MGF VVC suspension

[andyinthewoods]

Hi I have just bought a very nice 1998 MGF VVC.

However, the suspension is a bit jiggly and firm. I was just reading an article about hydragas suspension and Sir Alex Moulton, and it suggested that the car should have an almost magic carpet like ride. Well, it certainly isn't that!

So I read a few articles and measured the ride height and I find that I have ride height of 340mm all round instead of the recommended 368mm.
I also read that if you keep re-gassing the suspension then it can lock up when all of the Nitrogen has leaked out.

Now, I have no idea of whether it has been regassed already, but is it worth trying, or will it still be just as firm?

The current ride height is perfectly OK for practical purposes.


If it does need replacing, then I would really like to retain a hydragas system from a historical interest point of view - I like innovative British engineering. However, at the moment the only option I can see is to try to add a re-gassing valve to the upper sphere. This looks a bit scary to me, so I was wondering, does anyone supply modified spheres that have a re-gassing (Nitrogen) valve?

[ZSx]

These Guys will rebuild for you and do an exchange, or a fitting service. - https://www.facebook.com/groups/Hydrosuspension/

Failing that Mike Satur has an option, but I don't know if he fits or if it is just a part he sends out to you to fit yourself...

[Reckless Rat]

Your car is 20 years old and the life expectancy of a Hydragas sphere is 15 years so it's more than a given that the majority of the nitrogen in the gas egg has been lost. A ride height at 340mm is far too low and the car will effectively be riding on its bump stops. You could try a fluid pump which will bring the car back to where it should be, but that won't make much difference if the spheres are full of fluid and not gas. Continuing to drive the car in this state is likely to damage something.

Removing and replacing the spheres is not a difficult job, and Ian Kennedy will check and re-gas them by return of post. It is by far the best solution. I have heard various reports on Suplex and similar spring replacelments. They are expensive and if you're looking to recreate the original ride quality of the car they're not the best choice.

£350 for a set of four spheres, including delivery. My car was done last year and it's transformed it. http://www.hydragasandhydrolasticservice.com/

[John SS]

Before you set about regassing the spheres I strongly recommend that you should first try a pump up of the fluid to restore the car to the correct ride height. This can be done by a specialist or you can buy an inexpensive pump designed for the job, on eBay. (Don't bother with the low loss valve, I have never felt the need for it).
See how the ride is after this and whether the ride height is maintained, before deciding to go down the regassing route.

[FUSION]

My 1997 VVC had 16 inch wheels when purchased. Replaced these with original 15 inch. Made a big difference. Have recently removed the hydragas and replaced with a Suplex kit and gained further improvement. Have now obtained a torsional kit and mounts and full set of suspension polys and will be fitting soon. I messed about having hydragas pumped up twice and tried different ride heights but with little success. Took it to a so called MG expert (on MGOC 5 star suppliers list) and he told me the square root of nothin. Said that's how they are. He gladly took the £120 he charged.
Considered having spheres renovated but at nearly £400 for something 20 years old with no guarantee of the reliability of the diaphrams I kicked that idea into touch.

[Reckless Rat]

If your car is set at the correct ride height, (368mm) measured from the front wheel centre to the wheel arch it is reasonably easy to check whether the front spheres are still holding (some) gas. Open the bonnet and push down on the closing panel. The front suspension should be compliant. If it is hard then the spheres are depleted. It is harder to determine the state of the rear spheres because the set-up is firmer at the back.

There are plenty of Citroëns (and early BMC/BL/Rover hydragas cars) about with spheres that have been regassed and are still serviceable, the earliest Citroën examples date back to the mid 1950s.The loss of Nitrogen occurs over time by a process called osmosis, not (generally) by failure of the unit. A regassed MGF sphere should be OK for 10-15 years before it would need to be recharged again, which would be easy via the new schraeder valves.

Changing from 16" to 15" wheels & tyres will make a difference but only because the aspect ratio of the tyres fitted to the 15" rims is greater than the 16" ones - all you're getting is more flex in the tyre, not the suspension.

