Just a quick question whilst I pick up another crate of beer for the garage....

Is the automatic front/rear brake bias valve as fitted to the sierra required on a 7 type car?

I have sierra disk callipers front and rear if it makes any difference but dont want to fit the auto bias thing unless I have to.

Chears.

If you pass the wheelie bin on the way back with the beer put the valve in there.
Steve.

Would be hard to setup due to the angle of mounting affects performance.

If it were setup correctly would it be better than a normal bias valve?

What do most people use then?

Is nothing acceptable, or would I need a bias bar?

you can get away with nothing, as rear brakes need to lock up first for sva anyway.

Joel - no no no !!!! the fronts must lock first or you'll do an unscheduled handbrake turn every time you brake hard......
Bob

Do you need a bias valve if you have abs.

The vectra my abs unit came from doesnt have bias valves.

Darren

YOU CAN'T USE ABS FROM A MUCH HEAVIER FWD CAR ON A LOCOST !!!!!!!!!!!!!

I was more interested in the sva standpoint, one thing that concerns me with my vectra is if the abs goes will it have a tendancy to lock the rears.

My car isn`t a locost and will weigh 900kg.
As i have the abs wired/ plumbed already i cannot lose by tring it out. If it causes serious problems I can turn it off.

The other thing i said earier was that this abs unit is cleaver, in the fact it has a g sensor, so it gets feedback. I`ve onced braked mid corner (quit sharp) in the wet using the vectra (best bet as a pram rolled from the kerb into the road). It stopped perfectly, i was expecting it would slide off the road, advoiding the stupid mother and pram, but it stopped it dead no drama.


Darren

On ABS systems the mass and suspension frequencies of the vehicle are two of the vital factors ---- Unlike a Vectra a Locost type chassis is very light with high suspension frequencies --- consider what happens when the ABS cuts in, if the frequency of the ABS pulsation coincides with the suspension natural frequency the vehicle will become uncontrollable.


On a production car normally the ABS pulsates at a frequency well above the suspension natural frequency and there is no problem, in fact the ABS pulsation is not normally noticeable any any speed above 5 mph.

Most Locosts have a much higher suspension frequency than a tin-top -- perhaps 3 times as fast and because of the lmuch lighter sprung mass any vibration is going to have a larger amplitude.


A car should be design engineered not just a collection of random bits.

[Edited on 18/4/07 by britishtrident]

Hi, i`m not looking to fight over this, your point is quite valid, a car weighing 1200kg / compared to my 900kg may confuse it/ become unstable.

My best bet would be to see if the vectra is unstable when lowered/ uprated springs are fitted.

The abs pulse rate is 20hz, taking the lowest sub harmonic of 10hz I can calcutate the max spring rate.

When i decided on abs i was a relatiely new driver, now i can employ cadance brake to good effect, to the point where i find abs anoying when it cuts in.

That said there are times where i know it is important to have control when braking harshly in the wet.

I`ve already fitted the unit, so my worst case senario is to disconect the fuses after sva, and leave it in, using the brakes as normal.

The vx220 has abs, and has a similar weight/ spring ratio, so it might be better suited.

Darren