French Car Forum

ghostrider · Post by **ghostrider** » 15 Jun 2005, 03:55

I've just been reading the Xantia brake pedal spring thread and noticed that kowalski mentions that the C5 has gone to conventional brakes rather than off the hydraulic circuit, what are they like? Why have they done it ? the brakes were one of the things that attracted me to hydraulic cits. I remember spending absolutely ages bleeding the conventional brakes on minis and mk II, III & IV Cortinas, it never seemed to get the air out of the systems, I always wound up with pints of aerated brake fluid standing around, the Cit brakes were a revelation so why go backwards?
Apart from anything else the Cit hydraulic system has always been very reliable for me, most people who know nothing about them say they wouldn't buy one because of "the complicated hydraulics" Whereas those of us in the know are more concerned about the electrics, rust, general build quality, rear arm bearings etc etc. Now the japs have made reliable cars for ages, boring (in the average saloon category) but reliable. I've always been prepared to trade reliability for the advanced cit design, but if they are going to do away with it what reason is there to buy one?
________
Extreme Q Vaporizer

Kowalski · Post by **Kowalski** » 15 Jun 2005, 04:18

The C5 has ABS as well as EBD and emergency brake assist these are complex systems that cost a lot to develop and test. PSA could develop one set of systems for the C5 and another for the 407 but with economies of scale it makes more sense to engineer one car (as much as possible) and sell it as two cars.
The hydraulic suspension and ride quality are the selling points of the C5, I suppose they're trying to give it mass market appeal while still keeping the Citroen fans happy and they're not going to be able to do both perfectly. I think the Activa is probably the most Citroen like Citroen we're going to see for a while, unless the C6 is suitable charactorful / quirky.

406 V6 · Post by **406 V6** » 15 Jun 2005, 20:00

And note that the C5 has an electric high pressure pump, with a minimal acc. sphere-like space, no more usefull than for absorbing the pump oscilations.
Imagine the little bugger always working due to the brakes[;)]. It wouldn't be more reliable than a convencional pump.
As for EBD and emergency braking: Cits has them for some decades, now! What's all the fuss about?
With the C5, the pleasure of messing around with hydraulics is partially gone[:(], there's little to do but changing spheres and replacing the height sensors when they go bonkers.

bxbodger · Post by **bxbodger** » 15 Jun 2005, 21:51

<blockquote id="quote">quote:<hr height="1" noshade id="quote">emergency braking: Cits has them for some decades, now! What's all the fuss about?
<hr height="1" noshade id="quote"></blockquote id="quote">
Not quite!! True, Cits have had vastly superior brakes in the past, but the others have now caught up using conventional systems-drive a newish car and it comes as a bit of a shock to find out how good brakes now are.
What emergency brake assist does is take full advantage of a.b.s. and apply a lot more pressure in an emergency than the drivers foot can-It senses that you applied a lot of pressure or pushed the pedal really quickly and wanted an emergency stop-you lower the pressure slightly, panicing, whatever, and it piles it on for you. with safety at last being a selling point people want it and the C5 is difficult enough to sell without a discount as it is- imagine trying to shift a car in that market segment without one of the current must-have safety features!
<blockquote id="quote">quote:<hr height="1" noshade id="quote">what reason is there to buy one?<hr height="1" noshade id="quote"></blockquote id="quote"> None, really, thats why they are available at such a heavy discount- I notice they are starting to bargain bucket the C4 as well.

jeremy · Post by **jeremy** » 15 Jun 2005, 23:16

I thought there was a little more to it than that. Imagine - you're approaching a queue of traffic at 70 MPH. You don't know if its stationary or moving - so you brake gently - and suddenly you're too close to it and in trouble. Had you braked harder when you first applied the brakes you'd have had no problems. So EBA - senses this situation and puts the brakes on hard to begin with! - so safer!
Jeremy

Post by **CitroJim** » 15 Jun 2005, 23:33

Jeremy, very interesting. I have never driven with ABS but slightly off-topic here, now I've modded my brakes they are excellent. so much so that when I drive my 205 the brakes seem terrible although they're not in reality but the difference is staggering.
So, does the C5 still have the spheres and rams we love so much on the suspension. I heard the pumping is now electric and it uses fluid called LHS2. What sort of fluid is that and why move away from LHM? A non-LHM Cit is just not a Cit unless it's an early DS of course!

