Repairing a Classic Mini Rear Subframe

[JonnyAlpha]

Hi;

Having just removed the rear subframe on my Mini I've spotted a couple of dodgy areas that I need a bit of advice on.

There is some rust on the top plate of the RH main strut, these plates are replaceable so I'll either replace the plate or facilitate a repair to the existing one.

But there is a slightly more challenging rusted area inside the RH main strut in the bottom corner behind the Cone housing.

Another photo of the same area at a different angle.

Would this area be repairable by cutting out the patch and but welding it in place??

I'll manually clean up the whole sub frame to confirm the actual extent before starting to spend any time on it. I am on a very tight budget and a new Subframe is out of the question, old ones on E Bay start at around £50 but still need work?

Most of the Subframe looks sound.

 

[the snooper]

I though they stopped people repairing sub frames some tome ago, could be wrong

 

[lshigham]

Scrap it, the rust gets in all the seams and it'll soon hole somewhere else

 

[ronan]

I thought the way to go with mini subframes was to replace them.

 

[doubleboost]

Get a better one and soak it in waxoyl

 

[BChild]

I'm sure mini subframes are treated as suspension components and welding those is a big no no (unless the weld is well concealed and not visible)

 

[ronan]

I was going to buy a wolseley hornet a few years ago as a restoration project and reading up on them and the mini's (the real ones , not the mini panzers) i was amazed at the range of parts available for them. Someone is definately doing new subframes.

 

[Lawnmowerboy]

Your right about the repairing subframes. Just bin it and get another one. The rot you can see has probably stemmed from a seam where the steel has De laminated too. Will have no strength where it needs it. In the joints.

 

[marlinspike]

I've just looked on ebay and new ones are expensive, but I don't think you have an alternative to replacing it with new or a good used one.You really don't want to be driving round on a welded up subframe. If there's a part of the car worth spending money on, it's got to be the subframe.

 

[711jrp]

I think if you shop around a new one can be had for £140/150, your local motor factors might be your best bet.

 

[BrokenBiker]

i would never trust a weld on a sub frame no matter who did it. Would much rather buy new

 

[hotrodder]

I'm not making light of things as obviously subframes are pretty important parts and their construction often complicates things (rot 'travelling' along seams and remaining hidden until it's well advanced as said) making repair unecomonical but i don't get the dangerous/illegal thing...

1. subframes are manufactured by welding together pieces of stamped/folded metal. The 'no welding on suspension/steering components' is not an absolute rule when the part in question was welded together origionally. It's more about cutting/modifying/repairing parts that weren't welded during manufacture and often with good reason
2. Subframe mounting points are at least as critical as the subframe itself and no one has any qualms about repairing these beyond the usual need to know what you're doing/welding is to a reasonable standard and not a plate snotted over the rot

http://www.motuk.co.uk/manual_240.htm suspension in general including subframes which are at the end under G
http://www.motuk.co.uk/mot_appendix_c.htm which is referenced several times in the suspension section. Need to read the entire thing for proper context but basically it comes down to this...

Welded repairs to highly stressed components such as steering/suspension arms, rods, levers etc are not normally acceptable, other than where the component is made up of sections that are welded together. In these cases the repair should appear to be as strong as the original design.

 

[brightspark]

if it were mine i would have it shotblasted 1st that would eradicate any doubt about the thickness and quality of the part then take it from there

 

[KemppiFrog]

I'm with Hotrodder on this. I had a few Minis and rear subframe replacment was a common job. But they were cheap then.. Rebuilding one for a keen amateur would result in a better job than original, as the BLMC stuff was rubbish. Their jigs were often out of kilter (friend was in the company then)
BTW, shotblasting would expose the outer skin, but the problem was in the joins.

 

[JonnyAlpha]

Hotrodder;

Thanks for sourcing and clarifying the legal issue :-) and thanks to everyone above for all the advice

I am not in the business of cutting corners - especially where safety is concerned but my dear old granddad would never buy anything that he thought he could not repair and I try to follow the same mentality.

I have now stripped the subframe i.e. I have removed all of the external parts, radius arms, mounting brackets rear cones etc and cleaned off the remaining black gunk under seal.

I have also taken the subframe to a professional welder who having had a poke around basically said yes it can be repaired it just depends how much time you are willing to spend on it. He even suggested using slightly larger gauge metal to beef it up which would end up in a stronger rear end!!

Most of the areas that need repairing are relatively easy to replicate however once i removed the rear cones there are a couple of tricky round cup shapes which I will seek advice on in the metal fabrication area of this forum.

If I do repair / refurbish it then I will be confident in knowing that its safer than the original, by the way before we acquired this Mini it had not long gone off the road, I found a repair that had been made previously (not in a hidden area) and most of the rot has been there a while so god knows where it was last MOT'd !!

In case it is un-repairable I have started sourcing a replacement (I am on a tight budget) an old frame (less all externals) is about £40 and I spotted a decent one, again bare, but with postage its going to be £80 :-( may not sound a lot to some but sadly its out of my price range at the moment.

I have also posted on a Mini Forum that I have been using for the past couple of years looking for a replacement subframe in the South West however as yet no one has responded so I may have to repair this anyway.

Once again thanks.

 

[JonnyAlpha]

Just made a jig to hold the subframe together whilst I start to repair it. I'll be doing one side at a time so it won't get too weak.
Any comments on my jig i.e. will it do the job?

Its bolted to the front and rear of the subframe using existing holes built using a mix of different sized angle iron.

You can see the two front bolts, the rear bolts are at either end of the rear angle iron.

Most of the repairs will be to the underside of the RH and LH main front to rear strut, in this picture the subframe is up side down the holed plate in the bottom right of the picture is the underside of the LH main front to rear strut.

 

[doubleboost]

I served my time on minies 1300 ect
I have replaced many sub frames in my time (the new ones had rust on them)
Your jig looks like a proper job
I well remember "slotting" the outer radius arm mounting holes , to get the wheels pointing the same way lol

 

[lshigham]

I served my time on minies 1300 ect
I have replaced many sub frames in my time (the new ones had rust on them)
Your jig looks like a proper job
I well remember "slotting" the outer radius arm mounting holes , to get the wheels pointing the same way lol

They make posh brackets for that nowadays - I still prefer a round file personally!

http://www.kentautodevelopments.com/shop/product/kad-bolt-on-rear-camber-toe-adjustable-brackets

 

[KemppiFrog]

They make posh brackets for that nowadays - I still prefer a round file personally!

http://www.kentautodevelopments.com/shop/product/kad-bolt-on-rear-camber-toe-adjustable-brackets

When I were a lad, we made our own brackets. (we even made our own scratch..) Negative camber front and rear. On the front, by stretching the lower links, deff an MOT fail now.

 

[doubleboost]

When I were a lad, we made our own brackets. (we even made our own scratch..) Negative camber front and rear. On the front, by stretching the lower links, deff an MOT fail now.

Cut the bottom arms weld a 3/16 spacer in and plate the sides with a stick welder lol happy days