Rear brake lock before front

[Tom86]

The brake on my car keep locking up one of the rear wheel before the front when ever I brake hard. I don't think that it is a bias problem as it happened with my disc rear end (still use stock P-valve - which suppose to have less braking power).

Anyway its more like the rear lift up possibly from weight being transfer to the front? So whenever I drive the car especially in the wet I have to be extra careful as it would lockup when I have to suddenly brake, which is scary .

Anyone else have similar problem with their car? what did you do to fix it? I'm thinking about putting a stiffer springs up front to lessen the severity of the weight transfer from back to front or carry a bag of sand in the back of the car what you guys think?

[Mad RS]

So what your saying is that you have just fitted a disc rear end and now the rears lock first??
or
You have fitter a disc rear end before to another car and it didn't happen??

[damo101]

track car or road car?..i think for a road car its fine?coz as long as you dont lock up the front u can still maintain control of the car easily..might be wrong but yea..

[Mad RS]

Locking up the rear wheels before the front is never a good thing on the road or track. last thing you want is to get into a heavy braking situation and have the rear end lock up first and cause the car to spin.

If the rears are locking get an expert to look for any mechanical problems first but you may need to fit a adjustable brakes bias valve

[Tom86]

The brake on the car has always been like this ie lock the rear before the front.

When I had the drum brake on the back the rear would lockup first ( which suppose to be normal according to the guy at the brake shop) but now, I have the rear disc that suppose to be less effective and it still happened. This is why i think its not a bias thing its more like the weight transfer issue as only one wheel would lockup sometime the left one and sometime the right one .

Do you think stiffer spring up front would help this? anyone else locked the brake on their car before? which end give up first?

[omy]

I have just installed s13 brakes on the front of my 86 and still using drums on the back, the std brake master is locking up the back also, I think it is the brake bias, as the fronts need more volume to push the pistion. I run 8kg front springs which are stiff and the rears still lock. If everything mech is in good working order then it's the brake bias. Will be fitting a larger master today, I post the results.

[AEGZE]

i wish my car did that...i have trouble locking up my rears even with a handbrake. it might have something to do with the amount of tyre u have on the rear, because i run semi slicks..and i just cant get them to lock without pressing the brake a bit while i handbrake.

[damo101]

i agree with you on the car spining but it really depends what kind of situation you are in..for me its not a big problem as long as i dont lock the front wheels i would still have steering control of the car..if theres something in front of me during the hard braking then i would jerk the steering and let it spin to 1 side and stop there if enough space..otherwise just steer the car smoothly away from the hazard and control the slide..if the front were to lock up as well you cant steer the car anymore so youre in trouble..

with regards to the brake bias it might be wrongly adjusted in the 1st place..

[Mad RS]

If you believe that in a panic situation you can "control the slide" you are sorely mistaken my friend. Once the rear is locked you are in trouble, and the skill of drifting has nothing to do with it. I myself have completed 3 driving course and you learn very quickly to control the front brakes and I have also driven a car that was built to lock the rear brakes and the car was very uncontrolable when trying to replicate proper braking performance.

By having the rear brakes lock first means that the cars braking system is not working to its optimum. Front brakes are much more powerful that rears (or should be) and thus should be used to there optimum to stop a car quickly and safely.

Maybe you should have a look at the type/condition of the brake pads you have in the rear. Maybe you have rear pads with a higher grip co-eficient. Just a thought.

[Hen is a total nutcase]

Locking the rears first is bad. Front and rear should lock simultaneously in a perfect world, but in reality it is better to have the fronts lock slightly before the rears.

I've heard this is common on oz-spec sprinters with rear discs fitted. And I've heard you can fix it by taking the spring out of your proportioning valve. That's the block below the master cylinder on the strut tower.

Hen