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MG MGF Technical - Measuring Ride Height

Some of you may remember a post from me about the unusually one-sided camber readings even after a 4-wheel alignment on my F. Best advice from the board was to measure the ride height (even though I know that was reset for the 4-wheel alilgnment)and last weekend I got around to doing so.

After following the instructions meticulously and re-measuring a few times, I found that the rear right was slightly lower than the other three, but nothing significant. I then realised that I did not know whether to measure to the top of the wheel arch and stop at the metal or before that at the arch-liner. The difference is about 3-5mm and the ride height is a bit on the high side if measured to the metal.

Any ideas?

Chaz
Chaz

Hi Chaz, I usually measure to the liner, but for your purposes, that strictly doesn't matter insofar as you just wanted to make sure that there wasn't any gross abnormality in ride height.

Good news that there isn't. Still no good explanation for the camber problem, but if the car feels fine, then I would not worry too much about it.

T.E.D. had similar geometry issues - and these were solved by replacing all the bushes with PU items. Worth doing for other reasons, but expensive if only for sorting out a slightly odd camber setting.
Rob Bell

Thanks Rob, I agree that teh consistent and (even roughly) accurate ride height means that the one-sided in-spec but only just camber is not ride height related. PU bushes are definitely on the list as I suspect that my 7 year old's are getting somewhat worn.

One question, since part of me likes to be as obsessively accuracte as possible! When the manual says:

"trim height spec is correct at a nominal temp of 17 deg C. Setting trim heights at temps above or below 17 will cause the suspension trim height to be incorrect and should be compensated for by the factor of 0.5mm per 1 deg C when temps are above or below this figure."

Should you add .05mm for every degree above 17 deg and subtract for every degress below or vice versa?

Also how do people do this measurement? Do you estimate the centre of the wheel and the top of the arch and do you ignore the fact that the ruler is not vertical if touching both wheel and arch? (Told you I could be obsessive!).

Thanks

Chaz

Chaz

Chaz, I always thought that the figure was 0.4mm per degree C from 17C, so I looked it up in my old manual.

Mine states 0.6mm per degree change!

Anyway, yes, one is looking at approx 0.5mm per degree rather something a tenth of this value: this is one of the weaknesses of hydragas suspension systems.

Regarding measurement: approx wheel centre (easy to approximate using the MG logo), and the ride height values are used taking into account any difference in wheel hub displacement to wheel arch lip (angles are pretty acute, so actual value not all that different).
Rob Bell

OK, I can relax about the sloping ruler from an approximated start-point, but do I add or subtract the 0.5mm (or 0.6 or 0.4) per degree? I guess that the temperature could not have been more than 10 degrees C so that makes a plus or minus 3.5mm allowance - but which way?

Thanks
Chaz

Chaz,

If the temperature goes up, so will the ride height and similarly if the temperature goes down, so will the ride height.

Dave
Dave

So...at 10 deg C, I should expect the measured height to be lower than it would be at 17 deg C adn therefore i should add 0.5mm for each degree. In which case, the suspension, though consistent on my car has probably been set a little high.
Chaz

Yup, that's a pretty common mistake Chaz.
Rob Bell

This thread was discussed between 23/01/2003 and 27/01/2003

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