jeremy · Post by **jeremy** » 16 Jun 2005, 01:34

I think you mean EBA (or whatever its called) rather than ABS. I've got ABS (working) on my BX TD estate and must say of all the cars I've had its the one that needs it least.
I was interested in the theory of EBA and now consciously try to brake hard earlier in the situations in which it might function.
After powered BX brakes I always find the ZX brakes very soft and uninspiring! (and usually end up wondering if there is something wrong - but they've always been much the same and work a bit better with new front discs)
Jeremy

406 V6 · Post by **406 V6** » 16 Jun 2005, 02:25

Citrojim, Citroën made a suspension system for the C5, that, in it's history, is only found on the early ID's.
So, Citroën mechanics and engineers have managed to squeeze an acumulator, a pump, "height" correctors (actually, the valve bit of it) and little more into a small unit that you can hold with your hands (if it wasn't so heavy, you could hold it on top of one hand).
The fluid is not LHM2 but LDS (don't confuse it with LSD, that would rock any citroën[:P]), a completely synthetic fluid. It probably is compatable to some extent with power steering fluid, as i don't see citroën using different rubber o-rings as sealants on similar pumps. But then again...
Cheers!
BTW: the C5 brakes are as sensitive as an early DS (at least on the first inch or so of travel. good for waking you up!)

Kowalski · Post by **Kowalski** » 16 Jun 2005, 02:27

EBA is supposed to detect that your're slamming the brakes on for an emergency stop and slam them on faster than the driver would have been able to, I don't know how they compare for speed with hydraulic full power brakes though.
My understanding is that EBD is supposed to keep the car braking in a straight line, i.e. if it detects that the car is going to oversteer while braking it will use the brakes to steer the car straight.

fastandfurryous · Post by **fastandfurryous** » 16 Jun 2005, 03:13

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Kowalski

EBA is supposed to detect that your're slamming the brakes on for an emergency stop and slam them on faster than the driver would have been able to, I don't know how they compare for speed with hydraulic full power brakes though.
<hr height="1" noshade id="quote"></blockquote id="quote">
Close. In more and more cases over the last 10 years it was found that in emergency situations drivers were simply not pressing the brake pedal hard enough. This is partly to do with an ageing populus, and their inability to "slam" on the brakes, and partly to do with fewer and fewer people having any sort of understanding about mechanics and engineering, and thus how their car works, and how to use the brakes effectively. Crashes were being investigated that had no skid-marks from braking etc.

What EBA does is to detect the time from coming off the accelerator to going onto the brake, and if it determines that you are "panic" braking, applies full load to the ABS to make the car stop as fast as is possible. Personally, I can brake quite hard enough thank you, and wouldn't want any such sustem on my car!
<blockquote id="quote">quote:<hr height="1" noshade id="quote">My understanding is that EBD is supposed to keep the car braking in a straight line, i.e. if it detects that the car is going to oversteer while braking it will use the brakes to steer the car straight.
<hr height="1" noshade id="quote"></blockquote id="quote">
Nearly. That description is for ESP (electronic stability programme). Another system for people who have no idea about the dynamics of their car, and how to control it in an emergency situation. ESP monitors the requested direction change through the steering wheel, and if the car is not responding accordingly, it applies brakes individually to get the car to do what was asked of it. EBD is a fairly basic system that can only release pressure from brakes rather than actually apply the brakes individually (as ESP can)
Like all "safety" systems introduced over the last howevermany years, all these systems have done is to increase the speed at which a crash occurs, as people drive faster & closer to each other than they ever did before. Airbags, ABS, EBA, EBD, ESP etc etc are all well and good, but they have had no effect on road casualty figures worldwide over the last 25 years.
Whilst I am not advocating a return to 1950's car safety technology, the level of safety in the 1970's & early 80's was enough that you were more likely to survive a crash, but didn't have all manner of electronic systems artificially cushioning you from the real world.

