ABS in snow - help

[Mattsonics]

Driving on snow quite a lot over past two days - going up a very steep snow covered hill, had to reverse and take a different route, whilst reversing brake pedal started juddering pretty violently and with high pitch noise accompaniment!

had to use handbrake down hills after that, (obviously as little as poss etc.) as applying pressure to foot break resulted in sharp judder, noise and brake cylinder noise i think!?

importantly - i think - the wheels weren't locked - i.e. i wasn't sliding whilst this was happening.

i then tried on flat through town and with very little pressure got the same again.

Bongo is a 2wd P reg



help!

[mister munkey]

It will judder when the ABS kicks in. It works by releasing the brake for a fraction of a second on lock up, you get a fair bit of feedback through the pedal too.

Not too sure about your musical accompaniment though, fairly sure that doen't apply to mine.

[Mattsonics]

helpful advice! Ta

the musical accompaniment wasn't only whilst foot was on pedal in sync with feedback - it had a residual high pitch whine (not very loud but noticeable) that died down over about a five second period each time.

brake pressure still seems absolutley fine.



Matt

[missfixit70]

Sounds like it's doing what it's supposed to, stopping the brakes locking up, basically pumping them on & off, quicker than you could, to retain some grip. Stopping distance will be longer than normal but it should prevent/reduce skidding/loss of traction.

[jaylee]

In fairness though, would that not be noticeable with abs breaking at a higher speed..? ( Not that i have ABS.. But my partners Micra has!)

[mister munkey]

IMHO Unless you're doing over 90 on a wet cobbled road, you'd deffo notice it.

[jaylee]

IMHO Unless you're doing over 90 on a wet cobbled road, you'd deffo notice it.

Thas driving in in ye olde city of Georgian Bath for you!!

[missfixit70]

If it's happening when there's absolutely no reason for it, I wonder if there's an issue with one of the sensors after reversing in the snow as that's when it seemed to start?

[munroman]

I had a similar issue with a Hyundai Trajet, ABS kicking in as I was coming to a stop, even on dry and Shell Grip type surfaces.
Eventually traced to a known fault, the ABS has a sensor on each wheel which gets its speed info from scanning a toothed ring, on the Hyundai the front wheels speed was measured from a ring on the outside of the CV joint.
Problem was, the ring was made of cast alloy, the CV steel, so when the CV rusted, the rust burst the alloy ring. (In my case it was a very small crack, the system is very sensitive)
The 'Brains' of the ABS then saw a difference in wheel speeds, so activated the ABS, leading to the juddering.
A new toothed ring fixed the problem, I don't know if this might help find your problem, it might just be a broken wire

[New Forest Terrier]

I have abs on my Bongo and can feel it bumping on the pedal plus the limited slip diff locking and unlocking on icy hills. There is no noise accompanying it though.

The bumping is normal, I have had on Volvos with abs in similar conditions. Never any groaning or whining noises though. It sounds as though it all works properly which is the important bit. Any fault should activate the abs warning light.

Could the sheer cold be causing the noises? A sticky or stiff hydraulic valve on one of the wheel cylinders could be a cause of noise.

[Ron Miel]

Hope you get the problem sorted OK.

Meanwhile, although tangential, I hope this is useful and not off topic*: http://www.winter-tyres.info/faq.html - it describes in simple terms, the traction limits on snow and ice of ABS, LSD (simplified traction control), and 4WD.

*(It certainly isn't, relative to the subject title )

BTW, although from The Winter Tyre Co's website, it isn't wholly a plug for snow tyres, containing, as it does:

"Specialised snow tyres should only be used where and when they are needed – in alpine areas during winter. Few people in the UK will need specialist snow tyres. If you’re not regularly driving in winter conditions (on snow and ice, in temperatures below 7C), you don’t need snow tyres."

The pages "Winter Driving" and "Winter Driving Tips" are also worth a read.

[The Great Pretender]

Sounds like it's doing what it's supposed to, stopping the brakes locking up, basically pumping them on & off, quicker than you could, to retain some grip. Stopping distance will be longer than normal but it should prevent/reduce skidding/loss of traction.

Sorry, stopping distance will be minimised. As the ABS reads the wheel speed it stops the brakes locking a wheel allowing maximum grip to be exerted.

[missfixit70]

Sounds like it's doing what it's supposed to, stopping the brakes locking up, basically pumping them on & off, quicker than you could, to retain some grip. Stopping distance will be longer than normal but it should prevent/reduce skidding/loss of traction.

Sorry, stopping distance will be minimised. As the ABS reads the wheel speed it stops the brakes locking a wheel allowing maximum grip to be exerted.

As I understood it, with ABS the stopping distance would be a bit longer than normal (ie dry conditions) due to the brakes basically going on & off to maintain grip on a slippery surface while still braking, but I'll defer to your superior knowledge Mel

[Ron Miel]

Sounds like it's doing what it's supposed to, stopping the brakes locking up, basically pumping them on & off, quicker than you could, to retain some grip. Stopping distance will be longer than normal but it should prevent/reduce skidding/loss of traction.

Sorry, stopping distance will be minimised. As the ABS reads the wheel speed it stops the brakes locking a wheel allowing maximum grip to be exerted.

As it correctly says here, and as Kirsty correctly said, ABS doesn't increase traction, it just allows tyres to continue exerting whatever reduced traction they have on ice or snow, without total loss of traction due to wheels lock up - reduced tyre traction still means longer stopping distance: http://www.winter-tyres.info/faq.html

[The Great Pretender]

Sounds like it's doing what it's supposed to, stopping the brakes locking up, basically pumping them on & off, quicker than you could, to retain some grip. Stopping distance will be longer than normal but it should prevent/reduce skidding/loss of traction.

Sorry, stopping distance will be minimised. As the ABS reads the wheel speed it stops the brakes locking a wheel allowing maximum grip to be exerted.

As it correctly says here, and as Kirsty correctly said, ABS doesn't increase traction, it just allows tyres to continue exerting whatever reduced traction they have on ice or snow, without total loss of traction due to wheels lock up - reduced tyre traction still means longer stopping distance: http://www.winter-tyres.info/faq.html

That isn't what I said. ABS can't increase traction. ABS can maximise what grip there is by stopping wheels locking. Hope that makes sense.