Its All Locking Up

[driversdomainuk 8]

Hi Guys,

 

Having an ongoing issue with my 205.

 

Last season competing at Loton Park, at Hall Corner (for those who dont know, it is the square left at the start) I locked up and went sideways into it, putting two wheels on the grass and almost tipping the car over!!!

 

Anyway I though it must be the rear brakes locking, so recently I have fitted a brake bias and have a single copper line running inside the car where the passenger seat used to be......anyway I am still getting this locking up... it always involves the car under heavy braking, pulling/skidding to the left even in a stright line

 

I have reduced the Konis on the rear to soft from hardest setting - no real diff but as the car is so ultra light over the rear I though this could be the problem. However, still have this problem!!!

 

After doing these changes, I could feel the car more (i.e. dampers not being as hard and so could gauge more movement ) and it was only then I realised, I automatically thought it was the rears locking up - when in fact I am really sure now it is the front near side wheel (this would explain why if I use engine braking the lockup is not as bad)

 

 

Has any more experienced this before???

 

Am I right in thinking it is the front near side and not the rears?????

 

What is the best way to sort problem as I am racing this Saturday at Loton and dont want to be having to take it easy...

 

Cheers

[driversdomainuk 8]

Hi Guys,

 

Having an ongoing issue with my 205.

 

Last season competing at Loton Park, at Hall Corner (for those who dont know, it is the square left at the start) I locked up and went sideways into it, putting two wheels on the grass and almost tipping the car over!!!

 

Anyway I though it must be the rear brakes locking, so recently I have fitted a brake bias and have a single copper line running inside the car where the passenger seat used to be......anyway I am still getting this locking up... it always involves the car under heavy braking, pulling/skidding to the left even in a stright line

 

I have reduced the Konis on the rear to soft from hardest setting - no real diff but as the car is so ultra light over the rear I though this could be the problem. However, still have this problem!!!

 

After doing these changes, I could feel the car more (i.e. dampers not being as hard and so could gauge more movement ) and it was only then I realised, I automatically thought it was the rears locking up - when in fact I am really sure now it is the front near side wheel (this would explain why if I use engine braking the lockup is not as bad)

Has any more experienced this before???

 

Am I right in thinking it is the front near side and not the rears?????

 

What is the best way to sort problem as I am racing this Saturday at Loton and dont want to be having to take it easy...

 

Cheers

 

I have read that wheel bearings could possibly be responsible for this...?

[Emmy Seize 8]

Hmm, sounds exactly like one of my cars!

 

I converted two of my cars to the GTI6 setup with front/rear split and bias valve.

 

One car is absolutely fantastic while the other is an utter nightmare under heavy braking.

 

Both cars received the full treatment: Virtually every part of the brakesystem is new, shocks all round are new, lower arms up front are new.

 

On my car, I am pretty sure it is the rear lockong up, though. It had the habbit with the old standard brakes already and I thought all the new parts would cure it.

 

Best to find out which wheels lock up is to let somone watch your car while driving by and braking hard (at low speed, of course).

 

 

So, after much fiddling to no avail thus far, I´d be interested to hear how the bearings could come into play?

Edited March 30, 2008 by Emmy Seize

[driversdomainuk 8]

I am also starting to think, as there is effectivly no weight and thus no grip on the rear under heavy braking, any sort of frontal brake imbalance (i.e front left locking) will cause the backend to go which ever way gravety wants - in my case off to the left, giving into the force of the locked left wheel.

 

anyone agree..?

[Emmy Seize 8]

I am also starting to think, as there is effectivly no weight and thus no grip on the rear under heavy braking, any sort of frontal brake imbalance (i.e front left locking) will cause the backend to go which ever way gravety wants - in my case off to the left, giving into the force of the locked left wheel.

 

anyone agree..?

 

 

Mine usually goes off to the right, I can hear the right rear wheel locking up, so our problems might be the of same origin:

 

Two things to prove: a. I sit on the ohter side (in the LHD car) and b. I drive on the other side of the road here, so the road surface declines towards the other direction.

 

Problem is, that my car is a fully equipped road car, so there can hardly be a weight issue.

 

What's more, my other car is almost identical (appart from the colour) and works very well indeed.

 

What colour is your's?

Edited March 30, 2008 by Emmy Seize

[driversdomainuk 8]

Mine usually goes off to the right, I can hear the right rear wheel locking up, so our problems might be the of same origin:

 

Two things to prove: a. I sit on the ohter side (in the LHD car) and b. I drive on the other side of the road here, so the road surface declines towards the other direction.

 

Problem is, that my car is a fully equipped road car, so there can hardly be a weight issue.

 

What's more, my other car is almost identical (appart from the colour) and works very well indeed.

 

What colour is your's?

 

 

My car is white!!!!

 

I actually had someone try and turn the rear wheels when I applied footbrake fully with the bias valve on lowest pressure and they could still just turn the wheel when jacked - so the rear wheels cant be locking....NO WAY!!!!!!!!

 

I think I was confusing the rear wheels skidding side ways (Succumbing to the force of the locking front wheel) with it locking up in a straight line (as in braking pressure)

[driversdomainuk 8]

Just another thought...My CV book on the drivers side has split and there is a fair amount of grease leaking out some time ago...

 

 

May be wrong, but possibly some of this grease could have got on to the disc and contaminated the pad - which my explain under very heavy braking the other (left side) locks up..?????

[welshpug 1,626]

very possible, get the wheel off and check the pads, and get the CV boot sorted ASAP before it lunches itself.

