Springs / Rates for Coilover kit

Rogue_Wulff · 11-16-2009, 08:34 PM

Quote:

Originally Posted by Gravity Fed

Cars are such a never ending project.

True enough.

FWIW, I attended an autox drivers school last weekend, and the instructor was quite impressed with the ride/handling of my car. He couldn't recall the rates, but knew I had gone with a custom setup.
His only comment towards improvement, concerned the soft dampers. Coming from someone with National level skill in a Miata, I take his word pretty well at face value.

Whizbang · 11-16-2009, 08:39 PM

we do have to work with a limited after market sadly. What dampers are you currently using

Rogue_Wulff · 11-16-2009, 08:41 PM

KYB GR-2's. They came installed on the car.
Soon to be replaced with Illumina's (from billy, of course).

Whizbang · 11-16-2009, 08:43 PM

i have illuminas up front currently then regular tokicos in the rear.

Rogue_Wulff · 11-17-2009, 11:48 AM

Any idea of what you're going to use on the rear for springs?

Whizbang · 11-17-2009, 08:03 PM

im thinking about shooting for a 200lb spring to start with and see how that works out. Mostly just shooting at the dark.

Kentetsu · 01-05-2010, 11:59 AM

Wow, I can't believe I missed this entire conversation!

All good information here, but I just want to point out another option when considering your spring rates. Rather than going with high spring rates when I assembled my suspension, I went a bit softer (275/150) and made up the difference with swaybars.

My thinking in this is that the softer spring rates allow for a bit more compliance in keeping the rubber attached to the road. Too high of a spring rate, and you can get the same effect as a rock being skipped across a pond (the spring is so stiff, that the car can't absorb enough of the little bumps to keep the rubber on the pavement). I have actually seen this happening with a fellow competitor's RX7 that uses 450 Lb. springs on the front (not sure of the rear rate).

So, using a softer spring can make the car "stickier" and give higher traction. But softer springs will also cause more body roll, right? Well, that's where the swaybars come in. Running stiffer swaybars keeps the body roll to a minimum, without causing a (noticeable) increase in ride stiffness.

This setup has brought me great success in autocrossing in CSP, to the point that I am now beating the Miatas consistently (even those on race rubber Vs. my Sumitomos). And, even better, the car is perfectly capable of being driven daily on the streets. I even made the 800 mile trek down to Deals Gap last spring, quite comfortably.

So, there seems to be two basic opinions concerning spring rates. One is to go very high on spring rates, and sometimes even removing the swaybars altogether. The other way (like mine) is to go softer on the springs, and heavier on the swaybars.

I am very happy with the path I chose, and the car has been a real monster at the races. Anyway, I just thought I'd throw that out there for you to consider. Hope this helps.

.

josh18_2k · 01-05-2010, 09:47 PM

problem with sway bars is they are a non linear spring (rate depends on roll) so its harder for a damper to properly control the spring/sway combo. ideal damping at full lean will be underdamped at anything less

soft springs mean more pitching/squatting on brakes/gas, which are both bad for grip and handling

my local suspension guru chris billings swears by choosing springs for roll/pitch/dive/etc, and using ONLY a front bar to balance the car mid-corner

Whizbang · 01-05-2010, 10:27 PM

will the hill climb seasons coming up, i might just have to run what i have due to fiscal constraints and see how she handles as is and work from there. Find out what it wants.

Kentetsu · 01-06-2010, 01:05 PM

Quote:

Originally Posted by josh18_2k

problem with sway bars is they are a non linear spring (rate depends on roll) so its harder for a damper to properly control the spring/sway combo. ideal damping at full lean will be underdamped at anything less

soft springs mean more pitching/squatting on brakes/gas, which are both bad for grip and handling

my local suspension guru chris billings swears by choosing springs for roll/pitch/dive/etc, and using ONLY a front bar to balance the car mid-corner

You have to remember what the other end of the swaybar is connected to (yet another spring/damper combination).

"soft springs mean more pitching/squatting on brakes/gas, which are both bad for grip and handling". Absolutely not true, if combined with good swaybars.