[talkingcars]

Hi and welcome to the forum

Personally at this stage I would just get the fluid topped up, see how it goes.

James

[andyinthewoods]

Hi all

As a completely new user of this forum, I am completely blown away by the number and quality of the responses. Thankyou all very much.

I'm a new owner of an MGF and I was initially wary about my choice, but now I'm proud to have a car which is packed with so many interesting bits of British engineering (I appreciated the in built dipstick wiper for instance!). I can't wait to get it into a dry space where I can replace all of the belts and get to work on the suspension. But for now, I'll try restoring the ride height by pumping in some fluid to see what happens, however, if this doesn't work then I'll definitely take the advice about getting the spheres re-gassed.

I'd really like to know how well they should ride if they are sorted. I'm in Aberystwyth, so there is unlikely to be a sorted one for me to have ride in around here , so can anyone with a sorted car think of an arbitrary test to tell me whether my car is riding OK or not? I can tell you this; I have to slow right down for speed bumps in the MG, whereas I can drive over them in my MK4 Mondeo quite comfortably. The front suspension doesn't deflect much at all when I push down on the bonnet closer panel either. However, the high speed cornering and ride are perfectly OK.

Thanks again

Andy

[Reckless Rat]

A classic symptom of failed/gas free spheres is a very hard & jiggly ride. Potholes are to be feared, as are speed-bumps, road joints, cross trenches or any other road situation which would normally call for deflection of the suspension. If the spheres are gasless then all you're riding on is the air in the tyres and not much else. A good clue is to look at the state of the towing hook on the front of the front subframe, the under-body strengthening plate that covers the underfloor pipes and the flexible part of the exhaust. If they're showing signs of damage you can bet that the car has been run with the suspension not set at the correct height and/or with depleted spheres. I'm not saying that you shouldn't slow down for speed bumps but once the spheres are as they should be then negotiating them is not as tooth grittingly unbearable as before. The MGF is a sports car so it's not intended to give you a magic carpet ride. It will still be firm, but far more compliant. You will also notice that the handling is improved as the car will not be so skittish. Once you've had the work done, invest in a 4 wheel alignment, and be sure to have either Toyo Proxes or Falken 914s all round.

A standard MGF should sit at 368mm but if you want to set it lower, don't mess about with the fluid - fit a set of lowering pins from Mike Satur - the ideal time to do this is while the spheres are off as you need the system depressurised to do it. They will lower the car but maintain the suspension movement.

[Reckless Rat]

For information, the spheres on my MGF were re-gassed last year. I have taken a short video to show the degree of suspension deflection you should expect - if you're getting less than this then your spheres are probably needing attention.

https://youtu.be/kOmXgS8U13I

[andyinthewoods]

Hi Bruce
I really appreciate the link to the video. It certainly confirms that theres something wrong with my car. I think you're right; it's just bouncing on the tyres! Don't worry about sending the link by phone now.

Cheers

[Reckless Rat]

Too late!
Glad it was of some help.
If you're any good at car DIY removing & replacing the spheres is a reasonably easy job. The fronts are easier than the rears, but only because one of the nuts is a bit difficult to access - give the tops of the dampers a soak in plus gas and the 4 bolts on each sphere turret before you start. There's a how to do it link here: http://www.mgf.ultimatemg.com/group2/DI ... /index.htm

[Bigfootmgf]

Yes the best thing to do is re gas the spheres if you are keeping the hydra gas system.
The longer you leave it the more chance they are beyond repair but the Kennedys do have some replacements they can sell you!
http://www.hydragasandhydrolasticservic ... rvice.html
They are in Telford Shropshire and do a fitting service if that's more convenient (like me)!!

