Leftside to rightside weight transfer during cornering is a function of cornering g's, c.g. height, and track width. It is NOT a function of spring rate! Sway bars and different front/rear spring rates dictate how much of the lateral weight transfer is at the front and how much at the rear.

But the weight transfer side to side is not affecting the tire contact patch much yet while it is compressing/extending the suspension and the softer the suspension the less it transfers to the contact patch during this transition.

3000 lb. car with 96" wheelbase and 16" high c.g. cornering at 1g steady state is experiencing 3000 lb * 1g * 16"/96" = 500 lb. 500 lb. (total F+R) is added to the outside tires and taken off of the inside tires, whatever the spring and swaybar rates are.

The formula you provide is for steady state as you say when the suspension has "taken a set."

This is why I say a softer suspension reacts slower to input, so it is easier for drivers not to shock the contact patch into losing grip compared to the faster reacting stiffer suspension.

That does mean less sliding around for your umm... average driver.

Its like tire sidewalls.
What provides more cornering grip, a tall sidewall tire or a short low profile tire sidewall?

The lower profile tire has higher grip potential due to less contact patch distortion and less undamped suspension movement (tire sidewall flex).

However, again your umm... average driver slides around less on the taller sidewall tires so he says it has more grip.

--------------

I remember I let my s2000 friend autox my FD and he said he couldn't tell when it was hooked up and when it was sliding.

I said, exactly. What does it matter- was it heading where you wanted it to or not?

The seamless transition between grip and varying slip angles is much faster as you can guide it along the way with smaller corrections.

A softer suspension does affect the tire contact patch. That is exactly why softer rates have more grip seen not only by textbook theory but also real world experience.

What happens when you run a stiff spring rate over a bumpy patch of road. Does this effect the tire to road interface of the contact patch of the tire? Yes it does, the softer the spring rate and sway bar the more contact patch you have on the road. No road is silky glass smooth, the most compliant contact patch with the most force on the tires (all four) gives the most grip.


The reason for softer suspensions having the most grip is the outside AND INSIDE tires have the most force pushing down on the ground at all times through a corner with the most compliant contact patch. it also disturbs the body the least from bumps disturbing the contact patch.

Softer rate springs do slow down the drivers input, but it has higher mechanical grip. If you are a great driver on a softer sprung car, the car has higher ultimate grip.

When I mean softer rate springs, I am talking about optimizing the CG and running the softest spring rate possible for an "ideal" set up.

I was watching very stiffly sprung Porsche's run a hillclimb. these cars where all spinning out and sloppy as hell with their stiffly sprung spring rates. The corners and roads bumps aren't that much different from what I run on. Some set ups run really tall tires and you can see the tires damping the bumps. I am only talking about mechanical grip, not aero, and some of the cars are running some good aero downforce.

why didn't you say that!


the 911 is the worst example you could have picked, a few years ago dad and i went to rennfest at laguna, and they had 911's on the track with boxster/cayannes, and the 911 corners like a cartoon. its really obvious the engine is in the wrong place. the cayman/boxsters go through corners so much better its comical. the only reason the 911's keep up is because they have ~500hp turbo engines vs the 250hp cayman (or whatever its got, laptimes weren't all that different between the two)


off topically, after looking at 5,000 911's it was refreshing to see an Rx8. it was the most logically engineered car there. think about it, the Rx8 has the engine INSIDE the wheel base, its cooled with coolant, it doesn't have a randomly failing timing chain. the Rx8 also has a double wishbone suspension.

Plus they are cheap to attain (RX8) and handle like a boss. I might buy one in the future, wife wants a car to play with as well. which means I will be driving it mainly.

Lookatme:
Everything you've said up until now is just theory, until you actually do experimentation and actually prove your claims (which requires a closed course, and a stop watch and a lot of runs), no one on this board will take you seriously. Nothing you "feel" is valid. It's pretty common that something that feels faster, isn't.

I'm going to leave my suspension out of this, because no one on this thread will like it :) (really stiff springs and no bars)

but won't stiffer springs and tender springs get you most of the way to where you want to go?

big bars have pretty bad repercussions on bumpy roads too. They're not "free" roll resistance, if only 1 tire hits a bump (which is usually the case on a bumpy road) it's going to have a good amount of added bump resistance from the bar and it'll also try to pick up the other wheel too unloading that tire.

I'd also like to point out that the only reason this is even a talking point is because the FD has decent camber curves and bump steer (I assume) so roll isn't really that big of a deal.

but I still doubt the camber gain on roll overcomes camber loss (this never happens due to dive/squat issues) so you'll still have to run more static camber to combat camber loss during roll (to actually get a decent contact patch to generate that grip you want). This will decrease breaking efficiency, which is compounded by the greater brake dive which gains even more camber...

meanwhile with my car I just simply adjusted my brake bias so half the braking pressure (not to be confused by force) is going to the rear wheels so they can help the fronts which have less weight on them.

I'm not a mechanical engineer... but making the car more dynamic with softer spring rates seems like you're making everything much more complicated than you need to or even understand fully.

Yeah, FD has pretty good camber curve but it does not exactly match body roll.

