On The Ramp | Hydropneumatics simplified: Citroën brakes - Why are they so clever? (2/3)

[@isaacplaysbass8568]

I'm really loving how your presentation style and comedic delivery has continued to evolve; you're good at it.

[@smhorse]

All it needs now is a combination of The Tim Traveller and the spoof Open University programme "Look Around You"

[@stevedavis770]

So refreshing after all the shouty American ones.

[@RomainParis81]

As a french guy, with like "no skills", I have to admett that you are an excellent professor, you make me understand in a different language things that I donnot understand in french... thank you very much! you are so clear in your explainations!

[@UPnDOWN]

Thank you, that's kind.

[@DaimlerSleeveValve]

I once filled my BX19 Break with paper I bought at auction. Even the passenger footwell was full - that's a LOT of weight. Straight and level all the way home. Quite a lot of momentum to get rid of when the lights turned red. Those brakes worked a treat!

[@mfbfreak]

I never get sick of seeing a Citroen with the engine turned off respond to variances in load.

[@Thanos.m]

When I was little and these citroens were still about I would just look at them and think it's just an old citreon now when I see one I just stare in awe of the engineering marvels these were. It's sad that all the engineering led companies are either either gone or no longer what they used to be eg. Citroen Rover Lancia Jaguar etc

[@TheGalifrey]

Anti-Dive on the GS/GSA is superb. I never had an issue with the Brakes on my Citroens, you have to get used to the fact that because of the hydraulic pressure "fight back" it measures pressure rather than range of movement, the more pressure you apply to the pedal, the more the brakes work. If you stamp on the pedal, be prepared to remove your eyeballs from the windscreen 🤣

[@mr_nice.]

Trust me mate, that same effect on the rear when braking is also true for the GS/As. Manual also mentions bleeding the rear brakes on those, with the suspension in normal position, and a helper pushing - or pulling - the rear down (or a heavy lad sitting in the trunk...). 👍👍

[@UPnDOWN]

Yeah I'm sure it is.

[@johnlladron735]

This is bloomin' great! I always looked at Citroens as quirky cars that were just not that sorted, but this is revelatory. Thank you very much for these clear explanations of what a genius concept the suspension/braking system is.

[@UPnDOWN]

There is so much on a hydro-Citroen that people don't know about. They just think they go up & down.

[@jonjoyce3188]

Excellent video series, my dad used to have an F Reg BX 16TRS in Meteor Blue from new until written off in 2004 😩. You’re really good at this Richard, enjoy your style of presentation 👍

[@georgH]

I used a Xantia to tow a caravan in the 90s. Instead of having permanent extra springs like in other cars, the suspension did the right thing. It was really great and miss it so much.

[@v12mike30]

When you next talk about brakes, please mention that the doseur valve has pressure feedback so the pressure in the brake circuit is proportional to foot pressure. This is also why the brake pedal has good feel, despite having almost no travel.

[@UPnDOWN]

I'll try, but there's a lot to cram in as it is!

[@niallsommerville9941]

Boyles law, init. That pulled a lot of bits of disparate LHM info I'd amassed into a single big blob, thank you.

[@jorgefernandez-mv8hu]

That was a nice presentation of the brakes. That is one heck of a clever design. It makes the other systems seem quite primitive.

[@Canalsman]

Another masterclass Rich. I owned a BX GTI many moons ago, G reg, but had no idea just how well engineered it was. Thank you 👍

[@thomash2806]

You’re going to make me fall back in love with my CX…

[@tommussell5160]

Brilliant video Rich, I really enjoyed it! I definitely learnt a few things about the BX braking system - I think I need to bleed the rears on mine now 😅

[@mrcogginsgarage7062]

I rather enjoyed this Rich thanks,takes me back to when I'd just left school and had yet to start my apprenticeship,a friends father who was the workshop Forman at Beacon motors in Bristol who were for years the main Citroen agents here,gave me the run down on how the brakes worked differently on the DS. Really entertaining little series,keep it up.

[@sjtutty]

I bought my first car from Beacon Motors, a beige 1975 (HWT 781N*) Dyane with a knackered clutch in back (maybe...) 1984. *How come I can remember that but not my children's birthdays?

