Video není dostupné.
Omlouváme se.
On The Ramp | Hydropneumatics simplified: Citroën brakes - Why are they so good? (1/3)
Vložit
- čas přidán 9. 12. 2022
- You've heard people talk about the brakes on various hydro-Citroëns being razor sharp, or "strong enough to put you through the windscreen." You acknowledge it, and move on.
Why?
Why are they that good? What's different? What gives?
Well, in the first of three parts, I'm going to explain it in very simple terms (because I'm also very simple).
--------------------------------------------------------------------------------------------------------------------------------------------------------------
Want to support the channel? Become an official UP'nDOWNer!:
/ @upndown
Catch me on:
Facebook: UPnDOWNvids
Instagram: upndownvids
Twitter: @UPnDOWNvids
Did I mention I own an SM?
Hands up who remembers when Television was as informative as this?
Thank you. 👍
I've pressed my foot on a CX brake pedal a thousand times and never asked myself how they work. Now I'll do it in awe! Thank you.
I can hardly wait for part 2, finally someone is explaining citroens braking in detail. Bravo.
You don't have to wait, I uploaded it about 10 mins ago!
Fabulous video
You manage to entertain and dumb down complex and interesting stuff. Highly appreciated
Feeling spoilt, 3 hydraulic Citroen videos in 1 day, first 16valvers XM, then Chris on his black BX, and now the ring leader letting forth all his green oily knowledge.
In all of this forgot to Thank You for the video's you have put up. As a very, very long time Cit owner here in the US it is gratifying to see folks a lot younger than me take up an interest in the most innovative car(s) ever build. And that is also happening here in the US as us 'old farts' are dying off 😇.
Brilliant video and love the way you do it.
Similar story, I remember as a child being caught in a queue trying to get through a snow drift, my father got fed up with waiting, jacked the suspension up in our Ami 8 turned the car around and dived down what appeared to be a totally snow bound lane. We were there in minutes!
Ami is not a hydraulic Citroen.
@@richardsheil5289 : nostalgia does funny things to people's memories.
It nearly rode like one, though!
After I purchased my new BX19RD estate in 1987, I sent a letter to Citroen HQ asking for information on their braking/steering/suspension system. Got a whole bunch of detailed information back from them, which was really interesting. I was definitely a fan of power hydraulic brakes, being so responsive and after getting used to them, so controllable with minimal foot pressure. In fact I preferred the non ABS system as fitted to my 87 BX to the later ABS system on my 93 BX TZD. London Transport I believe specified power hydraulic brakes on their buses RT/RM models.
That was a fantastic. You’ve got a real talent for this kind of “how it works” videos.
Thank you very much!
I own a Volvo 480 and a Xantia. In terms of brakes; they are really the opposite of eachother,
The 480 has a lot of brake travel, although it brakes fine you really have to push the pedal quite deep to get the car stopping, the Xantia brakes really hard when gently tapping the brakes. When switching cars I really have to keep in mind not to brake too hard getting into the Xantia and braking hard getting in to the 480.
Great and educative video as always. ☺
Brakes on BX are great front especially they can lock wheels immediately.
Rear ones are completely different story they can work like a charm , or if you have leaky "doseur" they can give so low brake force on wheels.
Higher spec BX's were equipped with anti-lock brakes.
I've driven CXes in northern Sweden for more that 10 years (some years about 150 thousand kilometers) all year round including severe weather with minus 49 degrees Celsius and snow and ice in volumes not many people ever will encounter, not to mention driving in/on it. Picture driving the Paris Dakar rally but in Antarctica in July (the cold stormy season). My previous driving experience as a professional driver includes most half modern but also modern Mercedes', Fords, Audis, Volkswagens and a couple more including trucks, but none comes near the CX in regards to body/chassie stability, grip and general road holding, steering, brakes and comfort - all because of the very clever hydraulic system. And the steering isn't even power assisted.. hmm.. no, it's actually hydraulic as in Airbuses, Boeings and most fighter jets. The rear 'load-powered' brakes makes the braking extremely controllable and if you hit a big bump they push even harder on the disks as well as letting of pressure on the way down to prevent the brakes locking up - that is very very clever..
