Lowering Springs Making Handling Worse?

[Ubersuber]

I think the bottom line here is: always consider fitting more expensive dampers as likely you will feel an improvement, if you only want to change the balance of the car front to rear a little and maybe only at the front consider adding higher rate bars (and if you understand how they work maybe get "adjustable" bars bearing in mind that you may adjust them only once), always consider fitting better tires if you are after more grip.

Different rate springs should ALWAYS be fitted with new correct matched rate dampers or you are probably wasting your money. If you only add stiffer bars you may also really need better dampers so make sure you ask your supplier how much added spring rate the roll bars will give you. Roll bar spring rate can make the car pogo just as stiffer springs might.

If you want stiffer springs you are really after a lower ride height, although you can in theory fit stiffer springs and maintain stock ride height you generally want to lower the ride height by at least the difference in spring length. Decide how low you might want to go before you decide on the springs and dampers to get you there.

Finally, if you are unsure about the final destination of your handling package then think about the order you might acquire, pay for and install a series of improvements one step at a time. Try to advance window shop so what you do today will work with what you may want to add tomorrow.

[Racecomp Engineering]

Originally Posted by Ubersuber

Different springs should ALWAYS be fitted with new correct matched rate dampers or you are probably wasting your money.

Just curious, have you seen the shock dynos for the stock dampers?

- Andy

[Sleepless]

Originally Posted by Racecomp Engineering

Just curious, have you seen the shock dynos for the stock dampers?



- Andy

For me, it would more useful if you posted an explanation of the shock Dyno info and how it shows the range of spring rates that will work fine.

Otherwise, we have to go by past empirical experience.

In my experience , the big name spring makers will sell people lowering springs that aren't always a good match for stock dampers; they know most people will accept the ride/handling as a fine trade off for better looks.

I believe most of the lowering a springs are indeed targeted at buyers that simply want the look and don't care that much about ride/handling. Just look at all the slammed pogo sticks driving around...

[Racecomp Engineering]

Originally Posted by Sleepless

For me, it would more useful if you posted an explanation of the shock Dyno info and how it shows the range of spring rates that will work fine.

Otherwise, we have to go by past empirical experience.

In my experience , the big name spring makers will sell people lowering springs that aren't always a good match for stock dampers; they know most people will accept the ride/handling as a fine trade off for better looks.

I believe most of the lowering a springs are indeed targeted at buyers that simply want the look and don't care that much about ride/handling. Just look at all the slammed pogo sticks driving around...

I have a good post somewhere on that in this gigantic-ass monster of a thread:
http://www.ft86club.com/forums/showthread.php?t=45554

I'll do some digging and try to find it.

I agree that a lot of the time springs don't match the stock dampers well. I think a lot of the time manufacturer's will simply take the stock spring rates and multiply by 1.5 or something and call it a day (with a 1.2 inch drop). That doesn't quite give the effect most think unfortunately...

Also, there are a couple springs out there that are too firm IMO in the rear for the stock rear dampers.

- Andy

[wparsons]

Originally Posted by Racecomp Engineering

Just curious, have you seen the shock dynos for the stock dampers?

- Andy

Don't worry, even if he has he'll misread them and tell you that you're wrong.

He's never even been on a racetrack, and hasn't tried different combinations on his own car, but he knows more than EVERYONE else on here.

[gramicci101]

Here's another good source.
http://www.ft86club.com/forums/showthread.php?t=9936

[cdrazic93]

Originally Posted by bfrank1972

It's possible they will shorten damper life

Lot's of myth out there - sportline springs won't 'blow' your dampers. sportline springs won't *ruin* handling (nor will any other lowering spring)

Possible? No it's fact. The farther the spring is out of the critical damping, the more wear and tear it has on the strut.

Case & point; my friend had a 2002 miata that he decided to put some Tein springs on. Some ridiculously high rate, like 11k/12k. Something a daily miata didn't need. Around 6 months later, we're driving his car around town, hit a pothole and we hear a loud bang. The front slams on the ground and we had to pull over and call a tow truck. Yes, struts blew.

And as I have been lead to believe springs that leave the damper over or under damped in the system will either be super bouncy, or have not enough spring rate to absorb any high speed potholes. Critically damped springs is like the harmonics of their dampers, it sings comfort and performance in 1 note.

[Sleepless]

This thread is a very good read: http://www.ft86club.com/forums/showthread.php?t=44935

[gramicci101]

Originally Posted by Racecomp Engineering

I have a good post somewhere on that in this gigantic-ass monster of a thread:
http://www.ft86club.com/forums/showthread.php?t=45554

I'll do some digging and try to find it.

I agree that a lot of the time springs don't match the stock dampers well. I think a lot of the time manufacturer's will simply take the stock spring rates and multiply by 1.5 or something and call it a day (with a 1.2 inch drop). That doesn't quite give the effect most think unfortunately...

Also, there are a couple springs out there that are too firm IMO in the rear for the stock rear dampers.

