Rear brakes lock before front

[ShaneJ]

Hey everyone, I have my van rung again after installing new diff and disk brakes all round. Happy me 

Problem I have now is the rear brakes just lockup before the front. Not so happy me

Adding some weight to the back of the van would fix the problem but I am wondering if this is normal for the bedfords?

[MaTTe]

what sort of master cyl are you running?
Disc/drum masters have 10lb valves built in to keep the rear wheel cylinders from leaking back, which means your rear discs will be pre primed prior to using the brake.
Some masters can be modified to have the valve removed, tho i've never done it.

Short of modifying it, you could look into a disc/disc master if you have not already.

The only other think i can think of is a bias valve, however they usually give full pressure to the front and partial pressure to the rear, which would cause the opposite of your issues. Plus i've never seen a bias valve on my van, so assume this is common among all bedfords.

The next question is what condition are the front calipers in? Partially seized? or are the pads/rotors heavily worn meaning they require more significant pedal travel to make them operate?

A few thoughts for you to consider in your trouble shooting..
Good luck

[ShaneJ]

Thanks mate.

Master cyl is an XB disk/disk. Rear brakes are freshly reconed as are the front.

The poor tyres I have on the back may not be helping with the situation. They are balding LT tyres 

[rossie]

One of the better ways to fix the problem is by putting a portioning valve in the rear brake line that is adjustable

[ShaneJ]

I fitted an adjustable proportioning valve and it helped a bit but the rear wheels will still lock up first if you jump on the brakes. I'm thinking after fitting, sound deadening, a floor, a bed etc in the back that might resolve the problem.

[MaTTe]

I suppose I should have asked originally what sort of disks and calipers you have at the front, and what sort you have at the rear?

[ShaneJ]

Galaxie disks and calipers at the rear and falcon disks/commondore turbo calipers up front.

[MaTTe]

What is the size difference between the calipers at the front and rear? Are they Galaxie rear calipers, or fronts?
The point I'm getting at, is that generally the front and rear brakes are disproportionate to each other so as to put more load on the front to prevent locking up the rears.
If you look at a modern car, they'll have quite sizable front calipers with twin pistons, with minute single pistons at the rear.
This could simply be a case of your brakes at the rear being too good.

I'm not sure what size calipers they had on the rear of HZ/WBs, someone else may be able to shed some light on that further for comparisons.

I have some BA rear calipers kicking around in the shed if they suit your rear disc thickness and if you can be bothered making up a caliper bracket to suit

[Marky]

hi shane...
i had this problem

when i converted my standard booster to Lj..xb set up

even with prop valve..brakes were locking up on rear...giving me the right shits...as the brakes were even more touchy than before

after weeks of ripping my hair out n trying different things...

(my mechanics got their hot rod brakes done by Better Brakes on Gold Coast...awesome machinery/engineering workshop...a total 1 stop brake place!!!)

cant speak highly enuff of the advice....n help ...

Spoke to Wayne Mckew @ Better Brakes Gold coast ..he explained to me....

new master n booster...have increased bore...from beddy standard...i think the ford is 1'' from memory

his advice was to REDUCE the size of the REAR wheel cylinder bore.....think the new ones were like $12 each...im running a holden diff

Did that..n hey presto!!!!! stops like a treat!!! every time..never locks up...ever!!!!

hope that helps

[Dano]

hey Marky how much did you reduce the "bore"size.....from what to what? cheers dan