..and I almost forgot to say how much I love your videos, this one especially!
Of all the cars I've owned or driven since the BX I still prefer the way BX brakes feel. It was very easy to stop sharply (or skid, if you so wished) once you were used to them. Despite not having ABS I had more confidence in its ability to stop than any car I've driven since. I'd liken the amount of pedal travel from "hardly slowing" to "through the windscreen" to be about the same as the clutch going from slightly below the bite to fully engaged... if not a bit less.
Fantastically explained! Very entertaining video, looking forward to the follow up 😁
Love it, every time I watch a video I look for older hydro citroens then I realise that I haven't the time or patience to own and maintain another one (father issues he's had them since I was a kid)
These systems are pretty reliable, in fairness.
Another good video 🚗🚙🚘👍👍👍⭐️⭐️
A bit to Auto trivia :). In 1968 an Oldsmobile Toronado (the first FWD from GM) won the famous Pikes Peak (in Colorado) Hill Climb. In its next issue Motor Trend Magazine had a comparison of a DS21 and the Toronado with the headline of 'One can go but can't stop - the other can't go but boy can it stop'. The first paragraph in the article noting that the Toronado did win, they wondered how they ever got it back down.
Very enjoyable lesson look forward to the next.
After getting used to the brakes on my Xantia I honestly much prefer them to ''regular'' brakes with brake boosters. I don't think they're at all hard to modulate or ''too sharp''. The travel is so little that it feels like they're pressure actuated rather than travel actuated. And I quite like that feel.
Excellent explantion, well done! I miss my Xantia ('95, 1.8i, early 16V engine which burnt oil) with its superb comfort but the rear hydaulics let me down in the end. The servicing wasn't up to scratch and they couldn't get it right, a great pity ...
BX GTi 16v? Well, that was unexpected! I also own a BX, had to change that break valve, there is a small ruber part in it, it broke after 30y of service, and I had LHM coming into cabine. Got a new ruber for like 2-3 euros put the new ruber into the break cilinder and put it in the car. Works like charm, ready for the next 30 years or so.
A big advantage of glove based brakes is that you can break your spare wheel as well!
Yes, hadn’t thought of that. 🤔
Loving the use of anchor with a silent W
Spot on Rich.
I've learned something today, Kitch.
Thanks for explaining this so simply 👍
Thanks for another great video you would make a great teacher as well
'bout time somebody did a proper video about those beautiful brakes.👍👍👍👍
In the next segment you might want to add why Cit changed the bake valve actuation from the 'le mushroom' (D's/SM's) to a 'conventional brake
pedal :).
I don't know but I guess it had something to do with Peugeot taking over?
@@gerardnieborg - a reasonable assumption but no. The CX was designed long before Peugeot acquired Cit in 1975. For a lot the CX was the last 'real' Cit. All models after that shared a lot of parts with competing Peugeot models.OTOH my 92 XM shared the same platform as the 605 - the first to so.
That'll be part 3, which'll be 2023 sometime.
I noticed someone thought that a leaking brake valve would reduce pressure to the brake system. A leaky 'doseur' valve does not reduce brake force. There are no O-rings in that unit. Pressure is contained via machining tolerances between pistons and cylinders on the order of less than 1/2 of a wave length of light and a specific surface finish. Keep in mind that even the original 7 piston pump provide about 860 cc of hp fluid (1900 - 2350 psi) per minute at an engine speed of 600 rpm. The later cars - CX onward - use a 5 piston unit that provided as much or more volume. N2, OTOH, in the brake circuit(s) will give a feeling of a lack of braking force. As the brakes are a closed end system one would have to an actual external leak for brake pressure loss. All D's (with exception of some latter models) and SMs/CX's had a pressure back up for the brakes using a separate accumulator and valve system that would, if in good shape, provide for at least 5 or so panic stops from high speed with complete hydraulic failure with the main system. Edit - left out some very early ID's with manual steering. Did not use the HP system for the brakes - special master cylinder was use.
