Tyre blowouts and hydropneumatic suspension

This is the place for posts that don't fit into any other category.

Moderator: RichardW

User avatar
fastandfurryous
Posts: 1388
Joined: 07 Jul 2004, 17:57
Location: On the road, travelling at high speed. Meep Meep.
My Cars:
x 4

Post by fastandfurryous »

Kowalski wrote:
andmcit wrote:McPhereson struts!! That's where it all went wrong...
I'd want rid of the nose heavy front wheel drive setup and get the weight distribution more even (rear wheel drive) before I'd consider swapping struts for wishbones.
You have evedently never driven a CX. It is massively front heavy, but with dual wishbones it works properly. McPherson struts are a cheap compromise, and can't ever be anything but.

I was astounded at how bad McPherson struts are when I first drove a car with them fitted... I leaned to drive in a Talbot Horizon.. A car with dual wishbones (, twin-pot non-sliding calipers, independent trailing arm rear suspension and centre point contact steering) and I was evendently spoiled from day one.

Granted, the car rolled like a 2cv, but it outhandled most other cars, and just "felt" a lot safer on the road. Mainly due to expensive wishbones over cheapo struts.
This is not a signature.
andmcit
Posts: 4299
Joined: 03 Mar 2005, 17:59
Location: Swansea - South Wales
My Cars:
x 30

Post by andmcit »

I honestly didn't want to tread on Kowalski's toes to suggest he'd never been near a Cx or Gs! If you had, you'll never forget the sheer handling ability of the Gs. Yes the Cx is a hefty car better suited to the autoroutes BUT even the massive estate is a class act!

Car magazine in it's day stated the GS could hold it's own on the twisties against the then supercars of the day [bear in mind we're talking 70's here mind!!] complete with 1222cc engine flat fout air cooled motor revving it's nuts off!!
:lol:

Andrew
nick
Posts: 1079
Joined: 14 Mar 2001, 01:49
Location: Market Rasen, Lincolnshire
My Cars:

Post by nick »

ChevronMicky wrote:Andmcit, I'm certain the BX was advertised as one car not affected by blowouts.
Somewhere I have a Citroen UK all-models catalogue from about 1984 - there is a full page about the ability of the CX & GSA to be controlled safely after a blowout, but no mention at all of this being a feature of the BX.
User avatar
AndersDK
Posts: 6060
Joined: 21 Feb 2003, 04:56
Location: Denmark
My Cars:
x 1

Post by AndersDK »

The afore mentioned earlier models all have the king pin axis parallel to the mid-axis in the wheel due to the double wishbone layout = center steering. Hence the rock stable steering at speed even on a blow-out. The CX & SM further have the hefty Diravi type powersteering which helps the driver a lot stabilising the car at speed during any driving conditions.

This is not the case for BX,XM,Xantia & C5 with the McPherson strut. The thought "king pin" axis will follow the strut and hence be offset to the wheel's mid-axis.
I can warrant the heavy steering pull to the side you get a front blow-out on a BX :?
Exactly like any other "normal" car :(
Anders (DK) - '90 BX16Image
ChevronMicky
Posts: 17
Joined: 01 May 2006, 23:56
Location: Herts, UK
My Cars:

Post by ChevronMicky »

Ok you guys have convinced me the BX, Xantia and C5 won't behave like the GS and CX following a blowout. That explains Citroen's no longer using it in their ads, because it was a good selling point after all -- safety sells.

Given the self-levelling properties though, I still conjecture whether BX, Xantia and C5 might still behave better than other cars. I wouldn't expect these Citroens to collapse catastrophically on to the failed wheel like a normal car. Would you agree?


....Anders beat me to it and he obviously doesn't agree :lol:
2003 C5 2.2 HDi SX
1995 ZX TD Aura Estate
1989 BX 19TRS
1974 Dyane
User avatar
Kowalski
Posts: 2557
Joined: 15 Oct 2003, 17:41
Location: North East, United Kingdom
My Cars: Ex 05 C5 2.0 HDI Exclusive 145k
Ex 97 Xantia 1.9TD SX 144k
Ex 94 Xantia Dimension 1.9TD 199k

Post by Kowalski »

fastandfurryous wrote: You have evedently never driven a CX. It is massively front heavy, but with dual wishbones it works properly. McPherson struts are a cheap compromise, and can't ever be anything but.
I'm not saying that MacPherson struts are anything wonderful, but there are things about modern cars that cause them to be far worse handling than the compromises in MacPherson struts. I'd be hard pressed to name a front wheel drive car that wasn't nose heavy. A nose heavy car will handle properly until you get on the brakes or go over the wrong sort of undulation and then there is no getting away from the fact that the weight is in the wrong place, i.e. wishbones and the best anti-dive geometry can't change the laws of physics.