[@RustyRoseAdventures]

Very interesting to see Rich, amazing "whichcraft" suspension for sure!! Also great video presentation as always 👍

[@martincantrill39]

"It Burp's it self" amazing description, love it 😂 great video 👍

[@SeasideGarage]

This is very informative and entertaining... which is impressive to combine...! :)

[@jamesengland7461]

JayEmm, he's not fixing your car, he's playing with it and talking about it. You'll never get it back :)

[@hibbs79]

These videos about the brakes and how they work have been really interesting and fun to watch. Thanks for the time and effort involved in making them. Enjoy your channel mate cheers. 👍

[@UPnDOWN]

Glad you like them!

[@10rGreenninja]

Great explanation - the morre I see your videos on the BX's the more I want another one. Had 2 years ago a 16TZS. and a 14 someting, great cars shame it's so difficult to find a good one now.

[@UPnDOWN]

They do pop up, if you're not fussy on spec.

[@davidwarren1315]

I miss my bx,thanks for explaining the wizardry

[@brianiswrong]

All I knew before this video was, The rolls Royce silver shadow licensed the citroen hydrostatic suspension for the rear of the shadow, and when in parkthe self leveling rear suspension worked at twice the speed as in drive(so people getting in and out the rear of the car,don't unsettle the ride height). Now I know a bit moe👍

[@JLAGAN49]

And all without a microprocessor in sight...delightful. Hurry up part 3.😀

[@UPnDOWN]

To be fair, microprocessors are much smaller and lighter than a heavy hydraulic rig!

[@thegearknob7161]

I knew a bit about the anti dive, but not to that detail, thanks! BXs are the most comfortable car to brake in. The anti dive just makes it less sick inducing. It's one of the best features about hydro Citroens, and nothing else can really compare with them there.

[@UPnDOWN]

Anti-dive is at its best in a BX, too. CX is pretty good also.

[@hestjensen3876]

Always remember to do citrobics once in a while. Up n down.

[@bondbug73]

Super detailed explanation of Citroen's hydropneumatics Richard with some good wit thrown into the M-E-G-A-G-A-M-M-A mix.

[@scottishcarenthusiastsandtrain]

Another excellent and informative video Rich, really enjoyable.

[@CauliflowerMcPugg]

Great part 2. Very interesting once again. Now I have something to talk about at my work Christmas party 🥳

[@UPnDOWN]

How to make friends and alienate people.

[@Hugobros3]

I absolutely love this series. I wish someone made a "green blooded" Citroen in BeamNG, just so I could watch it in action

[@juuhelikkas151]

This. Sadly, haven't found a single proper citroen mod, and i'm too dumb to make one myself.

[@UPnDOWN]

There's a mod for the ETK 3-series Touring look-a-like to give it Comfort Air suspension, and that's about the closest thing I've found to a later Hydractive car. The DS rally car on Dirt 2.0 actually rides and behaves pretty faithfully to the real thing, compared with other games.

[@juuhelikkas151]

@@UPnDOWN By later hydractive, do you mean c5 - c6 era cars?

[@UPnDOWN]

Yup

[@micheltebraake7915]

Too bad you weren't my auto mechanic teacher, that made the lessons a lot more fun Rich!

[@kuutti121]

This is what is confirmed in @Number27 video on SM - no diving. No matter how heavy lump.

[@isaacplaysbass8568]

The hydaulics are so cool, I have Citroen envy.

[@grayfool]

clever buggers them French geezers. Still haven't found the rubber glove in my car though??? Oh well. . .

[@CauliflowerMcPugg]

Another great lesson 👍

[@manfredschmalbach9023]

"It is entirely normal behavior" ... despite the long reaction time. It might be the situation of "no front wheels", It might be a "16V" problem however, because people humping dry on "16V" and other "performance"-oriented hieroglyphs probably expect a more steel-springy sorta suspension-style, and the nightmare called "marketing" already did ruin quite some technical Citroën-decision by that time, be it "normal" instruments and switches and levers instead of bathroom-scale and satellites, be it more and more hardening suspensions, even replacing swingarms in driving direction with linear working single-elements directly above the wheel .... . Thanks for sharing!

[@thomash2806]

I had the same issue with rubbish spheres. Rock solid back suspension. Someone told me the ones you want are IFHS. I’m really satisfied with mine.

[@UPnDOWN]

Yeah, they're generally OK if genuine aren't available.

