Back end coming out when brakeing hard

[doug_sri]

Noticed this a few times in my nova, its a 2.0 16v with 2.0 16v front brakes and standard drums. When you hit the brakes real hard the back drivers side pulls to the left, sure if you didnt come off the brakes it would spin. Have had the drums off and there adjusted alright, only managed to bleed the passenger side drum as the drivers side thing snapped off so replacing it tomorrow. mechanic i was speaking to said it could be the valve under the brake fluid tank not working right, anyone else had this problem?

thanks

[MC]

I'd say that its just weight transfer. It's pretty bad in a standard Nova and gets worse with 50kg+ extra of a valver in the front. Is your car stripped out? If there is no physical problem, you can either fit a bias valve or have an adjustable pedal box fitted.

We've come accross the problem alot on track when you really are pushing hard, and it became un-driveable with the disc/caliper set-up that is on there now.

You are braking hard in a straight line aren't you?

MC

[doug_sri]

yeah its braking hard in a straight line. the car is stripped out but has a cage that is quite heavy. got a few things to try on it

[benji]

your rear suspension might be too hard

[Aragorn]

if u brake hard in a streight line it should pull up in a streght line with your hand OFF the steering wheel

if it pulls one way or the other then u have a sticking caliper or dodgy circuit

try putting it on a GOOD brake tester and see what braking force your getting to each wheel - might point out one corner is being less effective

[Chris]

if you have snapped the bleed nipple on the O/S, and it is pulling to the left then maybe the O/S needs bleeding?

[Dod]

All your weight is at the front of your car with the big engine and on top of that, when braking, the weight's being increaced and so it makes the rear very light, i'd get the drums adjusted properly, and maybe load the rear up with ice to weiggh it down a bit, better traction on both wheels.

[doug_sri]

it is stripped out as i am planning to use it on track days and have another car for normal use. I am bought a new cylinder today so will fit that tomorrow. also got two of the valves located under the fluid resivoir from the scrappy so will give them a try if fitting the new cylinder and adjusting them again dont work. Will let you know tomorrow if it solves the problem.

Thanks

[swebb14spi]

Just wondering whether it could be something to do with the load apportioning valve?And maybe there's a drum sticking or something?If it's all stripped out and a lot of weight in the front,plus if it was lowered that might screw the valve up?im pretty sure you can get competion one's that stop the car giving the rears too much force under brake'ing because the car thinks there's a lot of weight in there?...just a thought?

[MC]

Nova's dont have the load biasing valve.

Aragorn, you may be correct, there could be something wrong, but I disagree with your comments about braking in a straight line. With a front end heavy car being driven on the edge, it is possible for the back to step out. No surface will give 100% equal grip to both front wheels and one will brake traction before the other. If this happens when you have no weight over the back wheels and they are already locked up, it goes pear shaped. It's also difficult to gaurantee that you are 100% straight coming into the braking area. That's why in a track car you adjust the bias and stop the rear wheels from locking.

MC

[Aragorn]

yer ur your right

when i said it should pull up in a streight line i didnt mean under emergency stop style brake, firm but steady application of the brake pedal (ie hard but not right on the edge of grip) should cause the car to pull up in a streight line

i realise this isnt the situation that his car is stepping out in but it would give u an idea of the general condition of the braking system

try and get the car on a 4 wheel brake force/balance machine and see whats happening (if your stuck i think most kwikfits now have 4 wheel brake testers)

ooh and another thing, novas dont have load apportioning valve but they do have regulators for the rear circuits, maybe find a smaller regulator now that u have less weight in the back to reduce the rear braking force (saloon ones are smaller i think - the number is stamped on it)