Road course/street is usually 1-3 deg negative camber and autox is 3-6 deg negative camber.

A common misconception is a tire generates peak traction before it starts sliding. This mistakenly leads one to want to stop a tire from sliding to "preserve grip".

Tires actually generate peak traction around 6-10 degrees slip angle.

That isn't crazy angle drifting, but its what you see the F1 cars doing on the slow motion replays. If it is a 10 degree curve in the track they would be clearing it with the front tires straight in a zero counter drift for instance.

In autox/qualifying you typically come out hard at over 10 degrees slip angle to heat the tires and then tailor it back once they are up to temp -depends on tires.

So if you are slowing down when you feel the tires "slip" well, thank god and good for you if you are on the street!

But for racing peak traction is somewhere over the limit of "grip".

If you compare this footage from a safe runoff venue to the previous hillclimb venue you can see I am able to confidently drive up to the level of peak traction instead of driving up to the limit of "grip" where the tires start to slide some.

I did testing from my butt on my car. Others have done the testing. Also, a stop watch means the car if faster, doesn't mean it doesn't generate more grip. These are two different things.


The theory and observation is softer springs, sway bars, etc generate more cornering, acceleration and braking force at the expense of transitioning.

The theory is to start with the best height, and run the softest springs possible for the best mechanical grip. It does not mean its the fastest set up for every course, or even the best set up for the street or etc. Grip doesn't mean agility.


I am not claiming to know all this stuff about suspension, I simply use what I have experienced and have read in the race design books, engineers on forums who design suspensions, couple of engineers at work who worked at Chevrolet (but not in suspension dept), and see what they say.

I can understand how a slightly stiffer set up than ideal for grip might be faster due to a little better transitioning. The thing that confuses me a little is the extremes that some people are going on the spring stiffness. I could easily see a 50-100% increase in spring rates, but 350-500% increase or 4-6X the origional spring rate? It just seems that the order of magnitude from stock can't be THAT far off.

For the same reason they use rubber bushings everywhere. it's for comfort / decreased NVH. and also allowing the use of cheaper dampers.

Also, if you think about it in the terms where doubling the spring rates only halves the roll angle, ending up with a car that is 4 times stiffer for roll angles that are a quarter of what they are stock is completely valid.

I can understand how a slightly stiffer set up than ideal for grip might be faster due to a little better transitioning. The thing that confuses me a little is the extremes that some people are going on the spring stiffness. I could easily see a 50-100% increase in spring rates, but 350-500% increase or 4-6X the origional spring rate? It just seems that the order of magnitude from stock can't be THAT far off.

It is really interesting how much of it really is driver preference!

I have read a couple articles where they put a dedicated drift car up against a dedicated race car with the same tires and the drift car met or exceeded the race car's average Gs on the skidpad.

Shouldn't be surprising since a high level drift car is a race car set up to be easy to modulate front and rear grip bias whereas the race car is set up with some "cushion". It just wakes you up to the difference in real peak traction and stolid "grip".

Yeah, put me in the cars instead of the professional driver and I am sure the race car would turn out better G numbers on the skid pad since I wouldn't be able to "balance" the drift car at peak traction.

the Rx8 is so close to a great car its sometimes painful. the chassis/suspension is world class. its telepathic, very quick, and yet it rides great and has no vices. you can do STUPID things behind the wheel, and the worst that it does is pause, as if to say "really?" but it never bites.

its a good greatest hits of all the Rx's. its direct and simple like a 1st gen, its composed and utilitarian like an FC, and is still sharp like the FD.

it misses on it being a bit portly*, the styling in and out is a bit fussy, and there are things like the tail lights filling with water which, if you look how the drain is supposed to work, its either funny or sad.

its built like a lego, parts are cheap, and reliability is not nearly as bad as you'd think. the average Rx8 went ~80k with nothing more than oil changes

you don't need to watch the entire thing, but just skip to the FD and look at the body roll! and then watch as Mazda stiffens it up as it goes along.

EDIT: lol you don't need to watch it at all, look at the cover, that is your FD spring rate

You are misunderstanding the "theory" and misinterpreting your "real world experience"!

Not at all times. Hit a bump and with stiffer springs the contact patch gets bigger, quicker as it loads up more quickly. On average, the car continues to be supported by the road so on average the contact patch area (function of inflation pressure, tire stiffness and weight) is the same either way.
No, total force on all four tires on average is the same either way. More compliant springing does generally maintain more *even* force distribution over bumps, though.

Maximum ultimate grip is going to be similar with stiff or soft springs. However with stiffer springs you don't need as much static camber to develop maximum lateral grip, so you can indeed have MORE GRIP overall for cornering and braking and accelerating with STIFFER SPRINGS.


NOT TRUE. Total lateral weight transfer is THE SAME for a given level of cornering g's whether you're on stiff springs or soft. And either way you have tuning control over how much of the transfer happens up front vs. in back to tune under/oversteer.

??? The c.g. is fixed. "optimizing the c.g." means moving masses around. Adjusting coilovers pretty much only affects c.g. height and not fore/aft or left/right location. Choosing spring rates has nothing to do with "optimizing the c.g.", though c.g. location will certainly influence optimal spring rates.

