Abs sensor failure - what happens to rest of system?

[loggyboy]

After replacing my front wheel bearing at the weekend, the abs sensor appears to have become a casulty of the heat and/or impacts from getting the rust ring and old shell out.
The ABS and SERV lights are now on. I took it for a run and all seems ok but thought id try to see what effect having a failed sensor would do to the rest of the system under heavy braking. Judging by the 20m '11's and cloud of spoke I left behind It appears it shuts it off completely - does this mean that its defaulted the balance/bais to 50/50? as i didnt feel like the rear was locking at all, which if there was any more than 30% braking to the rear I would have suspected the rears would have locked 1st.

 

[Edges]

I had a broken sensor for ages and it seems it doesn't effect the bias too badly, disconnecting a sensor does the same thing. Just disables abs and TC/esp.Mot failure though

i think you'd be fine driving around.. I went to Bedford track day with mine not working and it didn't lock the rears.

 

[loggyboy]

Yes it was nice to really feel the brake limits without the over sensitive (IMO) ABS, might try out over next few weeks before ordering the new sensor. Have a possible day at Rockingham coming up so could be a real chance to test it.

 

[cheesegrater]

ABS looks at wheel speeds, it then compares them. If it can't see them it can't operate. Most systems simply turn off the ABS when in this failure mode.

 

[AlexW]

If three sensors stop working (for instance, rears unplugged) and one front, speedo will stop working properly, handbrake and stop light come on too.

 

[loggyboy]

ABS looks at wheel speeds, it then compares them. If it can't see them it can't operate. Most systems simply turn off the ABS when in this failure mode.

The ABS system on the 172s also control the brake bias, so usually any disabling of the system (ie pull the fuse) means (allegedly) the system defaults to 50:50 brake bias, which would fairly dangerous under heavy braking.

 

[AlexW]

Take the fuse out and you'll see how s**t they go. Even with one or two ABS sensors working, it doesn't feel as s**t as with the fuse removed lol.