MGF Suspension

By Richard Lomas

This may be of interest to any of our members who have Hydralastic suspension a very common suspension fitted to many BL cars from the early Minis right up to 1995 with start of the production of the MGF. I recently had my MGF changed to coil springs and shock absorbers by a specialist who deal in MGFs and TFs Mike Satur.
There are a number of ways to change the MGF to this system, although you can still repressurize the existing spheres they are all at least 15 years old. And no new ones can be manufactured at present due to Dunlop having destroyed all of the tooling back in the early 2000 after MGF production ceased and the TF changed to coil springs and shock absorbers.
The other options are to change the whole sub frame for the TF one this a major job and is an expensive option. The other kit available is made by Suplex which involves a Spring in a can kit to replace the existing spheres it also involves reinforcing the bodywork around the top shock absorber mounts.
The new kit by Mike Satur does not involve any strengthening due to the fact that all the stress is taken up by the existing subframe. The next part of this report is taken from Mikes web site (with his permission )

The long awaited conversion from the Hydragas spheres to a true coil over shock suspension designed by Mike Satur will give the MGFa new lease of life and bringsii it bang upto date for modern road and driving conditions NO WELDING REQUIRED BOLT ON DESIGN, DIY installation !

The Problem

The last MGF was made in early 2002 so now some 15 years old and some are 22 years old, as my own car is the Hydragas and units are well past their intended service life by some 10-15 years.The failings with the Hydragas units are corrosion , leaking fluid and eventual loss of pressure in the internal nitrogen compartment … something that cannot be prevented , as well as the fluctuation in ride height. This gradual loss of gas leads to a harsher and harsher ride which may not be noticed until too late and permanent internal damage has been done . The units can also fail at ant time without warning and if the suspension drops to it lowest position then the car becomes underivable and also very difficult to load on to a trailer without damage. This is not meant to scare people but to make them aware of the potential pitfalls of the Hydragas system and how it can affect you if you become stranded. A modern damper is a very similar to Hydragas they both have lucid ( oil) and gas pockets and controlled by internal valuing so a better ride can be achieved with the latest technology and designs in dampers and springs. It’s how this science is applied that is the secret of a suspension that works and suits the car .As good as hydragas was it ca be surpassed in the ride quality , reliability and adjustability.

Keeping it in mind that there are no new hydragas units available , matte some old stock but are likely to need re- gassing ( this is done by welding a boss and a Schroeder valve and regassing with nitrogen… this works but does not add any reliability and is expensive for the parts you get ( approx £350) just for re- gassing and around £130 -£150 for installing no 4 wheel alignment no other new oarts ) if put back into production would not be a cheap part and I would guess they would around £300 + each. Just look on EBay to see how much secondhand used units Re! A ‘ repair’ service can only be undertaken on old units so reliability could become an issue and a repeat of the costs involved as well as the expense of removing and refitting and repressurising the hydragas system yet again. At the moment there are enough spare ( second hand ) units to go around but this won’t always be the case. So the current solutions are not considered a permanent fix and in no way can they be guaranteed to last any length of time …you might be lucky. _unit Check out Dieters site for how your units look inside . Warning this site contains explicit pictures of Hydragas units dissected and may upset some MGF owners of a weak disposition.

Plus you have the same old issue with the height going up and down with the ambient temperature and the associated problems with the potential tyre scrubbing am
No lopsided appearance and trying to find a local garage with the. Knowledge and equipment that can check and adjust the height correctly we may be lucky here in the U.K. But many owners in Australia/ Italy/France/New Zealand/Switzerland/Austria/Belgium/Netherlands /Sweden/South Africa/Tasmania ( where we have now old FCCKits) may not have these facilities easily accessible and want reliability and better handling / road holding
For those that want to have a MGF in preference to a MGTF (which has coil over shocks) and change to a coil/spring set up then this new kit will suit your needs. You could fit the TF suspension but it had many design flaws and weaknesses, openly admitted by the design team that worked for Rover, some were partly addressed on the last models produced but IMO no eradicated and in any case the parts may need to be refurbished as they could be 15 years old … the costs of complete sub frame refurbishment and swap would therefore quite expensive even if you did all the work your self. They also have the habit of knocking out the lower shock bearing and snapping bolts .. new units are also getting rare and can be expensive . The stick TF dampers are non adjustable for either damping or ride height a dent set up will cost around £700 at least.

