Unsprung masses for Prado 120

[Whitey Shockie Maker of the Month Award Find all posts View Profile Close Whitey]

Hey everyone,

I just did a calculation from the front coil working height and ride height, which I measured at the time. Working backwards, and using the measured front weight of the car (taking off an ARB bar, which I've calculated is at least 65kg), I get the unsprung mass per corner at the front being 99.11kg.

So mjrandom was 99.11% correct with his first estimate of 100kg!

There's still a bit of hand waving with the figures, as the weighbridge rounds to the nearest 20kg, and I'm not sure how accurate 65kg is for an ARB deluxe bar (ARB told me 45-50kg, but I think more), and how much a factory bumper weighs etc.

I think it's accurate enough to say the unsprung mass per corner on the front is definitely up around 100kg.

Unfortunately I didn't get my coil working height on the rear at the time, so I've got to do some new measurements when I put my new suspension in, and I'll pin it down more accurately.

Lesson from this story is don't trust the scales...they might get the ratio of masses between front and rear close to correct, but not the correct masses.

With 100kg unsprung, the front frequency gets up to 1.29Hz.

Best

Mark

[Whitey Shockie Maker of the Month Award Find all posts View Profile Close Whitey]

Hey,

Just a small update, Toyota got back to me, and they had techs chasing data everywhere, but unfortunately there is nothing in the Australian Toyota databases which provide unsprung masses.

I'm confident we can work backwards from the coil working height on freshly installed and settled suspension to get unsprung masses, or at least to within a few kg.

Best

Mark

[Whitey Shockie Maker of the Month Award Find all posts View Profile Close Whitey]

Hey all,

Just an update so I have a few figures in one place;

OEM rim + bfg 275/65 = 34.3kg

OEM upper arm = 2.5kg

OEM lower arm = 8.3kg

Durashock strut + C59-300 + OEM strut cap = 10.3kg (x 0.5)

DBA T2 front rotor = 8.8kg (at 26.5mm thickness)

Swaybar + links = 8.5kg (x 0.5)

Caliper + pads = ??

Hub = ??

Tie rods = ??

CV = ??


So this gives my running total at around 63.30kg.

I still need the hub weight, caliper weight, the CV weight (x 0.5), and the tie rod weight (x 0.5) to give a decent final figure.

My ride height calculations suggest at least 120kg unsprung/corner, but my weighbridge measurements are not accurate enough for sprung mass, so I'll need to corner weight the Prado accurately at some stage!

Best

Mark