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Yet another rear X member

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About 6 years ago I fitted a replacement SPI rear cross member……….. even though careful attention made to rust proofing, the tapered area is completely rotten on both sides :angry: , however the centre section between the chassis rails seems OK. Rather than repair, I decided to fab up a new substantial X member and incorporate a winch mount……….

Now I guess there are X members and then there are X members……………. :rolleyes:

A quick measure of an OEM X member revealed that RSJ channel is available in a size almost to the mm………… quite substantial it is to, with a 6mm face and 10mm top and bottom webs :lol: ……… the inner rolled gussets are a little over 15mm

So after parting with £15 for a 1.6m offcut ………. A bit of cutting, grinding, drilling, & welding and we end up with this,


The tapered ends are welded both sides as its 10mm to 6mm…………..



The winch will sit almost in the channel and will be mounted on a 6mm sub tray. The winch will be bolted through the sub tray and x member both on the bottom web and the face............ effectively the wich will be pulling against a 12mm plate. The 50x50x4 will be welded to sit between the chassis legs and then welded to the rear of the winch tray.




All that remains to be done is the fitting ……………….. not difficult, just time consuming.


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Obviously I don't know the complete vehicle this is going on to, but I do have a query.

You wrote "The tapered ends are welded both sides as its 10mm to 6mm…………..", then later wrote "The 50x50x4 will be welded to sit between the chassis legs and then welded to the rear of the winch tray" (which is a 4 to 6mm joint).

At some stage this assembly has to be welded to the 2mm chassis, yes?

What design / welding technique will you use to handle the disparity in metal thicknesses at that point?

Is it just the cross tube (4mm wall thickness) that is welded to the 2mm chassis, or will the 2mm chassis also be welded to the 10mm top and bottom webs of the actual crossmember?

Thanks for any guidance.

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The vehicle is a 90 ........................ so the 6mm rear face X member will be welded to the ends of the chassis rails. Then (3 or 4mm) plates are used to join the top and bottom of each chassis rail to the top and bottom of the x member. Yes, you are correct in that the 50x50 is a cross tube that sits between the chassis rail and will be welded to the rear of the winch mount. The whole idea is to spread all the loads as much as possible.

Welding thick to thin is always difficult to get right. I normally use enough current to ensure the thicker material has good penetration. The trick is to concentrate most of the weld on the thicker material and carefully work the weld pool to ensure the thinner material is fully welded. Actually 10mm to 6mm is not really an issue .......... neither is 4mm to 2mm............... problems start to arise when the disparity is 10mm to 2mm, although is all possible with a little care.

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Ian, that crossmember is so heavy, it bends light..

One tip(a bit late, I know) is to make the crossmember slightly longer, so it fits hard in between the lh and rh wing panel. You can than rivet or bolt the sides onto the crossmember so you cannot push the sides in anymore, as this is always a potential hotspot for going messy.

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  • 2 weeks later...

This is the sort of poor fabrication that you get with an aftermarket rear x member :blink: ……………… you cant really see it until the corner gusset is cut out !


Here is the 6mm winch tray welded to the new x member ………………..


The finished structure ready for trial fitting



Well that’s ok then ………….. it fits.


Then the 50x50x6 goes into place to provide a little extra support to the winch tray :rolleyes: !


fitting complete ………… now I just need to fit the swivel recovery points and give it a coat of paint


In terms of weight……… all the old metal and carp removed weighed just over 45lbs…….. I haven’t weighed the new x member but it is an easy lift and I can support it with one hand , so I am guessing about 50lbs (ish)

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if its so light / not much heavier than std crossmember

then why 2 trolley jacks to move it into position ?



Its an optical illusion...........the chassis is supported by axle stands and the two jacks are supporting the rear axle under the trailing arms to stop the bushes being on full flex for over a week.

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  • 6 years later...

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