k24madness

iTrader: (6)

After swapping my stock CA bushings for delrin/sphericals the car was bottoming out worse than even with the old 850/500 springs. I wonder how much torsional spring rate I lost?

Sitting at 2,250lbs with driver & good aero bits.

After moving up to 245 Hoosiers I was overdue for a spring change. Based on good advice from Savington I am going to start with 1000/500 with 4.5" pinch weld height (have ELB's). I am currently running 27mm solid front with 14mm rear bars. Should I make a front bar change too? I ordered the RB 54106 from 949 to have on hand for Sonoma testing with Tim at TFB on 8/28. I also have 1100 & 550 springs ready to go in case the car needs more. I want to give him the best combo to start with and have good options on hand for changes if need be.

My goal is to create a stable easy to drive setup. I will likely stick with the 245 S80 slick for STU (295whp)and drop down to a 245 A7/R7 to squeeze into ST3 or possible ST4.

I read through past posts and want to thank Andrew, Emilio and BBundy for leaving such a good trail of bread crumbs.

emilio700

iTrader: (3)

lol. Andrew was on softer rates until just recently I think. We have been pestering him to run a bigger fsb and rates.

In any case, yes, you'll need the 54106. Car will be miserable with the peas shooter you have now. I'd start with 1100/500. FWIW, I ran 800/500 with aero and 54106 FSB on 225/45/15 R7's and it was not enough front spring. My S2 (no aero) ran 900/500 with a a softer 54104 fsb on much less grippy 225 RC1. 225 or wider Hoosiers always want 1000's and big FSB up front.

k24madness

iTrader: (6)

Thanks Emilio, I ordered the 54106 from you yesterday. I feel good about the changes. Will report back after 8/28 testing.

The current spring/FSB setup was left over from the TC Design days with 225 NT01 & C51 Hankooks. Makes sense the tires are overwhelming them now.

Junkwhale

Irrelevant to your actual question about what spring rates to go with, but wouldn't going from twisting rubber "bushings" to proper bushings actually increase spring rate?

I.e. with the rubber bushings you've got some added springs in series with the main spring. Remove them -> spring rate goes up?

MrJon

Pretty sure the bushings would be considered to be in parallel not series.

concealer404

iTrader: (3)

No, he's removed the stiction of the crappy rubber bushings, which allows everything to move more freely. Effectively a lower, but more consistent corner to corner and through whole "swing" wheel rate.

My car is rolling more now on 850/500 with the 1.25" RB bar front with delrin/sphericals than it did on 700/400/1.25" bar with oem rubber bushings. It's a bit bizarre.

emilio700

iTrader: (3)

Ride height is a key factor in roll resistance. The relationship is non-linear. At OEM ride height, the NA/NB has it's highest front and rear roll centers, just below the CoG. As the car is lowered F & R RC's descend faster than the CoG for every 10mm of ride height drop. Near full bump the delta widens more rapidly. This is why we run Xida GS with OEM sway bars at 6" ride height and get about the same roll stiffness as the same car at 4.5" pinch weld but with RB 1.125/14mm bars.

The advent of Bauer's ELBJ's allows a 4.5" pinch weld height which helps increase roll stiffness. Just adding big sway bars can increase individual wheel rate past where it needs to be for bounce frequency. This reduces compliance. Compliance equals grip. So we're always looking for ways to run things with less individual wheel rate, less friction but high roll stiffness for track use.

k24madness

iTrader: (6)

Understood. When control arms pass horizontal roll stiffness decreases. I learned that the hard way in another strut based car I have. That extra .5" over my past specs will help. God knows I can use the travel too.

JasonC SBB

The bushings add springs in*parallel* so total rate goes *up*

Rubber bushings have spring rate and *no stiction*. Poly bushings that lack lube can have lots of stiction.

concealer404

iTrader: (3)

Fair, my bad. Hopefully the point i was trying to convey wasn't lost with my incorrect usage of term.

k24madness

iTrader: (6)

Update....Got the 1.25" RB FSB installed along with 1000/500 springs. The 4.5" pinch weld ride height really helped me achieve reasonable castor numbers with the ELBJ. I also took the time to properly set bump stops at the limit with packers.