Hot Version Touge Challenge series uses the Gunma Cycle Sports Center track for a simulation of real mountain roads and pits tuner cars against eachother.

Cars are judged not only on fastest time, but on safety/comfort of set up for real world driving conditions with particular emphasis on suspension compliance- this course has lots of bumps.

RE Amemiya has dominated with FDs winning 3/4 series from 2004 to present. Most recently, I was blown away to see the stock turbo FD defeat the 650hp R35 GTR.

The Touge Monster FD uses DG-5 RE Amemiya Spec coilovers-
16K Front
18K Rear

This is on 255mm street tires!

Normal DG-5 FD coilover spec-
16k Front
14K Rear

Obviously, there is more than just spring rate to consider when a compliant, safe set up is being built.

I have seen all those clips. I know the japanese run high spring rates. The only thing that is different between what I do and them is my rates of speeds are higher than those cars. The togue is a small slower course, the straight they get into 3rd gear, but much is 2nd and 3rd. Where I see my car starting to go crazy is middle to top of 4th gear where the car has lots of problems with bumps. the high rate of speed is where the problems are. The speeds under 100mph aren't much of a problem with higher rates and bumpy roads. Those rates would be horrid going 120+mph on a bumpy road.

picture of the suspension on one of their cars.

They test the cars on the whole course. The timed section is the tight 2nd, 3rd and 4th section where vehicle handling counts.

The suspension test segment (over the gap) is filmed on the front straight.

Those rates would be horrid going 120+mph on a bumpy road.

It is speculation without driving the car. They seem to like it.

most race drivers want a car that responds very fast, but is predictable. they last thing you want is to be waiting around for the car to take a set.

as we know that "taking a set" is related to maximum grip, which is related to lateral G forces, the time it takes to "take a set" is a function of spring rate, and damper settings if they are too stiff

Here are the full laps for the driving impressions sessions on the MCR R34 and RE Amemiya Mahoo FD3S.

You can see the FD is in 4th at 4:50 (suspension check point), 5:21, 6:22 (touches 4th), 6:29 and 7:41.

In the faster R34 he is all over 4th and 5th on this tight little bumpy course.

All because the cars handle safe with their high spring rates.

Driver preference!

Here are specs from a 90s WRC tarmac setup:
Impreza 555 Group A specs

This is a professionally setup championship racecar with as close to similar driving conditions as you're going to find:

SUSPENSION
Bilstein MacPherson struts
Front (lb") Rear (lb")
Tarmac: 400-600 250-450
Gravel: 160-275 130-200

Front (mm) Rear (mm)
Anti roll bars: 15 17 20 25 28 28.5 30 15 17 20 22 25 30

Those rates are on mcpherson struts 1:1 motion ratio so the similar FD rate would be significantly higher.

If you use the formula that is supposed to convert to wheel rate 400 lbs/in wheel rate = ~1100 lbs/in on a 0.6:1 FD suspension or 19.6 kg/mm...

600 lbs/in = 1600 lbs/in or 28.5 kg/mm

i got curious, and rounded up the specs on all the JDM suspension sets i could find, and the average rate in the FC is 7.725F and 6.35R. its pretty funny that its exactly what the common wisdom is. 8/6.

For traction over bumps at high speed damping is going to be more important than spring rate.

Why? Spring rate is a rate (force and distance) and the hydraulic force to move the piston at a given velocity is a constant.

So, over small bumps at high speed compression damping is the main actor.

http://www.optimumg.com/docs/Springs...Tech_Tip_4.pdf

Blue, did you ever weigh your FC?

Yup, but I never did weigh the FC after I switched to the slightly lighter turbo set up. Probably only 5-10lbs off front end.
----------------

FC spec-
SSM compliant (full base interior/options) with the single exhaust was-

No driver, 13gallons gas

706__________647

_____2665

657__________655

Left=51.1%
Rear=49.2%
RF/LR= 48.9%
Right=48.9%

______________

With driver, 13gallons gas

777__________661

______2865

731__________696

Left=52.6%
Rear=49.2%
RF/LR= 49.8%
Right=47.4%

______________

Older FC spec
SSM compliant (full base interior/options) with the dual exhaust was-

No driver, 16gallons gas

688__________659

______2711

698__________667

Left=51.1%
Rear=50.4%
RF/LR= 50.1%
Right=48.9%

___________________

Older FC spec

With driver, 16gallons gas

772__________660

_____2909

766__________713

Left=52.6%
Rear=50.8%
RF/LR= 49.2%
Right=47.4%

Thanks! I wanted to see if I was close in weight to equivalent horsepower rotary FCs. I have the rear interior, carpet, headliner, audio and HVAC pulled, added a 4 point oll bar, front BBK, accusump and 9.5 quarts of oil, 275 tires all around on 17x9.5 inch wheels, dual 3 inch exhaust, aluminium hood.

I'm at 2686 full of fuel, no driver. 52.8% front, 50.1% cross.
2908 with me in it and 51.8% front.. Need to adjust cross weights for driver.

It looks like my V8 car has the weight bias 1% more to the front than yours.