kwerks

iTrader: (2)

I'm on a little different setup but which exact tires are you running and whats the psi when hot? Whats the tire temp across the board of the tire? (if you log them) Also what spring rates are you on?

I'm running a bit different.
Running. F. -2.1 camber, 6caster R. -1.9 camber , zero toe

wjp005

iTrader: (3)

Tyres are full slicks Michelin 240/640/18s

I run them at 16psi hot (about 12psi cold)

And yes the have even temperature over the surface of the tyre.

Spring rates I'm not sure on, they are Tein springs with Bilstein shocks.

Here's the results from my most recent event. I finished 11th outright amongst a field of very quick open wheelers. 3rd fastest tin top. New class record by almost 2 seconds, won the class by almost 2 seconds.

kwerks

iTrader: (2)

thats awesome congrads!

even tire temps? so you have more room on setup to go faster and you have no aero! I plan to eventually run additional 150-220 lb of aero which will easily land me quicker laps once setup is adjusted.

Fritz Flynn

iTrader: (263)

Congrats on the hill climb record!

Bob H

iTrader: (10)

I'm going to re-post this with the motion ratio's corrected.
-Bob

Bob H

iTrader: (10)

So I've been doing research on the springs for the Tein SS/HA/etc.. shocks.
For some background - I was concerned if I needed taller springs since they were a lower rate - i.e. they would require higher perch heights. I'm trying to keep the height adjustment in the ~ middle of the range. Right now to get ~25" ride height, they are up ~2/3 from the bottom with the 12kg front and 10kg rear springs. My concern was with softer springs, I need to move the perch up higher to keep the ride height the same. I don't want it at the top of the adjustment range. So I was looking at slightly longer springs.

Tein SS spring dimensions
I measured the stock 12kg and 10kg springs and here was their dimensions,(adjusted to match the stock Tein numbers - they were very close):

Fronts: 175mm free length, lower inner Dia: 70mm, upper inner dia: 90mm
Rears: 200mm free length, lower inner Dia: 70mm, upper inner dia: 100mm

I don't know why the rears have a larger upper inner dia.
Here is Tein's main website showing the Taper springs part numbers/dimensions:

(scroll down to the second set of numbers with title: Taper Type Springs):
http://www.tein.co.jp/e/price_list/s...d_springs.html

You'll notice they have three main free heights - 175mm, 200mm and 250mm.
That corresponds to ~ 6.9", 7.9" and 9.8"

What does that kg/mm rate equal lbs/inches?

BTW, for guys like me who like US numbers vs metric, here are the conversions:

12kg: 672lbs/in
10kg: 560lbs/in
9kg: 504lbs/in
8kg: 448lbs/in
7kg: 392lbs/in
6kg: 336lbs/in

I'll be using the metric numbers - but sometimes its easier to reference what your already familiar with.

Shock/spring movement with various weights and loading for reference

I then calculated the compressed distance for static and then at a ~1G load for a 3000lb car,(2800lb plus driver).
This number is not a pure 750lb/spring rate - I used the motion ratio of .6 for the front springs and .68 for the rears - if the spring rate is one you might use on the front or rear - I put the .6 front ratio first and the .68 rear ratio second. I did not calculate the spring angle effect - if someone has the accurate spring angle information - we can modify these numbers. Bottom line, they will be slightly smaller.

In addition - and very important - your sway bars will have an effect on this - and I don't know how to quantify it except that it effectively increases the spring rate under cornering - and with a bar like the speedway/tripoint - it can be substantial.


12kg: 0.67"
10kg: 0.84" / 0.91"
9kg: 0.89" / 1.01"
8kg: 1.0" / 1.14"
7kg: 1.31"
6kg: 1.52"

The same data for 1500lb load,(really just doubled since I wanted to keep it simple to compare)

12kg: 1.34"
10kg: 1.68" / 1.82"
9kg: 1.88" / 2.02"
8kg: 2.0" / 2.24
7kg: 2.62"
6kg: 3.04"

So the big numbers I wanted to compare:
Movement under 1G load for the various rates vs static: is the same as the static numbers.

