Car unstable on hard braking????


ash-EK4 said:
i was wandering this with my ek4....whe in press on the brakes hard the rear goes light and ends up going mental almost spins me out:shocked:
i wad thinking if a anti roll bar waould fix this as i dont have one at them moment? mabe a nice 24mm one from asr? and then uprate the front lower control arm bushes?
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NO it wont fix it!!, an anti-roll bar controls body roll when cornering...a beefier rear bar will dial out understeer, but make the rear more lively under lift-off & braking (whilst cornering) conditions...

The rear anti-roll bar, by limiting body roll, also limits the amount of the vehicles weight transferred onto the outside rear wheel during cornering. From this, the more vehicle weight that is allowed to act down onto the tyre, the more grip it will have.

Thus, the thicker the bar, the more the tyre is likely to slide out suddenly when it reaches its limits of adhesion as there is less vehicle weight acting down on the tyre during hard cornering..

From your description it sounds like you need to look at brake balance, or your suspension set up to prevent such weight transfer to the front end under heavy braking
 
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What ash-EK4 has just said is exactly whats going on with my car but i do have the ASR kit with a DC2 ARB on the rear. I think my alignment and my suspension need setting up.

James.
 
if your suspension is too soft on the front it will load up too much puttin very little weight over the back wheels
 
pimpinblackcivic said:
if your suspension is too soft on the front it will load up too much puttin very little weight over the back wheels
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The weight transfer will be the same during braking whether he has soft springs or hard ones. The only thing harder front springs would reduce during braking is dive.

chrismc_DC2 said:
NO it wont fix it!!, an anti-roll bar controls body roll when cornering...a beefier rear bar will dial out understeer, but make the rear more lively under lift-off & braking (whilst cornering) conditions...

The rear anti-roll bar, by limiting body roll, also limits the amount of the vehicles weight transferred onto the outside rear wheel during cornering. From this, the more vehicle weight that is allowed to act down onto the tyre, the more grip it will have.

Thus, the thicker the bar, the more the tyre is likely to slide out suddenly when it reaches its limits of adhesion as there is less vehicle weight acting down on the tyre during hard cornering..

From your description it sounds like you need to look at brake balance, or your suspension set up to prevent such weight transfer to the front end under heavy braking
Click to expand...
Your first paragraph is completely correct, but you're wrong on how sway bars work.
Yes, they limit body roll. The only reason they are used is to reduce body roll without having to use harder springs, which would make the car uncomfortable and less stable over bumps.
But reducing body roll doesn't reduce weight transfer to any significant degree. Using a stiffer sway bar in the rear will make more of the car's weight go to the outside rear during cornering, not less weight. Thus, on a FWD car setup for oversteer through a stiffer rear sway bar, the outside rear tire will actually break free because it has more weight on it and maxes out.
 
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Dino-Spumoni said:
The weight transfer will be the same during braking whether he has soft springs or hard ones. The only thing harder front springs would reduce during braking is dive.


Your first paragraph is completely correct, but you're wrong on how sway bars work.
Yes, they limit body roll. The only reason they are used is to reduce body roll without having to use harder springs, which would make the car uncomfortable and less stable over bumps.
But reducing body roll doesn't reduce weight transfer to any significant degree. Using a stiffer sway bar in the rear will make more of the car's weight go to the outside rear during cornering, not less weight. Thus, on a FWD car setup for oversteer through a stiffer rear sway bar, the outside rear tire will actually break free because it has more weight on it and maxes out.
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That was what i was trying to get at...but my explanation was slightly "flawed". I knew what i meant but went about the wrong way of putting it across. TVM for giving a clearer explanation:nice:
 
i know what the anti roll bar does!, i was jsut wandering if it stops one corner lifting why will it not help abit with keeping the back tyres on the road while braking? but i am asking for advise so im just going to try what evers thrown at me lol

my setup is very poor at the moment i need the suspension and camber etc sorted out and im running on old oem bushes that have done 120k:shocked: and d2 coilovers

so would a decent geo set up and some fresh bushes sort it out???
 
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1. You need to get onto changing the bushes for sure if they have done that kinda mileage...& defo go for OEM trailing arm bushes...

2. With regards to vacuum bleeding...Does it need it?? Pedal spongy?

3. Also your choice of pads needs looking at. Id advise against Green Stuff pads....they are VERY poor in my experience. I had Red Stuff in the Teg which were OK, but you really need to match the compounds front to rear in any case to make sure the front & rear are doing the correct amount of braking work....

The ARB helps stabilise the car body L to R whilst cornering, but serves no purpose whatsoever in keeping the rear tyres in contact with the ground during braking....

The only other thing i can think of is the coilovers are also set too hard...are they adjustable?
 
yeha they adjustable do you mean the damper? or the spring rate?
 
Dampers...if you have them set too firm the car will become all jittery & generally nasty to drive....

Could well be a combination of all the previous points mentioned IMO :nerv:
 
give it a go then.... uprated bushes or not? like you say keep the rear trailing arm bushes oem yeah?
 
my handbrake cable has seized but that wont be the problem on my car i dont think....
 
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