has anyone retro-fitted MG-TF rear suspension to MGF ?

[2woody]

I'm interested in retro-fitting the improved geometry TF rear suspension onto my MGF - has anyone done this ?

Specifically - I would only be interested in keeping Hydrolastic, which I suggest might be the biggest sticking point

views welcomed

[flyingbanana]

It's quite easy to individualise MGF suspension, much easier than a metro.

[Mykel]

I have been thinking about this myself for a while. IMHO it should be do-able, best use a complete TF subframe as starting point. First remove the struts, then the top wishbones and ball joints, as these are specific for the coil over setup. Replace with the smaller ball joints and the upper wishbones and knuckles from an MGF, which from memory should be a straight fit.

You will then have to use an angle grinder to chop off the top strut abutments on the subframe to make room for the hydragas elements. The mounting holes for the caps are still there (at least the two lower ones on each side), not sure about the top ones though.

This way you can use the rather more defined trailing arm and longer track rod setup from the TF with the hydragas system.

[quick_spider]

Tf rear top arms have spherical ball joints, whereas the MGF top arm is a roller bearing, so I suspect using the MGF arms won’t allow the suspension to articulate properly.

[2woody]

yes - I'd picked that up. Time for a re-think

[Mykel]

I have both a TF and an F rear subframe (both quite rotten) somewhere. Will give it a try sometime but without fitting the hydragas egg. It should be possible to tell from any stress or tension building up on movement whether it should work or not, but thinking about it, you’re probably right, Jon. The TF setup pivots around the front rubber mounting of the trailing arm which is bolted to the hub carrier, thus the latter will probably not just move up and down, but have a small variable angle towards the upper mounting in the subframe. this may be the reason for using a spherical joint rather roller bearings.

[mgtfnut]

The TF setup pivots around the front rubber mounting of the trailing arm which is bolted to the hub carrier, thus the latter will probably not just move up and down, but have a small variable angle towards the upper mounting in the subframe. this may be the reason for using a spherical joint rather roller bearings.

Yes, that's right. The spherical bearing in the top link is the same bearing as in the bottom of both front and rear dampers. It's a TRW parts bin bearing - probably about 8/10 years ago I lifted the spring clips on the rubber boots and squirted a little hypoid oil in both sides of all the "spherical bearings". Strangely it seems to have prolonged their life - bit of luck there with what I thought later was a bit of a silly thing to do

That front rubber bush is known as the "compliance bush" and is voided to provide compliance The whole rear linkage is very cleverly designed to provide optimum track/camber changes under braking/acceleration stress with little "friction", which could inhibit the designed suspension movement.

[2woody]

I must admit to having some other knowledge about this.....

part of the reason for changing the suspension for MG TF was because the MGF variant gives some very unpleasant toe-changes under extreme braking situations - this is also why the standard set-up is so front-biased.

I suspect that the greatest contribution to eradicating this for TF is in the difference between the lower link lengths

[Rob Bell]

Should be an interesting project - I had asked the engineers who designed the system the same question about 15 years ago. They didn't like the idea! BUT I reckon, with a bit of "engin-uity" [sic] I reckon this is doable. Best have a TF and MGF subframe and suspension systems together and then work your way through seeing how to replace the coil-over in turret with the Hydragas unit - and work out how to attach an extra, adjustable damper.

Watching with great interest

[2woody]

for reference, my little brother wrote off the very first prototype TF at MIRA in a "how much rear bias do we run" experiment. Almost exactly a month before I demolished the other side of the same crash barrier in a Volvo.

I'm looking into the geometry a little deeper, it seems the most important part is the longer rear track-control arm. There might just be a way to use this in isolation

[Tipper]

I have to ask, why keep the hydrolastic suspension?

The TF sub-frames are already available complete with your desired suspension geometry so surely that is the way to go. Add VHS Bilstein dampers which are what the designers wanted before the accountants ruined the ride with cheapo dampers and you're done. And no more worrying about hydrolastic pump-ups!

[2woody]

to me, hydrolastic is an integral part of the car - and inseparable from the point of having an MGF. Its really good in a number of fronts and ideally suited. Just as important as being rear-engined is to a Porsche 911 or auto transmission to a Royce.

pump-ups don't really bother me either - I have a pump

[Tipper]

OK but doesn't really make sense to me. A TF is an F but with better suspension IMHO.

But then again I chose a TF over an F because I didn't want to faff about with leaky spheres and all that goes with it.

[BodgeItAndScarper]

Not sure this is the place to have this discussion yet again, but I think there are plenty TFs around, and any number of sportscars with coil sprung suspension. Leave the Fs for those of us who appreciate the oddness!

I love this thread

[John SS]

Leave the Fs for those of us who appreciate the oddness!

I love this thread

Totally agree!!

[2woody]

Oh - what have I done.....?

will report back soon

[Mykel]

Oh - what have I done.....?

Well, you triggered the inevitable and ages old infight between followers of two different denominations

[2woody]

to me - the attraction of an MGF is the supremely intelligent use of Metro subframes into a genuinely world-beating sports car, together with the hydrolastic element. And that designed at a time when Rover wasn't in great fettle. The story might have been a little different if they'd taken up our PR2 instead

The conversion to TF, driven as it was by poor braking and the unwillingness to lengthen the licencing element from Moulton, kind of cheapened the whole package. It will undoubtedly have increased sales and would produce a firmer and probably faster-cornering car, but that's not what I'm after.

What I am after is the better braking from TF, through rear-end geometry which avoids one particular effect

to each his own, though.

[Rob Bell]

Great project: how is your research going? I’m sure much of the TF stuff is bolt on bar a central location of the lower transverse links...

[Tipper]

...
The conversion to TF, driven as it was by poor braking and the unwillingness to lengthen the licencing element from Moulton, kind of cheapened the whole package...

I thought it was because Dunlop refused to make them at a reasonable price because they had to remake all the tooling because it was worn out! I stand corrected.