BODY ROLL !!!

[monkeyboo]

Didn't know there's so much body. Already maxed out on the track pack. I dont really feel the body roll affects much on performance but it sure looks awkward.

[JLSELISE]

Would you prefer this ?

[Bavarian Motorist]

The RS behind you laughs at your body roll.

[Certified Lotus]

I've got the same issue. It does impact your cornering ability and time around the track. My friend, who bought Shinoo's Exige, goes around corners completely flat......primarily due to the Nitron GT3 shocks (which I am putting on my car). I have noticed that all the "pure" track cars have very stiff suspension that allow them to corner like they are on rails (plus slicks).

A guy I met at the track, who runs competiton Subaru's, told me that the right suspension upgrades are the best money spent over anything else you do to the car. He would be correct.

[fpitas]

The British guys swear by larger front roll bars:

Elise Parts -  >  > 1" Adjustable Anti Roll Bar

Elise Parts -  >  > Adjustable Anti Roll Bars

If you have questions they're good about answering emails. I'm very happy with the 7/8" bar I got from Blackwatch, but I'm not sure Fred carries them anymore.

[dmh]

...but there is no stock rear ARB. ARBs are best suited for mid corner, steady state, control of roll. The preferred method is to use triple adjustable dampers that allow for control of slow speed compression. Roll is a dynamic, low speed damper rod movement as experienced on corner entry and exit, braking, and throttle shut down.
(Important -- Just make sure your dampers have enough rod travel for tracks you drive on. We worked diligently with JRZ on this issue all summer long.)

[MickOpalak]

Remember, if your car is not a strict track car, some compliance on the road is very important.

[xtn]

Body roll BY ITSELF doesn't make any difference in lap times.

In his books Carroll Smith discusses this issue at length. He says that you want the car as softly sprung as you can have it while still meeting the criteria of not hitting the bump stops or reaching amounts of travel that are undesirable for reasons of bad camber curves.

He says that springing a car any higher than is required to meet those criteria actually makes the car slower assuming there are any imperfections on the track, and of course assuming you know how to set up your damping characteristics properly.

I personally found that a bit stiffer springs did help me go faster. But it wasn't because they made the car faster. It's just because they gave me a bit more confidence in the feel so I began to push harder.

xtn

[fpitas]

Originally Posted by xtn

Body roll BY ITSELF doesn't make any difference in lap times.

Body roll per se, no; but if you lean over a tire it does not grip as well. That's especially true for slicks. You can dial in static negative camber to compensate, but that can affect braking.

[buzzy]

I read somewhere that Lotus' engineers wanted it that way. I can't remember where I saw it though.

[spectre]

I have Read for a while that the springs on the track pack were not stiff enough but before just swapping things out I decided to get it properly setup, drive it to see if it bothered me. The first weeked at the track I noticed it and posted pictures on track pack lean. For me it can give an unsettling feeling but I think the biggest issue is when you get it completly loaded and hit the curbing as it unsettles the car which can cause a spin.

Link to the thread:
Track Pack Suspension Lean

[MattG]

Originally Posted by fpitas

Body roll per se, no; but if you lean over a tire it does not grip as well. That's especially true for slicks. You can dial in static negative camber to compensate, but that can affect braking.

True, though with the stock alignment settings, you WANT some body roll to compress the suspension and change the camber angle of the loaded tire.

Originally Posted by buzzy

I read somewhere that Lotus' engineers wanted it that way. I can't remember where I saw it though.

Exactly. We shouldn't be second-guessing the world's best automotive suspension design firm.

I had a chance to play around with some suspension design software way back in college. It's really interesting, how you can design the suspension so that a specific amount of body roll actually increases grip (in some cases...depends on the suspension design), mainly by changing the camber angle if I recall.

Body roll is not necessarily a bad thing. In fact, the only inherently bad aspect of it, in my opinion, is the time it takes to transition from roll one way to the next when changing directions rapidly (slalom).

[dmh]

Originally Posted by xtn

Body roll BY ITSELF doesn't make any difference in lap times.

