Myth or reality

[Philip Chidlow]

Gary Cole mentions in an article about the 16v he raced that competition brake pads were useless on a BX as the pressure exerted by the hydraulics (30 tonnes) does them in quickly. Also those tempted to lower their BX a tad using the height correctors or adjuster (the 'I'll put an extra slot for the lever' approach) won't be good as it puts too much strain on the driveshafts and other components - certainly not a happy situation on the track. The 16v ran with standard brakes and suspension. Impressive, given the results achieved.

[CitroXim]

Also those tempted to lower their BX a tad using the height correctors or adjuster (the 'I'll put an extra slot for the lever' approach) won't be good as it puts too much strain on the driveshafts and other components

I've heard the same Phil and also lowering the ride height has a very detrimental effect on ride comfort/quality.

I can well believe that's the case with the brakes too. A heck of a pressure is exerted if you get keen with the doseur, especially on a non-ABS car..

[Kitch]

I'm not convinced by the brakes bit, although it's not the first time I've heard that said. AFAIK, there are around 5 brak pad factorys in the world, and hundreds of suppliers. Citroen used to use Bendix/ATE pads for their genuine ones, and someone told me only genuine will do.

Well I put mickey mouse cheap ones in the BX about 3 years ago, and have noticed no difference!

In terms of the suspension, lowering it by the lever or height correctors (really doesn't make an ounce of difference which way you do it, except you get a more accurate height by getting underneath) isn't worthwhile on the road. The car will just bottom out more, as the suspension is no firmer...just lower. Cars that are tuned to handle well are lower and stiffer, not just lower.

By lowering the height of a BX, you just make it more uncomfortable as it just bottoms out alot. And if you stiffen it, you make it more uncomfortable by making it stiffer. Good for a track, but then a BX would be wasted on a track, as it's too good on the road and other cars are better on the track.
As with lowering any car, the CV's and other components will be put under more strain, although frankly how much strain is questionable. It all depends how much lower it is.

If you want the handling AND ride, get an Activa. That was Citroen's solution, just a shame no one listened!

[jonathan_dyane]

I once read a long, complex and somewhat technical document which suggested that when one lowers an axle with McPherson struts, one runs the danger of making the car handle *worse* due to it lowering messing up the geometry. Using the example of the Mk2 Golf GTI it 'proved' (apparently; I was lost...) through loads of complex principles and calculations that lowering it would result in progressively worse handling...

[Way2go]

I once read a long, complex and somewhat technical document which suggested that when one lowers an axle with McPherson struts, one runs the danger of making the car handle *worse* due to it lowering messing up the geometry.

It seems to me that the 'normal' setting for the ride height on the BX is also at the optimum geometry point because raising to intermediate gives a reduction in that 'glide' sensation.

Also despite lubrication of the linkage, I still have some problems of the suspension running lower than it should at times and with the condition of the roads today it doesn't take much for it to 'bottom out' & I have to give it a 'boost' with the lever. I suspect this is caused by the bush of which Aerodynamica speaks but it does demonstrate the poorer geometry and range at the lower height.

[Aerodynamica]

I suspect this is caused by the bush of which Aerodynamica speaks but it does demonstrate the poorer geometry and range at the lower height.

- it could be! but it's never alone in its mischief! the corrector valve being hard to move if it's sludged up and the corrector ball joint being worn also contributes to this.

In terms of the suspension, lowering it by the lever or height correctors (really doesn't make an ounce of difference which way you do it, except you get a more accurate height by getting underneath)

I don't agree - the manual lever in the car is actually an override whereas the lever connected to each roll bar moved freely of the override. There is clearance between the automatic levers connected to the roll bar and the manual mechanism. When the car is set to higher ride height, the clearance on the lever ends is not present as the manual mechanism is moving and holding the auto levers against the position set by the roll bars (it can be done because the rod that connects them is flexible) so in any position other than 'normal' you are exerting a force on the auto height levers and making a new notch in the gate, you're still applying an override force to them. When you change the height underneath using the roll bar clamps you're changing the 'normal' position ride height so whether it rides a bit lower or higher it still has the free clearance needed to move at the ends between the levers and the manual mechanism.

Another thing that can make it ride a little too high or low after you think you've set it right is that the free clearance at these lever ends should have equidistant dimensions to the rod thing for the manual height mechanism. It's adjustable seperately. If it's out one way or the other it restricts the auto height control lever and stops it correcting after going too high or low. Common on the rear of the CX as the clearance area on its rear lever has a much smaller hole in it.

