Hydragas front suspension

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Hydragas front suspension

Postby KevinM3Coupe » Thu Feb 20, 2014 9:45 pm

hi all,

I have just got the midas back on the road after 5 yrs.

All OK except front suspension is rock hard (perhaps less than 1 inch movement).

I have modified spheres with the valve on top.


Questions:

Can hydragas be setup to give proper damping . I.e without every road bump crashing through the body shell and jarring your teeth? (it must be possible because a metro would not have been so bad?)

How much suspesion travel could you expect.
How much clearance from front tyre to wheel arch when setup correctly. I currently have only about 1 to 2 inches.

How do I re-pressurise the nitrogen? I can do the fluid from a hydragas pump off eBay.




Thanks in advance for any help here. I must sort this out soon before all my fillings fall out.
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Re: Hydragas front suspension

Postby davidj » Fri Feb 21, 2014 8:00 am

Hi Kevin

Glad to hear that you have got your car back on the road. My advice would be to have a chat to Alistair Courtney at Alternative Cars, there is a link on the club web site, I am sure that he will be able to sort your problems. Your ride height sounds about right but I would suspect some air and no nitrogen.
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Re: Hydragas front suspension

Postby All That Glisters » Fri Feb 21, 2014 4:26 pm

Hi Kevin, can I suggest that you take a look at the Hydragas Register web site, it gives as much technical stuff about our suspension as you will need. I'm intrigued by your reference to modified spheres with valve on top as the top chamber is where the gas is normally and the bottom chamber is where the liquid is. As I understand it the gas can dissipate so pumping up the suspension normally involves putting more fluid in the bottom chamber which hardens the suspension (the gas is the springy bit so less gas means less bounce). The top chamber is normally totally sealed unless your modified ones do let you pump gas (nitrogen, air or whatever) into them, thats why I'm intrigued by your setup.

Regards Mark
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Re: Hydragas front suspension

Postby Stuart » Fri Feb 21, 2014 4:54 pm

Mark the gas valve mod is mentioned on the website you suggested.

http://www.hydragas.co.uk/tech/lowering.html
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Re: Hydragas front suspension

Postby Hans Efde » Fri Feb 21, 2014 8:44 pm

There have been many discussions on this forum about the hydragas suspension. Just do the search on "hydragas" in the header of the forum and you will have one evening full of reading.
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Re: Hydragas front suspension

Postby Stuart » Fri Feb 21, 2014 9:20 pm

another good article from a previous thread.

http://www.mgf.ultimatemg.com/group2/su ... sation.htm
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Re: Hydragas front suspension

Postby KevinM3Coupe » Fri Feb 21, 2014 9:40 pm

Thank you for your replies

I have been doing some backround reading here and online as sugested.
I found this article which is very informative also...
http://www.aronline.co.uk/blogs/cars/mg ... explained/

What I get from this is that the hydragas could be very good if you have interconnected front and back units. Compression of the front units over a bump raises the pressure in the rear units, raises the back, thus maintaining a level ride. Additionally on cornering, both units are compressed, thus effectively stiffening the suspension and reducing roll.
Should be good? Has anyone got this setup on their Midas?

Alas I have front only.
The following link also explains the modification I have...
http://www.aronline.co.uk/blogs/cars/au ... i-spheres/
I think I should be able to get the spheres charged to a maximum of 10 bar nitrogen at a tyre fitter.
This will be my starting point, then I shall get the fluid re-pumped and see how it is.

(Btw I am not convinced the front coil spring modifications detailed elsewhere on this forum give sufficient travel without being too firm? Do come back anyone and correct me on this)
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Re: Hydragas front suspension

Postby Stuart » Fri Feb 21, 2014 10:25 pm

I've been in two mk 3's that had full hydrogas suspension, one was very good and the other a bit soft and roly poly. Does yours have front dampers on too?
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Re: Hydragas front suspension

Postby mikeeskriett » Sat Feb 22, 2014 6:42 pm

I have Hydragas front and rear on my convertible in the standard Metro config (interconnected rears and independent fronts) it gives a comfortable ride for the commute to work and motorway driving though through the country lanes the handling isn't as sharp but at least on the fen roads it means you arrive at your destination with your spine intact.

The key with hyrdagas is to keep the system in good order and know what's fitted to your car there are multiple displacer types and certainly the fronts come in damped and non damped versions. From the factory the knuckle joint to displacer connection is shimmed depending on the model of the original donor and whether it was right or left hand drive.

The common faults tend to be:
- Air in the fluid side of the displacer where the line for the pump up machine has not been bled when the level was set which gives you a spongey wallowy ride
- Nitrogen leakage/seal failure leading to fluid entering the gas side of the unit - usually one side of the car will drop a little and if refilled bill be hard as nails
- Failed/Worn Nylon knuckle joint cups
- Perished bottom membrane leading to give in the membrane
- Cracked displacer base on rear units - Common one where reassembly after depressurising has been screwed up essentially the interconnecting rod between the radius arm knuckle and the displacer is out of line so it breaks the side out of the socket on the displacer and works it's way sideways in extreme cases it bursts the membrane on the displacer.
- Incorrect T piece fitted to the rear units - Symptom is comedy roll control, the T piece is not usually a bore for bore straight through unit so acts as a flow restrictor between the rear units.

Takes me back to my misspent youth working on Metro's salvaging serviceable displacers from damaged sub-frames and the Russian roulette of trying to remove seized valve caps from units only to discover the Schrader valve stem had a crack in it, getting covered in either fluorescent green or orangey brown smelly fluid gets old very quickly!!

Cheers,

Mike
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Re: Hydragas front suspension

Postby KevinM3Coupe » Sat Mar 01, 2014 9:08 pm

Yea! I have the suspension sorted.

I drew a blank on the nitrogen, but found a really nifty little pump in Halfords for pumping up mountain bike forks. Only £20 and can pump up to 20 bar. It has a pressure gauge and a de-pressure button too if you need to let some air out.
Now of course normal air is more prone to pressure change with temperature than nitrogen and oxygen in the mix allows rust. But then again I am just topping up so a suitable compromise I think.

I ordered the hydragas pump from ebay for approx £60 inc post for the fluid side.

So the nitrogen pressure was approx 16 bar (pressure should be measured with the suspension un compressed - I.e car jacked up to raise the wheel off the ground) I raised this to 17 assuming some pressure was lost over the years, but not wanting to over do it. I then pumped the liquid side up for the specified height centre of wheel to top of wheel arch of 12.5 inches. This worked out at approx 24 bar. This took quite a lot of fluid (I used 50/50 antifreeze mix) as my original height measurement was just 11 inches!
No wonder the suspension (I.e no suspension) was so bad before. I have to wonder what happened to the fluid that should have been there. I haven't seen any leaks and the height has remained as set so far ( only a couple of days)

We'll the little Midas is a joy to drive now - probably a bit bouncy but I don't feel the bumps or fear the pot holes anymore.
I think I need new front shocks too as one clunks a bit when you bounce it.

BTW does anyone else have a rattly heater control unit and is it easy to fix?


Thanks

Kevin
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