Higher Speed Transitional Handling, 911

[moneymanager]

Are we pretty much agreed that:
lowering the car reduces weight transfer?
stiffening the torsion bars and/or sway bars speeds up that weight transfer?
raising the shocks rebound/compression settings slows the speed of that weight transfer?
If these are true, it would also seem true that weaker torsion and/or sway bars wouldn't speed up the weight transfer so much, so would want to be paired with shocks on lower settings whereas,
stronger torsion and/or sway bars, which speed up weight transfer, would need to be paired with stronger shocks?
Is that about it?

[Pete R]

I'm just wondering if something simple like a larger rim with a lower profile tire may help him a bit. It sure took of the floatyness (I know that probably not a word) out of some of my cars

[Flieger]

Yes, you have it right.

Although, on the stffer dampers thing I am still not confident on saying stiffer is better here since I think there may be a difference between driven vs. undriven vibratory response and therefore load on the tires.

[Plavan]

Jim,

If I can find my notes (or look on my shocks for the stamping) I'll share my "secret" Bilstein valving with you. It seems to work well. I have 22mm/31mm hollow bars, with Tarret sways front and rear.

Always good seeing you at the track.

[moneymanager]

Thanks Max and Chad and everyone else who chimed in earlier. My shocks are headed to Bilstein for a little work, even as we speak. I'll report back on results.

[Flieger]

Question.

Does the weight transfer occur with a noticable delay after you get the wheel turned? Is that what is "spooking" you? If so, then you need to go stiffer (and with re-valved dampers to match) because the suspension is getting onto the bump stops.

If you are actually experiencing too fast of weight transfer, then you need to go softer. If the car just seems twitchy, then it may be too stiff.

[moneymanager]

No the transfer/lateral acceleration is instantaneous and goes away when you get to steady-state cornering. Don't think I'm on the bump stops.

[Flieger]

OK, then that sounds like too stiff.

[jluetjen]

[Flieger]

I was just trying to make sure I had not gotten away from his original comments in the course of the discussion and that I understood them correctly.

[Evan Fullerton]

I fail to see how you could possibly be too stiff with 23/26 torsion bars though I disagree with the balance, (ran 19/30 with my old set up and initial testing will be 24/550lb/in with the new setup) but let us know how it feels with the re-valved shocks.

Yes, I am ignoring swaybars but for reference my old set up was 22 Turbo front under body no rear and new is 28 front/20 rear as an 80/80 diff is part of the new mods. Should be a fun weekend at Buttonwillow in a few weeks shaking down the new setup.

[Flieger]

Well, if he says the weight transfer is too quick, it sounds too stiff to me. You have to count the anti-sway bars as well.

But, really, if the driver has to slow down because of the weight transfer being too quick for him, then the car is "too stiff". So "too stiff" can very between drivers and tracks.

[Plavan]

I have been in his car on the track. I believe he means that it "Rolls" quickly, with alot of movement, which makes it unsettling. I think his new shock valving will be very helpful. It is in no way too stiff.

[Flieger]

OK, I will defer to those who have actually driven the car. Kind of hard to diagnose over the internet.

[RaceProEngineer]

Is it just me, or is there an echo in this place?

Originally Posted by moneymanager

There are three places on our local tracks where I brake (generally in a straight line) to near 90mph and then enter a long sweeping turn. In each case I'm sure I could enter (and come out of) the turn faster if I weren't spooked by the abrupt shift of weight to the outside tires on entrance.

Originally Posted by cstreit

Transitional handling (weight shift) is managed by your shocks. Once your springs and sways are setup properly, I'd take a look at what you have for shocks.

Originally Posted by RaceProEngineer

Here you are identifying TRANSITIONAL chassis ROLL. As Chris so aptly points out, dampers play the primary role (not ROLL) here, combined with very smooth steering input, as others have said. In the absence of adjustable shocks, very STIFF dampers, ones that react slowly, will help here. At a minimum, the valving in your Bilsteins needs to be in top condition, and matched to your torsion bars.

Originally Posted by Evan Fullerton

To the OP, I would recommend getting your shocks re-valved for your current suspension and weight as from my personal experience new off the shelf Bilstein Sports are marginal at best with 30mm rear T-bars and get worse with age.

Originally Posted by burgermeister

I recently experimented with the adjustable Konis on my car. I was really surprised what a (positive) difference stiffening the shocks made during turn-in. Stiffening the rear more than the front made an even bigger difference on my intentionally understeering set-up. I am running a very soft car (19/25 Torsion, 23/23 ARB almost full soft).

So I agree empirically (as well as theoretically) with the "stiffer shocks" suggestion.

Originally Posted by Plavan

I have been in his car on the track. I believe he means that it "Rolls" quickly, with alot of movement, which makes it unsettling. I think his new shock valving will be very helpful. It is in no way too stiff.

[Flieger]

I was saying softer because I thought the weight tansfer and load spike on the tires and loss of grip were what was causing his uneasiness. If it is just body roll, then stiffer springs and a higher damping ratio is better. Softer was directed towards his comment about the abrupt weight transfer.

[RaceProEngineer]

Max,

I thought you had the earliest, the simplest, the best, and the least expensive solution right out of the gate:

Originally Posted by Flieger

You could try lowering the car to reduce both the total lateral load transfer a bit as well as have a greater effect on the roll center height.

I even said so . . . . .

Originally Posted by RaceProEngineer

As usual, Flieger has gone straight to the heart of the matter, with the simplest and least expensive solution with which to start.

[Flieger]

Yes, but he does not want to lower it anymore for street driving reasons, and if he did then I believe the roll center would drop more than the CM would, therefore increasing the roll couple since the tires would be a tiny bit grippier and the lever arm to the CM would be longer.

If he is being unsettled as a driver by the roll, then the car is too soft, even if that means the car may sacrifice some grip. (It could be a wash due to the camber changing less.)

He initially said the weight transfer was too quick but I cannot be sure if he has correctly diagnosed his problem (no offense Jim). Many pro drivers can't tell engineers what they want to know but they are retained due to natural talent. I believe Senna fell into this category somewhat. The true greats like Mark Donohue can engineer their own cars, of course, and the good drivers know how to talk to the engineers.

[jluetjen]

Really a good question might be how old are the shocks that moneymanager's using?

[moneymanager]

Moneymanagers shocks are 8 years/30k miles old. They will be as new in a few days! And stiffer.

Thanks Max for putting your finger on the issue. Like Senna, I can't precisely describe what my problem is. Fortunately for both of us, our talents made/make up for that!