[Geoffrey Gould]

Hello well taking ride height first, for a long time BYA had a habit of being high at the front and the ride was rather hard and harsh several attempts were made to adjust it to the correct height and it did make a difference until it decided to go back to being high again ( now cured and all better now.) so ride height does make a difference and if you really think about it it's quite easy to see why as it alters the geometry ( think levers and fulcrums etc.)
Drive shaft joints are designed to work in a straight line as much as possible so that if they run 'out of line' for most of the time as would happen if the suspension was altered then the wear rate will increase, with the questionable quality of some of the drive shafts that are available today then the life expectancy can be very short. There is some one on here that has had 4 new shafts in a row, 1 was completely U/S and did a few yards the others were not much better. All our shafts are fully tested Sir, .
Brakes are a very difficult thing because they have to be able to do all things well, there are reams of statistics that explain what happens to linings and discs or drums so I won't bore you but put simply they have to work in ALL conditions, stone cold or 1000 degrees wet or dry and there can only be a compromise at best. There are many different types or grades of linings ,soft which work well at low speed and when they are cold, you want them to work when you have just started off and have joined the morning 'rush hour traffic'. Also they have to work at the other extreme when having to slow from 60/70 mph (say). So taking into account the extremes of use then don't they do well. Combined of course with the requirement that they should last for a long time. Not much good if they will stop you in yards like a F1 car if they wear out in 5000 miles. Mr Joe Public would soon moan about that.
At the other end then competition pads come in different types to cater for a specific use. Short circuit many corners much braking up to very high speed and few corners but probably short hard braking etc. Life expectancy of the pads is only that they should work,do the job and not wear out before the race has finished.
By now ,if you are still reading this, then I expect you are thinking what the h*ll has this got to do with the original question, well as I see it quite a lot, Gary's car has been tailored to fit His needs, what he does and how he does it and obviously it works for Him. The 'works for him, being the crucial part' no two people are exactly the same.
It is Fact for him but if Every one said that it was the definitive answer for all then it would be a myth and a bl**dy dangerous one at that.
This is only touching the surface about brakes etc. the type of pad,calliper,disc material cooling could and has filled many a book.
Sorry to drone on but if it has got you thinking even just a little that,s OK.
Them's my thoughts.
Cheers.
Geoff.
BX's as standard, Very good, not perfect perhaps but that is not for this discussion.

[djoptix]

I don't think I understand the question

Lowering is good for handling because it lowers the centre of gravity, lowering & stiffening is even better on most track/fast road cars because you'll get better handling on a nice smooth dry circuit, but stiffness basically means less grip so it would go twitchy in the wet, possibly becoming unsafe on normal roads as a result.

So not messing with the standard BX setup seems like the way to go. However, I thought that Gary's car ran with standard suspension geometry but with the front spheres changed for 16v rears and the rears replaced with XM items regassed up to 35 bar - presumably to counteract the reduced stiffness of the standard suspension when running with a lighter-than-average load.

I'm not disagreeing with anyone here, just adding my thoughts to the melee!

Of course most people just lower their cars to look cool, and it's here the BX clearly has the best of both worlds! Park up, drop BX to the floor, take photos, raise BX, drive off. Win.

[Philip Chidlow]

I don't think I understand the question

Well TBH there wasn't one, more a topic for debate. Which it's provoked. All good stuff

[jonathan_dyane]

I don't think I understand the question

Lowering is good for handling because it lowers the centre of gravity,

Not necessarily the case I believe on an axle with struts, as due to ruining the geometry it increases the distance between the roll centre and the centre of gravity, resulting in the car actually rolling more and the now incorrect geometry making it handle like crap.

lowering & stiffening is even better on most track/fast road cars because you'll get better handling on a nice smooth dry circuit, but stiffness basically means less grip so it would go twitchy in the wet, possibly becoming unsafe on normal roads as a result.

I quite agree.

So not messing with the standard BX setup seems like the way to go. However, I thought that Gary's car ran with standard suspension geometry but with the front spheres changed for 16v rears and the rears replaced with XM items regassed up to 35 bar - presumably to counteract the reduced stiffness of the standard suspension when running with a lighter-than-average load.

Surely one of the principle advantages of hydropneumatic suspension is the fact that stiffness increases proportionally according to load, therefore a car running with a light load will have an identical level of compliance to one with a heavier load.

