What wheel widths and tire sizes are you running front and rear? Tire pressure?

I swapped my springs from 12KG/12KG F/R and also fixed tight rear swaybar bushings on my car. I went to an 8KG/6KG F/R. I used to have a car that would literally slide and would oversteer, not to mention ride like crap. The tight bushings (93 bar with 16mm poly bushing) was tight and increased my rear bar tension a lot which I think was the main problem. Now with the new set up I have a soft compliant rear end with a ton of traction. I have some understeer I think, not much testing and tires weren't heated up, so I need to do a lot more driving, but winter is here. I am running 285/30/18 front and rear with 18x11.5" wheels. Before I had a more even front and rear balance with slight oversteer with 265/35/18 on 18x10 wheels.

 

17x9 245/40/17 Toyo R1R F , and 17X9.5 Same tires , Rear

Tire pressures I'm running 32 PSI , started at 34/32 but eventually bled out hte front to help with the understeer , at 32 it started to roll onto the /_\ marks . so I left it there .

my alignment is

-2.4 Camber in the front , a tiny bit of toe in , 5degrees of caster .

rear its -2.2 degrees , tiny bit of toe in as well

 

The biggest challenge I have is controlling push when entering a corner really hot especially when autocrossing and I'd think removing the rear bar would cause even more push

Using less brake and going in with a balanced car really fast and being able to control/use the over steer is what makes me quick and I'd think not having a rear bar would make that harder not easier. Or in other words I'd push right off the apex.

The bar essentially ties the two springs together so if the rear springs are free both tires will have a lot of grip which would be great for getting out of the corner but suck a big one going in and through to the apex.

 

prettymuch sums up my issues . Ok I'm gonna go ahead and reconnect the bar today .

 

i've never raced an FD, but have done several different types of cars, and different setups for different drivers in the same car.

it has been my experience that the rear bar on a RWD car is mostly drivers preference.

for example, with the Spec E30 cars, they had slightly better traction with no bar, but turned in faster with the rear bar, so at thunderhill, which is big and open, we ran no bar, and sears point, which is tight, we ran the bar.

lap times bar vs no bar were not much different

 

Try swapping the rear wheels and front wheels and report back. let me know if it cures anything.

 

Thats tomuch work!

i reconnected the rear sway i'm gonna see how that goes first . , But I doubt the .5 inches of wheel width would cause the terminal understeer lol

 

you might be surprised.

if the tire tread width is slightly less than the wheel width you optimize the contact patch and also hold the contact patch into position. I bet if you switch the wheels front to back you might get what you want. less understeer.

try it out and report back. serious.

 

Tem,
Your r1r's have a tread width of 8.9". So the 9.5" width is about a perfect fit at that size. I know you say your car tends to understeer but does it snap oversteer when it/if let's go or understeers the whole turn?

I'm a new on suspension, so my question is for my benefit as much as it is yours. Lol

 

does anyone else feel like 25" ride height is too low for 8k/6k springs?

i have already gotten my car to touch the fender liners once, and i wasnt even on the track --just driving on the street.

i feel like 25.5 is probably going to be better to make sure i don't eat the fender liners.

 

I need at least 26 inches on track with a 275 40 17 tire and 780 springs to completely avoid rubbing

edit; don't think I've ever completely avoided it but lets just say to avoid seeing smoke LOL

 

No it under steers all the way through if I turn the steering wheel tomuch , it will eventually grip and then the car will snap towards where the wheels are pointing (this happened once )

 

I was smacking bumpstops on the rear end with 25". I raised the car all around .

And I ate through some wiring in the front as well or well the tire scraped the wiring .

 

let me re iterate , I am running 11.6 /8.9 KG depending on how soft i set my rear shocks it would bottom out .

 

Yes, it is too low. ~25 1/4" min to 25 1/2' work best for my car with my suspension setup and stock sized rolling diameter wheel and tire package on roads around me. The rear in particular benefits from a bit more suspension height and corresponding extra suspension travel on the street. At the front, the wee bit of extra road clearance keeps you from scraping on every frickin driveway out there.

 

I agree with the above.



Tem,
With regards to tire pressures, What you are aiming for is the hot tire pressure that works best for your particular tire. The hot temp that works best varies tire by tire and by intended use (track vs autox vs DD) so this concept of a "your tire pressure must be xx PSI cold regardless of tire and usage" is incorrect.

Here is a thread from another forum that touches on this topic but I'm sure there are others: Recommended Tire Pressure

For example, I run Toyo RA1 on my Spec Miata. I aim for hot pressures of 38 PSI. If it is a hot summer day, I'll start cold pressures at 30 PSI. If it is a cold fall/winter day, I start pressures at 32. Those are pressures at the very start of the day. If pressures go over my target hot temp measured immediately after a session, I bleed out so they are at 38 (assuming I was pushing it hard that session and didn't do a cool down lap). If I do a cool down lap and see the pressures at 39 PSI when I measure in the pits, I may bleed it down to 37 PSI to take the cool down lap into account and re-measure after next session.


