goin reverse stagger, maybe...
 

I'm thinking about going 255/40-17 front with 235/45-17 rears for Palmer next month, maybe even 255/225 :drinking:

I get a mid-corner push in some corners on 245-square with my unadjustable-except-front-camber setup, and wear the fronts much quicker than rears. Seems like it's worth a shot to try to beat the Miata that got me by less than a tenth at NHMS!

Anyway, just throwing this out there to get ridiculed and then do it anyway :cheers:

Can you stiffen up the rear bar? Is front camber maxed? Wondering if you decide on a reverse stagger if you can't just run something softer in front instead?

Stock non-adjustable sways, front camber at -3.5/-3.9.
Springs are Swift Spec-R: 4.4 F, 5.3 R (kg/mm), Bilstein B8 struts/shocks.
Car is 1.25" lower than stock all around. I think I'm soft enough that I'm riding on the outside front bump stop during hard cornering.

It'll make what you think it'll do (make car more tail happy) but it will do so by removing grip from the rear, not adding to the front. I dont think it'll be faster, my opinion, I have 0 experience behing a reverse stagger in RWD applications.

In other ideas, have you tried using spacers to change track width at one end only?

It'll make what you think it'll do (make car more tail happy) but it will do so by removing grip from the rear, not adding to the front. I dont think it'll be faster, my opinion, I have 0 experience behing a reverse stagger in RWD applications.

In other ideas, have you tried using spacers to change track width at one end only?

The camber seems about as much as you'd want. Ultimately you want to work on the end that is troublesome however it sounds like you've done about all you can do with the front of the car. At that point the rear needs to be considered. Balance is balance. Even though you'd be taking grip from the rear you may reduce push enough to make it worth it.

Going from 245 square to 255/235, for same overall tire points for classification (i.e. same competition weight).
So yeah, I am effectively trading rear grip for front grip and not just throwing away rear grip.

Or I could go 255/225 and shave off a few pounds!

Neither have I, but in this case, given modest power, 53.5/46.5 weight distribution, and a setup that *obviously* overloads the fronts and underutilizes the rears, seems like a decent approach.

Other pertinent related info: 245/40-17 A052s won't be available until after event at Palmer, but 255s, 235s, and 225s are in stock...

I have 3mm spacers, so not really enough to make a difference. With stock-length ARP studs I wouldn't/couldn't go any more than that, so the answer is pretty much no adjustability here.

Unless you zip tied your shocks to confirm you're on bumpstops that is a very broad assumption.

I'd rather play with rear camber and/or toe to your liking rather than take away tire...

Besides that, sounds like you need a shock revalve

I have no insightful knowledge to share but it will be interesting to learn of the outcome if you go through with this idea. But I agree that the car does tend to push at the limit.

In the end it doesn't matter whether it's that I'm into the front bumpstops or something else, but running out of front travel was a real issue with the Sachs struts, less so with Bilsteins but I'd bet I'm into the stops a bit. Which is actually a *normal* thing with these cars anyway...

But long/short, I need more front grip and this is one way to get it, whether the "problem" is lack of front bump travel or not.

Again, I'm not "taking away tire" overall. I'm adding tire to the end that's WAY into the nonlinear/non-productive portion of the load/grip curve, and taking away a smidge from the end that doesn't need it.

Rear camber and toe are where I want them, don't have the sheet in front of me but rear camber is -2.75ish and rear toe is in the zero to 0.1 degrees total range.

It's a mid-corner push, it ain't the shocks...

I too have removed grip from one end of the car to adjust balance, it never resulted in a faster time unless I was driving like an idiot before and then decided to drive less like an idiot, but it was always more fun to drive.

If you gave me your car to make quicker I'd toss a front sway bar on it (19-20mm), zero the toe, and stay 255 square. The front sway bar has shown to improve the front end grip and responsiveness over and over again.

That is assuming there isn't a driving issue that can be worked around. All this internet advice will pale in comparison to someone who knows their shit taking your car for a few laps.

That's weird, I don't have bump stop issues at all...

You're running a compromised setup trying to maintain point compliance.


IMO rear camber is too high especially if you're having mid-corner push. Shocks on entry can help you with aiding rotation, because that's really what you want in the end right?

To each their own, but this is a very backwards way to deal with a setup issue.

