I recent came across a deal on a quality set of dampers (AST one way) that were just too good to pass up. They're not perfect, one rear damper is frozen and one front one is close to frozen. I figured I can use them for a little bit and see whether to get them serviced.
I installed everything today and it looks like the rear spring perchs are about 1/2 an inch apart, to get the same height, but on the front the difference is close to an inch. The springs are new all around, so I assume that's not the problem, and certainly even if they're not exactly the same they won't be an inch apart. So I'm assuming this is due to two of the dampers compressing more than the other two. It's my first time on coilovers so that's the only logical conclusion I can reach. Am I missing something?
Also, will I have any issues with the setup the way it is? I don't want to pay for an alignment only to find out that I need them serviced very soon (will just take them off and send it in now). The car rides perfect so far (just a test drive, nothing aggressive), so not sure whether the issue noted above is serious or not...
Thanks all!
You will have jacked up cornerweights. Set the perches to be even side to side.
If two are frozen (shafts?), don’t bother installing them before you get them rebuilt. Quality dampers that are seized are junk.
Can you explain why the corner weights would be off, and the benefit of setting the perchs to be even (and have the R/L height be off by close to an inch)?
Too late on installing them... So far they seem to be working fine. Any specific signs I should be looking for in terms of them not working at optimal range?
Are the perches high on the same side or on opposing corners? If it’s the latter, the springs there are “fighting” each other and taking more of the load. It’s like a table with two long legs on opposite corners, those legs will take all the weight. By setting the perches the same side to side (not front to rear), you can ensure your diagonal weights aren’t all jacked up. It’s possible for a car to sit level but have terrible cornerweighting if you have a pair of opposing perches jacked up.
Now, if both high perches are on the same side of the car AND you have reason to believe that those shocks have also lost pressure, then it’s possible you’re compensating for the gas pressure. But a full inch seems extreme unless you’re running really soft springs. If that’s the case, I’d be looking elsewhere.
Are these one-piece shocks or ones where you can adjust the body length? What is frozen, adjusters or shafts? What kind of car is this?
In reply to Keith Tanner :
Thanks for the explanation! I need to go check tomorrow whether it's opposing sides or same side.
They're one piece shocks (not sure I've ever seen adjustable ones). The adjuster is frozen, the shafts are not. On the road they seem to be working perfectly (no noise, no leaks) - and very comfortable for 450# springs F/R. It's a FRS.
Edit: Def not adjustable shocks. One piece.
If they still have gas pressure (assuming they’re pressurized) and they were properly adjusted for the springs, then you’re probably okay with a frozen adjuster.
For the Canadians, having high perches on opposing corners is like portaging a canoe with two people. One person starts to push a bit too hard on one side, the other person compensates, the first person feels it and pushes harder and before you know it you’re both pulling down on one side and pushing up on the other and telling the other person to quit it...
I've tried to find someone else with a similar experience, and my problem seems to be close to this guy's issue:
https://driveviper.com/forums/threads/21252-Big-difference-in-perch-ring-turns-on-one-side-of-adjustable-coilovers
I'm going to check everything again tomorrow and see where I could've gone wrong...
Maybe if I can phrase the question a little bit differently - is it possible for the dampers to still have plenty of pressure/fluid and work fine (at least on initial drive), but somehow have different pressures (due to age / wear) and thus causing what I'm experiencing?
On a 450 lb spring, an inch of perch height means 450 lbs of load. Internal pressure is likely under 100 psi, and it would take a 2.5” diameter piston to exert that much lift. I don’t know how big the pistons are in those struts, but I doubt they’re THAT big.
Did the struts self-extend?
As for viper guy, I’ve seen that behavior with damaged springs and with collapsed upper mounts. It can also be the result of a twisted sway bar, which is one reason you cornerweight without sways. Also, make sure you’re fully unloading the suspension by rolling the car after every adjustment.
Did not test for self extension prior to assembly. I did push down on it a few times after adjusting the height to make sure there was no binding, and it bounced back with no issues.
Assuming I didn't screw things up through the process (e.g. crossed them) - would you recommend that I stick to uneven height and same perch position, vs. close to same height?
Keith Tanner said:
As for viper guy, I’ve seen that behavior with damaged springs and with collapsed upper mounts. It can also be the result of a twisted sway bar, which is one reason you cornerweight without sways. Also, make sure you’re fully unloading the suspension by rolling the car after every adjustment.
From an assembly perspective can I tighten everything down in the air, or do I need to do so when it's all on the ground (including sways)?
How level is the floor you're working on? That can be a cause for the uneven perches.
I would match the perch heights side to side.
If the car then sits unevenly, then I'd swap the spring/shock assemblies side to side and see if the problem follows. That'll help you identify where the problem is. Don't change anything else.
If it does follow the spring/shock assemblies, the next step is to swap the springs side to side while leaving the shocks where they are and see what happens. Then the upper mounts. This will help you identify if your problem is the shocks, the springs, the upper mounts or the car itself.
This is assuming you want to find the failed component.
For the assembly process, any joint that has a rubber bushing on it should be tightened with the car at static ride height. Bushings have a spring rate, and if you lock them in place at full droop they will try to return there. This inclues all joints in the suspension, even ones you're not touching as part of the install. Loosen them all, settle the car on its springs, tighten them up. Depending on the car design, this can have a surprising effect on ride height. NC and ND Miatas are very sensitive to this, earlier ones less so.
Thanks Keith. I was able to work on it a bit this morning and I think things are ok now.
Basically I set everything at the same turns from the bottom starting out (30 turns for back and 13 for front) and adjusted from there. I also loosened the sway bar in the rear, but couldn't do it in the front as I'm doing this in my garage without a lift. Surprisingly the ride heights were relatively similar with the same perch turns, so maybe the rear bar made a difference. I also measured from the top of the wheel to the fender vs. from the ground, and surprising there is a difference. I don't understand why, as all the air pressures are 38psi dead even, and I don't think there's 1/4 of an inch of less tire tread on certain tires vs. others. The car isn't aligned yet, so maybe camber is a cause.
Anyway. Using your table analogy, I also tried to raise/lower not only the corner I want to adjust, but also the opposite side, and that worked much better. I think yesterday as I was trying to set the heights on the fronts I didn't do anything on the rear, nor measure them really. That just ended up exacerbating the problem, I think. Today, having taken meticulous notes and also using your feedback, it was much easier. I ended up at 14/18 turns in front and 35/38 turns in the rear, so not exactly the same perch height but not dramatically off (~1/8 of an inch). It did take a long ass time though.
I can't imagine swapping dampers, then springs, then mounts just to figure out why it's not even!
Thank you again for the help!
Good, I'm glad you made progress!
When the car is at rest, the sway bars shouldn't have any load on them. The best way to check this depends on how the end links attach to the bar - if the holes in the bar are horizontal, then you should be able to slide the end link bolt in and out easily. If the holes in the bar are vertical, then loosening the bolts on one end shouldn't let the bar lift up and off the end link - you'd have to check both ends.
Best (consistent) way to measure ride height is from the center of the wheel to the top of the fender opening, as this is independent of wheels and tires. It's a little harder to be precise than measuring to the side seams or some other hard point, but it's easier to compare from car to car. Regardless, it's a good idea to make sure your tire pressures are even side to side and to make sure you're on a flat, level surface.
