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Unless it has diagonal members, I can't see that it would do much good.
And note that you do not have rear struts. You have a semi live axle with conventional shocks, so there are no 'stready state' suspention loads through the tops of the shock towers. So what body twisting are you trying to inhibit? What loads are there on the front of the venicle that are not non the front? If you have a stiff SAS type rear sway bar, that would create such a twisting load as the rear of the vehcile trys to stop the front body roll. The asymetric tortional load would tend to twist the body. Now when the body is twisted, does this make the cross section of the shock towers distort? With this type of distortion, mid body cross sections of the vehicle will tend to rotate with little change. So lateral or diagonal bracing would not increase the body's tortional resistance much at all. You would need front to back diagonal bracing to resist this distortion mode. Not something to do to anything other than a hard core rally vehicle.
In a hard corner, the outer wheels have a higher load than the inner. This will create a lateral asymetric load that will try to induce body distortion. This would need diagonal members in any bracing or nothing would be gained. G forces are trying to balance this 'sagging' load to some extent.
Note that the rear axle's anti sway resistance reaction forces are through the axle's bushing mounts! Good reason to go poly and trash the rubber mounts. The bushings connect at the floor pan to rear axle tunnel transition and there is a lot of metal in that area now. So that area appears to be quite stiff. Note the metal work in there and in the corners with the hatch floor.
Note also that spring reaction forces are not through the towers, but through the body. The spring seat to the chassis is not out at near the hub, but is closer in, perhaps 12" from the axle bushings. So this also limits loads to the rear body by being close to the stiffness of the area discussed in the above paragraph.
Whatever bracing that was intalled would tend to make a mess of the cargo area available when the rear seats are folded down.
For all the handling and suspension faults and inperfections of this vehicle, this issue is probably the least significant issue of all.
Twisting or 'racking' loads on a vehicle with a rear door are almost impossible to eliminate while maintaining the 'misson' of its cargo space. I did FEA (finite element analysis) structural analysis of LAV hulls. This family of LAVs is the same as the current fleet of LAVs used by the USMC. Not exactly the same as the US Army Strykers that are just showing up. But the issues are the same. A heavy vehicle that is driven off road with a large rear door. So in the case of the LAVs, the hull will twist under certain condtions and nothing can be done to stop this at all. The rear opening will 'rack'. One diagonal will get longer and the other shorter. The sides and floor pan are quite stiff and the roof is soft. The roof will distort in a compound curve. Stiffing the top door sill will do very little at all. It will just make more metal undergo the same distortion and strains! So one upper corner of the door opening will go into high compression and the other tensile... which would want to crack. We are talking balistic steel, but it still has limits. What one needs to do in any situation of this type where failure is an issue, not handling, is to distribute the distortion differently... you cannot stop the hull from racking! Corner gusset reenforcements will not help if they are uniform, just more metal sufering the same fate. A gusset is needed that does not alter the door opening. It needs to be wide in the corner and taper out to almost a point. The curve needs to be organic. One can distribute the distortion and strains so that it does not all pile up in the corners of the openings. So its really about distribution of distortion, not elimination of distortion in some situations where metal failure would otherwise be the result. And note that weight is very much an issue. The USMC vehciles have propellers are not submarimes. They need to float and swim. The army does not have that need to have a LAV that swims. This eliminates the weight of the drive shafts and gear boxes for the twin screws and rudders. And a "swimmer's" movable balistic steel front 'surf board' and the associated hydraulics are also heavy. (The production facilities (in Canada by the way) have changed ownership since I worked there.)
posted by 66.142.222...
http://www.army.mil/fact_files_site/stryker/index.html
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