Regarding sway bar,
Personally, I like having an adjustable rear sway bar for track use. Autox too but I don't do much of that anymore. It allows me to tailor the handling for the desired conditions and track. Adj shocks also help as does tire pressure. Tire pressure is the last thing I adjust to fix a handling problem since my goal with tire pressure is to keep it in the tire's happy spot which maximizes grip and wear.


Also don't forget that understeer can be driver induced. As Fritz mentioned, if you come in too hot or get your braking and turn-in not quite right, the front end will wash out a bit. Add throttle to it and it will wash out more.

I'd suggest you get video of your sessions and post them up in the race section askingn for critique and illustrating corners where you are having issues. That way people can see what's going on and try and help differentiate a setup issue vs something driver induced.

 

I recently went to a 8/6 KG spring set up fro a 12/12KG. I like the softer springs a ton. suprisingly the ride was stiffer than I intially thought it would be.

I am at 25" front and 25.25-25.5" rear. stock sway bars running 285/30/18 tires on 18x11.5 wheels. I didn't notice any rubbing at all. perhaps the 24.8" tire height is giving me more clearance.

 

I could post one up a little later .

as for tire pressures. when autocrossing I check them after every run . I ran reccomended tire from someone who ran those tires alot , and was very fast

But the car really was reluctant to rotate I dont doubbt I could of over cooked a couple of turns . but the car still felt slow on turn in , I rode with a friend and his car rotated somuch better then mine . didnt have issues with bump stops it was just overall somuch better composed

 

Cant believe I just found this thread. Great read.

 

How have these held up? A brief paragraph review would be much appreciated!

 

What a great read here.

Truly a very good write up Howard as it covers things in detail from their beginning.

9 years later i am also wondering though, how much of this setup details are the best way to get a finely setup FD chassis.

During the latest years i have seen cars wth unexpectedly high spring rates behave like they would have 8kg springs.

It looks like that some of the mass produced coilovers that are available (at reasonable prices) now can have great valving abilities to accommodate such spring rates.

Thanks for the topic

 

Another customer was reading this thread and came to me with the question... why do Ohlins and your FPSpec shocks run spherical upper mounts... Howard says your shouldn't use spherical upper mounts.

The answer is: Hysteresis.

Think of hysteresis as gear lash in your suspension (the amount of movement for all the seals to move into place and damping to start happening). Un-damped movement is harsh/uncontrolled/just the effect of the spring, so cheap sloppy high hysteresis dampers feel very harsh compared to highly accurate dampers with low hysteresis. For stock shocks with high hysteresis, that is correct it doesn't matter as the spring rates are lower and the hysteresis gets washed out in the low spring rates and long linear travel distances for each bump instance. For stiff spring rates, you need to be able to control movement over fractions of a mm... this is where hysteresis is important.

For Ohlins shocks for instance... spherical uppers are crucial to the pistons ability to sense the linear acceleration of the shaft and pick between three flow paths (low speed - rolling transition, high speed - bump, and ultra high speed - sharp bump like a pothole or curbing on track). We've measured rubber upper mounts on our spring dyno to be around 10kg rubber "springs" which mask the movement of the shock shaft - preventing the piston from accurately sensing the speed of the shaft by adding a delayed movement. Not a problem for stock shocks but for high end dampers like the Ohlins, this *induces* hysteresis and prevents the shocks from damping properly. So, to qualify Howards answer... it matters, but only in certain applications where high accuracy is important.

FPSpëc Ohlins DFV (FD3S RX-7) - SakeBomb Garage LLC
Ohlins Road & Track DFV Coilovers (FD3S) - SakeBomb Garage LLC

 

I an rather curious as to the 25" ride height recommendation, as would this not be directly relative to the tire height/ Profile? For instance 16" rims compared to 18" rims, and how they not only affect the ride height, and guard/fender clearance, but more importantly the suspension geometry?

 

can I upgrade my ohlins to your fspec? What are the upper and lower limit spring rates on the ohlins without revalving?
Thanks

 

Some parts you can retrofit yes, and we can bump your spring rate up. Shoot us an email... we have floating front and lower mounts, as well as various spring rates.

If you're looking for the Grand Touring setup you'll need the FPSpec Long Stroke.


https://www.sakebombgarage.com/fpspe...top-hats-fd3s/


https://www.sakebombgarage.com/fpspe...ment-wrenches/

info@sakebombgarage.com