heavy braking rear feels like it steps out

[Lozza-p]

hey guys on my 172 sport when i brake heavy my rear end seems to step out and i sort of have to steer into it just feels really unsettled.

i thought this could be the brake load valve but after getting it on a ramp at work i have found it dosnt have one and only has the light adjuster on the rear beam.

dose this have EBD on it?

has anyone else had this sorta thing just feels abit unsettling.
i dont seem to have any seized brakes either

 

[DrR]

Dampers?

 

[Aluco]

Tyres
Tyre pressures
Dampers
Brake bias fucked ?
ABS fuse gone
Just in your head


Ones of the above.

 

[Lozza-p]

Tyres
Tyre pressures
Dampers
Brake bias f**ked ?
ABS fuse gone
Just in your head


Ones of the above.

tyre pressures are ok
tyres are ok
abs fuse gone my light would be on wouldnt it?
the dampers were dry when i looked
sure its not my head infact know its not

 

[DannyR]

abs fuse gone my light would be on wouldnt it?

I don't think it does, only if a sensor is disconnected. If you were braking really hard then it may of tried stepping round, due to the nature of the car the back end is really light. I get it happening every now and again when breaking really hard, but I do have to be stamping on the pedals biting at the ABS!

 

[Aluco]

Well unless you have a calliper sticking intermittently then you have a phantom in your car causing it to step out under braking.

Dunno if light comes on, just remember when I took my abs fuse out of my 1.4 when it snowed the car went sideways if you touched the brake, good fun though !

Maybe your brake bias is fucked up and braking more at the rear than the front, or more than it should be at the back, think it's only supposed to be 20% ish on the rear brakes.

 

[Henry]

is this straight-line braking? something's definitely not right if it is. and is it triggering the ABS? any steering involved, and it's probably just weight transfer (short wheel base, nose heavy)

 

[realnumber 1]

When braking very hard from around 120 I found mine to weave about a bit and feel very light at the back. I'm used to it now and don't notice it any more. Apparently (iirc) new springs such as sportlines can help the stability when braking hard but I haven't had mine on long enough to find out yet.

 

[Jonny1*2]

When braking very hard from around 120 I found mine to weave about a bit and feel very light at the back. I'm used to it now and don't notice it any more. Apparently (iirc) new springs such as sportlines can help the stability when braking hard but I haven't had mine on long enough to find out yet.

Agreed. Hard braking in a car where most of the weight is in the front will cause the car to pitch and go light at the rear. In a straight line it is usually fine though. I might be that looked at if I was you mate? If turning slightly then issues might arrise, but not a straight line.

Brake balance maybe?

 

[realnumber 1]

imo I think undulations in the road surface might be causing the problems the OP is having. Thats what I find causes it in a straight line.

 

[Jay Payne]

Kind of normal, worse on cars with stripped rear

 

[Mark One]

Kind of normal, worse on cars with stripped rear

+1
unsteady under heavy braking if even just off straight. I'm told that Eibach sportlines make significant improvement.

 

[Aluco]

Just to add, it's not because your roads have been gritted is it ?

The gritters round mine have gone nuts tonight, just taken the GF home and the back end kept coming out on the faster corners. Nearly did a poo !

 

[Struggler]

just to add, just because the dampers are dry, does not mean theyre working fine,

they can go, and not leak,

bounce test them to be sure, push it down, if it comes up and settles, then its fine, if it keeps bounching, then theyre pooped.

 

[Lozza-p]

little update just got back from a long drive and been testing the brakes. If i really hit the brakes real hard the abs works as it should and it dosnt really move on the rear. if i do it a bit lighter not so hard the abs comes in it goes wiggly at the rear. also some times with lightish braking the back seems to move always seems to go left.

the road surface dosnt have any effect on it. dose upratted suspension help then?

as they dont have a brake load valve how dose it decide how much pressure to send to the rear?

 

[Aluco]

I thought they had a brake balance valve type thing ?

 

[Jay Payne]

Not with ABS they dont

 

[Aluco]

That's me told then

How does it determine it Burp ? I seem to recall a sensor or something on the rear axle :S

Supposed to adjust depending on how heavy a load you're carrying ? or am I talking out of my arse ?

Just guessing now.

 

[Dangerous_dave]

less tread on your tyres at the back than the front?

 

[Dangerous_dave]

That's me told then

How does it determine it Burp ? I seem to recall a sensor or something on the rear axle :S

Supposed to adjust depending on how heavy a load you're carrying ? or am I talking out of my arse ?

Just guessing now.

i once failed an mot on this and they told me to put a load of crap in the back and it will be better ! no word of a lie ! (because it was stripped out)

i changed the rears discs pads and bearings bled the brakes and tightend up the handbrake cable and sent it back in and it was fine. didnt bother with the suitcase of lead in the boot.

 

[Jay Payne]

That's me told then

How does it determine it Burp ? I seem to recall a sensor or something on the rear axle :S

Supposed to adjust depending on how heavy a load you're carrying ? or am I talking out of my arse ?

Just guessing now.

howstuffworks.com/anti-lock-brake.htm

 

[Aluco]

i once failed an mot on this and they told me to put a load of crap in the back and it will be better ! no word of a lie ! (because it was stripped out)

i changed the rears discs pads and bearings bled the brakes and tightend up the handbrake cable and sent it back in and it was fine. didnt bother with the suitcase of lead in the boot.

They shouldn't have failed you on that mate, 172 cups have are excluded from it being tested or something. Try a search there is the page you can print out to show to the MOT tester.

 

[Aluco]

Edit: Ignore previous comment I've just seen what I was looking for.

 

[Dangerous_dave]

They shouldn't have failed you on that mate, 172 cups have are excluded from it being tested or something. Try a search there is the page you can print out to show to the MOT tester.

i did take a copy to the retest and they said it wasnt related or some Bullshit but it passed so whatevers... need to change the rears discs n pads any way the bearings were doing my nut so thought sod it o the lot.

 

[Henry]

Not with ABS they dont

that's what i was wondering about - presumably the ABS deals with the brake force distribution? (know nowt about ABS)

to the OP, if it's really that marked, i'd take it to someone who knows the car so that they can have a drive and make some suggestions. it's going to be something to do with either the brakes or the suspension if there's a problem

 

[H182]

Its normal I think, mines always been a little light. Only happens under extreme braking.