Bah! There is plenty of rigidity in the rear end.
Have a look at some of the turbominis.co.uk cars putting out over 200hp and they have reduced the rear subframe to this:

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Too many cars, and too little time.

I thought the seams were spot welded together. De-seaming and then welding the entire length of where the seam was would have to improve rigidity if done correctly, but that's only my opinion on it...

I like both looks, the de-seamed look makes the car look a little more modern and the next one I buy will get it done to it.

Do you want the a piece of the seam that I'm getting cut off soon

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-Alan
I blame my dad for my love of minis. I think I was conceived in the back seat of one
I also blame my Dad for me being 6' 1" - not really the optimum height for driving a Mini.

I deseamed the front of my car (the rear was already done by the previoud owner to an OK standard)

You should leave a little proud as the others say and if you really want you can use a 3mm bar and tap it in there so that when you weld you not only give you some metal to weld to you reduce the heat you put into the pillars (less body work to do later). It also replaces the seam on the inside.

Whether or not it is necessary I'm not sure. The seams are not there to provide rigidity, they are there so that the body could be spot welded from the outside. It would be interesting to test a before and after comparision. From a safety point of view I shouldn't think deseaming (if done properly) would reduce the safety of the car but it would probably reduce the stiffness.

Either way doesn't bother me, the engineer has to sign off all my other mods so it's just one more mod to pass.

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1964 Morris 850, 1330 Supercharged - 81.8hp atws.
1975 Leyland Mini S 1100S powered - Nice and reliable.
1977 Leyland Mini LS - Project LS-T

A flat plate vs one with a flange in the middle is no comparison on the torsional or bending front. Granted the seam was a cost measure but my guess is that the stiffness that these cars achieved was a side effect of the seams.

The car may work without them as plenty of de-seamed cars prove however as mentioned previously the proof would be in a test/deseam/test routine.

The important question I would ask is if the deseam would hinder the already low safety of these cars. I think they would.

My last word is that the seams are part of the charm. Leave them there or get a bini

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Cheers
Alec
1275LS - July 78 - XNFAD18Y/102918

the seam forms a "T"section to give the joint stiffness. To remove it and just butt weld will weaken the joint. Replicate the seam but internally with some 3/4"x 1/8"flat bar on edge.When you get the car checked they just run a ultra sound over the joint and will pick up the new internal rib.
The rear seam I use a piece of 1/2"square tube bent to the body profile and weld on the inside of the joint.

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Research is the difference between speculation and investment. Anyone who copys some one else will always be second
www.minisprintgt.com

That's exactly what they are there for. As mentioned above, the seams are an integral part of the car's shell. All cars have them, but on the mini they're external rather than internal purely for ease of construction. And as mentioned, you can deseam a mini but it needs to be done right, not just for your safety but the safety of passengers and future owners of the car.

Just cutting off the seam and running a weld in its place is a recipe for disaster if not death. Plus your car is effectively worthless.

I actually like a deseamed rear end (on a mini...) and am thinking of doing this exactly mod. I'll leave the rest of the seams, but the 'smooth round bum' look is quite appealing (and yes I'm still talking minis...). The decision as to do it or not is hinging (almost literally) on my plans for a flip front which are with the certifiers at the moment.

Maybe I should rephrase as that is a little out of context.

Seams in general exist for rigidity but the reason behind exterior seams on a Mini do not. I agree that if you remove them you should replace the strength you took out which is very easy and actually makes deseaming the car easier.

However, I believe the seams were not designed for rigidity but for ease of manufacture. Stiffness is a by product in my opinion.

Either way, you should get an approved, chartered professional engineer to analyse your work and provide you with an approval certificate that you can show your local transport authority when you road worthy the car.

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1964 Morris 850, 1330 Supercharged - 81.8hp atws.
1975 Leyland Mini S 1100S powered - Nice and reliable.
1977 Leyland Mini LS - Project LS-T