How much more movement w/the 6kg rear spring vs the 10kg supplied spring?
So if you had your ride height at 1/2 way up the range with a 10kg rear spring switched to a 6kg spring, your talking a 0.61" higher spring perch height to get the same ride height, and a 0.61" greater movement of the spring/shock under 1G.

How does this compare to the max travel we are targeting?

Per earlier post discussion, we should target no more than 2" of wheel travel to keep the camber gain to 3 deg max. That correlates to 1.2" in the front shock and 1.36" in the rear shock. That discussion is per post #100 and the bottom of post #82

So with that in mind - the 6kg rear shocks may not be the best solution as it is moving 1.52" under a 1G load? (that correlates to ~2.25" of wheel mvt). What if your pulling 1.1, 1.2G's? Now the sway bar mitigates some of that - but I have no idea how to quantify its reduction?

My new lengths based on the lower rates

So I'm moving from 175mm to a 200mm free length in the front and keeping 200mm free length in the rear when I put the lower rate springs on. Why? I'm trying to keep the adjustment in the middle of the range for the coil-overs.

The 12/10's I have now are a stiff ride - and don't really work on the track. I was initially thinking the 450/350 like Howard mentioned earlier. However, I want to retain the stock upper shock mounts - I drive this thing 75+ miles a day 5 days a week. So the Taper type springs are my only choice to retain adjustability.

How stiff is too stiff and how does that compare to the BMW/Honda/etc.. car I had/rode in with XXX springs in it?

I do track my car a lot, so I can live with a little stiff ride. Which led me to consider the 9kg/7kg setup. 10/8 seemed too much - 560 lbs/in in the front is my upper limit. I've driven many a BMW's with 500-6000lbs springs in the front, (mac struts though - which means a direct 560lb wheel rate, no motion ratio).
With the Motion ratio in the FD - a 500lb wheel rate would require a 300lb spring rate for the front.

What are the actual wheel rates vs the spring rates - what do you feel?

For reference, US measurements are:
504lbs/392lbs with the 9kg/7kg springs.
448lbs/336lbs with the 8kg/6kg setup.



Wheel rates for those two are:

9kg/mm = 840lbs/in front, 7kg/mm = 576lbs/in rear

8kg/mm = 745lbs/in front, 6kg/mm = 494lbs/in rear


Lots of pwr, stock springs = nose high attitude!
I've been riding around on stock springs for the last few weeks - man does the nose of the car spike up/rear squat - and I have the 5 way tokico shocks all around in good shape- I just got used to the nose staying flat with high accel rates,(because I had the 12kg/10kg springs). Not the case with much softer stock springs and 320 rwhp and torque.


Looking for any thoughts on the 9kg/7kg setup and I wanted to put that information up in this thread. I will be calling one of the main distributors of the springs this week to see if they can get the ones listed on the Tein website and what the leadtime is. It is possible you can't source the 9kg/7kg springs.
I also wanted to discuss the increased travel and potential height issues with a much softer spring if your already near the upper portion of the adjustment range on the coil-over as I am.
-Bob

kwerks

iTrader: (2)

what tires are you running?

Bob H

iTrader: (10)

Track - will be eventually running a square setup - 275's all around. Street - 255f, 275r Currently on 17" rims, will be moving to 18's.

kwerks

iTrader: (2)

Which tire compound? That ill dictate spring rate more than anything.

Bob H

iTrader: (10)

This is a dual purpose car as the intent of this thread is.
Even if I run a dedicated track rims setup - for the past 7 years, I've always run street tires. So 200 compound approx. Tires like Pilot Sports, Falkens, maybe the Sumitomo's, etc..
I'm not trying to set spring rate based on my driving, I'd pick 10kg/8kg if that was the case - but to keep it from bottoming out or having too much travel. I do track my car a lot - sometimes 2 times per month,(not recently), but I also drive it 70 miles a day. I'll trade on-track ultimate performance for livability. 8/6 would be more comfortable - but would 9/7 be a slightly better compromise. I've been driving for the last 8 mos. on the 12/10 setup and its too much if the roads are poor. Its ok on nice smooth roads.
I predict I'll see about 1.1, 1.2G's max at the track based on my driving.
I instruct, so I'm not going for absolute best lap time, but consistent performance.
-Bob

silverTRD

iTrader: (37)

so i have a softer tread compound, its 140 actually. i would then need stiffer springs than someone with a 250 tread compound? just want to make sure

kwerks

iTrader: (2)