Front wheel drive is a far bigger compromise than the macpherson strut. Having the engine in front of the front wheels isn't wonderful (thats where it ends up on the majority of front wheel drive cars, some incline the engine backwards but there is no getting away from the fact that the crank is ahead of the axle line and. you end up with weight overhanging the front wheels. Power understeer is what I get with my car and its only got 90 bhp, safe but not much fun. Powersliding oversteer is far more fun, its fun all the way to the scene of the accident :twisted:
rossnunn
Posts: 1254
Joined: 09 Aug 2003, 03:00
Location: Boston, Lincs
My Cars:
Contact:

Post by rossnunn »

the nice thing about oversteer rather then understeer is you won't see the tree that kills you.
Image
alan s
RIP 2010
Posts: 2542
Joined: 26 Jan 2001, 15:53
Location: Australia
My Cars:
x 6

Post by alan s »

I owned CXs from 1984 up to a couple of years back and still have a couple that "one day" may once again see the light of day and have to agree that they were a rare beast when it came to blow outs/flat tyres; first you knew was when the chunks of black rubber spraying past the drivers window began to get to around shoe sole size and were banging off the underguard area. :shock: It was often said that tyres on a CX were there mainly to stop the rims getting damaged by the road surface and not much else.
However, I have had one instance that gave me a great insight into how well a BX will handle in certain circumstances.
A couple of years ago, I bought a cheap 16Trs from about 400 klms away from where I live. We went down to inspect it with cash in the pocket and bought it on the spot. My son (in his wisdom) then suggested we go another 120klms round trip to get a Pizza he had put great wraps on, so I set off at around 8pm after having settled the business, to get aforesaid Pizza but left the Trs where it was.
Called back and collected the car at about 10pm, we set off home and without going into all the gorey details, we hooked onto the back of an overnight truck that delivers papers all up the coast here and covers about 1000 klms a night and he really flies. To make a long story short, we did one stretch that normally takes about 1 3/4 hours in around 1 1/4 hitting speeds up to 170 kph and sitting around 130 - 150 most of the way.
To put it into perspective, I was a race and rally driver at a reasonably high level many years ago and he currently drives sprints and hillclimbs so we both knew our limitations. I noticed he occasionally fell back on us and I would slow down to let him catch up. When we got home, I asked him how the Trs handled and his response was "fairly good but seemed a bit loose in the back end at times" which caused me to look at the tyres. One was almost dead flat; then it dawned on us. The guy we bought the car off commented on how he had left the spare on the floor of the boot because he had been driving the car with it on as the normal tyre had a slow leak. Idiot didn't tell us he had refitted the tyre with the slow leak without bothering to get it fixed, so our little sojourn down for the Pizza gave it time to deflate. Image
Moral of the story is that if the flat is on the rear, it's still not easy to pick and it definitely is well above the performance of an ordinary car.


Alan S
RIP Sept 19th 2008.

She said "Put the cat out" She didn't mention it was on fire!!
Peter.N.
Moderating Team
Posts: 11563
Joined: 02 Apr 2005, 16:11
Location: Charmouth,Dorset
My Cars: Currently:

C5 X7 VTR + Satnav Hdi estate Silver
C5 X7 VTR + Hdi Estate 2008 Red

In the past: 3, CX td Safaris and about 7, XM td estates. Lovely cars.
x 1199

Post by Peter.N. »

The last car Citroen made that was truly not affected backward pressure to the front wheels was the CX. The essential difference it that the steering knuckle assembly was right in the centre of the wheel, so any rearwards pressure would only serve to slow the wheel down and not cause it to turn outwards, which is the effect you get with macpherson struts. All citroens since then have the pivot point of the wheels inboard of the center so any pressure against the wheel whether it be water or drag due to a flat tyre will cause the wheel to turn outwards. I think it was purely down to cost that the CX system was abandoned, as it was only used on the CX.

I can attest to the effectivness of the CX suspension as in the early days of the M5 I drove for some distance with a flat o/s front tyre, I thought that the road surface was a bit rough! but it had no effect on the steering. In fact the car handled like no other car I have ever owned, if you held the wheel straight the car went straight, to overtake on the motorway you only had to move the wheel a few degrees, it handled like a 17' mini !

The surperb handling was more to do with the steering design than the hydropnumatic suspension.
andmcit
Posts: 4299
Joined: 03 Mar 2005, 17:59
Location: Swansea - South Wales
My Cars:
x 30

Post by andmcit »

You PILOT a Cx, nothing as vulgar as steering it!! :lol:

There are few cars that feel just do damned stable a high speed than a CX Safari. Guess what I was just out barnstorming in about half an hour ago!? \:D/ 8)

God I love 'em!!
Me biased? Hell yes, so...?

Andrew
User avatar
AndersDK
Posts: 6060
Joined: 21 Feb 2003, 04:56
Location: Denmark
My Cars:
x 1

Post by AndersDK »

Andrew -

Any chance of pics on your latest CX finding ?
Anders (DK) - '90 BX16Image
deian
Posts: 1729
Joined: 26 Feb 2006, 10:53
Location:
My Cars:

Post by deian »

Ok so now I wish the Xantia had double wishbones and rear wheel drive.

I wonder why Citroen never did a 4x4 version of the Xantia (think 4x4 activa v6 manual, or 4x4 diesel, and a 4x4 2.0turbo etc), it would have been a great idea with the ability of the suspension to lift for ground clearance! On silly terrains, or with the torque of V6 on a race track to help with the handling, etc
rossnunn
Posts: 1254
Joined: 09 Aug 2003, 03:00
Location: Boston, Lincs
My Cars:
Contact:

Post by rossnunn »

I think they did look into it, I've seen a photo


*goes off to find it*
Image
rossnunn
Posts: 1254
Joined: 09 Aug 2003, 03:00
Location: Boston, Lincs
My Cars:
Contact:

Post by rossnunn »

found one of them:

Image

edit:

Found the rest here's the link:

http://www.kolumbus.fi/perhe_pitkanen/xw/styling.htm
Image
deian
Posts: 1729
Joined: 26 Feb 2006, 10:53
Location:
My Cars:

Post by deian »

whoa check the link out, coupe and a convertable, so cool, a 4x4 v6 coupe would have kicked ass!
Post Reply