About to take the 70 fhc to the alighment shop and want to leave the bonnet off for access. Will have to add weight to make up the difference. Can anyone tell me what the assembled bonnet weighs?

Submitted by NE40-48370 on Thu, 09/22/2011 - 07:21

Kerry, the alignment shop should be equipped to reach everything just fine, as William said.

If you really wanted to leave the bonnet off you could just load up the picture frame until the ride height measured underneath is the same as it is with the bonnet on, assuming the ride height is fine with the bonnet fitted.

So long as the ride height ends up the same after loading (and rolling to and fro), the torsion on the springs must be the same, give or take. By measuring the effect on ride height you avoid the need to calculate weight distribution. The mass you place on the picture frame may be different from the mass of the bonnet, but the effect will be the same if you read it off as your desired parameter - in this case an identical ride height.

If you really wanted to know the weight of the bonnet you could stand it up on the rear end with a scale under one fender and a block of wood the same thickness under the other. By reading mass each side and adding the two numbers you'll get your total bonnet weight. But as William says this is moot because some of it is hung out front and some behind the front axle. So technically, if you were being exact, loading the picture frame might not give you an identical ride height to the same weight distributed by way of a fitted bonnet.

If you still weren't happy and for some reason you really want to know exactly what weight to put on the picture frame ahead of time, you'd have to work it out from first principles as follows:

1) With the car sitting correctly at a good ride height, measure the clearance to the ground anywhere convenient, such as under the picture frame.

2) With the bonnet off it will be higher of course, so measure clearance again under those conditions after you've rolled the car to and fro a few times to overcome the sideways scrubbing of the tyres as the car rises.

3) With the bonnet back on and the car rolled to and fro some more, put a bathroom scale between the jack and the jacking block and now raise the car to the same height as it was without the bonnet and read the value on the scale. That will be the weight you'd need to place above the picture frame to get it back down to the same as when the bonnet is fitted, but it may not be the exact same weight as the bonnet measured standing on the floor.

However, the simplest thing is to just take your car down and let the shop worry about settings as per the manual instructions.