So i installed truhart coilovers. The ride was perfect, but i had set the ride hide a bit too low in the rear where every speedbump was final destination. It would rub on the rear on medium to big bumps. Once i adjusted the ride height by about half an inch, the rubbing stopped, but the ride became unbearable. I would feel every bump on the highway and for the bigger bumps, it feels like my rear end would kick up catch some air.

There is no dampening adjustment on these. People are also saying that coilovers are supposed to be like that, but thats not true since they were perfect before readjusted ride height.
Could ride height possible affect the ride quality?

People also say that you should be able to spin the spring with your hand, and then other people are saying how you should be able to fit the spanner wrench between the collar (4mm preload).

 

Remove spring, set the suspension travel. Install spring and set ride height with preload.

Enjoy the car

 

how do i set suspension travel?

 

^ youtube.

 

The coilovers has an adjustable body, the common fool uses that to adjust ride height. Remove the spring, install the wheel , set the travel when it will be belificial. I like about 1/2 of my travel to be use use up, and the other half...... install spring when finished and set the ride height with preload.

 

Yesterday i fixed the problem and just wanted to give an update since there might be other people with this issue. I called truhart and they specifically asked me about how i adjusted the ride height. They did say the proper way to adjust it (at least for their coilovers) is to take it out and adjust it although i understand that the whole point of coilovers is that these are supposed to be easily adjusted without having them taken off the car. In addition, they said that the preload should be zero both front and back.

Once i took the coilovers out, it was almost twice the length of when i first installed it on the car. My guess is that the dampening was played out so i was just relying on springs (bouncyness). Anyways, any future adjustments will be done while the coilovers are out of the car. the z drives perfectly and DONT BE FOOLED!

COILOVERS ARE NOT SUPPOSED TO MAKE YOU "**** BLOOD"
dont listen to people in other car forums that say coilovers are supposed to ride harsh, cause thats not true

 

Zero preload will yield a falling rate at droop and as your spring settle in will continue to get worse - the spring will eventually fall away from the collar at droop. Effectively this will make your damping rebound useless at the bottom of the stroke. Makes sense to follow what the manufacture said, but keep in mind you'll likely have to pull these out again to adjust the preload or lack thereof.

Also, when talking about suspension it's damping. Dampening is making something wet and should only be used when talking about your weekend with a lady friend.

 

Lol what are they going to settle an inch so the spring gets floppy in the perch?? Doubt that. And you are really going full send "motorsport" if you are worried about the OP effectively utilizing the last mms of suspension travel at full droop. I like your level of detail though for sure.

Somewhat to your point, OP should put a nominal amount of preload on the springs if he chooses to follow the manufacturers recommendation for setting them up. Which is hopefully what he meant when he said Truhart recommended "zero" spring preload.

 

Springs should last years without a change in droop.

Ive set some fast and well handling cars up for the roadcourse , preload has always been of little concern to me.

 

To Mully's credit, the point he made which is a valid one, is that if the spring comes loose in the perch (has excess rebound stroke between that point and full droop), you have no spring force to counteract the road forces in that range of travel, which is (im sure you know this already), why it is better to use a helper spring with some spring rate vs just a basic low rate tender.

Anyway, I agree with you that final spring preload is a function of corner weight, and irrelevant in any absolute sense, except of course for the relationship between pistion position in the damper and min/max stroke. Which is why (we have discussed this before), manufacturers just use the aforementioned recommendation of leaving preload alone...they now know the user is going to be "in" the damper range irrespective of ride height.

It is safer for them from a risk standpoint (end user less likely to shatter the shock internals), and the only real consequence is that, assuming an overly lowered car, the tire will rub well before hitting the bump stop, eliminating it as a useful tuning tool at the limit, and shredding tires too. It is a bit dramatic to call anyone who follows this route a "common fool," lol. For most street users following what Truhart and almost every manufacturer recommends is JUST FINE. Assuming of course the physical damper dimensions are "correct" for the chassis in question.

 

https://my350z.com/forum/brakes-and-...-question.html

 

I should have prefaced my response with the fact that I come from the off-road world (prerunners and trophy trucks) where we usually run 1" of preload minimum to limit falling rate. I was bringing similar logic into street / track suspension since 0.25" of falling rate with minimal suspension travel may be more critical than a relative amount on an off-road truck with 18"+ of travel. My off-road experience was that it made the rebound very difficult to dial in if someone didn't set the preload correctly. I'm relatively new to the track cars, so I'm still learning.

I understand what you guys are saying about preload as it applies to the Z. Particularly anyone running inexpensive coil-overs may not be as concerned about that last 5% of suspension travels.

I'm glad the OP got it all sorted out. Drive the Z hard - the car deserves it.

 

I think you give them too much credit, I don't know how many sets I've installed and wondered what they were thinking with the body length included in the kit. It's like the vast majority of adjustable body coilovers are kinda thrown together with a "it works and they won't know the difference " thought process.

 

I hate to break it to you, all dampers are just a combination of off the shelf parts tailored to an application even the big brands. Though contrary to your experience, of all the "i dont know how many" kits ive installed and setup, I havent encountered one that was grossly mis-dimensioned. I guess I (and the OP for that matter) got lucky then.