managing kungfu grip
 

Gents,
I currently have 700f 400r xida-s on my 00 Miata. I just switched over to 15x9 with 275 a6 for autox this season. I have done one shakedown autox on this setup and found it to be a bit soft. I also use the car for track events but will use slightly more durable tires for those events.

Will 800f 500r be enough spring rate to deal with the new kungfu grip? Or will I need even higher rates than that?

I run 850/500 with the hoho's. With no aero its fine, with aero its not stiff enough. I'm thinking about 1000/600.

Ok, so it looks like I am in the right ballpark...

For track days I do have a wing and splitter but will be using my z2s until they die on me. After they are done, I may switch to a track duty rcomp, but it wouldn't be any more than a nt-01 for the sake of longevity.

You also have your aero setup for meaningful downforce at autox speed... So I can see how you would need spring rates that high on a road course with the big rubba.

Wouldn't you also need to revalve your ASTs for spring rates that high?

Oh no, the fastest this car has ever gone with the aero on it was a touch over 100mph, and that was on the highway on its way to dyno, corner weight, and align. I need the higher rates with this aero at auto-x speeds. The wing does have a "low" downforce setting if I ever track it, but its still like 600 pounds at 100mph. :giggle: I'm not sure if the ASTs need a revalve yet. They're gen 1 units which emillio listed as good up to 850 pounds in the front and 500 in the back iirc, the gen 2 valving would cover the rates I want to run. However I only run it currently 6 clicks from soft in the front and 8 in the rear with the 850/500 springs so I have the head room "in theory". I'll play it by ear. If the car gets bouncy as fuck I'll drop back to the 850/500 springs. Its not like it takes more than an hour to swap springs.

800/500 seems to be on the edge of not stiff enough for this level of grip. I wouldn’t go lower than that. A lot of the time it is about the perfect level of stiffness however. Soft enough to keep tires in contact with the ground over roughness and stiff enough to still have some travel left when loaded in a corner. I would like to try stiffer I think just to see where performance drops off. Also would like to try stiffer springs with less sway bar. Currently I run ISC sways. Front bar is set effectively half way between the two stiffest racing beat front bars and the rear is set so it is slightly softer than a OEM Mazdaspeed bar for track use. For autocross I take the rear bar off entirely.

For autocross I have a double element Cero design rear wing and splitter sticks out 6" past the bumper. For the track the splitter is reduced by 4" and rear wing is a APR GTC200 mounted high but soon to be replaced with a GT250 when I get the mounting done. 275 hoosiers on 10" for autocross and thinking about 11". 245 Hoosiers mounted 10's for the track because of NASA rules give me an advantage to run 245 and under for TT.

autocross on 275's I'd suggest either 800/500 or 900/500. Fpr track use 900 or 1000 fronts, depending on aero and weight.

At Nationals this year with medium front downforce and 225 R6's on 9's an 2150# I was running out of front spring with 800/500.
We have ran 1000/400 with no aero on 205 R6's on 15x9's and it was good an all but the roughest tracks. OTS Xidas are quite happy with 1000's.

Emillio that's great to hear on the 1000's. With the 850 fronts now I'm pretty much on the bump stops as soon as I turn the wheel. Which isnt awful since these bump stops engage so smooth. But its certainly not helping the cars front grip.

I know some are using 1000's up front to help make up for lack of roll stiffness in using stock sway bars while playing the nasa points classification game.

With my current setup rub marks indicating I used 100% of available travel including a fully smashed bump stop is quite common while autocrossing. when people set up a course that runs predominantly east/west at Packwood it can be rough as hell going across the grain direction in which the lot was paved.

Yeah and the 275s CAN fully smash the bump stops which put the tires like 1/4" into the shock tower. Part of me really wants to use the 1" 1lb rule and move the section of chassis sheet metal near the mount up a bit.

We have used 900's with a 54106 1.25" RB front bar successfully. It is not beyond reason to fully utilize 1000's on a Miata with 275 Hoosiers

Wish you guys were as light as me. This thread is making me wonder if I am running a heavy enough spring up front.:confused:

With the avons and less front aero. Hard to tell. Some of its from straight up grip but some of it is just due to aero squat, which is where a 3rd spring setup would be cool.

Hoosiers, but correct, no aero. However, more grip than the 275s and we are adding aero. At least springs are relatively cheap.

What kind of weight are you guys running these rates with? I imagine a car on sm6s that weighs 1900 wet could get away with 700/400 quite well? Big RB bar up front, stock NA6 bar out back.

My last weigh in was 2260 with a full tank. My class minimum is 2060.

See that's my issue. I have no comparisons at 1750lbs with 11.5" slicks on 12" wheels. Currently running 800/450 (I think :o ).