One more time, I'm *adding* grip to the end that needs it. Outside front is well into the nonlinear portion of the load/grip curve, outside rear not so much... Adding front tire and taking away the same amount of rear tire should give an overall INcrease in grip. Critically, it should allow me to get harder on the gas sooner exiting critical corners without the front end washing out as much, which should benefit me all the way down the straights.

Tires ordered so we'll see!

That would take away front grip and exacerbate the problem. Thing to do would be bigger *rear* sway bar, but then I'd have to add 41 lb. and possibly get into the realm of unloading the inside rear too much for the Torsen to deal with.

Rear toe is near-zero. Don't have the sheet in front of me but it's a bare smidge of rear toe-in, in my experience (and I've experimented with rear toe a lot, intentionally and unintended "blind" testing) 0.1* isn't hugely different from 0.0* for mid-corner balance. It's around 0.05* total IIRC. There's nothing *magical* about zero rear toe, optimal toe is a range and -0.05* to +0.15* doesn't make all that profound a difference. Particularly for a relatively softly-sprung zero-downforce street car on "street" tires...

I've never run 255 square. 245 square at the moment. I've also run 235 and 225 square.

Maybe for autoX, but it's gonna hurt mid-corner front grip for sure.

He already has ;)

Also maybe look at your throttle input and see if maybe too early?

I said the same thing until I did it, the front rolls too much with the stock sway which reduces overall grip. Didn't decide to do a full suspension analysis just took the win and rolled with it.

Good luck.

Is your setup identical to mine? -1.25" lower so that's a lot of bump travel gone right there, plus another 3/4" or so taken away by the Raceseng camber plate roller bearing.

Every setup is a compromise... But yeah, mine is particularly compromised because it's my daily street car as well, otherwise I'd get good coilovers with much stiffer springs.

Speaking of "throwing grip away"... If reducing rear camber *helped* the issue, it's only because it will have taken away lateral grip at the rear. No bueno...
Again, the problem isn't rotation on corner-entry, it's mid-corner push.

IMO I think it's pretty spot-on. Reducing rear camber is the backwards way.

Outside front is for sure overloaded. Adding 10mm width up front should add a decent amount of front grip. Outside rear is underutilized. Taking away same 10mm of rear width will not take away as much rear grip as what I'm adding to the front, as the outside rear is in the more linear portion of the load/grip curve.

In the end I don't expect the change to be profoundly earth-shattering, but should help a bit.

Thanks!

But note that front and rear roll *the same amount*. Unless you're getting a HUGE amount of twist in the chassis! I.e. you'll reduce roll at both the front and the rear with a stiffer front bar, or with a stiffer rear bar.

Get rid of the roller bearing and go standard thrust sheets would help a ton. I personally hated their bearing design because of exactly that, it takes up bump travel.

As far as me, I'm fairly low as well...I don't run bump stops and never have had issues. I have MCS 2W so the canister is outside the shock which alleviates any and all travel concerns. Obviously I know you're point limited so a 2 way shock especially remote isn't the answer, but there ARE solutions to common issues on this chassis.

https://scontent-ort2-2.xx.fbcdn.net...74&oe=60C875AA

Regardless, I'm curious to see what the result is. Doing back to back testing same day?

That's part of the problem, having to delay full throttle. I'd like to be foot-to-the floor *sooner* to improve exit speed, in addition to carrying more speed mid-corner. Need more front grip...

Yeah, I was strongly considering machining down the Raceseng upper mount (stock-diameter spring size) and eliminating the radial bearing and letting the spherical rotate. Bad idea some peeps assured me! Throwing in some kind of low-profile rotational thrust bearings w/ needles, or thrust sheets(?), maybe even Igus bearings, and getting back that bump travel would be a good idea!

Yeah, I think one big part of it is I'm set up a bit soft for the track at 4.4F/5.3R... Bumping that up to 8/10ish and getting stiffer front and/or rear sways would be a lot better for track.

Yeah, I'm going to put the A052s 255F/235R on for 1st session on June 19th then go back to 245/40-17 square CR-1s for my other 3 sessions of day1.
For day2 I'll put the A052s back on for practice 1, if they seem like their def. gonna be faster than CR-1s I'll just leave them on for practice 2 and then run them in the time trial.

So yeah, testing A052 vs CR-1 at the same time as 255/235 vs. 245/245 :bonk:

Depending on your shaft size, MCS sold a set of SCCA Compliant stock spring perch set. Might be worth taking some measurements and getting away from Raceseng's perch (or fabbing up your own).