[@davidsharp9166]

More like this please

[@YoniZarruk]

very informative thanks, as for your knowledge is that normal on a Citroen XM when the engine is stopped and the brake pedal is pressed the rear suspension goes down and after releasing the pedal goes up for initialize height

[@UPnDOWN]

It might drop a bit, yes. The rear brakes are powered by the rear suspension, so if you take pressure away from the suspension to apply the brakes when there is no supply to restore it (as there would be when the engine is running) then it would quite likely drop a bit. It shouldn't be too much though, just a slightly change as opposed to dropping to the floor!

[@lesklower7281]

You covered all the luxury brands covered those diesel engined cars getting very good mileage

[@aslandama]

Very clever stuff for sure and well explained thanks.

[@craigwilliams6734]

Had a GS for ten years & a CX for five years - I used to be a proper Citroen nutter!!! 😜

[@shauntvr4312]

I loved my A reg bx 1.6 petrol

[@SB-vb8ch]

If you think of the nitrogen "envelope" as a spring (which it is) then it makes it easier to understand. No nitrogen = no spring as the fluid is not compressible (no sort of, it isn't, if the pressure is raised then something somewhere in the system will be absorbing the energy (think of a spring again) you're putting in to raise the pressure probably by means of physical distortion of parts of the system containing the pressure). Exactly the same as Hydragas but obviously that used a passive fluid circuit. It's a neat system. Not convinced by your take on them being impervious to weight....constant ride height doesn't mean limitless springing, you will eventually run out of spring. The brake bias ratonale isn't quite on the money either, weight transfer due to braking is a bigger factor, you can't magically put more weight on the rear end by keeping a constant ride height, certainly not to the point that will make any practical difference for a front transverse engined car anyway. You need weight transfer to generate grip too so it's not a bad thing! There is some very clever thought that has gone into that system but as ever it's a cost vs benefit thing & passive springs & dampers are cheap!

[@UPnDOWN]

Fluid being non-compressible, I know, but I'm trying to explain it in a way that makes the most amount of sense to the most amount of people. The end result is the same; the pressure increases. Regards the being impervious to weight, again no they can't cheat physics but in an over-simplified way, they do, because they retain ride height; increase braking power relative to load and give far less clue to the driver that the car is carrying any significant mass. Try that in a non-hydropneumatic car. As for the brake bias rationale, I never said it was bias-adjusting. The rear pressure is proportionate to weight, so the rear brake power only increases with changes to the weight of the car. I suspect in terms of actual bias, it makes very little difference at all. I didn't suggest more weight is being put on the rear end by braking at all. What I said was that under braking the rear suspension compresses due to the geometry of the suspension hardware, and that because it compresses, it increases the rear braking power; The harder you brake, the stronger your brakes get. It's not actually getting heavier, it's just acting like it has. Anyway, sounds like you need to do a video of your own!

[@bobr9731]

Thank you for another entertaining video lovein the content.

[@kornelschwarcz9104]

break load balancing was already invented in the DS, also to avoid diving

[@UPnDOWN]

I'll come to the DS in the final video.

[@kornelschwarcz9104]

@@UPnDOWN Sorry, if being a bit impatient. 😅

[@MrLekatt]

Great, Brilliant, Excellent... I agree.. you, the car, all of it 😁 Actually, even the 2CV has a few of of those festures: front and rear axles/springs are coupled, but mechanically, the anti dive front axle and the squatting rear axle is there since 1948. Not the constant ride hight though.. 😎

[@UPnDOWN]

The 2CV suspension system is genius. The car I most want to drive in the world is a Citroen M35 Prototype.

[@MrLekatt]

@@UPnDOWN Completely agree.. in my 2CV haydays I met people from Norway who met a guy who had put a m35 drivetrain in a 2CV.. that was hilarious 🤣

[@Fractal_CZ]

Ouch. Is there part 3? Don’t be mad at me, it’s friday 😊

[@GoldenCroc]

Good stuff, very interesting. 👍

[@jimcrichton8028]

I have never owned a citroen, so I am assuming that at working temp and driving engine speeds the reaction times to different loading is much quicker. If not when you brake hard and initiate the front suspension to raise to avoid nose dive it will be to late by the time it responds? Or am I completely wrong here. If it is the wishbone geometry that stops it diving surely there will still be some downward movement before the car pumps up in response, which if I understand you correctly will cause the anti dive to not work. My middle name is pedantic by the way...

