My astra g van Locking rear wheels after drum to disc conversion

White_estate

Ok i know this isn't a 2.2se engined Astra but I'm after some advice ?
After bouncing a few messages back and fore to EvoCarlos i took his advice after fitting vxr rear hubs he advised me to disconnect ads sensors to rear and then try the brakes but its still locking the rear brakes before the fronts.
As the Van did have drums and abs i have a funny feeling the abs ecu applies more pressure to the rear than is needed for the new disc setup
Even with the abs light on surely it still should not lock the rears.
Ive got a 2.2se abs block and abs ecu which is non esp that I'm going to try to fit as the van abs block has less solenoids in it due to not having t/c so i may also need to rewire the abs multi plug hopefully not.

Just hope someone has had a similar issue on doing a disc conversion ?

dewismotorsport

I don't think it's a abs issue, you've just got too much rear braking, I imagine there isn't much weight in the rear of the van either so will always want to lock up.

Few cheap fixes:

*lower rear tyre pressures say from 34 to 26-28psi

*lower the rear more, astra's have a natural rake from rear to front, by lowering the rear more you can shift more weight back over the rear axle.

*fit a in line bias valve and reduce the efficiency to the rear. Best option but requires the most work.

vocky

if you disconnect the rear abs then you must also disconnect the front abs, otherwise the abs ecu will get confused and send all the braking to the rear.

White_estate

If i fit a bias valve it will have to be a 2 line bias as there are 2 feeds from the abs block for each wheel.
Think I'm going to change the hubs to the correct ones on the rear and clear all abs faults and see if this improves things but i will try to disconnect all abs sensors as a test and will report back thanks

corsaZ22se

on the corsa's we tend to fit in line restrictors for the rear brakes after drum to disc conversion to prevent rear lock up.
they can be found cheap in the breakers on non abs corsa c's.
just go in the brake lines to the rear brakes.
used them on my old corsa b for many years with out fault.

White_estate

Thats a great idea will see if i can get hold of the restrictors suppose its just a bush with a suitable hole in it to restrict the flow ?

corsaZ22se

i think they are 1 way restriction, free flow back.
i know they are around £30 each new

corsaZ22se

items i and 2

corsaZ22se

http://www.autovaux.co.uk/product/9191559-modulator-brakehydr.aspx

evocarlos

vocky said:
if you disconnect the rear abs then you must also disconnect the front abs, otherwise the abs ecu will get confused and send all the braking to the rear.

disconnection of one sensor at the rear disables the abs system altho the lamps on it why i recommended he try it 1st to see if it was the abs or a braking issue 🙂
i never even knew about the restrictors

White_estate

After doing some reading the abs units on the astra are coded to their variant model i.e. sri gsi van estate ect.
So it is clear drums are less efficient to disc and callipers so require more brake pressure for them to function as well so when i upgraded my van from drums to discs the abs ecu is giving more pressure to the rear as it thinks the drums are fitted hence locking first.
It looks like the abs ecu controls the bias I'm certain, so when the variant is coded to the abs ecu for i.e. say with discs on the rear it lowers the brake force to the rear by decreasing or increasing the pwm to the abs block to close the fluid valves to the rear brakes enough to compensate for the bias.
Options are find someone with tech 2 to code variant with disc brakes or find suitable abs ecu (2.2se one will not work as it requires can from ecu) or as corsaZ22se has mentioned fit the corsa valves to the rear.
I honestly didn't think this would cause so much of an issue but it makes the car almost un drivable and dangerous lol