Many chuckles amongst the excellent info here, cheers Richard :D I do wonder if my Dad might've been fully converted to Citroen-ness if he'd bought that GS we looked at in the late 70s...white it was, nice and boingy. We spent enough time in France despite being from Newcastle so he'd definitely have had places to get it fixed...
had a red H reg BX 1900 diesel & loved it (right down to sitting stationary with the anchors hard on then releasing the brake pedal & getting it to launch its bum into the air).
It does them no good, doing that...any yet I used to do it a lot, too!
Nice video!
You could have titled it "Nerding out about Citroëns"
😉
The only time I’ve noticed any brake dust on the back wheels of my Valver is when I’ve been towing my caravan to CCC events. A tonne of Swift Corniche definitely gives them a well deserved workout.
Shouldn't have more than 75kg noseweight on there, in fairness!
So in essence, braking force in a 'real' Citroën is proportional to the *displacement* of the brake pedal (or button) rather than the *pressure* applied to it. That makes sense 🙂
great content. and even breaks being ferocious is ahead of its time. they are all well strong by now. cheers
edit: Merchandaise idea; cult symbol. not that I'll be able to buy it but would be a great little easter for "exclusive" followers
Downside to the rear brakes being fully proportionate *AND* the handbrake being on the front was they hardly ever got used. My parents BXs used to end up with crusty rear disks because of that.
Still, pretty minor downside all things considered.
Really interesting thanks - we are trying to get our heads around a 79 Maserati Merak (in bits) which has Citroen LHM brakes, clutch and pop-up headlamps (why????). Has normal brake and clutch pedals. And normal suspension. In the Bora Citroen decided power steering and seat adjustment should also be hydraulic!. In the Merak those are just muscle-powered 😃. Thankfully Ray Calvert in Bradford is helping us out….
Citroen wanted to showcase how clever their hydraulics were by having exotic sports cars use them - it wasn't just cos they wanted Maserati to make the engine for the SM!
Brillant video! Well done
Can we start a petition for TSW Venoms to be the official wheels of the Tractiva?
Just the name "TSW Venom" makes me think of ridiculosly lowered Vauxhall Corsas bouncing down the road just from driving over a leaf, all the while blasting obnoxious music for some reason.
You can start it, but I doubt you'll create any meaningful change! haha!
I found it was a scenario of "Systematicdesensitisation" or Something you just get used to.
Interesting fact you may not know, about the early ID19 brakes. Although they were not powered off the suspension system, they had a 'failsafe' system built into the master cylinder, that if triggered by a master cylinder failure, full pressure from the suspension was applied to the front brakes, causing a rather rapid (and probably dangerous) stop. Never happened to my ID, but read about it on the Southern California (socal) citroen facebook group pages. My ID19 (a Slough built example, delivered new here in New Zealand), required repeated work to unfreeze the 'conventional' front brakes. As the local service manager said at the time, the DS brakes were far better. The ID did however benefit from the anti-dive characteristics of the suspension under heavy braking though. Instead of the back end of the car rearing up like most cars, the rear suspension also plunged downwards, giving spectacular stopping power. My current C5-X7 V6 Exclusive (a 508 in disguise really) still sports hydractive though, and its rather a shame that PSA gave the system up about three years ago.
😀- why my mother with our first ID19 referred to them as the 'Jesus Brakes' as the first time it happened to her what came out of her mouth was "Jesus Christ"....However that system was only the lowest spec ID's that did not have PS and the system use a single piston pump. An ID with PS used the brake valve we all know and love.
I need to learn about the early ID brakes. Some say they're still powered ones, just simplfied versions, and others say they're conventional - with master cyl etc.
@@UPnDOWN The early ID (mine was a 1961), had a master cylinder and unpowered brakes and steering. Still inboard disks though. The DW a few years later had the DS powered brakes, but retained the ID manual gear change. Later ID models, I am not sure about.
@@murraygnz - All had front discs/drum rears regardless of model. The DS19 'Grand Route' was the first DS model with a manual transmission.
Brilliant vid Rich - thx!
I miss my old BX accumulator tick 😥
The one time I had to brake very hard in a Citroen XM (on a motorway) it felt like it had been grabbed by an aircraft carrier arrestor hook.
