Development follows predictable paths but has a critical point that i will explain later.

Sprung weight is the portion of the vehicles total mass acting on the un-sprung weight, the larger the ratio of sprung weight to un-sprung weight, the less the vehicle is affected by the road condition, in other words lowering contributes a major initial factor towards rigidity. Immediately evident is the movement in the roll centre has allowed the geometric conditions to become refined. However still as the vehicle rolls the roll centre tends to migrate and can lead to stability problems.

An obvious solution is to up-grade the sway bar. In a turn the sprung mass wants the car to rotate around the roll centre, if the vertical distance between the roll centre and the centre of gravity is not equal then the centrifugal force (times) the roll centre will cause the body to lean toward the outside of the turn, which reduces the cornering grip.

Braces retain flex Diagonally/Longitudinally and reduces the position of the roll centre (times) centrifugal force increasing cornering grip but this is not without consequence.

Frame Rigidity if taken to extreme would deny absorption from the road condition or indeed the turn. Fundermentally the centrifugal and vehicular polar forces must be restrained. If the coils/sway/braces fail to absorb the roll centre then the weight transfer and centrifugal force will win.

That's not really a discussion starter, more a piece of fact

Just to add something useful, sway bars are more commonly called Anti Roll Bars (ARBs) this side of the pond.

Valid addition jon...Terminology tends to differ even between car makes in the UK.. my post is worthless if the reader cannot identify the components!

Sorry, bit late with a reply, but what your saying really is, an overly rigid frame will cause the suspension problems in absorbing anything the road throws at it and may become dangerous??

If this is the case, how far should are mainly road car go with rigidity?? I.e. Coilovers, ARB's (swaybars) strut braces, under body braces, roll cage etc ...

Independent progressive steps.....Always consider your modifications as unique.. The most impacting mod is the suspension... if you run Coilovers take time to conclude the height and dampening before thinking of adding more additions to the car.... Then consider your reasons for progressing further.... What is the end goal?

Over exploration in modifications does worry me!.. Since suspension travel is intended to absorb weight transfer, re-define the Geometry positions and allow the roll centre to graduate, Over-modification could leave you with a road Go-Kart.

To quote from a book...

"Here is the secret of chassis tuning:
THE SUSPENSION WITH THE HIGHEST ROLL STIFFNESS WILL RECEIVE THE LARGEST PORTION OF WEIGHT TRANSFER CAUSED BY BODYROLL"

Now add the sway % (times) the camber curve (minus) the KPI/SJI.... Also jon isn't that proportion diagonal to the Polar centre?

I don't know?... nor am i the law in Geometry but i welcome education always!

I set a MX5 on coil-overs -25mm, dampening ratio 60/40,up-rated sway bars F/R, Cradle braces F/R and a chassis brace fitted to the rails along the entire length of the car... The Geom positions finalised at track level with a slight over-steer.... once done I had a drive.. ..... Well kiss my cat what a complete combination.... The car could turn at right angles.... At speed your retina detaches ... My thoughts toward suspension absorption has been moved to another level.

wim says: Although the modifications allows for an exiting ride i don't feel this is for the road or indeed the wet, the roll centre is vastly improved by the chassis rail brace (longitudinal) which is an interesting new concept (American) by design.

but surely a rigid frame makes all geometery settings more stable, albeit the suspension components are under greater load, but given that the frame doesnt twist around its axis 3 dimensionally the suspension will act exactly the same under every different condition once the varibles are dialled into the suspension..

i know that after the braces were fitted to the Blue drift car, the shell seam welded, the roll cage fitted, and the car corner weighted, and the geometery set up, that the car was predictable time and time again

Certainly for racing the rigidity is a major factor in chassis dynamics.... within limits.. The camber curve during weight transfer must be permitted, more importantly is that during the turn the inner wheel extends the castor trail, the rigidity -V- trail will remove weight from the inner rear wheel, even lifting it off the ground, this phenomenon is very evident in the likes of the Clio Cup.

I admit the MX5 fully braced was an eye opener, and i enjoy working with this type of car since as you say the fluidity of the Geometry is removed, so the overlapping dimensional forces need less calculation..... My concerns are that you cannot drive a Go Kart around London in the wet and live very long.

Although I've just scanned this post.

Setting up an MX5 with stiffer bars has provided some good/bad feedback from owners (well the ones who know how to drive)

I decided against it as I've seen some horrible results in contrast to some great results.

