xantia abs sensor air gap

[saeedm]

how much air gap is acceptable for xantia abs?
this one have 6mm air gap!! -heat shield over sensor-

[xantia_v6]

The series 1 sensor is longer than a series 2, so if that is a series 1 hub, it probably has a series 2 sensor fitted. I think it will work if you modify the mounting lug to move it closer, but I don't know the correct clearance.

[saeedm]

the car is mk2 and the sensor is the original one - i think!-
you mean cv joint by saying hub?
cos abs gear is over cv joint.
i think it is peugeot 405 cv joint !!

[white exec]

Gap is usually around 1mm.

[saeedm]

i measured abs gear outside diameter and it was 90mm. so this is correct for xantia - i think!-
if cv jont and abs sensor is the right one so it can be from knuckle!!!

[saeedm]

The series 1 sensor is longer than a series 2, so if that is a series 1 hub, it probably has a series 2 sensor fitted. I think it will work if you modify the mounting lug to move it closer, but I don't know the correct clearance.

you are right
update:
until 1995 Xantia had 90mm abs gear with 48 teeth, and 29.8mm abs sensor length
From 1995 onwards Xantia have 99mm abs gear with 48 teeth, and 25.2mm abs sensor length
the sensor air gap can be from 0.6mm to 1.8mm

source: xantia manual

as shown in pic:

[captainkephart]

Hi All,

Brakes have been fine on the car for months.

The brake warning light has come on on my xsara picasso (no fault codes) after removing the front abs sensors to clean them (as part of changing pads).

The sensor to ring gap before removing was barely 2 thou inch (0.05mm) at the high point on the ring where two to of the ring 'teeth' are shiny (so assume sensor is just touching there). The rest of the way round the gap was just under 1mm (30 thou). Is this right?

I assume the teeth tell the sensor how fast the wheel is turning and the high point enables it to count wheel revolutions?

Anyway, I checked the sensor seating and it was not clean enough when I re-fitted it first time. ABS now OK, but still puzzled about the high spot ... any advice? The ring is firmly attached, no rattle, and there is no bearing wear. Wheels are also properly balanced.

Thanks, Captain K

[white exec]

Gap should be constant. ABS just counts the teeth, with some cars getting their road-speed/distance data from that (as opposed to a gearbox output sensor).
Haven't found a specific Xantia figure, but looks to be 0.5 to 1.8mm on several websites.
Basically, the closer the better (without scraping), as this gives a cleaner waveform.
The rotational (mounting) orientation of some sensors is important, so could be a good idea to use specified original sensors.

[captainkephart]

Thanks ... Ah! ...
So the high spot on the ring means what? It's on both front wheels so assumed it was part of the design ...

[white exec]

ABS rings have been known to rust, snap and distort. Should be properly circular.
The tip of ABS sensors is also strongly magnetic, and can attract ferrous dust/debris from general road use, and brake disc wear.
Ferrous debris clinging to the tip of the sensor will disrupt its action, or can look like sensor failure.

[captainkephart]

Hi Chris,

Thanks, but, sorry, should've made clear that my questions refer to a Xsara Picasso petrol 1.6 2009 (I just added to the Xantia post because it was the same topic ... probably not a good idea!).

Could the rings be different on the xsara? As both the front rings have the identical high spot in the same way and place how could that occur if it is just 'everyday' distortion?

Not questioning your knowledge, just trying to understand whats going on here.

Thanks again, Capn K

[saeedm]

replace abs gear or cv joint