Agreed that BX brakes are superb but the C5 ones are pretty damned good too.
Nearly shit myself when trying the GS brakes for the first time.
Great informative video I am unfortunate to have the later Citroens with the peasant braking system! Know I know what it means by LHM being the life blood of Citroens with it having to do brakes, suspension and the likes.
Same - the C6 also has peasant brakes. Phale.
Maybe jumping in too soon but as you say - the same mechanics - pads on discs (except ds/id). My problem is control. Ok all or nothing on a racetrack but not so much around town. Speaking as a previous Citroen windscreen headbutter
That, typically, is the result of gas in the brake system. Causes a lack of initial brake function and then as one presses harder they came on all at once. OTOH the Cit brake system - especially with the activation in the D's and SM's - did require a bit of getting use to. OTHO once one did, all other systems felt sluggish by comparison. With the CX and latter models the mechanical resistant was increased to provide more 'feel' if you will.
As suggested, that's probably air/gas in the circuit. The cars with ABS do have a duller pedal on BXs, and the Xantia has a horrible pedal feel as they tried to 'normalize' it by adding springs.
@@UPnDOWN - XM's with ABS are the same. Not sure if you are aware but LHD V6 XM.s with DRAVI are also equipped with a brake accumulator and the only model so equipped. Same exact unit as found in CX's. Was a bit surprised when spotted.
if you drive one for more than a day you rapidly get used to it. Even now after driving and owning several much more modern cars I would prefer the brakes to feel like they did in a BX.
At last, someone who doesn't insist on calling it hydro-pneumatic. There's neither water or air in the system. Truly it should be oleo-gaseous - LHM fluid (oleo) and Nitrogen (gaseous) behind the diaphragms in the spheres. Wish I still had my BX TZD estate.
I do, most of the time, as it's just the conventional norm for these cars (what does it matter, as long as you've conveyed your point?) But I do stop every now and then and laugh at the fact that strictly-speaking, they aren't hydropneumatic!
Then again, maybe they are; Maybe the definition is just a fluid and a gas.
I will be on the lookout for a BX16V in the New Year if you know of any likely to come up for sale please let me know.
MEG is still on eBay now 😔
@@UPnDOWN Yeah saw that but it looks fairly tired now and doubt it has had much work done to keep her going since you sold it so I will keep looking.
" Is the high pressure hidraulic system used how servo assistance producing high power brake actions on piston calipers "...! Yes are power brake action system 😊
Erm...yes! Or no.
Hi
Is the first C5 a proper Citroen ? I'm about to get handbrake cables on mine but I heard that sticking handbrakes/front calipers are problematic. Do you have some good info on this issue? Does the C6 or related Peugeot have the same compliant ?
Thanks
The C5, for me, isn't really a 'proper' Citroen. It's too far removed from what Citroens used to be about, despite the suspension still being hydro. I don't like them myself, but they're a competent and practical car, for sure. Only my own views, of course!
The C5 is the only hydro-Citroen to use regular DOT4 brakes, too. The front calipers are basically a larger version of what most cars have on the back, and many cars these days suffer seized rear calipers (the Saxo does!) With green-blooded cars, you're much less likely to have the issue as LHM isn't corrosive or hydroscopic like regular brake fluid, so I can imagine that it's a problem almost unique to the mk1/2 C5.
The later C5 and C6 are totally different, with the handbrake acting on the rear wheels, but still normal brakes (and bang-average they are, too).
For those with newer Cits, 2001 and onward, LDS is nothing more than synthetic LHM. The airline industry went to synthetic hydraulic 'oil' as it has a higher flash point than non synthetic or mineral based oil. LHM is nothing more than high quality mineral hydraulic oil with a green florescent dye added. In the mechanical world 'hydro' refers to any liquid used in pressurizing systems. LHM/LDS have a viscosity of 15 (fluidity) and a VI, viscosity index, a measure of a fluids ability to resist viscosity changes with temperature changes. LHM had VI of 300, LHM+ is 320, LHS was 280. Have no info for LDS but would be surprised if any real difference compared to LHM+.
