Is my coilover spring rate too high?

[AlbatrossCafe]

Did this last weekend. I swapped the rear 5k springs with the new 3k springs. What I found:

1. Removing the spring from the bottom was indeed possible and it prevented me from having to get another alignment! Yay!
2. It was a HUGE PITA and required a ton of grip strength to turn that stupid coilover body over so many threads haha but still worth not paying $75+ for alignment
3. I put the 25mm longer spring exactly 1" lower. My car is about the same height (plus/minus 0.25"). What that does for this height debate is unknown lol sorry I couldn't settle it more!
4. Having a 3k spring vs. a 5k spring in the rear handles almost identical in the limited street driving (15 miles) test I did. I still slam my head into the ceiling when the rear goes over small speed bumps. Grr.... maybe I need rubber bushings again.

Proof:

[Zed Head]

Good that you're confirming.  I learned something.

I don't think that changing them from the top would have changed your alignment though.

Slamming your head in to the roof would be from your shock damping, probably, not the springs.

[AlbatrossCafe]

5 minutes ago, Zed Head said:

Slamming your head in to the roof would be from your shock damping, probably, not the springs.

Yeah, that's what I figured. It has 15 damping settings. I've tried 1/15, 5/15, and 15/15. I'm toast no matter what lol. I'll try to get video of the shock to see if it is bottoming out or something.

[LeonV]

Sounds like you're slamming into your bumpstops, did you have a look at them when you disassembled? We had a similar problem with my friend's Z, the bumpstop had disintegrated after 40 miles. 

I bet your ride will improve if you preload your springs by an inch and drop your shock body by an inch to maintain ride height.

[Zed Head]

Do you know how much travel you have, and where the the travel is at ride height?   Are you saying that the front suspension handles the speed bumps well but the back doesn't?  Seems like you could do some simple inspection and comparison to understand your problem better.  If I read your posts right it sounds like nothing has really changed.  Might be time to stop and study.

[Jason240z]

I think half the problem with these budget shocks(bc/stance/etc etc) will be the quality of the dampers.

you can go up on spring rates if you've got good quality dampers to control it.  these just wont be.

[AlbatrossCafe]

On 9/17/2018 at 11:06 AM, Zed Head said:

Do you know how much travel you have, and where the the travel is at ride height?   Are you saying that the front suspension handles the speed bumps well but the back doesn't?  Seems like you could do some simple inspection and comparison to understand your problem better.  If I read your posts right it sounds like nothing has really changed.  Might be time to stop and study.

Not sure where the travel is. As cgsheen1 said, you don't preload the spring at all. So it is just wherever the coilover rests. Maybe that means I barely have any uptravel, I don't know. I think I will try cranking up the preload higher and lowering the height adjustment to see if I can gain some uptravel.

Either way, I'm gonna put a go-pro on the suspension to see what is going on when I feel those bumps (i.e., is it compressing all the way? Is it not moving?)

 

2 hours ago, Jason240z said:

I think half the problem with these budget shocks(bc/stance/etc etc) will be the quality of the dampers.

you can go up on spring rates if you've got good quality dampers to control it.  these just wont be.

I got Stance because they were supposed to not be the same el-cheapo china coilovers like BC, Megan Racing, etc. While that is true, I guess that doesn't mean they are a superior product. Knew I should have just went with TTT all along.... I got everything else from them anyway.

Edited September 20, 2018 by AlbatrossCafe

[Jason240z]

9 hours ago, AlbatrossCafe said:

Not sure where the travel is. As cgsheen1 said, you don't preload the spring at all. So it is just wherever the coilover rests. Maybe that means I barely have any uptravel, I don't know. I think I will try cranking up the preload higher and lowering the height adjustment to see if I can gain some uptravel.

Either way, I'm gonna put a go-pro on the suspension to see what is going on when I feel those bumps (i.e., is it compressing all the way? Is it not moving?)

 

I got Stance because they were supposed to not be the same el-cheapo china coilovers like BC, Megan Racing, etc. While that is true, I guess that doesn't mean they are a superior product. Knew I should have just went with TTT all along.... I got everything else from them anyway.

they are though. 

 

Not made in china, I think its Malysia.

Lots of other options from others apart from TTT, my money would go with a suspension specialist, not a cnc machine shop.

[Woody928]

Interesting to read this, I'll caveat any of my comments before I start as I am no expert on suspension. This is just my personal experience... 

I have a very similar setup to you, I am running TTT control arms, tension rods etc and BC racing coilovers with 4/4kg springs all around. I am also running ST sway bars with 205/55/16 tyres on 16x7 wheels. There's a link below to my thread where we did the install. 

Spring rates seem to be a funny one as there are so many different idea out there, most places as you observed seem to suggest 4/5kg setups with some people going with much higher. I have no idea where these figures have been taken from as they are wildly different from any factory rates. I have been told that a lot of the aftermarket coilovers setups were adapted off the back of later S bodied cars (S13,14,15). On the basis on the factory rates I decided that I didn't want to go over 225lbs (4kg) for a road car personally. What size wheels and tyres are you using? (as that will also ave a big effect on your ride).  

Now for me the car rides really nicely, it is firm I would say however the car absorbs bumps very well, doesn't skip and gives a sporty ride without being unpleasant. I would say the car is comfortable and would happily tour long distances in it. BC's seem to be given a hard time but they have a solid reputation and are built to an extremely competitive price tag. Yes there will be better coilovers out there with higher quality dampers to match exact springs rates and corner weights etc however they are in a different league budget wise as well. 

If your expectation was for a ride anywhere near stock using solid mount TTT control arms then you would be disappointed, think how much rubber has been removed from the suspension. It's probably more down to the control arms than the coilovers if I hazard a guess, the whole combination will all add up to the final result though. I cannot confirm how your coilovers spring rates may be influencing but it could be down to the dampers as well. Just thought I'd share my 2p for what its worth...