[@jimcrichton8028]

Ok,Ok, It is the rear that needs to clamp down not the front up, I think I get it know. Maybe. loveyourinfo videos.

[@UPnDOWN]

The hydraulics play no part in the anti-dive, it's the geometry of the suspension working against them.

[@jimmyquinn9639]

Another good video 🚘🚙🚗👍👍👍👍⭐️⭐️⭐️

[@mcplutt]

If the car gets heavier in the rear when braking, it has to go lighter in the front. I don't believe that is even possible?

[@UPnDOWN]

It isn't actually getting heavier, it's just the suspension acts like it does.

[@robertsedgwick1629]

a GSA has got anti-dive

[@UPnDOWN]

I suspected as much.

[@Nino500]

You're like a drug pusher... Go on, buy a Citroen, just try it once, it won't hurt you. Here, take this one, you can owe me till next week...

[@rimmersbryggeri]

I agree this is proer engineering. German engieering is just making things a convolutetd as possible for no aparent reason. (Other than making serciving difficult and expesive)

[@oxulucozcan4923]

in a sense, it almost pushes rear subframe in between the load and braking force. is this a limiting factor on a conventional suspension (because the control arm cant be nearly flat because suspension travel is not enough)? because if this is not the reason, the conventional producers are just idiotic thanks my friend

[@amgvrn]

This is such a great series! Also it is worth to note that the doseur valve itself is a marvel of engineering. Especially in the late models of Xm or Xantia. There is no rubber seals - just precise metal to metal contact. But they wear out and leak pressure internally :( Especially late ones, CX and BX versions are bulletproof. And guess what - it is impossible to buy a new one now, the plant was closed long time ago. And because of such high tolerances nobody was able to reliably fix one, at least to my knowledge. The level of raw engineering in this system is just something else. I miss my XM :(

[@UPnDOWN]

The level of machining in components like the doseur and height correctors is aircraft-grade. It's exquisite.

[@stevedavis770]

There were some available from JCB dealers as they employed the same hydraulics. Possibly DJB articulated dumptrucks as they were the same, long gone now, taken over by Caterpillar.

[@Czechbound]

Interesting subject matter. Excellent information. Very engaging presentation. Great editing and visuals. This channel should have at least 10x subscribers, and the videos should be getting 10x the views. The YTube algorithm is strange.

[@UPnDOWN]

High praise, thanks!

[@MrManBuzz]

The more videos I watch on BXs, the more I'm genuinely starting to want a GTI 16V.

[@martinwhitaker5332]

I remember driving my 19 RD quite spiritedly on twisty back roads and it never dived on the front, ploughed a bit on sharp corners but what car wouldn't. Really enjoy your sessions.

[@PaddyWV]

Pondering now about the last (Rover) Metro suspension set up when they finally connected the four corners with Alex Moulton's system.

[@NikolaMatic987]

It will be soooo nice to have a couple of tea or beer and just talk with you about expirience with Citroens. Love BX, have 2 of those master engieneering. Sorry for bad english and hallo from Serbia.

[@Tagora2664]

You must be a good teacher, I got that, and I'm as thick as a plank.

[@darrellbrain829]

This is my sphere, there are many like it, but this one is mine !!

[@jamesmasin159]

Great little series here, learned some interesting new facts in this one. Would you do some about some XM specifics in the future as well? ('92 XM V6 owner here)

[@torbendk2777]

a 1999 (y4) XM 2,5 td here 😀

[@UPnDOWN]

Thanks. To be honest, the XM works pretty much as per the BX (it's effectively just a bigger BX underneath). The suspension itself is where the XM starts to differ, with the introduction of Hydractive.

[@JasperV70-205CT-BX]

Rewatched it again,since it is so brilliant 😊 Did you take part 3 down Kitch, or was it never released? I dont remember it

[@UPnDOWN]

Never did part 3...it was meant to feature Clement 😭

[@michaelheimbrand5424]

You don´t even have to have a blown sphere to get gas in the rear brakes. Over the years, normal diffusion (if that´s correct english) of gas through the membrane on a molecular level finds it´s way in to the rear brakes. Makes them "funny". But unlike ordinary brakes, they don´t get spungy, they just instead gets a delay. Very "interesting" feeling when you suddenly get much more braking a second into your "brake session". But what did you mean when you said something about that it has to be on it´s wheels when putting it to max height? I didn´t get that. I mean, the manual height lever is a mechanical override, and you can have the car on jackstands and still get full system pressure on all four corners. As usual, thanks for a really good video. p.s. The delay on the rear brakes of my DS is now almost two seconds which is a personal record. That´s what blowouts of fully filled 700cc spheres gives you together with a bloated reservoir. (guess why the reservoir lid is "pop-off" on newer models...)

