ABS retro-fit

[rpmag]

Has anyone seen an ABS system retro-fitted to a vehicle not originally designed for it?
The reason I ask is that I have recently received information from a respected driver about a new vehicle he has just tested (sorry cannot disclose it). It has switchable ABS. With ABS braking was described as stable and incredible, without the car was described as 'a bear with a hornet on it's arse'.
Seems an interesting area to follow up.

 

[GregLocock]

Needs more front bias.

Um, no, I've never heard of retrofit ABS, it'd cost more than the changeover cost for the car.

It isn't impossible, but I can't imagine anyone doing it.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[rpmag]

Yes, probably true, but is an endurance racecar from a major manufacturer in the UK.
I believe the Daytona Reps produced in Melbourne have an ABS system adapted from a current HSV and partially controlled through a motec dash.

 

[GregLocock]

Oh, for racing, yes, that isn't /too/ hard. That is completlely different to the requirements for a production car.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[rpmag]

Good to know...production cars are far too complicated for me!

 

[IRstuff]

Straight retrofit and designing for retrofit are two entirely different things. One can easily imagine designing an ABS car and then not implementing all the hooks until later. Even at that, they might elect to have the car wired and plumbed to handle ABS.

That's quite different than wiring and installing the sensors and gadgetry required for ABS into a 1982 Plymouth Arrow, for example.

TTFN

FAQ731-376

 

[BrianPetersen]

If a particular car doesn't have ABS but there was a version of it in the same model year that had ABS (or close enough to the same model year that "it's the same car"), then generally you can obtain and install all the ABS-related parts (hubs, sensors, wiring harness, controller, probably master cylinder, brake lines, deletion of proportioning valve, add ABS pump and valve module, probably instrument cluster to include the ABS warning lamp). Even this is no small feat because these components are spread out all over the car.

Putting ABS on the above-mentioned 1982 Plymouth Arrow (or any other car that was built with no consideration whatsoever for ever being equipped with ABS) would be a challenge.

As for the original poster, a vehicle that is tail-happy and wants to swap ends without ABS needs attention to the front/rear brake bias, as others mentioned. Even without ABS, it should not be like this. The front wheels should always be arranged to lock first. I've had some production cars (first-gen Honda Civic) that had too much rear brake bias, and it is indeed a handful. If the vehicle in question has switchable ABS (which I've never seen! I wish I could switch ABS off in my car, but I can't) then it's possible that the system is designed so that the ABS is responsible for controlling the rear brake bias. In other words, the rear is over-braked by design, and the ABS is used to keep it under control. This is how so-called "electronic brake force distribution" works - they just chucked out the old fashioned mechanical proportioning valve and let the ABS controller deal with it.

Race cars don't commonly have ABS ... in many cases the rules require that an original-equipment ABS be disabled.

 

[rpmag]

It took me a little while to find out what a plymouth arrow was!
The ABS is there I believe to assist the driver in adverse conditions, particularly as the fuel load is at least 100lt and is positioned behind the rear axle.
Thank you for the information.

 

[dgallup]

I've driven a number of old heavy duty pickups that had the brake proportioning set up for hauling a thousand pounds in the bed. Hitting the brakes with no load, especially in the rain, would easily get the back to pass the front. Keeps you on your toes and makes for long stopping distances.

 

[GregLocock]

The serious solution to that was a load sensing BPV. My old truck had a mysterious chain between the rear axle and the chassis - that was the load sensor.



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.