Thoughts on weight distribution

[mcbutler]

Hi All,

Whilst zipping back to Plymouth from Yeovil yesterday, over 10deg C so roof off of course.
I was thinking, after a porky boxster S passed me, about weight distribution.

What are your thoughts on, or does anyone know how it changes with the roof down compared to roof up?

Roof is heavy so you are not only shifting CofG a lot lower but shifting weight to the rear.

Come on then, anyone have any ideas??, or a weighing setup?

[Pbondar]

Hi All,

Whilst zipping back to Plymouth from Yeovil yesterday, over 10deg C so roof off of course.
I was thinking, after a porky boxster S passed me, about weight distribution.

What are your thoughts on, or does anyone know how it changes with the roof down compared to roof up?

Roof is heavy so you are not only shifting CofG a lot lower but shifting weight to the rear.

Come on then, anyone have any ideas??, or a weighing setup?

A technical analysis would say f^&k all effect!

The roof top section is aluminium, which is the bit that moves the most, the glass, the heaviest part moves only a small distance, most of the other stuff, pumps, cables etc don't really move..

When you calculate the CoG you take the masses that you move multiply by distance from the datum and then compare with the whole mass multiplied by its distance fro m the datum..so with 1350 kg of mass and say 50kg at worse of moveable stuff, most of which moves less than 0.5 metres its not going to do much, a full fuel load probably has more effect..

In the aviation world we did these calcs all the time, as the consequences of too aft CoG were catastrophic..

What you need to look are things outside the wheelbase..like that big 6 pot engine vs the 4 pot!!

Bound to create a flame war now!

[john-e89]

A heavy car with a chassis that simply cannot cope with it roof up or down to be anything other than a nice comfy cruiser. Add dead steering to the mix and weight transfer ceases to make any difference.

Very nice car but finesse levels of a barge.....

[flybobbie]

Supposed to have 50/50 weight distribution, but is that roof up or down?
And what of the effect of drag with the roof down.
I always find the gear changes are smoother with more load in the car such as a passenger.

[Brasseye]

I think the roof was quoted at 30kg so not huge but not tiny.

Driving at top French motorway speeds with roof down ac on got 35mpg over 500 miles, with net fitted & earplugs!

[Pbondar]

Supposed to have 50/50 weight distribution, but is that roof up or down?
And what of the effect of drag with the roof down.
I always find the gear changes are smoother with more load in the car such as a passenger.

You need to add the other variables like most drivers are greater than 68kg...also pax at say 85kg, plus luggage effects..

As I said in the concept of a non F1 car I think these things are de minmis..

[chilistrucker]

Just for a curve ball, I'm a wagon driver by trade and weight distribution, C.O.G and other factors can all have a big effect on the handling characteristics of my works vehicle

[Pbondar]

Just for a curve ball, I'm a wagon driver by trade and weight distribution, C.O.G and other factors can all have a big effect on the handling characteristics of my works vehicle

That’s for sure but the differences between an empty truck and a fully loaded truck are night n day compared to the changes in load that a Z4 can accommodate..

[ihadablackdog]

I’ve just lost 6st in weight....what does that do to the cog?

[Brasseye]

2011 E89 sDrive20i

I don't know about the COG but you gained an extra 4.2 bhp per ton !

[ihadablackdog]