[@UPnDOWN]

I've had occasions where I've jacked a car up (so the wheels are drooped), selected high, let the car down and the suspension has sunk to the bump stops, before suddenly realising and lifting itself up. There's probably more to it than that, but it's easier to just advise people to put it on high first, which is the correct way anyway.

[@stuwhite2337]

GS anti dive is absolutely brilliant. If anything better than on a bx.

[@UPnDOWN]

I can believe it.

[@Lou-f]

Hagarty has the BX on there bull list, they must have been watching too!

[@UPnDOWN]

I'm clearly a trend-setter.

[@nealjones9068]

Thanks again, that was very usefull. I remembered after what you said about the Ami 8, it was later on than I thought and we were in my fathers GSA.

[@LeighParkin]

Brilliant explanation. Got me wondering now. How does the abs work?

[@UPnDOWN]

It's actually completely conventional, for the time. Has an electronic 'pump' and a control unit. It's a Teves system on the BX, so nothing specific from Citroen, as such.

[@rosomak722]

Grat way to spend time on YT with U. I remeber, that anti brake roll in CX was managed by brake valve on brake pedal. It reduced prassure from rear suspension to avoid front axle dive durring braking. Whole car at braking was siting slightly to the ground equally on both axles. When brake valve was broken, after few minutes (engine off) rear axle was on lowest possition.

[@UPnDOWN]

Did it? I'm not sure, I think the CX behaves like the BX. Could be wrong, I confess I've not read up on it, though I agree the anti-dive works very well.

[@uwekall6281]

I can't wait to hear about the DS braking system. In mine I feel a difference in braking power while applying the brakes and the compression cycle goes off (when the idle goes down and the pump makes noises). I am not really sure why this happens, but probably it is the same as with the tomato - there is gas in the wheel cylinders... So is the DS brake comparable there?

[@UPnDOWN]

The DS system is actually more complex than the BX, but air in the circuit would have the same effect as any hydro-Citroen: Brakes that do little and then do a lot, suddenly!

[@426baron]

While we're on about brakes : my '91 Rover is fitted with Honda's ALB. I can't for the life of me fully understand how it works, but it looks very Citroëny, sphere included. Is this fascinately complicated thing somehow Citroën-related or inspired ?

[@UPnDOWN]

I couldn't tell you. I had a 1986 Honda Prelude that had 4WALB emblazoned on the bootlid, but I don't think it ever worked properly! If it has a sphere it'll be pneumatically actuated, I suspect. Possibly a vacuum from the engine is stored in the sphere and then dissipated into the ABS controller, somehow (as opposed to an electric solenoid/pump).

[@426baron]

@@UPnDOWN thank you, I think mine works correctly. If you of all people can't fully explain it, I feel less dumb. I'll give another read to the manual, I don't think I got the vacuum part correctly before you mentioning it.

[@DaveAber9999]

Stop doing these videos! You'll end up talking me into buying another BX at this rate.

[@colingarner6175]

Why the hell did Citroen drop this astonishing system . Having driven Several CX models and all the BX models I loved them all .😢

[@GoldenCroc]

I am sure it was a rethorical question but if not: Cost.

[@smhorse]

Money always trumps engineering.

[@UPnDOWN]

I believe it was a combination of the fact that vehicle dynamics were improving (even if ride quality wasn't) and the need for more advanced ESP systems, which wouldn't have been as easy to integrate in this (therefore, more costly). And I suppose there's good old ignorance - most people have no idea how clever these brakes are, they just get written off as being 'sharp'. Old Citroens were very good at masking their own excellence, and not so good at hiding their inadequacies.

[@CathodeRayNipplez]

Best Citroën stand up comedy show on YT! 🤣

[@UPnDOWN]

Best/only...no matter, I'll take it.