Fronts at 800 = 14(.2) kg, that is understandable.
Rears are more of AX special, 1400lb = 25kg

Think about it 14/25, ...its not your average Joe's top pick.

It's interesting how the front rolls under side-grip load, that looks to be quiet a "big angle".
Have you tried to estimate roll-angle: front outer wheel seems to have just enough camber- and caster-induced camber, to match the load-induced chassis roll: great.


For my own sake, this tells me for track application, something about 14/16 kg front/rear is enough for 335s so more than enough for 295s. And with little less grip I may get away with 12/14kg rates using your uprights and 295s.

 

A lot of what you see in my roll angle is certainly driven by the steering angle that you wouldn't see on track. But rear spring will basically be how much can you tolerate. The more rear spring you run, the more front grip you'll see. So you have to find your own comfort zone on rear bias to find how much spring you cant drive. At sub 100mph speed, I can just crank it to the max but on track I would certainly use the bars to help stabilize things if the aero balance wasnt enough.

Its now time to figure out how to use 100 lb/in more front spring (rear springs will grow as well) . But cant do that on shocks I have.

 

Bro-stance lol. You really do have significant ride height in the rear to clear a 25.6" tire that much.

Not a ..huge..fan of the blue, would deff prefer the gunmetal. But at 900 bucks a wheel I'm stick with the TC105's for now lol. I say that now right....

 

If the fenders werent cut, I would be sitting the fender thru the tire for reference. I cut about 2.25" up and I have 2" of clearance.

And the blue is amazing! Ive never had so many comments on a wheel at an event as I have with these. They seem to be most a hit. But at 20lbs for an 18x12, thats why I have them

 

You've got the matte blue gunmetal, right? That picture explains "make the front do more work" and your spring rates so well.

 

Rather than running such a high rear spring rate, why not run a really big rear bar? Is it about bumpy surfaces and minimizing weight, or something else? I’ve wondered if I should go to a smaller rear bar than my 27mm solid bar and increase rear spring rate but am unsure.

 

Ya Dallas, why all the rave about springs And here comes the SSB school of roll lol.

 

Hahaha

Well I cant prove it but I feel the rear bar needs something to torque off of and once you lift the wheel in the air the bar is about done contributing. So more rear bar only goes about so far. My rear bar is also at 35% of overall rear roll rates and going beyond that is starting to do funny things with shocks in bump vs roll.

I will try a couple things at the ProSolo this weekend. First I can raise the roll center a little more with my adjustable ball joints. Im at 0 or +5mm right now but didnt change after I lowered when I cut the fenders. So I'll go the max +10 so it'll be +60mm total correction from stock. On the second session Im going to run the front bar at full stiff (OEM with cusco brackets) and see if that gives the rear bar more to leverage on or if it just causes push. Then I'll take the combo I think is best for sunday morning.

 

By your line of thinking it does have leverage, it'd be pushing against the opposite side wheel and spring, no?

I think bar translation effort may be something to look into. Removing friction from the bar will give it a more predictable and smooth input as roll rates change through a corner. It's the reason I showed you those solid mount brackets I'm making 😬

 

The part that I havent figured out how to prove in math is my empirical test where I tried equivalent front roll rates but one being no bar and high spring vs a little less spring but soft bars (the actual numbers worked out closely, it was 900 without spring and 750 with OEM bar on soft). Without the front bar the car was a mess, I tried for a year to get the back end to do anything and kept ramping up the rear bar from my hotchkiss 25mm hollow bar up to full stiff on the 26mm bar. It just didnt do anything till I added front bar. So Im adding it to my testing this weekend also to see if the front bar again gives more leverage for the rear bar to work on.

 

Dallas,

Interesting that you had to put in your front bar to get the rear to work.
In UK it was a "secret" setup by APtuning and their friends Ross Sport to remove the front bar, raise roll-center with ~1" long Momentum Motorsport Ball-Joint Extended Studs.

Maybe because it is often wet, it had some different effect, but I doubt it. Miata - I had 6 of them - also theoretically works good without front bar, on soft springs. Once you up the springs, you can almost remove the rear bar, but you need to up the front bar for car to 'feel right".

Will you try a stiffer front bar? Like WL 26mm? To just see what is the effect?

 

I certainly tried to make the no front bar setup work, for a year. And I would love to not carry the bar weight up front but it just never felt right and things got significantly better once I added it back in.

Seems the bar has two effects, the main being a single axles roll rate change and subsequent change in that ends contribution of total weight transfer. And also a cross talk between opposite corners. And again I havent tried proving this with math or modeling, its just a feel from trying so many combo's of springs and bars.

Will report back after next weekend the effects in 5mm RC adjustment, and 30% bar adjustment (will change on different sessions of course).

 

Just took a lunch break to swap out one of my old ball joints with the new adjustable style and I had an OEM length in there. Wasnt sure if it was OEM or +5 so that makes me happy the adjustment will be the max range going +10mm of extra correction raising RC about 30mm. Also adjusted the steering link for bump steer, that part is important. WIthout a bumpsteer gauge, making the steering arm parallel with control arm gets you very close since front camber gain isn't something we typically have. YMMV though.

 

Adjustable Ball Joints: please tell us a bit more, Dallas.

 

My control arms have a ball joint with 2-5mm spacers. So it gives an OEM to +10mm adjustment.