- Andy

Found it.

Originally Posted by Racecomp Engineering

Since we were lucky enough to have a preproduction car for a little we figured a few things out:

Stock shock manufacturer - Showa non inverted twin tube
Stock spring rates BRZ - 185 lbs/in front and rear
Motion ratio in the rear around 0.75

18mm front sway bar
14mm rear sway bar

Fronts are 2011 WRX pads and rotors. Rears need confirmation (I think Legacy GT though).

6 inches total suspension stroke front (bump + droop).
About 2.5 inch bump travel and 3.5 droop, but that bump travel includes the bumpstop.

shock dyno for BRZ


I have more info coming soon and more things to work on with the car but we are incredibly busy this week and I'm at home now. Will try to post some next weekend.

- Andrew

From this thread.

[Racecomp Engineering]

^ Word. I also have a post somewhere on how to calculate % critically damped from the shock dyno.

- Andy

[bfrank1972]

Originally Posted by cdrazic93

Possible? No it's fact. The farther the spring is out of the critical damping, the more wear and tear it has on the strut.

Case & point; my friend had a 2002 miata that he decided to put some Tein springs on. Some ridiculously high rate, like 11k/12k. Something a daily miata didn't need. Around 6 months later, we're driving his car around town, hit a pothole and we hear a loud bang. The front slams on the ground and we had to pull over and call a tow truck. Yes, struts blew.

And as I have been lead to believe springs that leave the damper over or under damped in the system will either be super bouncy, or have not enough spring rate to absorb any high speed potholes. Critically damped springs is like the harmonics of their dampers, it sings comfort and performance in 1 note.

Case and point? A Miata (a different car) puts ridiculously stiff springs on (not sportlines, prokits, anything mild like we're talking about here), hits a *pothole*... and something breaks. And you "have been lead to believe" that <insert sweeping generalized statement about springs> will be super bouncy etc.

Look - all due respect, I hear what you are saying, but not a solid case. I understand that lowering springs *may* reduce life of dampers - but the clock is ticking on dampers no matter what you do. They'll give out over time even at stock ride height. I've seen *no* evidence on these cars where someone has put springs on cars and they have 'blown' - with the exception of botched installs where they spin the shaft on the dampers. There are way too many factors - if you are on stock springs and keep running over potholes you can damage your dampers. If you are a track maniac on stock spring, you're likely going to wear your dampers faster than normal.

My point - I'm happy with my springs, I plan on getting plenty of miles out of my stock dampers with them. Having perfectly matched springs and dampers is obviously the ideal - anyone who is using lowering springs should be aware there are compromises - one could probably argue anything below a $12000 set of coilovers is a compromise!

[gramicci101]

Originally Posted by Racecomp Engineering

^ Word. I also have a post somewhere on how to calculate % critically damped from the shock dyno.

- Andy

I have too much time on my hands.

Originally Posted by Racecomp Engineering

To actually calculate the critically damped ratio use this equation:

Critical damping = 2*sqrt(springrate*sprungmass)

Then divide by the actual damping.

Careful with units! Especially stupid english units.

So, if you're damping force is around 65% of the critical damping rate at the piston speeds you're interested in, you're in the right neighborhood. It gets way more complicated of course but this is a start.

Example for a front BRZ coilover with 450 lbs/in springs and your damping of 450 lbs at say 2 inch per sec or whatever. Corner weight (sprung) of 700 lbs off the top of my height. I'm going to roughly convert to SI units because they are better in every way.

2 * sqrt( 80000 N/m * 300 kg) = 9797 N*s/m = 9.8 N/(mm/s)

That is the critically damped force per velocity.

To be critically damped at 2 inch/sec (51 mm/sec) you need a force of 9.8 N/(mm/s) * 51 mm/sec = 500 N.

500 newtons is about 112 lbs. If your damping is 450 lbs at 2 inch /sec you are 450 lbs/112 lbs = 4.02 --> 400% critically damped. So...very very stiff.

To be the "ideal" 65% damped you'd want to be around 73 lbs at 2 inch/sec. IMO that is too soft for what it's worth.

- Andy

From this thread and this thread.

[Racecomp Engineering]

Oh man, thanks a ton! I really should save some of the things I write on here.

- Andy

[cdrazic93]

Originally Posted by bfrank1972

Case and point? A Miata (a different car) puts ridiculously stiff springs on (not sportlines, prokits, anything mild like we're talking about here), hits a *pothole*... and something breaks. And you "have been lead to believe" that <insert sweeping generalized statement about springs> will be super bouncy etc.

If you understand what I'm saying than you understand that higher spring rates outside of the critical damping means it will shorten the stock dampers life. 1.2 inch drop is hardly mild. RCE yellows .8 inch drop is mild.

It's not a sweeping statement when I see cars with high sprung suspension and bouncing around like a bobble head. It's because their dampers aren't meant to damp at that high of a spring rate.