common approach to have between 1/3 - 2/3 (street use) to 1/2 - 1/2 (track use) as setting ratio for the "compression stroke" and the "extension stroke". For this example, the compressed part could be 2" and the extended part 3" for a mixt use. That means if the suspended load at the front wheel is 600lbs at the shock axle, you have to find a 300lbs/inch spring to have the correct 2" compression strock (stand by position). Finally, you have to check that this spring of 8" total length and 300lbs/inch is able to have a 5" compression with some gap remaining between each turn. When you install the spring in the shock, you will unscrew the lower retainer by .25" to have a free space without spring compression and to facilitate the shock installation (remeber that you have only 13" between both fixing points). Hope these informations could help you. All the best for your project.

blykins · #5 (**permalink**) 03-27-2005, 11:48 AM

This is my prelim way of thought at this point....

At 13" between shock mounting holes, the car is basically sitting level. So even at this point here, if I install the shock from SV, the shock will be installed at full extended length. There's no travel whatsoever left in the down direction.

Having said that, I would still like to raise the front a touch....and I wouldn't be able to do that.

In my mind, I need a shock with an extended length of about 15".

Sydney · #6 (**permalink**) 03-27-2005, 01:07 PM

I'm not sure what shocks you have. Mine are the Aldans. With my ride height set pretty close, I have a 12 1/2" measurement between shock holes.

At that ride height, the shocks are within 1/4" of being right in the middle of the 5" travel. I don't know what the total lenth of the shock is, but the exposed rod at full droop was about 5".

Sydney

blykins · #7 (**permalink**) 03-27-2005, 01:13 PM

Syd, is your frontend complete? Are the shocks installed?

nanard289 · #8 (**permalink**) 03-27-2005, 01:18 PM

Sorry, I had understood that 13" was the total distance when the wheel was in the lower position (out of the floor). If 13" distance refers to the normal position, you have to measure the minimum distance when the shock will be fully compressed. If for example you measure 8" you will obtain a compression stroke of 5". Then you apply the 1/3 - 2/3 rule and you will obtain 2.5" for the extension stroke (note that in this case the track rule is not applicable due to the large suspension stroke). It means that when the wheel will be fully extended the shock length will be 15.5". So you have to provide a coil over shock 15.5" fully extended and 8" fully compressed. In order to have the correct 13" distance in normal position, the spring will be define as previously indicated. In this case, the spring length shall be about 10". If the suspended load at the shock axle is 600lbs (for example) you have to calculate the spring as follow: 600:2.5= 240lbs per inch. It means that when the coil over will be installed the load on the spring will be 600lbs and the spring length will reduce of 2.5" accordingly. To have the complete shock stroke (7.5") the relevant load will be 240 x 7.5 = 1800lbs (about 3G for vertical acceleration). Remember that you can always adjust (as final action) the trim by using the lower spring retainer to modify the spring load.

Sydney · #9 (**permalink**) 03-27-2005, 01:24 PM

Yep..... Mostly done except for body work and interior.

blykins · #10 (**permalink**) 03-27-2005, 01:27 PM

Syd, you got any side shot pictures of how your car sits?

SVMCOBRA · #11 (**permalink**) 03-27-2005, 01:40 PM

Bly, my car is complete. It sits just almost level. I to wish I could get the front up a little higher as their is only about 4" of gorund clearance from the bottom of the oil pan and radiator.
Ray Hedden

Sydney · #12 (**permalink**) 03-27-2005, 01:49 PM

Here's one. Frame rails are 5 3/4" above floor. 3 3/4" oil pan ground clearance. [IMG]

[/IMG]

blykins · #13 (**permalink**) 03-27-2005, 01:52 PM

SVM....what shocks do you have?

Syd....very nice looking ride. Very nice. You don't happen to know the compressed/extended lengths of your shocks, do you?

SVMCOBRA · #14 (**permalink**) 03-27-2005, 01:58 PM

The shocks I have are coil overs that I purchased from Shell Valley. 350# front spring rate and 250# spring rate in the rear. Both front and rear are adjusted up quite a bit to get the ride hight. My car sits just like Syd's.
Ray

blykins · #15 (**permalink**) 03-27-2005, 02:06 PM

I can't figure out what's going on with my car. It just doesn't seem logical to me that the SV shocks would have adequate travel.

Syd's measurements are close to mine...he's sitting at 12.5" ride height. He's 1/2" from me. The stock SV shocks are extended at 13.25". That means Syd would have 3/4" downward travel. I would have 1/4".

Not only would I not have any adjustment to raise the front end if I wanted....but if I were to hit a pot hole and the shock needed to extend, the most that I could get would be 1/4". If Syd were using the same shocks, he'd get 3/4". That just doesn't seem like much at all to me.

Syd says with his Aldans, he's midway through the stroke at where he sits....that makes more sense. I just need to find out what the compressed/extended length of these Aldans are...and compare them to the other ones that Shell Valley sells.

blykins · #16 (**permalink**) 03-27-2005, 02:14 PM

Here's what my eyesore of a Cobra looks like right now....actually this was awhile ago....there's been a lot more done to it since then....but anyway....It has the coilovers that SV sells on the rear....and it's got 2x4's for front shocks....The front's ride height is 13".....and as you can see it squats just a tiny bit in the rear.....

Sydney · #17 (**permalink**) 03-27-2005, 02:18 PM

Mine are the adjustable Aldans that SV sells. Don't know what the total lenths are, but I have a good 2" at least of shock travel up or down at the current ride height.

You might check www.aldaneagle.com under their street rod section for all of their offerings. I'll bet SV uses one of those, not sure which one.

SVMCOBRA · #18 (**permalink**) 03-27-2005, 02:24 PM

Bly, I have about the same shock travel as Syd. I just installed the shooks and use the collar to ajust the ride hight. The springs are pretty well compressed.
Ray

blykins · #19 (**permalink**) 03-28-2005, 03:55 AM

OK....one of my buddies has a Shell and Aldans on his.....he gave me the part #.....

I looked it up on the site and they are: 10.2" C, 13.4" E. So Syd, you have .9" of travel in the downward direction.....but you say it's halfway through the stroke. I'm definitely looking at something wrong.

I must be missing something......