In his books Carroll Smith discusses this issue at length. He says that you want the car as softly sprung as you can have it while still meeting the criteria of not hitting the bump stops or reaching amounts of travel that are undesirable for reasons of bad camber curves.

He says that springing a car any higher than is required to meet those criteria actually makes the car slower assuming there are any imperfections on the track, and of course assuming you know how to set up your damping characteristics properly.

I personally found that a bit stiffer springs did help me go faster. But it wasn't because they made the car faster. It's just because they gave me a bit more confidence in the feel so I began to push harder.

xtn

Excessive body lean, such as in the picture at the beginning of this thread, most definetly affects lap times in a negative manner. That is why practically any race car you see doesn't exibit it! Suspension engineers work tiresly to eliminiate it.

When Smith writes about softly sprung he is not speaking of street suspensions but rather race setups. Soft as possible, yes; Lotus's street setup, no.

The following was sent to me years ago:
I beleive the only true Full active suspension that is double acting actuators was developed by Lotus. Description below copied from another site explains...........................
Theoretically fully active suspension is the nirvana of the motoring world.

A true active suspension has double-acting hydraulic actuators instead of springs and dampers. As tyres meets bumps, the wheel's acceleration and vertical load is transmitted to a computer which calculates the required wheel velocity and displacement and sends control signal to the actuator.

As this dialogue is conducted hundreds of times a second, the wheel accurately follows the contour of road and bumps, protecting the body structure against unwanted forces.

Active suspension :

Question: "Bump encountered Vertical acceleration sensor and speed sensor says the bump is quite high.
Answer "Allow suspension to compress"
Action "signal the wheel actuator to compress 10 mm progressively"

Question: sensors tell me it's not enough.
Answer "Allow suspension to compress some more"
Action " signal the wheel actuator to compress another 8 mm progressively"

Question: sensors tell me it's not enough.
Answer "Allow suspension to compress some more"
Action " signal the wheel actuator to compress another 6 mm progressively"

Question: sensors tell me it's not enough.
Answer "Allow suspension to compress some more"
Action " signal the wheel actuator to compress another 4 mm progressively"

Question: That seems to be it, now we are going down
Answer release the suspension a bit
Action: Release Actuator 4mm.

Question: we are still going down
Answer release the suspension a bit more
Action: Release Actuator 6mm more.

Question: we are still going down
Answer release the suspension a bit more
Action: Release Actuator 10mm more.

Question: we seem to be flat now
Answer: Okay lets wait for the next thing.
As you can see, active suspension is a perfect concept. Theoretically it could absorb all the shock while maintaining the car body totally stable. Lotus that put it into reality.

Lotus started researching active suspension in 1981, originally intended to equip its Formula One racing cars. The active F1 ran in Brazil and Long Beach '83 in the hands of Nigel Mansell. Despite lacking competitiveness in other areas, It proved that active suspension could withstand hard use at 180 mph and 3 g lateral acceleration. The development team went back to drawing board and did more tests to improve the software. It was not raced again until 1987, when the Honda powered 99T won 3 races in the hands of Ayrton Senna.

However, the active suspension did not offer sufficient advantage in F1 racing. Theoretically, it could raise cornering speed considerably. ("Cornering at 200mph" used to be Team Lotus's slogan when defending this technology.) But on the down side, its hydraulic pump consumed horsepower. we don't have the exact figure, but years later Lotus told us the active suspension in its Excel development car consumed 4 - 4.5 hp on smooth road and up to 9 hp on rough roads. Worst of all, Team Lotus did not get the specially developed tyres needed to extract its potential.

As the active suspension reduced tyre's slip angle, the tyres generated insufficient heat to attain the necessary working temperature, and as a result always ran cold.

Just after the F1 debut in the 1983 season, Lotus Engineering started developing the active suspension technology for production car use. It used the Esprit as the development platform. Like the racing car, the hardware - hydraulic actuators - came from aerospace industry, where active suspension was used in advanced jet engines. According to the engineers involved, the most crucial part was the software rather than hardware. They had to road test for a lot of hours to acquire the necessary data in order to write the program.

The first 2 generations were spring less, but the Mk III and Mk IV system, which were equipped in the Excel development cars, had springs as back up in case the active system broke. The software was gradually improved.

