Welcome to our resource for MG Car Information.



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 - Replacing hydragas units

I wonder whether any of you people have ever managed to replace the hydra suspension units of the F with some other device. After consecutively blowing three of my hydragas units I am looking for any other possible solution to this problem. Would it be possible to interpose a damper or anything similar?. Or to stuff the units with a coil?
JP Banks

interesting as I have been thinking in the same terms...Unfortunatly it seems that ordinary "coilover" (adjustable springs on the outside of the shock) isnīt a good thing as the pickup points both at the top and the bottom are a bit weak. Maybee possible if the upper point are reinforce-welded AND the lower point has some fork attachment instead of the now used off-side with heavy load on one side of the bolt.
What are the options of emptying the spheres from both gas and fluid and fill up with something more solid like silicone rubber or any other stuff that at least wonīt leak out when cured? Maybee something to test on an allready damaged sphere ? True old Mini style ! There is of course also the way to use suitable small coils in place of the sphere but use the original fastings etc. Take a look at the rear coils from a SAAB 900 94-97 (or any other make with the same ball-shaped compact coils) Surely such a coilpack could be substituted for the sphere and still retain the lower "knuckles"..
Assume You have searched Dieters excellent site with lots of info and pictures. Let us know how You get on !

BR, Carl.
Carl Blom

Take a look here it seems like it can be done.

Ken Waring

Following the earlier(much) suggestion of Carl's, I am experimenting with the spheres on my race car. I looked at the price of new "Cup" specification spheres or up-rated "Trophy" spheres and decided that by the time I shipped them down-under the cost was prohibitive. So I have purchased four S/H spheres and modified them to my specs. I drilled a small hole in the top chamber to release the gas. Then I TIG welded on a fitting which enabled me to re-charge them with nitrogen to whatever pressure I desire. Once fitted to the car I re-charge the fluid system to a fixed pressure (400psi) and then adjust the ride-height via the pin that activates the lower bellows. In my case this pin is adjustable in length rather than being simply shortened as is the normal case. Thus I am able to play with the nitrogen pressure at will to determine the "stiffness" of the effective spring. All fittings are plumbed remotely so that I can play with it from either the tyre well or the boot. Obviously they all run independently with no inter-connection. The nitrogen is available in a small bottle and I use a pressure regulator fitted to it to adjust the fill. This gives me the facility to alter the spring rates. To date it is working reliably and has enebled me to reduce my lap times significantly. The fitting are an amalgamation of my own lathe work and commercialy available hi-pressure plastic lines fitted to truck brake systems. The total cost of the fittings was no more than $60AUD or say 20 quid and this includes making them all independent.

Hope this is of some help and interest.

David Mottram
David Mottram

David I am most interested. One the hydragas units in my F has recently bursted -with 20,000k only!-. Same as you I lived in the far south of the world and hydra units are not available and are to be imported.
I would be very grateful whether you could send me detailed instructions of your modifications. Photos or drawings, may you have, would be most helpful.
Many thanks
JM Vega-P.

Very impressive sounding modifications David. Do you have any pictures of the changes you made? As you say, spring rates are adjustable according to nitrogen pressure - so that you can readily alter your spring rates is a huge advantage for a circuit racer! :o)
Rob Bell

I don't think I can attach pictures in this Forum. I do however have some digital shots of the fittings etc and installation which I could post as JPEGs to interested parties upon request.
As I understand it the original pressure in the nitrogen sphere was 250 psi. and some of the Cup spheres were as low as 100 psi. I have not gone that low as yet..........130psi is my lowest experiment. It certainly makes a difference but introduces a whole range of tuning options which can confuse if not careful. Clearly the damper rates need to be adjustable as do the anti-sway bars. Fortunately my dampers are adjustable. I have doubled the stiffness of the sway bars simply by running two standard bars in parallel but really need to have more adjustablity and will probably look at having them cockpit adjustable if I am going to go the the trouble of making some bars.....the next project.
It is all good fun and better than watching TV in the evenings. I run the F in our State Series. Last year I finished 12th our of 52 runners (28 regulars), and this year I hope to finish around 5th or 6th. This is not too shabby given that I missed one meeting out of eight when I was in Nepal.
Our series is fantastic. We have three classes. Firstly there are the Open class cars which are pure fully developed race cars (usually V8 MGB's, Race midgets etc). I cannot keep anywhere near them on the track. The next fastest class is in fact my class called Fast Road. We are allowed to modify as we wish but the cars must run on road tyres and be road registered. The final class is Historic and these cars are very quick despite being constrained in the specifications. I have trouble keeping with a few of the really quick MGB's in this class. Interestingly a group of us are currently building two new cars in the Histori class (MGBs) to take to Spa next year for the 6hr Race in September. Perhaps we might see a few F people there. There is also a local MGF Trophy series here at a National level (about 25 cars). This is a buy a drive series that is far too much money for me..........around $100,000 pa and they will not let me enter in my have to use their cars and pay the $50,000 entry fee!
We have a web page where anybody interested can see our cars.mine is #11 white MGF.

