Gen III wIRS roll control...

[Dave Tabor]

Hi Folks,

I'm on my 6th track day with my Gen III Coupe (302/TKO/IRS) and have decided that I need more roll control AND more suspension stiffness.

My coil-overs are currently the kit-supplied Konis with 500# front and 400 # rear springs.

Would a bump to 550# front and 450# rear be a good starting point?

I'm tempted to get an entire new set of coil-overs with stiffer springs so i can preserve the original set, ride height setting, etc.

Thanks,
Dave #17

[Gordon Levy]

A set of double adjustable shocks and a ton more spring rate would help a lot. We have those as well as billet gun drilled aluminum control arms bushings. There is is a ton of setup stuff I can help with if you want to give me a call sometime.

[Logan]

You need more than just a 50lb increase in spring rate.

For example, in my ‘17 Mustang GTPP and a friends GT350, we approached the problem from different angles, but in the end arrived at nearly the same conclusion. Double the spring rate on the front, compared to stock. Wasn’t even as dramatic of a change as you’d think, reading that. Not suggesting you double the spring rate on your Daytona, but certainly going to need more than +50lbs to notice a change.

The first question is, do you have sway bars? If not, need to start there. That’s basically 100% roll control, while keeping soft spring rates for good weight transfer (grip).

[Dave Tabor]

Logan,

Yes, I have the sway bars front and rear that came with the kit.
I'm one hole away from full-stiff on the front (can't get to it due to clearance) and two away in the rear.
The car handles quite balanced as it is and does not noticeably understeer.

Do you know what Miata (NA, NB, etc.) these were originally sourced for?
I see lots of aftermarket options available- maybe I can find a stiffer front bar.

I'd rather control the roll issue with sway bars but I also bottom the car at the exit of the corkscrew at Laguna Seca.

My ride height is currently 4.5" front and rear and I'd like to lower the car a half-inch as well.

Thanks,
Dave

[Logan]

Dave, I did a great deal of investigating back in January/February regarding swaybars for the FFR. The swaybars that FFR offers are indeed for a Miata. Specifically, the rear bar for any 1990-2005 (NA/NB) Miata. Manufactured by Hellwig, and sold by Flyin’ Miata. The same bar is used for either end of the FFR, i.e. rear Miata bar on the front of the Daytona, and rear Miata bar on the rear of the Daytona. Unfortunately, I never found the rates per-hole of this bar. Hard to get Hellwig to put an engineer on the phone to give those specs out apparently.

Specs:
PN: M13-36520
Hot-formed 4140 chromoly steel
5/8” (0.625”) solid bar
Coined ends, 4 holes for the bars sold by FFR

Interestingly, I cannot find the “exact” bar on Flyin’ Miatas website. The part number shows the same thing but only 3 holes in the ends. Maybe this is a newer revision of the same bar? Does the currently-supplied FFR bar come with 3 holes or 4? I only have one bar, and it has 4 holes.

[Dave Tabor]

Hi Logan,

Thanks for this great info.

I ordered 'front' and 'rear' bars with my kit (#17) and they both have 4 holes.

A stiffer front bar might work for me but I'll try 750# front springs in the meantime.

I see that John George had raced with 900# front and 700# rear springs.

Next track day is Laguna Seca on 11-9.

Dave
Gen III Coupe #17

[Logan]

Dave, your swaybars should be identical. The only thing front/rear about them is the different brackets. I plan to calculate the rates of each of the four holes, but haven’t gotten to it yet.

Good call on switching to 750lb front springs. Do you happen to know the inside diameter and free length of the springs FFR includes with the Koni’s?

The Coupe-R comes from FFR with 750 front / 500 rear according to the website, although my Coupe-R came with 750/400....not sure why or when they change stuff like this, but I simply try to maintain all possible data.

John George used 900/700 but that was at 3” ride height and the FULL aero package with loads of downforce. If you don’t need to support the hundreds of extra pounds of downforce, 900/700 would probably be too stiff. So the sweet spot probably lies somewhere between your current rates and these rates.

Good luck! Looking forward to hearing your race report from Laguna Seca in a few weeks!

[Dave Tabor]

I was sort of joking when I stated 'front' and 'rear' bars knowing there are the same bar.

I could measure the Koni coilover spring/body dimensions but I ordered a pair of QA1 single-adjustables with springs so it will be an easy swap, adjust ride height and go.
I'll get them on Friday night.
I'll address the rears after this one change.

For a street car/tires the kit setup is fine. At the track with NT01s and traction, the car has a lot of roll and is a bit annoying on right-hand turns as you are on the 'low' side.

Dave

[Dave Tabor]

Ok, I went with QA1 single adjustable front coilover shocks (15" length) and kept the Konis in the rear.

Springs are Eibach 700# front and 500# rear.

Coilover Spring Inside Diameter (in):2.500 in.
Coilover Spring Length (in):8.000 in.

I went with 8" springs to try to save some weight. FFR-supplied springs were 8" and I don't think I'll get into coil-bind.

I put about a hundred street miles on the car and it's all good, but I do think it could use more front sway bar.
The rear is still a bit 'soft' over dips in the highway but I'll keep it like that for the next track day.

I ordered what I think should work as a stiffer front sway bar:

Product Line:ST Suspensions Rear Sway Bars

UPC:611512511757
Sway Bar Position:Rear
Rear Sway Bar Type:Solid
Rear Sway Bar Adjustable:Fixed
Rear Sway Bar Diameter (in):0.750 in.
Rear Sway Bar Diameter (mm):19.05mm

Dave
Gen III #17

[Dave Tabor]

Ok, all done with QA1 single adjustables all-around.

Eibach 700# front 500# rear.

Another 100 miles today with the dampening 3 clicks from full-on.

All good and I'm happy with it.

My existing sway bars are 7/8"each so I'm pretty much done there unless I can get a linkage that allows the use of the stiffest hole.

Dave

[Logan]

What is the interference that prevents you from using the stiffest swaybar setting? Is the end link too long, or put at too severe an angle if you try to use the stiffest hole?

Shocks look good! Thanks for posting specs.

[Dave Tabor]

It's the end link binding- I did not cut them down like the manual said- I saw no need for it at the time and I'm not convinced this would help anyway.

I'll get a pic next time the car is up on the lift.

Looks like today will be a 'donut-pad' session at Sonoma Raceway- not a good way to test out roll-control but something to do.

Laguna Seca HPDE is Monday and will be the real test.

Dave