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RoyChristie
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Re: abs or no abs

Post by RoyChristie »

Kowalski wrote:
RoyChristie wrote: I fail to see where ABS would have helped in this case as there is no reserve of braking assist in this instance.
The ABS could have stopped the wheels from locking and stopped the engine from stalling assuming it could work quickly enough. The problem here was that even if without power assistance on the brakes, he locked his wheels. ABS could have helped if there was a gap big enough for the Xantia to fit into, bit it seems that was not the case.

....
thanks Kowalski,
my logic had skipped that bit
I learn every day
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Re: abs or no abs

Post by bencowell »

Kowalski wrote:The ABS system on the Xantia was far from perfect, the Xantia's wheel base length changes when the rear suspension moves, I found that putting one wheel into a pothole would sometimes momentarily trigger the ABS....
That would be because putting a tyre into the pothole makes it leave contact with the road and the brake makes it lock up momentarily.

Braking hard on cobbles does the same thing.
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Kowalski
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Re: abs or no abs

Post by Kowalski »

bencowell wrote:
Kowalski wrote:The ABS system on the Xantia was far from perfect, the Xantia's wheel base length changes when the rear suspension moves, I found that putting one wheel into a pothole would sometimes momentarily trigger the ABS....
That would be because putting a tyre into the pothole makes it leave contact with the road and the brake makes it lock up momentarily.

Braking hard on cobbles does the same thing.
I thought that too but sometimes the right sort of undulations that wasn't really a pothole or a bump would do it too. It may just have been dodgy ABS sensor wiring though.
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Mandrake
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Re: abs or no abs

Post by Mandrake »

Kowalski wrote:
bencowell wrote:
Kowalski wrote:The ABS system on the Xantia was far from perfect, the Xantia's wheel base length changes when the rear suspension moves, I found that putting one wheel into a pothole would sometimes momentarily trigger the ABS....
That would be because putting a tyre into the pothole makes it leave contact with the road and the brake makes it lock up momentarily.

Braking hard on cobbles does the same thing.
I thought that too but sometimes the right sort of undulations that wasn't really a pothole or a bump would do it too. It may just have been dodgy ABS sensor wiring though.
Mine used to do that too.

Driving to work every day when I went over the curb turning into work, (a relatively high curb) as the back wheels hit the curb one after another if I was pressing lightly on the brake pedal as they went over, I would feel the pedal pulsing from ABS action.

There was no chance of the wheels locking up due to the lightness of pressing on the pedal, so I can only assume that either the wiring to the rear sensors was slightly dodgy and going open/shorted with violent movements of the rear arms, or the sudden instantaneous change in wheel velocity when the wheel climbed the bump confused the ABS system...

Regards,
Simon
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Post by Citroenmad »

I cant understand anyone ever wanting to disconnect their ABS, its crazy, its a very important safety feature which is quite rightly a requirement on any mass market car produced from late 2003 onwards.

The main objective is to allow you still to turn when braking hard. This is especially helpful in poor conditions such as rain, snow, ice etc.

Locking the wheels is a bad idea, as the car just slides and the wheels act like skies. Ok so maybe in deep snow you can get a build up of snow infront of the tyres which slows you, but you still wont be able to turn. Very bad if your heading down an icy hill with a bend at the bottom! You have a better chance of steering around something than stopping before it on ice with or without ABS, so surely ABS is the better option?

All C5s have ABS and EBD, which sends more braking pressure to the wheels with more grip. This really seems to make the car pull up very evenly, in a decent amount of time and without drama.

Our streets around here are just ice now, i tried to walk the dogs earlier but turned back after 5 minutes as it was so slippery, i spent the whole time grabbing onto the walls to get back, the paths and roads are like walking on polished marble in socks. So you get the idea, just ice.

After that i thought id try out see how ABS fairs, first i went out in our little Seat, which does not have ABS, it does have very good michelin tyres with lots of tread though. I went down our road at about 20mph and pressed the brakes, the car locked up and started sliding for the curb due to the camber on the road surface. I had to come off the brake and steer into the middle of the road to avoid colliding with the curb, which is what would have happened had i kept the brake on. I must stress our road is very quiet and open, i was also miles from the curb but thats the way it was heading.

Then i jumped in my C5 and tried the same thing, this time it stayed straight and didnt veer off for the curb, it stopped in a reasonable time and without any fuss. I didnt even get stopped in the Seat as it was sliding around.

I know they are two totally different cars but it does rather prove a point to me that id much rather have it than not. Although im not sure if the fact the C5 did well braking with ABS has anything to do with it having EBD too, maybe a car with normal ABS brakes would perform differently. Had there been an Xm easy to get at i would have tried that.

I also tried it around a curve, braking while turning, the C5 still turned ovbiously as the ABS was working, but the Seat went straight on.

I also tried the facelift C5s traction control system, as i had not had any need to use this before i was interested at how it works. I just tried it on the drive which is very slightly uphill and covered in shiny ice, pulling away normally it spun the wheels, i kept the revs on and the wheels kept spinning, but the car was moving forwards. I had thought it wasnt working as the wheels were spinning and the revs were not dropping. However the key thing was the car was moving. After i turned the traction off i tried it again and the car just sat there spinning its wheels and not going anywhere.

What it seemed to be doing was applying the brake to one side and the then other to try and get grip. It worked well as it did pull away unlike with the traction turned off.

Ive only had the ABS come on a few times with the C5 in the snow/ice as ive been careful, but its very nice to know its there and it has been helpful at times. This has been my first winter with an ABS equiped car, so im well away of driving with no ABS in bad conditions and i much prefer ABS.

Ive not had it come on without me needing it. Yes ive had it on over potholes a few times when braking hard but thats expected. Im quite hard on brakes and never find any problems in day to day driving with it coming on when not needed, its just nice to know its there if i do.

Im all for these electronic safety measures, ive never had them come on when ive not needed them but they have been brilliant when i have. The Xms ABS saved it a few months ago when a stolen car drove straight out infront of me in the rain, without ABS in sure it would have been a write off as the speed he was going it wouldnt have been great to be involved in an impact with it.

Ill have to try the Xm and see how that performs.
Chris
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