British magazine Fastlane tested them twice, once in the '87 Mk III and then in the Mk IV two years later. In the latter it reported significant improvement in ride quality and body control. It also expressed optimistically that the system would go into mass production within a few years, probably under the name Volvo, Chevrolet or Mercedes-Benz, as they all had been consulting Lotus.

This did not come true. The main reasons, are likely to be cost, and reliability. The only successful application was still in motor racing - between 1992 and 1994, F1 championship were dominated by the active Williams and Benetton. As F1 was at the stage of running Turbo power with a surfeit of BHP the losses presumably were not a problem.

Meanwhile, The DTM series also saw active suspension's superiority in Mercedes C-class and Opel Calibra, it was too superior, the FIA banned it.

The last time Active suspension reared its head was in 1995 (?), when Lotus showed the Esprit SDIII development car. After that, the automotive world seems to have forgotten about Active suspension.

Which is a shame because if you look at all the suspension designs out there you will see how they, all compromise something in some way. The compromise is almost always caused by body roll, and so far active suspension is the only way to eliminate body roll whilst, actually having suspension which can deal with bumps proficiently.

Why, well :
Assuming, that the active system is set to give zero roll then it is becomes very interesting to follow through the implications for the cars geometric roll centers.

If we have no roll then the roll axis becomes irrelevant, as does the need to have suspension layouts that try to keep the outside wheels upright under cornering roll, rather than under all conditions.

Active suspension could mean a return to parallel equal length wishbones or perhaps even , the cheaper trailing or leading arm systems.

These designs suffer because of changes in roll centre positions, and the associated camber angle varying with the roll angle of the body, but if the body does not roll ????????

[buzzy]

Interesting read. It reminds me of the suspension Bose have been working on for over 20 years : Bose Learning Center - Bose Suspension System

[monkeyboo]

Interesting, It doesn't feel like its taking away my speed at all Down at Corner 3 Mosport. Has anyone fitted rear sway bars? Stiffer springs would need a re valve job correct? Don't want to spend a fortune one a new set of suspension.

[dmh]

Originally Posted by monkeyboo

Interesting, It doesn't feel like its taking away my speed at all Down at Corner 3 Mosport. Has anyone fitted rear sway bars? Stiffer springs would need a re valve job correct? Don't want to spend a fortune one a new set of suspension.

Q: Are you the instructor in the driver seat giving a ride? Or are you the student with an instructor in the passenger seat? What is your experience level?

[monkeyboo]

XTN where did you purchases stiffer springs? Did it affect your rebound a whole lot?

Originally Posted by xtn

Body roll BY ITSELF doesn't make any difference in lap times.

In his books Carroll Smith discusses this issue at length. He says that you want the car as softly sprung as you can have it while still meeting the criteria of not hitting the bump stops or reaching amounts of travel that are undesirable for reasons of bad camber curves.

He says that springing a car any higher than is required to meet those criteria actually makes the car slower assuming there are any imperfections on the track, and of course assuming you know how to set up your damping characteristics properly.

I personally found that a bit stiffer springs did help me go faster. But it wasn't because they made the car faster. It's just because they gave me a bit more confidence in the feel so I began to push harder.

xtn

[fpitas]

Originally Posted by monkeyboo

XTN where did you purchases stiffer springs? Did it affect your rebound a whole lot?

It's in his sig, he has Nitron SA coilovers. They come with 425/550 lb/in springs standard, or 525/650 lb/in springs as Nitron Sport Pro: Nitron Sport PRO Suspension - Sector111 - Tasty Bits for the Elise and Exige

[RoadDad]

I've got nothing to add. Just wanted to one up dmh's cig smoking Obama with a doobie smoking Obama.

[xtn]

Originally Posted by fpitas

Body roll per se, no; but if you lean over a tire it does not grip as well. That's especially true for slicks. You can dial in static negative camber to compensate, but that can affect braking.

Doesn't need to be static camber. Can be dynamic camber gain. It's all a balancing act between effects under different variables; like under braking as you mentioned.

My point is that body roll does not necessarily equal tire lean.

xtn