anti roll bars and wheel reactions

[ed_172_cup]

does anyone know a bit about wheel reactions with regard to suspension geometry and roll bar stiffness etc?? im doing some work at uni which involves discussing how the addition of arb's effects the loads on the 4 wheels resulting in either understeer/oversteer characterisics. iv found that adding a stiff arb on the rear has;

decreased load on the outside front wheel,
increased the load on the outside rear wheel,
decreased load on the rear inner,
increased load on the front inner......
Does this mean the car will oversteer? any useful comments would be appreciated!

 

[Fred@BTM]

when i was working on this little toy

we had to disconnect the rear ARB as the driver was getting too much oversteer on turn in IN THE DRY

it depends on a lot of things such as is the car FWD or RWD? where's the engine

tyre pressures is a massively important area

touring cars in the wet run with the ARB's disconnected

 

[ed_172_cup]

the car we have been given data for is the Formula Student car so its RWD mid engine short wheelbase...set new record of 1.41 G round the circuit!

 

[Fred@BTM]

well ask yourself what would happen if the car had no suspension at all, the wheels were rigidly fixed in position (like a go kart almost)

 

[ed_172_cup]

ermm..well thered be a lot less weight transfer, but the loads would still be shifting about. if the loads on the front wheels are greater than rear the back end is going to slide out yeh? obviously zero weight transfer is what u want but thats just impossible (make ur CoG 1mm off the deck and u might get close lol)

 

[Fred@BTM]

ok that was a bad example

what i was trying to highlight if the car is too stiff it will understeer and oversteer all over the place

 

[Mark One]

you at brookes then ed? I havent seen your car around.

I woulda thought that with an ARB on the rear, you would find decreased load on the rear outside because the car doesent roll over and sit on it. that would then mean increased on the rear inside.
I wouldnt know about the effects of that with regards to over/under steer

 

[ed_172_cup]

yeh brookes mate...you? yeh the whole thing of trying to relate it/visualise what the car will do under these conditions is what im struggling with

 

[jez4130]

grab yourself a copy of forza 2 for the xbox and have a mess around with the tuning! it gives you telemetry readouts aswell!:approve:

 

[ed_172_cup]

grab yourself a copy of forza 2 for the xbox and have a mess around with the tuning! it gives you telemetry readouts aswell!:approve:

haha. yeh i wonder how accurate the readings are actually?! shame i havnt got an xbox

 

[Mark One]

Yeah I'm in brookes on my 1st year of the mechanical engineering course.

If you work backwards from what fred has said, then it seems to me that if the car has increased load on the outside rear it grips better - Kinda like a clio cocking the inside rear wheel in a cliosport tripod! Williams Mk1 was the best for that.:evil:

Good luck with it anyway mate. I think you probably need a book about it but i'd assume they are few and far between for such a specific subject.

 

[ed_172_cup]

yeh i think i better get down the library and read up on this stuff.! Wot car u got mate? black 172?

 

[Fred@BTM]

get to a trackday, that'll help you!

 

[White16valver]

hehe 'research' is a good excuse to go

 

[ditz]

my car has one end link snapped on the anti roll bar, havnt got round to fitting a replacement yet but to be honest i prefer the way it handles without the front arb

 

[Mark One]

my car has one end link snapped on the anti roll bar, havnt got round to fitting a replacement yet but to be honest i prefer the way it handles without the front arb

You prefer wot? Madness surely

 

[Mark One]

yeh i think i better get down the library and read up on this stuff.! Wot car u got mate? black 172?

silver 172ph2 and my old valver that I'm selling. Can't keep the car at uni as im in halls

Your car looks plush mate, do you keep it in oxford?

 

[ditz]

my car has one end link snapped on the anti roll bar, havnt got round to fitting a replacement yet but to be honest i prefer the way it handles without the front arb

You prefer wot? Madness surely

i may be imagining it but down bumpy lanes as speed increases im fighting with the wheel less to keep the thing straight
the front end does feel softer though

 

[GordonD]

does anyone know a bit about wheel reactions with regard to suspension geometry and roll bar stiffness etc?? im doing some work at uni which involves discussing how the addition of arb's effects the loads on the 4 wheels resulting in either understeer/oversteer characterisics. iv found that adding a stiff arb on the rear has;

decreased load on the outside front wheel,
increased the load on the outside rear wheel,
decreased load on the rear inner,
increased load on the front inner......
Does this mean the car will oversteer? any useful comments would be appreciated!

Yes.

If you want a car to understeer more you increase the front roll stiffness, and if you want it to oversteer more you increase the rear roll stiffness.

Generally speaking. That general rule assumes that the suspension geometry is good enough that all the tyres are on the ground and generating their best theoretical grip. If that's not the case then the general rule may not apply. So on the Clio Sport for example, it has so much more weight on the front than the rear that if you increase the rear roll stiffness you just get to the point where it picks up the inside rear wheel, and any more roll stiffness doesn't make any difference because its a three-wheeler. There are enough cars that have suspension gemetry issues and sufficient weight difference between the two ends that out in the real world you can't rely on the general rule.

 

[ed_172_cup]

yeh i think i better get down the library and read up on this stuff.! Wot car u got mate? black 172?

silver 172ph2 and my old valver that I'm selling. Can't keep the car at uni as im in halls

Your car looks plush mate, do you keep it in oxford?

haha cheers mate, altho i feel i should admit the pic in the avatar is not what my car looks like - its a photoshop ! Its not that low and the wheels aint anthracite! but apart from that.... lol! yeh i keep it here but have suffered a few bumps due to d***head cyclists dropping their bikes into the car! very annoying!

 

[ed_172_cup]

does anyone know a bit about wheel reactions with regard to suspension geometry and roll bar stiffness etc?? im doing some work at uni which involves discussing how the addition of arb's effects the loads on the 4 wheels resulting in either understeer/oversteer characterisics. iv found that adding a stiff arb on the rear has;

decreased load on the outside front wheel,
increased the load on the outside rear wheel,
decreased load on the rear inner,
increased load on the front inner......
Does this mean the car will oversteer? any useful comments would be appreciated!

Yes.

If you want a car to understeer more you increase the front roll stiffness, and if you want it to oversteer more you increase the rear roll stiffness.

Generally speaking. That general rule assumes that the suspension geometry is good enough that all the tyres are on the ground and generating their best theoretical grip. If that's not the case then the general rule may not apply. So on the Clio Sport for example, it has so much more weight on the front than the rear that if you increase the rear roll stiffness you just get to the point where it picks up the inside rear wheel, and any more roll stiffness doesn't make any difference because its a three-wheeler. There are enough cars that have suspension gemetry issues and sufficient weight difference between the two ends that out in the real world you can't rely on the general rule.

yes i have been reading up on it and it seems that wot uv said is the general rule....for road cars in any case. i think this system can be reversed on proper race cars ie F1, F3000 etc but as a general rule it seems sound enough. Theres just so many variables that couls sway the rule this way or that!!

 

[Mark One]

^^ jesus does that happen alot? Do you keep it on the road or have you got off road parking?

Is the anthracite wheels on the wish list then? I'm thinking of it with my standard wheels. Or i might get turinis

 

[ed_172_cup]

just to show the difference....actual:

ideal:

 

[Cupdom]

Sorry to bring this thread back up but that sounds alot like MVP coursework yes? (thatt'll make sense if im correct).

Not seen your car about, mines always sat at uni, im just finishing my BEng.