I should have been more specific.
54107 for DOT tires. I use the 54106 1.25" bar for anything 225 Hoosier or bigger. I think Bundy uses a custom 1.25" too.

I’m using the ISC racing bars. 1.25"X0.25" wall up front but the arm length has like 4" of adjustment range to the longer compared to the racing beat bar where I have it set second from the stiffest setting so it is not as stiff as the Racing beat 1.25" bar but it is stiffer than the 1.125" bar actually closer to the 1.125. Rear bar is 5/8" but again it’s got a way longer arm length and I run it full soft so effectively it's closer to a 13mm bar equivalent. The 1.25" racing beat front bar is hugely stiff compared to the 1.125” the difference between the two is drastic if you swap between those two you will likely have to do other changes to get some balance back.

Yup. 250 in/lbs raw rate difference and they don't overlap. I found >1100lbs/in sway bar rate started to become necessary at around 1.55G sustained at typical race ride heights and 2100-2400lbs, give or take. So that's 225 Hoosiers or more. We use the 54106 for that. For 205 Hoosiers or harder compound 225's (less grip), the 1.125 x .188" wall and the 14mm seems to work over a variety of spring rates and vehicle weights.

Crusher on 225 R6's with full aero at NASA nationals (Miller) was seeing sustained 1.6g on the flat turns with long peaks of 1.75g in a few of the slightly cambered turns. That was 900/500 with the 54106 bar IIRC.

I think I’m marginally stiff enough. Thought it might be better to go to stiffer springs versus stiffening the bar though. Currently 900/500as well. I might try stiffening one notch front and rear on the bars or maybe just the front. It would be bout like the big racing beat 14mm combo then. With 245 Hoosiers on 10's it has ridiculous grip. Turn 2 at Pacific 180 degree flat sweeper taken in 5th gear. Not too long ago I would have thought that would be insane and I don’t remember when exactly I lost my sanity.

Bob with the aero grip I'd agree with going stiffer on the springs vs the bars. But you (and I if I did track) are probably approaching the level of downforce where a 3rd spring setup would be a good idea.

I really appreciate people like Bob and Emilio coming out and letting the world know what they run. Miata racing is some of the most competitive racing EVAH, and these guys give you this information to set your car up to a race-winning level FOR FREE. That also means you won't spend a lot of time making mistakes, buying the wrong parts (over and over), and simply getting frustrated. Pretty cool, IMO. :2cents:

Dean Thomas just did a 1:43.7 in my car the first session out on old R100's. We lost RR tire. Swapping out for new ones now. Thinking a 1:42 or less is possible today. He really likes the setup.

Tweaks I suggested worked OK then?

Yes! Dean and I thank you very much! The car feels soooo much better. Turn in is awesome with the 14mm rear bar.

After we installed new 245/R100 tires Dean did a 1:41.6

I managed my personal best time of 1:47.2

I bled pressures to 24 hot (from 26) and the car feels even better. Gonna send Dean out again after lunch and go for the 1:40.xx

The afternoon sessions were no faster. Mostly
1:42's. The track got really hot and tires were starting to get greasy. Overall I am thrilled with the way the car felt
and the results. Thanks everybody for the help dialing out that turn in oversteer. Props to Emilio for sharing his expertise.

I believe a 1:41.6 is a new Miata lap record for Sonoma.

Oh man... now I see this.
(I was looking for something to do today, could have come watched you at SP.)

Sounds like the car is all set. And a new record?
Congrats!