Yep, MGF uses the last ever iteration of the Hydragas system, a system that dates back to Sir Alex Moulton's 1960's original Mini Hydralastic suspension.
The design changed radically over the years and wasn't always 100% successful - it also carries it's own unique set of pros and cons, but we shall come to that later.
Hydralastic became Hydragas with the Metro and this system was redesigned again to suit the MGF. Whilst it is true that the two cars share similar systems, there are no interchangable parts between them (shame - cheap spares!) The Metro system was fully independant on the front and interlinked across the rear, with internal displacer cones shaped to suit the heavier front / lighter rear nature of this car. Lastly, the two rear Hydragas spheres on the Metro are slung under the rear subframe, at an angle of roughly 10 degrees from the horizontal, resulting in unique external fittings to allow fitment in this manner. The F has two separate 'circuits', with the left side linked and the right side linked front to rear, also the internal displacer cones are shaped to suit the more even (55% rear, 45% front) weight distribution of the F. All 4 Hydragas units on the F sit upright, on top of the upper wishbone. Displacer cones are metal elements within the bottom of the lower Hydragas sphere that move with the suspension wishbones, the shape and size of the cones 'displace' a similar amount of fluid and thus determine spring rates.
Hydragas gives a small car an unbeatable (IMO) ride quality, a properly set up F is a joy to drive and soaks up the lumps/bumps of the road surface in a manner that sets it apart and above all the competition - it really is that good. In an F it also delivers handling that is at least as good as the competition at launch. Lastly it contributes massivesly to the character of the car, there really is no other sports car that rides like an F. As you can tell i am a bit of a fan.
It is far from perfect though, just like the F it is a system with it's own quirks, one of which is it's susceptability to temperature and muppet dealerships who are up against the clock and don't give setting the system up properly the time it requires. The ride height of the car is determined by the pressure of the fluid in the system, high pressures = high ground clearance, and the reverse is also true. Therefore the F exhibits a seasonal peculiarity, in so far as when the ambient temperature drops, the fluid contracts and the ride height drops marginally. Likewise at the height of summer, there seems to be a lot of high Fs tooling around. This can be compensated for by making small adjustments to the fluid pressures once or twice a year, MGR will charge you £50.00 plus per visit for this pleasure, so a group of us in the Essex Roadsters each put £50.00 in a pot and between us we bought our own Hydragas pump. The first time we each used it we made our money back and we now have complete control over our cars' suspension and ride height and can set it to suit our own preferences (which are not in line with MGRs recomendations!)
Dunlop made the Hydragas units for MGR, they had a long term agreement where the unit costs were kept down and in the favour of MGR. This agreement came to an end in 2001 and Dunlop wanted to renegotiate a significantly higher unit price. Remember that by this time, the F was the only car to use the system and thus Dunlop were not making the same money they used to (when it was used on the Metro). Given the amount of Fs being sold (it was still the UKs #1 selling sports car right up to it's demise) it became feasible to redesign the suspension of the F to use (much cheaper per unit) coils and springs, based on a return projected in sales over a given time period. So this is what they did and the result is the TF.
The TF though drives completely differently to the F and has it's own very definite character. It is one of the reasons the TF was highly praised when launched as the changes went a lot deaper than a mere facelift, and it is also the reason the TF is viewed as a model in it's own right as opposed to simply a 'Mark 3 F'.
Sadly it is also the reason i will never buy one, going to shocks and springs took away the one thing that made the F unique for me, the TF competes on the same field as the competition these days, whereas the F was always that little bit different. Sure it was far from perfect, but it stood apart from the crowd, from it's 'baked bean' looks, to it's quirky fluid suspension - it delivered in areas the others didn't, and we are not talking ultimate speed/handling here, rather the ability to soak up thousands of miles and deal with the drudgery of comuting with equal aplomb to a few laps of the Nurburgring. I suppose it's a question of focus really - the TF is more focused on handling, at the expense of comfort. The F was less handling oriented, instead trying to be a great all rounder (in the true MG tradition, why do you think they sold all those MGBs? The B was never the fastest, best handling car in the world, it simply ticked more boxes than the competition).
And that's why i love it.