In simple sense , YES!
But always remember to check what spring range your shocks are valved for. Example Tein SS come with 12kg and 10kg (based on "stock FD corner weights") if you run something super sticky you will want to try higher spring rates and tein says 16kg is approaching the limit of the shocks valve range. (if you set them to 3/4's hard on 16kg spring that will be over 90% limit of the valving range)

One of my old friends in osaka used to run his track FD on yokohama racing tires @ 16kg/17kg based off his corner weights. (by the way his car was setup up by RE-Amemiya for him, if i remember correctly it was in the 2400lb range and 400+hp w/ TD07 single)

Bob H

iTrader: (10)

I had my motion ratio computations backwards - the wheel rate should be lower, not higher... Will update tomorrow and see if I can get the original one edited. Thanks to jkstill for the good math!
-Bob

Bob H

iTrader: (10)

Ok, update on the original post,(#581).


I did my math backwards in that post - I used the Motion ratio and divide by rather than multiplied by the spring rate. The result is the wheel rates were way too high. It was late and I missed that. Thanks to jkstill for sending a PM with the corrected math.

What are the actual wheel rates vs the spring rates - what do you feel?

For reference, US measurements are:
504lbs/392lbs with the 9kg/7kg springs.
448lbs/336lbs with the 8kg/6kg setup.

Using the previously discussed motion ratios of .60 and .68:
-of note, I've also seen .67 or .64. The fronts on mine measure out to .64 vice .60- so we can look further into that.


Wheel rates for those two are:

9kg/mm = 302lbs/in front, 7kg/mm = 263lbs/in rear

8kg/mm = 269lbs/in front, 6kg/mm = 228lbs/in rear

So the 12kg fronts supplied with the Tein SS kit put the wheel rate at: 403 lb/in and the 10kg rears put the rear wheel rate at: 380 lbs.

All those numbers are for reference - until someone measures and verifies the actual motion ratio for the FD. However, it provides some comparison numbers to use and a basis for discussion.
-Bob

wickedrx7

iTrader: (14)

I am basically in the same boat except I don't drive my car daily (track occasionally, but don't want a really stiff ride). I just picked up a set of tein SS's with 10K&12k springs and was going to give them a shot. I am thinking differently now, I should probably just change the springs out so i don't want to do it later.

Right now I am running Koni's with RSR super down springs which are about the same rate as eibach's. They are actually pretty good on the track and fine on the street except they are to low. I scrap everywhere in the city so that is why I wanted the coilovers.

I am fine with a little stiffer spring and was leaning towards 10k&8K. I don't want to go 8&6, that seems to soft for the valving and also I would be concerned with not being able to get the ride height to the appropriate height.

Bob H, any update on finding the 9-7 combo?

jkstill

iTrader: (11)

I did that just the other day on the front, haven't checked the rear yet.

Measured center to center

Control Arm mount point to shock mount mount: 8 inches

Control Arm mount point to wheel ball joint: 12 inches

motion ratio = 8/12

motion ratio = 0.666...

call it 0.67

I will measure the rear tomorrow.

Bob H

iTrader: (10)

If your primarily doing track - don't go down from 10/8. I haven't called around about the 9/7's yet. I'm still trying to figure out the exact wheel rates - as you can see from the post above - the motion ratios we had don't appear to be correct. I want to know what I'm dealing with first so I can keep a common reference to wheel rates as I may change them later. I thought the 12/10 setup was too stiff in the front compared to the back - understeer a lot, esp on turn-in and the first half of the turn. I tried softening up the shocks - helped tiny bit, but not enough.
What can be said - Howard has run the 8/6's and loves them on the track - so those or the 10/8's should be good regardless of what we come up with for wheel rates. I will say from personal experience, I don't like the 12/10's on the track.
Important note, I run close to street tires. You run R compounds or better and a big front sway bar like the Tri-point, it may or may not be a good match. That's beyond the discussion here and tire temps/pressures would need to be logged and analyzed to see what your setup requires.

