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RE: Why Unibody

To: MG Listserver <>
Subject: RE: Why Unibody
From: Chris Attias <>
Date: Wed, 22 Dec 1999 08:33:38 -0800
At 2:05 AM -0700 12/22/99, Tim wrote:
>Here's one I haven't seen...why did MG decide on a unibody versus a
>traditional chassis.
>I'm sorry if this is one of those "obvious things that every MG owner
>should know", but I just thought it would be alot easier to do the body
>work (sills) if it weren't structural.

My understanding is that it has to do with cost and a lot to do with 
rigidity and weight, and therefore gas mileage, required engine size 
/ performance, etc.  A ladder chassis is not nearly as stiff, at 
least not until it gets heavy (apologies to Triumph owners).  And,I 
imagine, panel fit was faster and cheaper when everything was welded 
in a jig on the assembly line rather than fitted and bolted.

As for alternatives, space frames are really expensive to make and 
repair; the backbone chassis creates a large central hump which isn't 
great for passenger cars.

Unit bodies didn't really get popular until the advent of independent 
front suspension--e.g. Morris Minor, Magnette ZA, and Mini.  Rigidity 
prevents"cowl shake" on roadsters like the MGB--a good thing.

Morgans are famed for using the light weight chassis as a flexible 
member of the suspension, and Daimler Darts were famous early on for 
the doors flying open as the chassis flexed.  Early attempts to use 
unit bodies on mass produced 4x4s (American Motors?) were criticized 
because some weren't rigid enough, and would bend and deform over 
rough terrain, doing things like preventing doors from opening. 
Flame on...

Chris Attias
'64 MGB
'84 Alfa Romeo GTV-6

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