We are going to test Monday the 28th at Sonoma. With various springs/sways on hand I hope we can get the setup dialed in.

Goingnowherefast

iTrader: (1)

Please report back. I'm in the same boat as you with the spring rates.

emilio700

iTrader: (3)

Start a new thread with your set up. The more info the better

- weight w/ driver
- tire size and model
-wheel width
- wheel offset
- F & R camber
- F & R sway bar diameters
- whp
- aero?
- LSD type
- engine swap if applicable
- Usage (TT. w2w, HPDE, canyon, etc)

k24madness

iTrader: (6)

Started with the 1000lb/500lb, 1.25" RB FSB, 14mm RSB

I managed to sneak in a few laps yesterday afternoon with Hooked On Driving at Sonoma. Struggled a bit getting use to it. It has a TON more front grip in high speed heavy loaded corners. It pushes a bit in the slower stuff like 7 and 11 at Sonoma. As I changed my driving technique to adjust to the new setup (loading front/trail braking in slower turns) I knocked 2 seconds off my personal best for the year with the new setup. .

I still plan to test/tune/coach with Tim @ TFB Monday. I have to believe there is still room for improvement with the setup. I struggled a bit yesterday with the car being real tail happy. After dropping the rear one turn on the coilover and softening rebound the car became much more settled.

I use to run REALLY low. Somewhere between 3.6"-4.0". With the new 1000lb fronts & FSB at 4.5" ride height I am still bottoming out the right front sometimes on turn 1. I also realized with the higher ride height I mush have more camber at full compression vs being lower due to camber curves. The tire wear looked great.

The rest of the season is going to be about getting seat time and coaching with a few races sprinkled in.

k24madness

iTrader: (6)

Productive test day at Sonoma today. Tim @ TFB did a great job driving and tweaking the setup. We made great strides over the course of the morning optimizing what we have. In the end he feels it still needs more spring. Gonna jump up to 1100/550's and test again. He commented on how well the Aero was working on the car. Between that and the grip of the slicks it just wants more spring. Still good for low 1:41's on a less than ideal day (very hot).

Thanks again to Andrew and Emilio for proving stellar guidance!

mx5-kiwi

Are you running a splitter?

I have the stock Xida setup (800/500?) with 6" splitter and Gtc200 wing with either NT01 or Z214's with 25mm FRB and 15mmRRB....and have ended up with Xidas on full hard front 2-3 from hard rear....And feel like i could do with more spring as well....interested in anyone's thoughts here...

emilio700

iTrader: (3)

Assuming 225./45 on 15x9,yes 1000/500 and ditch those ways bars. You'll want a 28.6 front and 14mm rear.

If you are at 2-3 clicks, I'm guessing they are gen 1's (black spring perches). They are valved for 1000 lbs max on a light car. Gen 2's can handle up to 1200# springs or you can get your gen 1's revalved. If they are gen 2's you'll probably be able to dial the shocks back a click or two with the bigger springs and bars.

mx5-kiwi

Thank you.

yes 225x45.

I believe they are Gen 2's, nearly 1 year old.

k24madness

iTrader: (6)

MX5-kiwi, I also wanted to add don't be afraid of the additional spring rate and roll stiffness. It's still amazingly compliant on the 1000/500 combo with the 32mm/14mm sway bar combo. Are you really running 225/50/15 tires? Can you get them in 225/45/15's?

mx5-kiwi

Thanks K24...yes my signature is wrong from when we started out on 03g 225 x 50's. Definitely on 45's these days. must correct that one day.

F'ing hell you run a 32mm sway bar!!!

We are still freaked out about Emilio's 28mm suggestion and you pop that shot across the bows...

Keen to try the 1000 spring but after tomorrows race meeting we will wave goodbye to the 1600 motor and go to our new 1800. We "think" it best to stay with what we know until we get our heads around the extra (hoped for) 150 whp and what that might do to our setup.

Suspect it will put a larger emphasis on requiring a 949 Giken than anything else to start with...