Anyway, I am not going to start an argument in this thread. As I have said, there are two schools of thought on this matter. I am of one, you are obviously of another.

But while you are here, why don't you take a look at this video. Maybe then you will consider that there might just be a slim possibility that maybe, potentially, I really do have a point.

http://www.youtube.com/watch?v=rWpEYAKo0fU

Rogue_Wulff · 01-06-2010, 02:32 PM

Quote:

Originally Posted by Kentetsu

"soft springs mean more pitching/squatting on brakes/gas, which are both bad for grip and handling". Absolutely not true, if combined with good swaybars.

The swaybars have no effect at all under accel/decell conditions, regardless of whether they are 1/8" or 5" dia. Spring rate and dampers are the only things that have any effect on dive/squat, aside from geometery.... Springs determine how far it goes, and dampers determine how fast it gets there.

Otherwise, you do have a valid point. Softer springs can be benefitial on rougher courses. Can go fast with the tires dribbling......
A wise man once said to me "Stiffer springs and swaybars will usually make a car faster, but harder to drive". Of course, he was refering to handling, not straight line speed. It was during an autox/road racing suspension seminar......
He also said to use springs to adjust the car, and swaybars to fine tune the springs.

Kentetsu · 01-06-2010, 05:36 PM

You are correct RW, I mistated that (was thinking roll, as opposed to dive). Still, not a problem with my car. Maybe it has to do with the ride height? Or maybe the Illuminas?

"He also said to use springs to adjust the car, and swaybars to fine tune the springs."

I have read that in some books as well, but like I said, it did not strike me as the way to go (especially while trying to preserve the daily driveability of the car). My goal is to get the absolute best handling, while still being able to comfortably drive the car to work every day.

A fellow competitor with a RX7 did have the 450 Lb. springs on the front, and when the car was later up for sale he freely admitted that it was not driveable on the streets with those springs on it. That is definitely not the state I want to end up in.

Rogue_Wulff · 01-06-2010, 07:16 PM

450 is a bit too high for a 1st gen on the street. In fact, too high for "drop-in" strut cartridges to handle without premature failure due to internal heating.

11-16-2009, 08:39 PM	#17
Whizbang Respecognize! Join Date: Jul 2008 Location: Δx = ħ/2Δp iTrader: (5) Posts: 3,190 Rep Power: 20	we do have to work with a limited after market sadly. What dampers are you currently using __________________ For current updates and event coverage check out Follow on Twitter! @WhizbangRally Whizbang Rally's Webpage \| Facebook

11-16-2009, 08:43 PM	#19
Whizbang Respecognize! Join Date: Jul 2008 Location: Δx = ħ/2Δp iTrader: (5) Posts: 3,190 Rep Power: 20	i have illuminas up front currently then regular tokicos in the rear. __________________ For current updates and event coverage check out Follow on Twitter! @WhizbangRally Whizbang Rally's Webpage \| Facebook

11-17-2009, 08:03 PM	#21
Whizbang Respecognize! Join Date: Jul 2008 Location: Δx = ħ/2Δp iTrader: (5) Posts: 3,190 Rep Power: 20	im thinking about shooting for a 200lb spring to start with and see how that works out. Mostly just shooting at the dark. __________________ For current updates and event coverage check out Follow on Twitter! @WhizbangRally Whizbang Rally's Webpage \| Facebook