-Bob

jkstill

iTrader: (11)

I took measurements at the rear today.

As the rear suspension has the shock mounted on the upper arm, it wasn't as easy as measuring the mounting points on the lower control arm, as can be done in the front.

For the rear, I have the shock removed, and let the suspension fully droop.

I then measured the distance from the floor to the hub mounting bolt, and the shock mount on the upper arm.

Then I jacked the lower arm up to about where it would be at rest if the car were on the ground, and took the measurements again.

Finally I jacked the arm up to where it would be if the shock were fully compressed, and took the measurements one more time.

Here they are:

============== hub mount ==== shock mount
fully extended 8.5 18.75
flat 11.25 20.75
fully compressed 14.5 23.00


The motion ratio changes at bit as it swings through the range of motion.

The one that is the most meaningful is the second one, which yields a motion ratio of about .69.

(23-20.75) / (14.5-11.25) = 2.25 / 3.25 = .69

The spring angle is 12 degrees yielding a wheel rate ratio of about .404

( 2.25 / 3.25)^2 * cos(12) = .69^2 * cos(12) = .404

The wheel rate ratios for the front and rear are quite close.

The attached Excel Workbook will let you input different spring rates and get effective wheel rates for the FD.

Formulas were taken from the "Automotive Math Handbook" by Forbes Aird.

wickedrx7

iTrader: (14)

Thanks for the info, going to order some 8K's on Monday and put them on. I will report once I get them on. I do run Toyo RA's on the track with stock sway bars. Plan on eventually getting a tripoint bar eventually.

n2o4fun

I have recently duplicated Howard's recommendation on coilovers. Tein SS with 8kg front and 6kg rear springs. I installed the rear coilovers only at this point and I'm having problems getting ride height high enough. With the collars at the top of their adjustment I can barely achieve a ride height of 25". I'm also concerned with the amount of travel left in the coilover. Just a quick ride around the neighborhood fells like I am hitting the bump stops. Is anyone else running Howard's exact setup? If so where are your collars adjusted to in order to achieve a decent ride height?

habu2

What is the part # of the rear spring you are using? I ordered ST060-01175 for the rear and had the same problem. I returned them and ordered SH060-01200 springs, they are ~1" taller than the 175s. Here's my thread detailing my experience. My car is currently (still) in the paint shop so I have yet to install the longer rear springs.

n2o4fun

Update:
I made some 1.5" spacers for the springs and still had to run the collars up over half way. I am sitting at 26" to the fender lip so if your going lower than that the 1" longer spring should work.
I would love to hear from Howard on spring part numbers though.

ArmenMAxx

iTrader: (21)

I just finished my track day yesterday and have a small concern with my FD's handling. I have koni shocks and tein S-tech springs stock swaybars w/ widefoots mounts. Handling is very balanced by my car leans a lot and makes it feel somewhat "loose" when at the limit which I believe is actually lowering my cars overall handling limit. I have never tracked any other car and maybe im expecting too much from my fd. Was wondering if I should switch to a slightly thicker swaybar to resolve this issue.

When my tires are cold my car understeers which I persume is normal. Ounce everything is at temp its balanced. If i get into a corner too hot the car oversteers half way through which again is very normal. Im just worried that if I get thicker swaybars my balance might get thrown off or I might loose overall grip.

Here is a pic of me leaning on a not so sharp or cambered turn. Im on 225/50/16 Birdgestone Re01r tires which really arent any big deal. If i was on R-comp wider tires I would expenct to lean more with the added g-force.

Mahjik

iTrader: (1)

You have a street car, not a race car so it's going to corner like a street car. You will have some lean, which is not a bad thing. I would suggesting keeping the car as is until you have more track time under your belt in the car.

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/do-you-got-lean-470255/

n2o4fun

I'm a big fan of "soft spring/big bar setups". In your case you may be hitting the bump-stops and unsettling the car. I will echo Mahjik and say more track time might be needed but I would also check suspension travel just to be safe. My 2 pennys.