The MGF suspension parts are quite robust and parts that tend to wear are relatively cheap .. ball joints and bushes for example ,so keeping the same basic layout and improving the weaknesses makes sense ..In my opinion the attempt at a multi link rear suspension on the TF does not work as well as the.FCCKit/ MGF set up and does not have the expensive spherical bearings that are prone to failure as the TF

Current Solutions

The current offering of a coil in a can(CIAC) solution just does no work( Based on actual feedback from owners in Australia /Japan /Canada/U.K. ) as a suspension should and Ian’s a compromise with the ideal design solution and is not sold as an upgrade ! Remember the Hydragas uses both a gas pocket Spring under pressure and a fluid under pressure so these act against each other in a controlled manner and requires less leverage than a conventional steel Spring would.. using a steel Spring to replace the hydragas is asking to much. For such a small amount of leverage .ie the point at which the leverage acts on the spring ( the knuckle joint) will only give 15-20mm of vertical movement for the amount the suspension moves because it is to close to the pivot point and therefore insufficient leverage and is more of a rocking movement hence it is also known as a rocker/roller joint and the contact points are designed for this type of movement not a impact load a Spring would impart. The hydragas unit has a socket that the knuckle joint fits into which is flexible so allows the rocker movement the Ciac solution does not allow this and this is another source of potential problems. The relationship between the wheel and the spring/shocker movement is termed the motion ratio the ratio of vertical travel the shock will move is 3”as is the FCCKit. In case of the CIAC solution this equates to 5” wheel to 0.5”spring ( approx) any spring designer will tell you it is not a viable task to ask of a Spring and for it to be effective. The solution for the TF was to move the fulcrum/leverage point away from the pivot point to approx 3 times the distance of the knuckle joint position and therefore allowing the spring /shock 3 x the vertical movement . A motion ratio of 5”” to 3”” … sufficient to allow the spring to work as it should. Also critical is the angle of the spring/shocker to the vertical movement of the wheel …the more you go away from the vertical the more the spring becomes less effective as it has to cater for the bending loads as well as compression loads . TheFCCKit is 15 degrees which is considerably less than the TF .This can compromise spring design and spring life .

Despite claims of two years testing ( that’s a lot of coffee) . Time has shown the damage to the chassis the CIAC conversions can cause via the shock absorber, resulting in cracks in the chassis around the mounts ( this weakness was fully known/common knowledge about at the time of developing the CIAC so why would you want to add additional loads to these points without some sort of bracing ??). They are not owner serviceable ,difficult to adjust do not have adjustable dampers and can be quite expensive £800-£900 plus fitting and you have to keep the old top arm/bearings and knuckle/rocker joints, which may need replacing from people with this type of conversion have had to replace the knuckle/joints after installation, hardly surprising as the higher impact loads were not a design factor when using the hydragas. Parts alone could cost you another £300 . This makes the kit quite expensive with ongoing repairs and also puts you back into a specialist part supplier if one goes faulty with potentially the car being stranded somewhere waiting for a replacement unit. Some of these units come with a warning of serious injury or even death !. So NOT something you would want to try and repair in a roadside emergency. Responsibility for the warranty seems hazy with poor feedback from current users trying to get some help…’Trusted’ MG suppliers should avoid retailing these in my opinion. and therefore for the above reasons the CIAC is not a good solution despite the manufactures claims.

Design Requirements
A new suspension kit that transfers the load into The subframe not the body shell. YES

Has adjustable damper settings YES

Has a choice of Gaz or Spax specially developed for the kit .YES

Has height adjustability and choice of spring rates YES

Improves the safety and reliability. Yes

Allows camber adjustment Optional camber kit)/full wheel alignment YES

Has easily sourced replacement parts .YES

Does not require specialist equipment such as the hydragas pump/ welding YES

Mechanic or DIY friendly (DIY time approx a weekend experienced MGF familiar mechanic 6-8 hrs) YES

Does not have you weaving around avoiding speed humps or uneven surfaces. Lets you look at speed humps with contempt. YES

Designed and made in the U.K. for a British car by a long established MGF specialist British company YES

Offers a Track/race version and custom specifications.Soon to be approved for race Regis. YES

Offers expert back up and assistance by telephone and email .YES

And finally a suspension kit that allows you to fine tune to you requirements and does what it says on the can without having a can YES

Solution. (FCCKit )F Coil Conversion Kit)

The new suspension kit fulfills all the above criteria and comprises of 4 shock turrets, 4 springs and 4 adjustable shocks 4 new design top arms and bearings with all the required nuts and bolts to fit and also offered with the option of a camber adjustment kit.

Of course to fit the new kit will involve removing some or all of the old hydragas units, pipes and the top arms/bearings so a car hoist is advisable but we have tested the fitting by using a trolley jack and axle stands, so it is within the scope of a DIY installation providing the hydragas fluid is de- pressurized correctly ( after raising the car) The condition of the existing subframes should be examined first as many are now corroded and may need replacement or repair.

As a bonus the old hydragas units and parts can often be re-sold so recouping some of the cost and helping other MGF owners.

I have had this fitted to my MGF By Mike , his mechanic in Barnsley Jamie was excellent in the way he went about the job explaining as he went along, with photographs and updates. The difference to my car is hard to explain,but it now feels like it is a new car as the ride has been totally transformed.

The technical information was from Mike Saturs Web site and copied with his permission

Richard Lomas