I just got the JIC FLT A2 set up and am wondering how to tune the rear ride height. On our cars, the spring is independent and inboard from the strut. On my JICs there is a ride adjustment on the rear lower spring seat, but you can also adjust the height of the rear strut independently. Since the rear spring and rear strut are 2 separate things, how do you tune the rear ride height? The front is very straight forward. I will be getting the car corner balanced soon anyways, but I'm having trouble figuring out the rear. One could set the ride height on the spring first, but have the strut set way too high. HELP!?!

 

I asked this same question nearly a year ago, so I'm curious to see what kind of responses you'll get.

I hate to say it, but I eyeballed it. I lowered the spring perch and the shock body height the same amount.

 

The ride height should be and only adjusted by the spring perch.

Avoid using the damper perch to adjust ride-height. The adjustment made there is meant for positioning of the shock body in preventing piston bottoming under full suspension compression. You can seriously damage your shocks if it sits too high.

I hope that answers ur question.

Oh and btw ... this also applies to the HKS and Tein coil-overs.

 

Thanks, but I think my greater question is what is the relationship between the spring ride height and the height of the strut? How would I know after I set ride height witht the spring, if the strut is set at the optimum height?

 

Come on...

 

i have mine set at the lowest for both the spring and the shock perch. Let us know if you have that rattling noise that almost all JIC user gets. I still have no clue of how to get rid of the rattling noise

 

What does the lowest setting mean on the strut? It supposedly comes set from the factory (even though both of my rears were of varying heights.) How would I know if my strut is set too high? What does one look for in setting the strut after adjusting the spring?

 

come on...

 

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Hello?

 

the mech at avalon racing told me to set the shocks to the lowest if i have the spring perch set at the lowest. You can try emailing JIC for how to adjust them

 

setting the strut independently of the spring is tough, even for front struts or on just about any car where you can adjust the height on both the strut and spring. hopefully this will make some sense.

On a front strut the key is to have enough preload on the spring so it doesn't bounce around in in the spring perch/seat, yet adjust the ride height with the actual shock so you don't compromise suspension travel. If you raise the car up using the spring, you risk losing droop travel on the shock. My 240SX rear suspension suffers from not enough droop travel so when I hit a bump, it feels like the rear tires are coming off the ground.. and on certain bumps they actually do because when the rear end becomes light and wants to "lift up", the shocks can't "sag" enough for the rear tires to stay on the ground. Easiest way to see this is when you jack the car up. You can jack up a stock Z a few inches before the rear tire comes off the ground. Thoeretically if you had no droop travel, the tire would come off the ground the instant you start raising the car, or jacking it up.

If you lower the car too much using the spring, you lose compression travel and the car will bottom out everywhere.. You do track events, so you'd really notice it because when the shocks are bottomed out around a corner, if you hit a bump it'll just transmit into the chassis instead of being absorbed in the suspension.

This is what I would suggest doing..

I would set the rear strut so it's in the middle of the lower mount. If there are 20 turns worth of thread, thread it on 10 turns. After everything is installed, lower the car down and set the desired ride height with the spring. Measure the gap between the top of the tire and the fender. Jack the car up and put it on jackstands (both sides). Measure the distance between the top of the tire and the fender. Take this number (let's say it's 5") and subtract the distance between the tire and fender from when the car was on the ground (let's say 2"). This means you have about 3" of droop travel.

Take the jack and jack up on the control arm or ball joint to compress the suspension until the gap between the tire is the same as it was when the car was on the ground. Take off the wheel and measure how much travel you have on the strut, or the length of the shock shaft between the top of the strut and the upper strut mount. There should be a good 4-6 inches.

If for some reason you have 1" of droop travel (not enough), I would lower the strut perch, which is effectively raising the ride height of the car, then lower the right height using the spring. do both equal amount of turns so your ride height doesn't change. You will lose some compression travel by doing this, but there should be a median, or middle point where the ideal compression and droop travel measurements meet up. Normally you have a few inches of lee-way inside that ideal range to mess with. Like for example on my 240SX, I've had to adjust to get more droop travel 2-3 times by lowering the rear of the car, but there's a ton of compression travel left over so it doesn't matter.

Once the measurements appear to be correct, the only way to tell for me at least is by driving it. If you go over a sharp cresting hill, railroad tracks, fast over a speed bump or just quick around a sharp corner and it feels like the rear tires are coming off the ground or is very abrupt on rebound, that means I need more droop travel because the tires don't want to stay on the ground when the car is in the air or raised up. For compression, I simply lower the car down, reach under there and put a zip tie around the shock shaft. Fly around some tight corners (autocross type where you'll get a lot of body roll) and check to see how far the zip tie is on the shock shaft. If it's all the way at the upper mount, you probably need more compression travel. If you have an extra inch or two, you should be ok.

it's not the most scientific method in the world and surely there is an easier way to figure it out, but when I got my coilovers for my other car they were in a zillion pieces so i had to set them up like this. i'd like to think it's pretty close to being dialed in. let me know if you have any questions.. i am going to be doing Tein coilovers on my Z within the next month so I'll know more then, but surely it'll be too late. anyways, sorry for the long post.