[driversdomainuk 8]

very possible, get the wheel off and check the pads, and get the CV boot sorted ASAP before it lunches itself.

 

 

I was not aware a worn CV boot would have such a dramatic failure - its not even making a noise yet..

[driversdomainuk 8]

Problem sorted - have now disconnected and closed off the rear brakes totally. It feels fantastic, much safer than before..

[Anthony 1,000]

Problem sorted - have now disconnected and closed off the rear brakes totally. It feels fantastic, much safer than before..

So you've got no rear braking effort at all now?

[Batfink 201]

had you checked the bias valve is working ok? I take it you dont have rear compensators anymore

Edited April 4, 2008 by Batfink

[driversdomainuk 8]

So you've got no rear braking effort at all now?

 

 

zero

[driversdomainuk 8]

had you checked the bias valve is working ok? I take it you dont have rear compensators anymore

 

 

We did a test - I applied a degree of brake pressure on the pedal, held it, and whilst the car jacked up a friend turned the rear wheel. As I turned the bias value the pressure required did not change.

 

Bascially the bias is not working.

[chownr 0]

A few suggestions -

 

Is the Bias Valve plumbed in the right way round? - In at the front out at the back?

 

Can you bypass the bias valve to see what happens with it disconnected?

 

What make of Bias valve have you got? Ive had issues in the past with Compbrake ones and used to use Wilwoods or AP. I have a spare but its not going to get to you for the weekend unfortunately

 

Rich

[driversdomainuk 8]

A few suggestions -

 

Is the Bias Valve plumbed in the right way round? - In at the front out at the back?

 

Can you bypass the bias valve to see what happens with it disconnected?

 

What make of Bias valve have you got? Ive had issues in the past with Compbrake ones and used to use Wilwoods or AP. I have a spare but its not going to get to you for the weekend unfortunately

 

Rich

 

 

yes checked all that - to be honest, I am happy with the setup - the car is so light the back end was just a damn pain in the ass..

 

I made the silly mistake of telling my mum when I saw here I have disconnected the rear brakes. Mums being how they are, and also knowing nothing about cars was not happy...my dad just looked at me as though I was deranged....

 

Perhaps I sould keep quite in future about these things???

Edited April 4, 2008 by driversdomainuk

[Anthony 1,000]

Be interesting to see how you fair, as in my experience, cars with low/no rear brake effort feel very unstable under moderate-hard braking

[driversdomainuk 8]

Be interesting to see how you fair, as in my experience, cars with low/no rear brake effort feel very unstable under moderate-hard braking

 

Thats interesting, as I noticed how benign the car now feels under braking - just can feel it so much more in the part of the car which is most important - the front.....

 

I do have a 25mm arb in the rears mind - maybe that is setting it up better?

 

Will be cautious on practise runs either way...will let you know when I return home saturday evening...

 

That is if I have not been killed....

Edited April 4, 2008 by driversdomainuk

[welshpug 1,626]

I'd rather run more rear braking effort than none!!

 

Do you still have the compensators fitted?!

Edited April 4, 2008 by welshpug

[taylorspug 7]

Even if you were to lighten a 205 as much as you possibly could at the rear, you would still need a degree of braking effort. Id imagine the car will still be very unstable under heavy braking. In my experience a bias valve isnt enough to dampen down the rear braking effort if you have anywhere near standard front brakes. My old 205 with full 1900 brakes, no compensators and Wilwood bias valve was always locking the rear wheels, even with the valve fully towards less rear bias. My advice is to put a 1600 or 1900 compensator in line aswell as the bias valve. Or if you already have compensators then one or both of them are probably knackered!

[James_R 3]

I've had no issues as above with a wilwood bias valve and std brakes, infact the cars going through rear pads more than previously, and feels much more stable under braking, you can just bank on the anchors and no hassle.

 

My 306 running 23mm MC and 6 brakes also improved form more rear braking effort. :s

 

Has the MC been swapped at all aswell??

[driversdomainuk 8]

Even if you were to lighten a 205 as much as you possibly could at the rear, you would still need a degree of braking effort. Id imagine the car will still be very unstable under heavy braking. In my experience a bias valve isnt enough to dampen down the rear braking effort if you have anywhere near standard front brakes. My old 205 with full 1900 brakes, no compensators and Wilwood bias valve was always locking the rear wheels, even with the valve fully towards less rear bias. My advice is to put a 1600 or 1900 compensator in line aswell as the bias valve. Or if you already have compensators then one or both of them are probably knackered!

 

 

I do not have the original compensators - I only have a single copper line running inside the car, which now leads to no-where.

 

so how come I have not experienced any instability..?

[driversdomainuk 8]

I've had no issues as above with a wilwood bias valve and std brakes, infact the cars going through rear pads more than previously, and feels much more stable under braking, you can just bank on the anchors and no hassle.

 

My 306 running 23mm MC and 6 brakes also improved form more rear braking effort. :s

 

Has the MC been swapped at all aswell??

 

 

yes, new MC and brake servo, along with new copper pipes all round and goodridge steel braided hoses

[welshpug 1,626]

one thing I have found that affects behaviour under braking is the rear ride height, check that its sitting fairly level.

[driversdomainuk 8]

one thing I have found that affects behaviour under braking is the rear ride height, check that its sitting fairly level.

 

 

it actually rides quite high at the back (and the front) see this pic of me braking from around 90mph...

 

http://www.driversdomainuk.com/images/166LN06.JPG