bxbodger · Post by **bxbodger** » 16 Jun 2005, 04:50

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Whilst I am not advocating a return to 1950's car safety technology, the level of safety in the 1970's & early 80's was enough that you were more likely to survive a crash, but didn't have all manner of electronic systems artificially cushioning you from the real world.<hr height="1" noshade id="quote"></blockquote id="quote">
I'm sorry, thats total conkers!!!It wasn't until the mid 80's that even rear seat belts appeared!!!!Its as much there to protect you from other people as yourself. Here's the scenario-
Imagine your'e pootling along the local high street, minding your own business, in a C5 ( or any other modern car, come to that ) and Mr spotty twocker comes hurtling broadside across the junction straight at you[:0] doing 60 odd- you have no chance to avoid him- the airbags go off,side & front, the pretensioners yank you back, the crumple zones crumple,EBA stops you quicker, lessening the impact,the fire brigade cut you out- off to hospital[B)].
Now, same scenario, my BX- a 70's design- the fire brigade cut you out, off to the morgue......[xx(]
In the 70's & 80's apart from Volvo, no-one sold safety: the only improvement over 50's design was a bit of crash padding internally, belts (but only in the front.....) and collapsible steering columns. Some, but not all 70's cars got front discs and radials appeared. That was it!!!

dillosk8ter · Post by **dillosk8ter** » 17 Jun 2005, 00:42

<blockquote id="quote">quote:<hr height="1" noshade id="quote">
In the 70's & 80's apart from Volvo, no-one sold safety: the only improvement over 50's design was a bit of crash padding internally, belts (but only in the front.....) and collapsible steering columns. Some, but not all 70's cars got front discs and radials appeared. That was it!!!
<hr height="1" noshade id="quote"></blockquote id="quote">
True the Volvo 300 series launched '75 had built in safety cage, crumple zones, side impact bars and seat belt 'grabbers'...also duel circuit brakes I think...which puts my '93 ZX to shame!!! lol

fastandfurryous · Post by **fastandfurryous** » 17 Jun 2005, 00:51

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by bxbodger
Here's the scenario-
Imagine your'e pootling along the local high street, minding your own business, in a C5 ( or any other modern car, come to that ) and Mr spotty twocker comes hurtling broadside across the junction straight at you[:0] doing 60 odd- you have no chance to avoid him- the airbags go off,side & front, the pretensioners yank you back, the crumple zones crumple,EBA stops you quicker, lessening the impact,the fire brigade cut you out- off to hospital[B)].
Now, same scenario, my BX- a 70's design- the fire brigade cut you out, off to the morgue......[xx(]
<hr height="1" noshade id="quote"></blockquote id="quote">
I agree completely with that. The problem being why was Mr Spotty Twocker doing that kind of speed and driving so damn dangerously in the first place? Possibly because he is aware that the car he is driving is a lot safer than cars of old, and is driving faster because of that (OK, this is only one possibility, but it has been proven to be true in many cases)
(Actually there's one point I don't agree with. EBA woudn't make MY car stop any quicker, because I can brake quite hard enough thank you)
I absolutely agree that if everyone drove their modern cars in a safe manner, then modern cars would be safer than 1980's ones. Unfortunately modern cars don't get driven like that. People tailgate, brake at the very very last second, swerve in and out of traffic, and generally drive like complete twunts. (Not everyone, just some people).
What is needed is driver testing. You can have every electronic gismo under the sun, but the driver is the problem. If you were to put the same dangerous driver in a car with NO safety features, not even seatbelts, how do you think he would drive? I think a lot slower, and an awful lot safer.
If you were to tell every person in the UK that their car has been filled with explosives, and if they hit another car then they are guaranteed to die, I bet you would see a dramatic reduction in casualties.

Kowalski · Post by **Kowalski** » 17 Jun 2005, 02:11

The other thing about 70s and 80s cars is that they used to rust making them even weaker, CXs did and BXs seem to as well, but cars from the 90s (e.g. Xantias) don't seem to be loved by the tin worm.
Traffic density has a lot to do with accident rates, I was thinking the other day that there is no way I'd want to be teaching somebody to drive with traffic density being what it is.

jeremy · Post by **jeremy** » 17 Jun 2005, 04:10

I think you'll find that both Ford and Vauxhall are keeping the rust tradition going - just look at some rear wheel arches when one is alongside you in a traffic queue. Now Mk11 BX's don't do that , nor do ZX (similar construction to Vauhall & Ford.)
Jeremy