[DavidRutherford]

In terms of the suspension, lowering it by the lever or height correctors (really doesn't make an ounce of difference which way you do it, except you get a more accurate height by getting underneath)

I don't agree - the manual lever in the car is actually an override whereas the lever connected to each roll bar moved freely of the override. There is clearance between the automatic levers connected to the roll bar and the manual mechanism. When the car is set to higher ride height, the clearance on the lever ends is not present as the manual mechanism is moving and holding the auto levers against the position set by the roll bars (it can be done because the rod that connects them is flexible) so in any position other than 'normal' you are exerting a force on the auto height levers and making a new notch in the gate, you're still applying an override force to them. When you change the height underneath using the roll bar clamps you're changing the 'normal' position ride height so whether it rides a bit lower or higher it still has the free clearance needed to move at the ends between the levers and the manual mechanism.

Another thing that can make it ride a little too high or low after you think you've set it right is that the free clearance at these lever ends should have equidistant dimensions to the rod thing for the manual height mechanism. It's adjustable seperately. If it's out one way or the other it restricts the auto height control lever and stops it correcting after going too high or low. Common on the rear of the CX as the clearance area on its rear lever has a much smaller hole in it.

^^
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This is all truth.

The only way any Hydro-cit can actually work properly is with the height lever in normal, which effectively means the height lever is NOT connected to the height correctors, and they are able to detect and correct the height to normal running.

With the height lever in anything other than normal, the closed-loop-feedback of the height correctors is being interfered with. Effectively, the height corrector reads the height of the car incorrectly, and compensates: With the lever in "low", the height corrector is fooled into thinking the car is too high, and hence dumps all the pressure from the suspension. Same is true with the lever in "High": The corrector is fooled into thinking the car is too low, and so pumps the suspension up.

The only oddity is "intermediate". With the lever set to intermediate, the height corrector is just given a little nudge into thinking the car is too low, and so it raises the car up. The nudge on the corrector is sufficiently small, that when the car does come up a bit, the height corrector linkage presses back on the height lever linkage to create equilibrium, and hence the car stays at whatever height this is.

It's all a bit crude really, given that it's based on bits of springy bent steel rod pressing on various other bits of levers, hence why the system only really works with the car in normal.

[Kitch]

In terms of the suspension, lowering it by the lever or height correctors (really doesn't make an ounce of difference which way you do it, except you get a more accurate height by getting underneath)

I don't agree - the manual lever in the car is actually an override whereas the lever connected to each roll bar moved freely of the override. There is clearance between the automatic levers connected to the roll bar and the manual mechanism. When the car is set to higher ride height, the clearance on the lever ends is not present as the manual mechanism is moving and holding the auto levers against the position set by the roll bars (it can be done because the rod that connects them is flexible) so in any position other than 'normal' you are exerting a force on the auto height levers and making a new notch in the gate, you're still applying an override force to them. When you change the height underneath using the roll bar clamps you're changing the 'normal' position ride height so whether it rides a bit lower or higher it still has the free clearance needed to move at the ends between the levers and the manual mechanism.

Another thing that can make it ride a little too high or low after you think you've set it right is that the free clearance at these lever ends should have equidistant dimensions to the rod thing for the manual height mechanism. It's adjustable seperately. If it's out one way or the other it restricts the auto height control lever and stops it correcting after going too high or low. Common on the rear of the CX as the clearance area on its rear lever has a much smaller hole in it.

^^
| |
This is all truth.

The only way any Hydro-cit can actually work properly is with the height lever in normal, which effectively means the height lever is NOT connected to the height correctors, and they are able to detect and correct the height to normal running.

With the height lever in anything other than normal, the closed-loop-feedback of the height correctors is being interfered with. Effectively, the height corrector reads the height of the car incorrectly, and compensates: With the lever in "low", the height corrector is fooled into thinking the car is too high, and hence dumps all the pressure from the suspension. Same is true with the lever in "High": The corrector is fooled into thinking the car is too low, and so pumps the suspension up.

The only oddity is "intermediate". With the lever set to intermediate, the height corrector is just given a little nudge into thinking the car is too low, and so it raises the car up. The nudge on the corrector is sufficiently small, that when the car does come up a bit, the height corrector linkage presses back on the height lever linkage to create equilibrium, and hence the car stays at whatever height this is.

It's all a bit crude really, given that it's based on bits of springy bent steel rod pressing on various other bits of levers, hence why the system only really works with the car in normal.

Well thats kinda what I was trying to get at, but explained ALOT better

Having done both, I agree yes if you adjust the corrector links seperately, you allowed the car the natural adjustment it would have had all long inside (although everything will sit slightly lower)
But AFAIK the correctors are only designed to work at a certain height, and the fact is lowering the car without stiffening it in any way will just make it crap. I know, I've been there!

As optix says....best to leave it alone, or if you must track it I'd just fit stiffer spheres and let the system run normally. COG won't make much difference over the slight difference in height you'd actually make, and you'd have more effect with stiffness and tyre choice.