I have driven one single BX, and i found the brakes a lot harder to modulate than on a GSA which i felt were 'just right'. Is there a significant difference between the two, or are they supposed to feel the same and was it just a car-specific thing?
The ABS-equipped cars are a little dull on the pedal and the reactions aren't quite as linear as the non-ABS cars (Which are more like a GSA).
So I'm seriously looking at purchasing a 1991 Citroen Bx have many questions about the maintenance of this vehicle and how the car operates over all. Watching and listening to you going over all of this is very informative and I'll be watching through your 3 part series. That said, are there any things I should be looking out for specifically when I go to purchase the 1991 model that are red flags?
Rust!
@@UPnDOWN from what I can tell from the one that's being sold, it has a minimal amount of rust from what I can see in the pictures. Would it be possible that I could forward you the link to the one I'm looking at purchasing?
Oh, another question I have is how hard is it to aquire repair parts for it? I'm in the US so I'm sure it'll be a bit more difficult, but if they're scarce naturally then that's another thing I'll need to think about before purchasing it.
10:28 ... didn't see that coming ... nope, not one little bit ... 😆😆😆
Probably one of those things that should be on every car enthusiast's bucket list ... drive a Citroen with this type of brake system to feel what real brakes can do.
Loved the brakes on the citroen bx when i used to own a few many years ago far superior to anything else id driven back then.
Thanks for the explanation... so there's no conventional brake fluid in this system? Replaced by LHM?
Correct. Same fluid does suspension, brakes and steering (on cars with PAS).
The answer is in pt 2! 👍
So, if your suspension had a bad enough leak would the brakes not work?
Eventually. If you spring a leak bad enough to lose all the hydraulic pressure, the security valve closes and the brakes end up being a closed circuit. You get around 30-40secs of time to apply the brakes before the pressure dissipates, so you will lose them eventually (as you would if a regular car sprang a hydraulic leak in the brake circuit), but you wouldn't lose them straight away as the system prioritises the brakes above everything else.
@@UPnDOWN awesome reply, loving learning about these systems. Your YT makes that learning heaps easier! Cheers
Cool, and so much needed. Being used to the LHM system of braking, where you vary the braking force by applying different pressure to the pedal. On the other hand on vacuum assisted brake I get the weird feeling that the brakes are “sucked in” and I have to release the pedal. Is that just me, or is this general behaviour of conventional cars?
I suppose they kind of are being 'sucked in' if you have a servo. They're just assisting you really, but through vacuum.
@@UPnDOWN the LHM Citroën type of brakes just feel more „linear“ than the other ones ☺️
Hydropneumatic suspension was also used under licence in the Rolls-Royce Silver Shadow, I believe the same hydraulic system was used for the brakes, but I am not 100% sure.
I think only the rear suspension but I am not 100 % sure either.
Depends on who you ask 😀. RR, based on sources, used it for braking and body control and for suspension - not just with the same model. OTHO Mercedes did licensees the system - not sure if still using. Maserati used on the Bora when they were owned by Cit back in the early 70's - surprise, surprise.
RR licenced the Citroen system for the Silver Shadow. As the shadow platform was carried through for later Spirit/Spur and Bentley counterparts the Citroen system features all the way to 2003 when the Continental R ceased production. But the system is modified by RR, the cars have a mix of Citroen suspension and conventional. Other than very early Shadows, the cars only have Citroen self leveling on the rear. The braking system is another hybrid, being LHM, but also some more conventional elements, it's a very complicated system.
Knew that the early cars used it for suspension. Rebuilt more than a few of the spheres for folks here in the US. RR had their own sphere design including the flow control valve used in the neck of the units. But that is were my info and interest ended. Thanks for the added info.
@@highlandmalt6368 Yes, thanks for extra info. I though RR only used it on the rear. Trust them to make it more complex. Did not know they had LHM involved in brakes too. Cheers.
I love my BX break brakes. 🤔
What i have any clue of..and then the ABS come it didn't work or..the French has good ideas.traction advance is my dream car..
Half time entertainment for the England game 😀
It's a kind of " common rail" braking system right?
One way of looking at it!