01-05-2010, 11:59 AM	#22
Kentetsu RCC Contributor Join Date: Feb 2008 Location: Grand Rapids, Michigan iTrader: (1) Posts: 530 Rep Power: 17	Wow, I can't believe I missed this entire conversation! All good information here, but I just want to point out another option when considering your spring rates. Rather than going with high spring rates when I assembled my suspension, I went a bit softer (275/150) and made up the difference with swaybars. My thinking in this is that the softer spring rates allow for a bit more compliance in keeping the rubber attached to the road. Too high of a spring rate, and you can get the same effect as a rock being skipped across a pond (the spring is so stiff, that the car can't absorb enough of the little bumps to keep the rubber on the pavement). I have actually seen this happening with a fellow competitor's RX7 that uses 450 Lb. springs on the front (not sure of the rear rate). So, using a softer spring can make the car "stickier" and give higher traction. But softer springs will also cause more body roll, right? Well, that's where the swaybars come in. Running stiffer swaybars keeps the body roll to a minimum, without causing a (noticeable) increase in ride stiffness. This setup has brought me great success in autocrossing in CSP, to the point that I am now beating the Miatas consistently (even those on race rubber Vs. my Sumitomos). And, even better, the car is perfectly capable of being driven daily on the streets. I even made the 800 mile trek down to Deals Gap last spring, quite comfortably. So, there seems to be two basic opinions concerning spring rates. One is to go very high on spring rates, and sometimes even removing the swaybars altogether. The other way (like mine) is to go softer on the springs, and heavier on the swaybars. I am very happy with the path I chose, and the car has been a real monster at the races. Anyway, I just thought I'd throw that out there for you to consider. Hope this helps. . __________________ "Learn from the past, or it will become your future...." '85 GS 12a + LSD/Sterling carb/Respeed coilovers/Respeed front swaybar/Respeed adj. rear spring perches/Illuminas/Bilsteins on rear AutoX vids @ http://www.youtube.com/user/Kentetsu1

01-05-2010, 09:47 PM	#23
josh18_2k Rotary Fanatic Join Date: Feb 2008 Location: Gresham, OR iTrader: (0) Posts: 473 Rep Power: 17	problem with sway bars is they are a non linear spring (rate depends on roll) so its harder for a damper to properly control the spring/sway combo. ideal damping at full lean will be underdamped at anything less soft springs mean more pitching/squatting on brakes/gas, which are both bad for grip and handling my local suspension guru chris billings swears by choosing springs for roll/pitch/dive/etc, and using ONLY a front bar to balance the car mid-corner __________________ Last edited by josh18_2k; 01-05-2010 at 09:50 PM..

11-16-2009, 08:41 PM	#18
Rogue_Wulff Non Member Join Date: Jun 2008 iTrader: (0) Posts: 310 Rep Power: 17	KYB GR-2's. They came installed on the car. Soon to be replaced with Illumina's (from billy, of course).

11-17-2009, 11:48 AM	#20
Rogue_Wulff Non Member Join Date: Jun 2008 iTrader: (0) Posts: 310 Rep Power: 17	Any idea of what you're going to use on the rear for springs?

01-05-2010, 10:27 PM	#24
Whizbang Respecognize! Join Date: Jul 2008 Location: Δx = ħ/2Δp iTrader: (5) Posts: 3,190 Rep Power: 20	will the hill climb seasons coming up, i might just have to run what i have due to fiscal constraints and see how she handles as is and work from there. Find out what it wants. __________________ For current updates and event coverage check out Follow on Twitter! @WhizbangRally Whizbang Rally's Webpage \| Facebook

01-06-2010, 05:36 PM	#27
Kentetsu RCC Contributor Join Date: Feb 2008 Location: Grand Rapids, Michigan iTrader: (1) Posts: 530 Rep Power: 17	You are correct RW, I mistated that (was thinking roll, as opposed to dive). Still, not a problem with my car. Maybe it has to do with the ride height? Or maybe the Illuminas? "He also said to use springs to adjust the car, and swaybars to fine tune the springs." I have read that in some books as well, but like I said, it did not strike me as the way to go (especially while trying to preserve the daily driveability of the car). My goal is to get the absolute best handling, while still being able to comfortably drive the car to work every day. A fellow competitor with a RX7 did have the 450 Lb. springs on the front, and when the car was later up for sale he freely admitted that it was not driveable on the streets with those springs on it. That is definitely not the state I want to end up in.

01-06-2010, 07:16 PM	#28
Rogue_Wulff Non Member Join Date: Jun 2008 iTrader: (0) Posts: 310 Rep Power: 17	450 is a bit too high for a 1st gen on the street. In fact, too high for "drop-in" strut cartridges to handle without premature failure due to internal heating.