I have a small spacer I made that's probably 3/8" in total height on top of my normal spring perch with these guys on the top and bottom, FWIW:

https://www.swiftsprings.com/products/misc/

Personally, I think that adding a front bar is worth an additional 41 lbs. In lieu of that, I'd go stiffer on front springs if possible.

If front grip issues are related to roll stiffness, adding front grip without stiffness is only going to exacerbate that by getting you to that unhappy place earlier in the turn. And possibly more frequently. And you've added a gearing and rake change to the equation.

If mid-corner front grip issue is related to roll stiffness (whether due to front camber loss or outside front on the bump stop), better to add roll stiffness to the *rear* of the car, not the front. Fronts are palpably overloaded during steady-state cornering, and front tires are wearing a lot quicker than rears. Adding roll stiffness to the front is a backwards idea, it might alleviate camber loss and being on bump stop by a bit but that would be offset to some degree by the increased front roll stiffness acting to load the outside front. I'd sooner add rear roll stiffness to achieve the same end of reducing mid-corner roll, while redistributing some of the cornering load off of the outside front and onto the outside rear.

With the same roll stiffness (which is what it's going to be as I'm not going to trouble with sways or springs at the moment), going to wider fronts should increase the load at which the grip/load starts to nose over, so grip should be improved at the same load. We'll see!

You're sorta making the argument I once heard regarding a tire test where lower-profile tires on +1" diameter wheels tested at less lateral grip vs. same make/model same-width tire with a taller profile on smaller diameter wheels (similar tire OD). Tire representative said: The +1 is making more grip, which gives more roll, which causes LESS grip. So yeah, arguing that having MORE grip gives LESS grip, hmmm...

Gearing:
My fellow BRZ class competitor and I compared data between his '13 and my '17 (both at the limit of class-legal points, equalized on power/weight) at Palmer. 4.1 diff vs. 4.3 diff. We turned similar lap times and our acceleration plots down the straights fell right on top of each other. Going from 245/40-17 to 235/45-17 rear tires is same as going from 4.3 gearing to 4.17 gearing. I'm not worried about losing time from that, at this track. "Better" gearing isn't always faster at the track anyway...

Rake:
Going from flat rake with square tire setup, to 25.2" OD 255/40-17 fronts and 25.5" OD 235/45-17 rears gives 0.15" more rear ride height, sin-1(.15"/101") = less than a tenth of a degree change in rake. That might make a difference on an F1 car, not so much on a softly-sprung, "heavy", near-zero lift/downforce BRZ.

In the end, this is an experiment, if dry weather is forecast I'll take both sets of tires, 245/40 square and 255/40 front 235/45 rear. If there's time and I feel like it, I'll also try "normal" stagger with 235F/255R.

Thing is, the 245s are Nankang CR-1 and 255/235 are A052s, so that's a big joker card right there!

In fact the main reason I'm doing this is because I was beaten by a tenth at NHMS and I want to see if A052s will give me an advantage. But 245/40-17 A052s aren't available until after Palmer event! While 255s, 235s and 225s are. Reverse stagger had been a goofy notion I've thought about doing with this car for a while, given how much it abuses the outside front. This situation kind of gives me the excuse to try it ;)

Okay.

Recently I experienced something similar. Maybe you can learn from my mistakes. Recently my front right height was lowered by an alignment shop. Suddenly the car would understeer in high lateral g turns. I raised the car back up to where I had it before (a little more than one inch lower than stock), and the understeer went away. I raised it a little bit at at time, and each time it got better.
If you really want to address the root cause, I doubt wider tires on the front will do it. It may even make it worse if you are getting into the bumpstops.

Yeah, again my suspicion is I'm on the outside front bump stop, loading up the outside front.

Ultimately might go to RCE Tarmac springs to raise ride height about 1/2".

In that sense, the way to make it "better" is to go slower. Hell, going to 205 all-seasons all around might make it "better" in the sense of not having nearly as much roll and not being as hard into the outside front bumpstop, But ultimately I'm looking for tenths of a second in lap times, so I'd rather carry more speed and be a bit further into the bumpstop. If I end up with the same mid-corner push but at a higher speed, that's progress.

Anyway, hopefully time allows and I will be able to isolate the differences between A052 and CR-1, as well as the differences between front- and rear-stagger.