'and I'm going to bleed the rear brakes now...... After I've fitted the engine'
Nah, I'm so good I can do it without!
@@UPnDOWN you've got better lungs than me if you can blow that hard!
Is your workshop anywhere near Norwich perchance?
Nope, quite a long way from it!
@@UPnDOWN Ok, you have a good collection. I went to the Lotus factory once and saw some lovely garages and Coventry too, nice industrial car places. Are you North, West or East?
I got to be honest, I am dying to get a citroen again, but in that case I would want the C5 gen 2 with the latest hydractive system. I would also like AWD, and my question is as follows: Do you know why citroen never made any AWD cars in modern times? No market for it is the obvious answer, but that seemingly hasnt stopped them before from producing stuff no one buys😆. Just company policy or technical issues making it very cost prohibitive? Cheers.
There's no real need for AWD, I think. It's extra weight, extra rolling resistance and saps performance. I guess Citroen's logic was that markets that actually *need* it (Scandanavia, Canada & very N. America...etc) were so small it wasn't worth dealing with.
The only hydro-Citroen that received AWD was the BX.
@@UPnDOWN You are absolutely correct about the need for AWD, and even though I am in a scandinavian country, almost no one needs it even here, unless they are doing something very atypical with their car. Its a bit of a bugbear with me, and I say exactly the same as you do to almost everybody thats asks... (I am a pro driver, so I get a few questions)
However, my usage of the car is sometimes just such a case: Towing 6-7000 lbs up extremely steep and slippery "hills". In this case you need enough pressure on the drive wheels, and no FWD consumer car built can provide such, sadly.
My mk2 C5 (facelift first gen) did very well for what it was, but it couldnt cheat physics. RWD could possibly work, but I would like a citroen again. I have been toying with the idea of mounting "Tractor weights" on a bracket on the front, but I am unsure of how much is needed and if its even possible to make a bracket to place them..
Anyway, very good answer from you. Thanks.
nice vid thanks
Early DS'es had LHS. It was somewhat agressive to the sealings as I recall..
LHS was a glycol based (ie like DOT 3/4 brake fluid). Problem was/is that glycol base fluids absorb water. Not a real problem in a closed systems - normal braking systems. The Cit system is 'open' as the main reservoir is open to the air. This the LHS systems, over time, become contaminated with water. This led to accumulation of water in the brakes and rear suspension units causing rust and corrosion problems.
@@citroenfan8930 well explained. Thanks.
@@citroenfan8930 Thanx for the correction. You are right.
@@uwekall6281 No need really - lots and lots of folks get confused about the very early cars - coming on 66+ years. And why they used LHS - was made to their specific formula - in the first place still puzzles a lot of us. Mineral based fluids where already in use by the airplane industry and had been for some time.
BX brakes, suspension and steering are just in a power of a tini belt. No belt no driving or worse, no braking. 😅
That why is good to have hand brake on front wheels. ☺️
Well, about 30secs of braking, if your system is in good shape!
Am I right that the early BXs also had the mushroom brake pedal?
I think they stopped using the 🍄 in the GS already.
I think the last models to use the 'mushroom' were the D's/SM's. The CX has a 'conventional' brake pedal.
No, it was only the DS & SM (plus the odd variant of D Super/ID).
@@UPnDOWN It was also a long time ago when I was an apprentice car mechanic that I was allowed to drive a BX into the garage and experience the special braking, but you showed in the video how it works with the BX.
I found the same sharpness on a K10 Micra - then again they had a sharpish servo and I was driving a car with non servo brakes so duuurrrrr
However good they are, I can guarantee you that they're not like these!
After getting used to the brakes on my BX, conventional brakes just feel wrong.
Conventional brakes ARE wrong!
What on earth are you taking about? There are no rubber gloves in my car but the brakes work. I done geddit???
What about the GS & GSA?
They work in pretty much the same way. It's only really the DS & SM that differ in complexity (they're even more advanced).
A cliff hanger! No!!!!
Haha!
Mk1 C5 **squeaky fart** 💨💨
Good of you to take the engine out just for this video 🤣
Yeah, and so quick too. This man is worth a higher hourly rate. 😆
I aim to please!