In general I'm always trying to run the softest springs I can and still have target roll stiffness. Lowered Miatas gain a whole bunch of roll moment from the lowered roll center. Couple that with lower offset wheels (effective track width increase) that lowers effective wheel rate then cornering at about twice the lateral acceleration of OEM (.85 vs 1.7g) and the giant rates are unavoidable. If the front suspension is bottoming and you have enough camber (good tire temps), try softer springs.

It's also course dependent. 700/400 seems to be the upper limit for standard weight street Miatas. On smoother race tracks, we run 800/500 on a standard weight Miata with no aero. Add big Hoosiers and aero and it's 800~1000 fronts

I'm at the too light end of springs. Similar weight but 600/350 springs. Added bunch of aero last year = Understeer hell. Some changes off season but no spring changes yet. Before the aero the car was pretty easy to drive. But had tiny 20" diameter FAs and 13x10 wheels. The difference in unsprung weight is stupid compared to the 23.5x11 & 15x10 I have now.

Don't take my results at events as how well the setup is. I'm pretty freaking slow. I lift way too damn much. <=:noob:

Another thing since this is autox talk, you have to consider your site(s). Some are pretty smooth, others...... I've driven another Prepared car that kind of skip over the surface due to the bumps. Softening that car by 100-150ish really helped that car.

What shocks were on the prepared car? My co-driver at nationals is a real old salt, said this year was the smoothest lincoln had felt to him. He's a koni for life guy though, last year I think he was in an ES miata on yellows, and the year before in his crx on custom valved DA yellows. I was crewing for a friend running B-mod and one of the guys next to him was complaining about the bumps hurting, he goes "what bumps? I dont feel any bumps. Must be those Ohlins".

People always talk about running softer springs at lincoln, but out of any site I've run at it's got the grippiest surface so it wants the stiffer springs, but that only works with baller shocks.

The other car was a NC based D Prepared Miata on recently rebuilt/valved Ohlins. Locally, our lot is bumpier than a cheese grater which probably part of the problem.

Most courses at Nationals have sections that have bumps/ripples depending on the line through them. This year the left/west/whatever had a section with a bump that was avoidable if you took it just right.

I'm going to have to stiffen the car more than likely. Moving to 23.5" diameter tire puts it into the shock tower/rear tub far too often.

The only bump I actually noticed was the one in the right hander after the slalom on the east course. 100% superdrifto'ed the entire offset section after it on my first run when I wasnt expecting it.

I might have slipped a bit with a hammer when installing my shocks. I like to use a big hammer. Its not too noticable.

5mm spacer is required with 15X10 6ULs on my car otherwize there is serious issues with the front near the shock tower and the sidwall of the rear will just scrape the two botheads just above the top of the rear shock in the wheel well.

??? Did you mean to say "isn't bottoming"...

I couldnt get it to move significantly with the hammer. And yeah I had my spinwerks made to the same offset as the 15x106uls + 6mm spacer. Still an issue, but not like complete death like the 6uls without the spacer were.

Doh. Yes

OK maybe a bit of angle grinder. It's actually thick right there looks more like the tire rubbed it off than you went after it with an angle grinder.

Hahaha!

Whatever it takes.

Hopefully someone can help me fully understand the relationship between front roll couple and balance. I'm in the process of overhauling my car and moving points around for the 2014 NASA PT/TT season in my 97. I was running 700/400 xidas with the thick wall racing beat tubular up front and the 14mm mazdaspeed rear. Car weight was #2105. Was was pretty good on smooth tracks lick road Atlanta but a little tail happy under acceleration at Sebring(bumpy). (EP air dam with no rear wing and 205a6).
I am now switching to stock swaybars to have enough points for a wing ( custom apr gt-250 like crusher). The "BTM" swaybars for the 97 are 19mm front and 11mm rear. So obviously I'm going to need to play with spring rates to adjust the roll couple etc.
After spending some time on the FCM suspension calculator I determined that the previous setup had a 59.3% front roll couple with an overall roll stiffness of 3900 something.
By using 900/400 with the stock swaybars it puts me at 60.2 % FRC or so with an overall roll stiffness of 3700 something. What affect will this have on the handling characteristics? I already put the 900's on but I haven't driven it.
If I went with 850/400 with the stock bars it would give me a 59.4% FRC.

Keep in mind I am planning on adding some weight, most likely around 100-175lb depending on how the new engine shakes out. And as mentioned earlier, will have the rear wing.

Thanks for any advice!

900/400 is a good starting point for your setup. I'd suggest installing brand new OEM end links. Theyre not strong and old ones might be suspect. Adjustables not an option with you points config.