I have nothing productive to add but just a reference point for reverse staggered. I have a buddy with an RS3 and it seems they run reverse staggered from the factory which is certainly interesting. 255/30r19 & 235/35r19 which sounds awfully similar.

No, that would not address the root cause. The root cause of your understeer isn't too much grip, although it is a factor. If my theory and personal experience hold true in your case as well, the root cause is ride height and/or spring rate which determine how much you get into the bumpstops.

Yeah, I agree, my thoughts exactly. Higher ride height and/or more roll stiffness (via springs or sways or both) would help if I'm loading up on the outside front bump stop. I don't think that trading 10mm of rear tire width for 10mm of front tire width will make it worse, though. More speed through corners is a plus and any additional understeer by being harder on the outside front bump stop should be offset by additional front tire grip, and having the outside rear closer to the nonlinear portion of its load/grip curve.

See how it goes! If it's still an issue I might get those Tarmac springs. Or get coilovers...

I also think the fix would be to add ride height and roll stiffness.

If you haven't tried adjusting your line or driving yet, I would try to get the car rotated more on corner entry and go for a point-and-shoot approach. Do you have a video clip of this track?

OK, I changed my tire order from 255/235 reverse-staggered to 235-square.

Thanks to all who contributed their $0.02! I decided that it would be a better approach to increase roll stiffness than to go with wider fronts. 245/40-17 A052s aren't available, so going with 235/45-17 and using the half-classification-point saved to partly offset the 1-point added with aftermarket sway bars. Might need a few pounds of ballast, but can use that to slightly improve weight distribution...

Thinking about getting Eibach sway bars, if anyone has opinions feel free to share here or in the separate thread I made. Specifically interested about Eibach sways compatibility with Bilstein B8, -1.25" ride height (on stock-diameter springs), and maxed out front camber at -3.9 degrees (via camber plates).

Thanks again, all!

I don't even track, but this thread was educational. Thanks!

Good move. I've run 225,235 and 245 squared with NT01's and I like the 235's the most. I have the Eibach bars and B6 Bilstein's, dropped 1". Great combo. Camber is -3F and -2 R. The bars were at the soft setting and was getting some push so will be stiffening the rear with the adjustment provided.

I really like 235's square as well. Though I am running 245's in RT660 and 235's in SX2 this year.

The 235's just feel right. Great combo of grip and responsiveness IMO. For FI I think the 245 or 255 would be the call

So what was the outcome?
Is this NASA or SCCA TT?

Good result at Palmer (CW), where midcorner understeer can be an issue. Much improved with the Eibach sways (front at softer setting, rear stiffer setting)! Better balance through 4, better drive onto the straight between 4 and 2. Won TT by healthy margin, 0.78 sec. Won next event at Thompson as well. Competition bought new Hoosiers for the next event at Palmer (CCW this time), and killed me. But I got him back at Watkins Glen. I'm up by a couple of points going into New Hampshire South Oval this weekend.

This is with COMSCC, regional club here in New England.
https://www.comscc.org/events/results/

(For infrequent thread checkers like myself)
The good results are from 235 square, not reverse stagger?

I ran full tread-depth 245/40-17 A052 rears with 235/45-17 fronts one session at Watkins Glen to check how the gearing would be, but the rear was way less planted vs. the well-worn 235s and I went slower, so I just went back to 235 square for the TT. The plan had been to run sticker 245s all around for the time trial...

I ran New Hampshire Motor Speedway South Oval this past weekend, I ran the newer 245/40s all around for Saturday's sessions. 1st practice Sunday was on 245/40 fronts and 235/45 rears, I didn't change fronts due to front right lug nuts being kinda "stiff" and not freely spinning off, so I just torqued them back down with the 245s up front. I set similar times as Saturday (1:14.3) despite errors and the track being slower (i.e. known references were going ~1/2-sec to 1-sec slower. The gearing was just way better with the tall 235/45s, saved me an upshift before entering the South Oval, before Turn 3, and before Turn 11. I did 2nd practice on 245/40s all around and did a 1:14.77, so I went back to 235/45-17 rears with 245/40-17 fronts for the TT. Made mistakes and didn't go faster but 1:14.79 was good enough to win my class by a lot and barely get the COMSCC T50 lap record :)

Now I'm even more confused :bonk: