Lowering hydrolastic suspension

[cooper98]

Hi all, can anyone tell me if you can lower a hydrolastic car by simply releasing pressure/fluid from the rear valves? My car is a 67 998 austin cooper and I would like to lower the ride height- might be a dumb question but I would rather get the right info - cheers

[Peter Laidler]

The short answer is that yes, you CAN lower the car by decreasing the pressure in the system. That's what happens when you drain the system. BUT..........

The hydro system is a 'whole system' and is at it's best and most mechanically effective when the height is such that the front driveshafts are parallel to the ground. The trouble with lowering the car a tad by simply decreasing the hydro pressure is that the heavier front will lower slightly more than the rear due to the volumetric displacement/transfer of liquids from one end to the other - and some other stuff

My opinion with hydrolastic is that if it ain't broke, then don't fix it (unless you feel the need to drain down, flush through and re-fill with new, clean hydro fluid

I hope someone else comes on board and tells you the practicalities as opposed to the theories

[Hippo]

You can lower it but you’ll need to turn down the ends of the trumpets and maintain the correct pressure,
I think vizzard refers to this in his book.
if you want it to handle better put some front shocks on it.

[rolesyboy]

When you say turn down the ends of the trumpets do you mean the Hydro struts or displacers? (There aren't any trumpets on a wet system??)
Might be lost in translation or my misunderstanding here?
I haven't got access to Vizard's book
Thanks

[Hippo]

Sorry trumpets wasn’t the right word. And I spelt Vizard incorrectly.

[surfblue63]

From How to Modify Your Mini, ISBN 0-86343 0414 (UK)

hydro lower.jpg

[Hippo]

Did you seek permission to republish that ?

[johnv]

As mentioned, front shocks and 1.5 degree negative bottom arms work really well together

[Peter Laidler]

As a bit-part long time served engineer I'm not too sure or even happy about the notion of reducing the height of the knuckle support in the bottom (end) of hydro unit. No doubt, the really clever ones might come up with a method of how you hold the pliable and flexible rubber rubber mounted knuckle support firmly enough (hydro unit in a lathe...?) and cut .2" off it. Whatever/however you hold the hydro unit, that knuckle support is STILL rubber mounted, pliable and flexible.

Doing the rear is simple...... Just machine off the strut. But it don't work like that at the front.

One thing that should ring alarm bells is the fact that using the rubber inner UJ's that a Cooper is fitted with, with lower suspension is the death knell for them. They can NEVER retain a neutral stance. Parallel is always the optimum.

But, engineering mechanicals are always at best, a best compromise. Maybe Cooper 98 ought to read and digest the first 7 lines of Martins red-outlined article. If it ain't broke, don't fix it.

[rolesyboy]

Did you seek permission to republish that ?

Is that question serious ??? So many problems in the world right now!!

[Spider]

BMC's Special Tuning's advice;-



I gotta say though, I'm with Pete, I wouldn't be lowering any Mini for road use.

[cooper98]

Thank you for the replies, all read and understood, if it ain't broke do t fix it, I will leave it alone

[Peter Laidler]

Wise move. And let's hear from you more often. There's a lot of Kiwi's visit this site and another won't harm anyone!
Pete the Pom.

[Terence]

Thank you for the replies, all read and understood, if it ain't broke do t fix it, I will leave it alone

Good call!
Lowering an Hydrolastic mini is cool, but re-alignment is required afterwards, as dropping the level will
add toe out & negative camber.
If you don’t, front tyre wear will increase significantly…don’t ask me how I know this

[Roadrunner]

IMG_20190906_0003 (2).jpg

Bit extreme this but I let all the fluid out prior to changing the rear subframe. I considered lowering it but left it and fitted Special Tuning Bump stops

[cooper98]

thanks guys, yes i am sure i will be on here a bit - the last 998 cooper i had was 20 years ago and i have regreted selling it every day since!! - i was happy when this one came up for sale at a price i could afford, i know not everything is original but i don't mind, the plates are all matching and i can work on it from there - can anyone tell me where i can do some tracking of what month etc it was produced? - it's a 1967 Austin 998 cooper - cheers Mark

[InnoCooperExport]

Did you seek permission to republish that ?

Is that question serious ??? So many problems in the world right now!!

Not to change subject completely but I would imagine this would fall under Fair Use. Other than that I agree with Rolesyboy, of all the things to worry about!

[Peter Laidler]

Chaps........ I think that there was a bit of irony in Hippo's remark.

[cooper98]

So further to this - I have fitted front shocks and Progressive bump stops front and rear and left the ride height standard - its like a completely different car!!! - handles beautifully while still riding very smoothly, thank you for all the help

[BAD942B]

One thing that should ring alarm bells is the fact that using the rubber inner UJ's that a Cooper is fitted with, with lower suspension is the death knell for them. They can NEVER retain a neutral stance. Parallel is always the optimum.

one of the major manufacturers did a clever joint with a std u/j fitted into nylon cups, the rollers running direct on the hard nylon, much longer lasting than the rubber doughnut. i think it was QH