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MG MGF Technical - What difference does a millimetre make?

Glancing through the spec sheets for the MGF and TF whilst updating a section in my web site, I noticed that the TF specs now include the anti-roll bar (ARB) diameters. Couldn't find these figures in the MGF literature, so I went out and measured them.

The official TF figures are-
Front: 20 mm
Rear: 18 mm

Measured on my F-
Front: 19 mm
Rear: 17 mm

So the TF benefits from a 1 mm increase in ARB diameter front and rear - which presumably means a greater roll stiffness.

But how much of a difference??? Would you feel the difference fitting them [the TF ARBs] to an F?
Rob Bell

I'm sure you will feel the difference.

If I haven't mistaken, 1mm extra on the rear anti-roll bar, means 12% of extra section area. So the torsional stiffness of the bar (if the same steel specification and if the connecting points are all in the same position) will be greater improved. That, of course, is worse when wet or damp.

HTH, Valter.
Valter

That was my thinking too Valter - though obviously, the rear section goes up relatively more than the front for the same 1 mm increase in diameter

Front:
MGF area = 3.142*19^2 = 1134 mm2
mgtf area = 3.142*20^2 = 1257 mm2

= 11% increase in cross sectional area

Rear
MGF area = 3.142*17^2 = 908 mm2
MGTF area = 3.142*18^2 = 1018 mm2

= 12% increase in cross sectional area

Hmm, not too great a difference though. Means that TF ARBs could be fitted straight onto an F, and shouldn't harm the chassis balance...

Interesting :o)
Rob Bell

And better still!
You can now have a combination of set-up's. Front ARB from a TF will, for example, improve corner entrance. And a softer rear from a F would benefit traction, and so on. Itīs a game now! :o)

Cheers, Valter.
Valter


Hi all,
main question : Are they interchangable between "F" and "TF" ? May-bee the diff. in bar thickness is because longer "arms" on the TF due to revised suspension.If so the force will be about equal for the cars. Again something for Rog to answer ....

BR, Carl.
Carl Blom

I think we can be 100% confident that the front bars will use the same pick-up points as the MGF Carl - because essentially, the front suspension hasn't been altered all that much (other than the conversion to coil springs). The rear however is a little more tricky to predict.

I reckon that the rear ARBs probably are transferable - but this, as you say, requires some further investigation.

Valter - you read my mind :o)) Keep the front @ 19mm, and increase the rear to 18mm, and the rear end will become a little more lively ;o)
Rob Bell

Rob,

I haven't the information directly to hand, but I think the actual effect on roll stiffness is actually multiplied beyond the actual increase in cross sectional area. I shall see if I can dig this up.

The rear bar has a completely different shape in the 6" or so before the eye bolt, but is the same basic overall length. Using a TF one would require the bar to be heated and bent, then correctly tempered again.

It would probably be cheaper to see a spring specialist manufacturer, give him the MGF bar as a pattern and say please make examples in bar sizes of 18mm and perhaps 19mm. The same can be applied for the front where you may want to have a 21mm bar made up to keep the front to rear bais the same.

Rog
Roger Parker

Thanks for the information Rog - shame about the rear ARB being a different shape :o(

I wonder if Rover sport did different sizes of ARB? I haven't heard about them in the UK, but seem to recall that Japanese racing specialists talking about different ARB sizes.

WRT altering handling balance, increasing rear stiffness a little bit should help reduce understeer a little, and increase the tendency to oversteer. Experimenting with this should be a lot of fun! ;o)
Rob Bell

This thread was discussed between 04/09/2002 and 08/09/2002

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