Any reason not to use ABS?

[mr henderson]

One of the hassles in building a kit car is to get the brake balance right. This means using a balance bar and twin master cylinders, or using a conventional tandem cylinder and finding a way of ensuring the rears don't get enough pressure to lock first under any circunmstances.

And that's the problem- ensuring the rears never lock first usually means that on some surfaces they won't be doing much at all, in other words, adjusting for every situation means compromising some of them.

Seems to me that if I was to use the ABS system from any car that would provide a suitable unit, and find a way of mounting the associated individual speed sensing equipment to each wheel, then I would get perfect braking every time.

Anyone want to shoot that idea down?

[HandyAndy]

i don,t think there is reason to shoot the idea down,

i,m not a mechanic & struggle on some of the things others take for granted knowing about how a car works/or not etc,

but the way you,ve described the idea makes sense to me, i suppose if a cheap solution was available & it solved the prob then surely why not indeed?

good idea

andy

[deezee]

First off you would need compatible hubs and drive shafts for ABS..... so there is 90% of the Sierra donors out the window. Then you'll need to install the ABS controller, which are pretty big. Then you'll need the ABS ECU, which you'll have to get out of the loom from the donor car. Then depending on how advanced the controller is, it will automatically sort out the bias, but not all of them do, so you will still be left with crap bias.

Or just use drums and discs, like from the donor. I've never heard of that combination locking. Of course the super cheap option is just to buy an inline, adjustable restricter and limit the rear breaking until it stops locking.

[AshG]

i retro fitted the abs from a fiat coupe to a fiat bravo once.

was a pretty easy job had to get all the sensors and sensor rings off the coupe and fit them to the bravo then installed the abs pump and coupe master cyl. made up all new brake lines wired abs into the brake pedal light (thats how it picks up on fiats) and power. hey presto it worked and passed all its mot's ever since. i have pictures of fitting it all if you fancy a look.

p.s if you go for a fiat/bosch unit they have the ecu's built in on top of the pump and are a pretty compact unit. the higher models do independant front abs and joint rear.

[mr henderson]

Thinkng about this queston leads me into thinking about how braking works generally. It seems to me that as long as none of the wheels is locking (which, of course, is what ABS prevents) then having full braking power available at each wheel has got to be the best option.

The alternative is to artificially limit the braking power at the rear wheels, by whatever means, bias bar, limit valve, weaker brakes, means that full braking power is not available at the rear wheels just in case it might lead to the rear wheels locking.

So, no wheel locking, no problem. Or so it seems to me.

[alga]

Ford Scorpio/Granada used essentially the same drivetrain as Sierra with a bit longer wheelbase, and had ABS as standard.

[aaronbassett]

and 5 studded wheels to

[miles50]

I am using Scorpio brakes but not the ABS. The master cylinder and associated hardware weigh in at over 11 kilos and is massive. Plus the disc pads have wires running out of them and are costly. The car is so light compared to the Scorpio I figure a bias adjustment should suffice.

[mr henderson]

The car being light doesn't necessarily help stop the wheels from lockng, if anything, with there being less weight pushing down on each tyre, the problem cold actually be worse. I agree that as long as the bias is adjusted to send most of the braking effort to the front wheels then there won't be any involuntary "handbrake turns", but what I am looking at is ways of geting the rear wheels to do their share of the braking, up to the point at which they would lock if ABS was not fitted.

[AshG]

you wouldnt be able to do that. If the abs were to fail the braking has to work as normal. To test at iva they remove the abs fuse. You would be totally relying on the abs to stop the rear wheels locking. If the abs stopped working it would be over braked at the back resulting in the back end coming out.