[resiak]

On an old car like that, the nitrogen part of the sphere has lost the nitrogen. The system works by having the top of the spheres filled with high pressure Nitrogen, and the lower side filled with mixture of antifreeze and water (50/50)
Pumping the liquid side (as opposed to the gas side) will achieve absolutely nothing, except restoring the height, but the "spring" of Nitrogen has gone, and the space been taken up by extra liquid.
As you might know, liquid is not compressible, as opposed to the Nitrogen gas, so you have no springing left, at all, if the Nitrogen has gone and its space taken up by liquid.
I had exactly the same happening to my car, and I took the spheres out, fitted a valve and pumped the gas side up. Then I filled the fluid side, and the car is like new! Just mark where the valve can be fitted before you take the spheres out. No problems really at the back, but you will most likely find that the best place is on top on the two front spheres, and then drill the plate above the front spheres with a 20mm hole.
So that is the way forward.
If you can see leaks from any of the spheres, then they are beyond saving. If you can't, I think you stand a good chance of saving them.
I did mine about 3 weeks ago. One has since dropped part of the gas, and I re-pumped the sphere with the unit in the car. It took all of about 2 minutes! and now it seems to hold, indicating a small piece of dirt in the valve might have been the problem.

And, while not "riding on a carpet", the system is competent and comfortable, yet firm. I would certainly suggest you fix it properly.
I think it is a unique part of what makes the F such a stunning small sports car! and you will love the handling, it is brilliant!
Write me, if you need pics or info! willdoATicon.co.za

[Reckless Rat]

Just to clarify. Rover hydragas fluid is a mix of antifreeze water and alcohol. The antifreeze (green not oat) is diluted 50/50 with water and then that solution is added to wood alcohol in equal portions.

[resiak]

The alcohol is the green antifreeze!

So it is a mixture of that and water. Originally there was a tiny amount of a third component added, I forget which.

https://www.clinicaladvisor.com/critica ... le/586526/

[Reckless Rat]

Official Recipe for Hydrolastic Fluid:
The liquid is a solution of 49% alcohol, 49% distilled water, 1 % triethanolamine phosphate and 1% sodium mercaptobenzthiazole, which is of constant viscosity and has a freezing temperature of 31 degrees C. According to BMC, the particular reason this fluid is used instead of distilled water with an antifreeze is that this fluid IS an antifreeze solution of constant viscosity containing a rust inhibitor with an agent added to make the fluid distasteful. (This last was a legal requirement.)
A 50-50 mixture of methylated spirit and antifreeze (with a little radiator anti-corrosion added) can be used successfully with no adverse effects.

There were variations in the formula for Hydrolastic fluid between the UK and Australia. The firm of H.C. Sleigh (Golden Fleece) marketed a fluid to the following specification: Alcohol 50%, Water 24.45%, Bentmazol 0.05%, Ethylene Glycol 3%, (Bomar)? 0.50%, Union Carbide HB5100 22% (this is a viscosity improver).

[resiak]

What you, correctly, call alcohol - is what most people would call ethylene glycol, or green antifreeze.
So for the man in the street, the mixture for refilling your liquid side is indeed 50% water and 50% green antifreeze.
Most, if not all, antifreezes will have built in corrosion inhibitors, usually a silicate.

I used propylene glycol, which is the blue anti freeze.

I would agree to stay away from the organic acid products, as they are relatively new, and there has been some concern that it damages the silicone in engines, and I don't want to risk a possible reaction with the rubber diaphragms in the spheres.

[NapalmNick]

As another experience...
My 2000 vvc was at 340 when I bought it. Got Hydragas pumped up and the ride was instantly transformed back to loveliness.
But it took a higher pressure than stock to get it up to 368mm which has me a bit worried lowering pins might already be fitted and I can't suss out how to be sure/check easily without some dismantling pain. It could also mean the nitrogen is depleted so extra pressure is used to take up the gas height loss but all corners spring quite nicely.

I'm concerned about the extra pressure on the old spheres so might settle to lower it to about 360mm.

But i would pump it up and see if it's a revelation before doing anything drastic

[Reckless Rat]

If your car is fitted with lowering pins then it should ideally sit at 350mm. You could try releasing some pressure to allow it to settle at that height and see whether you are still getting the suspension deflection that you're currently getting. Without removing a suspension knuckle it's difficult to tell. - have a look at these pics:

https://www.the-t-bar.com/forum/21-davi ... on-knuckle

By the way the 400psi pressure is purely a guide - it's the height that's important. have you considered asking the previous owner if they are fitted?