One owners got his MX5 lowered onto the same setup as mine (stiff FM Springs on KYB AGX shocks), bolted on some stiffer rollbars, dialled in Lanny Settings, and urrrr put his 5 in a ditch, he says diesel on the roundabout (fellow driver and good friend of his says driver skill) yet other owners have said they are a better mod than uprating the suspension.

Further conversations with a Performance Mechanic who carries out this mods for owners suggests that breakaway is less progressive than under normal sways, there's even people in the states that remove the sway bars completely!

So without really coming to a conclusion, that's ummm my urrr feedback.

Valid thoughts... As discussed manufactured rigidity for the track relates to reasonably constant variables (you know the track) whereas a fully armoured MX5 on the road, as you rightly say is subjected to unpredictable breakaway, i personally think this is dangerous since the moment of transfer around the polar centre becomes virtually undetectable.

During any turn the camber curve needs to absorb the roll centre so that the loaded camber/scrub radius can react to the centricities, accentuated by the cornering demands..... Belay this then it's ditch time!

wim is going to measure the reactions with corner weighting and pull downs for exploration into the actual viability of bracing... As time and examples have progressed my thoughts on bracing have been expanded..... not a lot but nevertheless expanded.

As a late comer i didn't see this thread earlier.

In my experience bigger/stiffer anti roll bars on a road car rarely improve things. Roads are generally anything but flat. If you want a car that you can make progress in on the average british B road, you need some suspension compliance.

Bigger anti roll bars are not going to help this.

When setting up 944's in particular, i always try to establish what the owner is going to do with the car. Many are now used as occasional track day cars, and a lot have been set up with big anti roll bars etc focused primarily at track work. Try driving one of these at speed along my journey home and you will end up in a ditch! And thats actually an A road - allegedly!

Track car, yes definietly a good idea. On a road car, not so sure.

As far as bracing is concerned, i'm open to suggestions. A flexible bodyshell can't be a good thing i don't think?

Had an interesting conversation with an engineer at the old TWR set up who were asked to sort out a certain sweedish convertible. In order to resolve some issues, eventually the anti roll bar was binned, and the spring rates upped instead. Result was, i am told, superb, but sadly for marketing reasons it went into production with one albeit a small one. Okay a convertible, but relevant i think.

Post is a bit unstructured, but hopefully it makes sense?

The compliance needs consideration... i am looking forward to some pull-downs on the 3D Arigo.

Eh? What does that mean?

That means i agree with you... the suspension logically needs compliance, our problem is were to stop the modifications for the road when the customer is modding with track materials and a smattering of knowledge.

Bump.
No reason just an interesting read for the newbies out there

i await the "new" feel of the monster when its BTCC welded in roll cage comes back from cambridge,

coupled with the chassis ladder brace, front and rear turret braces, uprated roll bars and Coilovers, it should be very bloody stiff, couple that with the uprated bushes, i do belive the feel will be somewhat spot on, infact much better than the blue drift car ever had, as the cage in the blue carw as a 6 point bolt in, the new cage is a 18 point weld in

add to this also that the Monster will have shed another 70 kilo of weight.........at least by loosing the fuel tank, crazy front bumper, most of the wire loom, all the interior trim, a considerable part of the dash structure, and instruments, and anything from the heater/aircon system thats not used, will also be dropping one of the rear exhaust boxes........

so, a much lighter shell, with much less complience...should make the car far more interesting.......

Interesting... Understatement of the year methinks Mat! It seems the new Monster is designed for the real deal not just good looks as with the last Monster (old blue ) Can you please keep us up-dated with the feel of the new revolutionary chassis.. Also i assume some dynamics in regard to indexing is planned and although this is somewhat secrete a few teasers would be very welcome.

What chassis is the 'monster' based on?

is200/altezza



Tony......your doing it remember

there will be no secrets....

mine will be the only Lexus competeing, so my settings wont benifit anyone else

I know i am doing the Geometry but until we are in the new centre i cannot do the corner weighting or Dynamic Indexing..... Once wim is open then yes 'Happy days' all round

Frame Rigidity.....









are there any updates on when WIM will be in operation....(pm me if needed)

Nice Mat!

I hope you haven't thrown out the passenger seat Mat

thanks




no ---no, was just removed for the cage, the drivers seat had to stay in to guage rollcage distance.....

Stunning Mat... Have you driven the car yet?... if yes how is the initial feel.

erm, nope, theres alot that needs doing, like all the electronics, and re-instaling all of the dash

Oh yeah I was so busy looking at the cage i missed the dash.... or lack of it rather.

Any why would you put the dash back in? Far too much weight

I'm desperately trying to find a good cage for my SW20, that looks really good Mat.

Mat who made the cage.