MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGF Technical - Just had the hydragas topped up...

Hi all, hope we are all enjoying the new year, aside the weather! Had my suspension regassed last week on my 99 mgf 1.8i, as it had dropped so low i was bottoming out on speed humps. Was gassed back to factory standard, can now get over speed humps no probs, but the car looks a bit silly now as there is such a big gap between the tyres and wheel arches. Will it settle down again, or is it worth taking it back and getting it lowered a bit? Mnay thanks, Matt.
m hart

The ride height does sink over time, as gas escapes from the nitrogen chamber. Therefore it's often worth suffering a ride height slightly above what you'd like, as it lengthens the period between top-ups. Plus it helps keep the suspension & steering geometry within tolerances for longer, giving you maximum life from your tyres & optimal handling and ride quality.

If the car is at 368mm at the front now when ambient temperatures are teetering around 0 degrees, it will theoretically rise by 0.6mm for every degree increase, but that will be counteracted by whatever rate the gas is escaping. The post-pumping 'settle' usually occurs within a few days, so presumably it has now stabilised. I'd be inclined to wait a few months and see what change occurs compared to ambient temperatures, and then decide whether to adjust it. Losing a few mm is easily DIYable, Rob's site has instructions - http://www.mgf.ultimatemg.com/group2/DIY/suspension/howto_lower.htm
bandit

Matt, the suspension is not regassed, that is not possible it has more fluid pumped into it.
Bandit, I assume you mean that liquid leaks out over a period of time and needs replenishing, if the gas leaks out then the suspension unit is junk.
Robert (Bob) Midget Turbo

Correct Bob = the gas is trapped in the top - or should be!
Ted Newman

Agreed in some cases a drop in ride height is as a result of liquid leaking out, but the chances of the rubber membranes & jacket that contain the nitrogen gas still being 100% after a decade are a bit slim. Rubber can fully contain gas at 400psi when it's relatively fresh & new, but as it ages microscopic cracks will form, leading to gradual escape of gas and corresponding drop in pressure. It is certainly a contributing factor in why the hydragas system needs regular topping up. A unit that has begun to leak gas slowly can still be functional & adequate for the task, with regular top-ups to replace the escaped gas with fluid to restore ride height. Eventually however there will be so little gas left in the nitrogen chamber that the unit will lose its spring function and indeed will then be junk. Hence why so much interest in availability of new stock of hydragas spheres, or the possibility of adding a refill facility to existing spheres. Ditto the possibility of replacing the spheres with coil springs without going the TF subframe route.
bandit

As far as I remember, the Hydragas also provides some of the damping. If so, replacing the units with steel springs would probably leave the separate dampers incorrectly matched to the springs. For best results, it would need some work by the wizards at VHS to some up with a set of bespoke dampers. That would probably also make it necessary to beef up the mounts, which can be done. The very stiff steel springs and the design of the assemblies would again be a natural job for VHS to tackle - perhaps they've thought of it!
Mike Cunningham

I suspect in that replacing hydragas with springs, it would be easier and cheaper to use second hand TF parts. But whether it would be possible to mount a spring turret utilising the hydragas attachement points? It may well be possible, and I agree, chatting to Andy Kitson et al would make a sensible approach. I also agree that any spring conversion kit would also have to come with separate dampers. As such, any conversion kit along these lines may not prove to be all that cheap - but might be the easiest option for many who may not be able to access complete TF subframes.
Rob Bell

Just mulling this situation over myself. I believe that there is a Spring / Shock conversion coming on the market very soon. This has been developed by a large automotive suspension / spring company and will be a direct 'bolt in' replacement and will NOT require the replacement of the F frames with TF units.
Also development of the damping / rebound rates have been carried out to match the F's O/E set up.

Does anyone else know of a similar system....?

Mark.
M T Boldry

Discussing this in the MGF General thread "Hydragas survey" at the moment. Still in development, no costs known at this stage. And likely an ideal solution for you :o)
Rob Bell

This thread was discussed between 12/01/2010 and 26/02/2010

MG MGF Technical index

This thread is from the archives. Join the live MG MGF Technical BBS now