Regards..........David M
david mottram

I'd love to see the pix david - I could host the images too if that was okay with you? (

Regarding the anti-sway/ anti-roll bars (ARBs), an easy way to make the existing units adjustable would be to drill new mounting holes so you could move the drop link mounting closer to the point of pivot, effectively stiffening the bar. You are probably after a much stiffer bar in any case, so if you have them made up, just get them drilled at pre-set distances: this is how the MGF Cup cars are set up. Note too that the front subframe is not all that stiff (you may have discovered this already): when using stiffer ARBs, the subframe can twist before the bar does - Cup cars get around this problem by mounting to the floor pan behind the subframe.

Some of these options are a little too extreme for a road car, but I'm planning on fitting the ARBs from a TF (already 1mm thicker than those on the MGF), and playing with the mounting as described above...
Rob Bell

Hi all,
one way to use the exsisting ARBīs but "fatten" them a bit by welding a suitable steel tube that has been cut into 2 halfes lengthwise. I have done this on several cars (for track and road ) during the years. By doing it like that one can avoid to make the re-inforcements where the rubber parts are = no change of diam. at those places.But for the "F" there are of course the restrictions to the subframe mentioned by Rob... Just wonder - how much improvement is there in a seamwelded subframe compared to an original spotwelded one ??
Carl Blom

That's pretty cunning Carl :o)

Not actually sure how much more stiff the seam welded front subframe is. Cup cars' subframes are so prepared, and they still twist. Mind you, Cup car ARBs are pretty thick!!!
Rob Bell

Rob Bell, I tried to link to your ultimate site via the hotlink but it cannot find it. What is your direct e-mail address

David Mottram

Hi David - it's robert dot bell at ucl dot ac dot uk
Rob Bell

What would you think of this?.
I took a broken hydragas unit to a friend -a mechanical engineer- and he suggested a suspension modification. The cover of the unit could be kept in order not to change structures and keep the unit retaining plate. However emptying the hydra unit, placing a steal cilinder inside -closed at the top and with a lid at the bottom-. Inside the cilinder a coil which at the bottom would be adapted to the receptor of the knuckle.
Do you people believe it possible to be done? And more important, would it do the job?
JP Banks

Holy resurrected thread batman!

I came across an article on Rob Bell's site about hydragas units and once again was reminded of this article. Given the current hydragas situation I thought this would be useful to ressurect.

I may even suggest Rob tries to contact David for pictures of the repair as it seems he's got 12 years experience more than the rest of us!

Leigh Reid

Looks like I'm 5 years behind the times, and this has been and is being done on a regular basis now!
Leigh Reid

Just fitted the Suplex kit to our Trophy and although it's early days yet, it seems very good.
We had run out of suspension altogether with the Hydragas and the car was horrible to drive but now it is quite smooth and the handling is still as sharp. The only issue I have is with getting the ride height to the standard Trophy 348 front and 343 rear. I can get both the fronts to sit at about the right height but the best I can get at the back is 340 and the right rear wants to sit 10mm lower than the left rear. I think this must be down the shape of our car. If I try to wind the right side up I end up with the spring unit 'coil-bound' and a clunk when I bounce that corner of the car, so for now, I've set set it so that bounce feels about the same, side for side. I have also found it best to adjust the units a small amount and one at a time, because adjusting one unit will have an effect on all the others. I also disconnected one side of the anti-roll bar whilst adjusting just in case that might have some effect from side to side.
All in all I'm very happy with the set up so far.
P.S. you will hear some horrible noises on your first trip out after fitting!
Lindsay Sampford

Further to my previous posting about the Suplex spring conversion kit: The problem with getting the ride height right at the back was nothing to do with the kit at all! On the left I had a broken knuckle joint seat which showed itself by popping out completely when I jacked the car up. On the right hand rear, the knuckle joint boot was missing the clip at the top, which had allowed the ingress of water which had rusted the whole joint, limiting its free movement. With the two rear knuckles sorted, it now sits at the correct height at the front and back. The clunking noise is down to a worn upper ball joint (which I am about to replace) on the right rear.
Lindsay Sampford

This thread was discussed between 26/10/2003 and 29/09/2015

MG MGF Technical index

This thread is from the archive. The Live MG MGF Technical BBS is active now.