19 replies to this topic

[miniyellowmini]

I have currently have the rear subframe off my Mini to do some work on the heelboard. My subframe was rusty and pretty bad in places so I decided to replace it. Managed to get a very cheap genuine replacement subby but it does have a couple of holes that could do with having patches welding over them. The rest of the subby is solid and only has minor surface rust I have cleaned back to bare metal. The holes are not huge roughly about 20mm dia in a couple of places. My question is can the subby have a patch welded in and will this be ok for the MOT?

I have read conflicting information some people say it's OK to weld but others say the subframes cannot be repaired and will fail the MOT automatically.

Does anyone have a definative answer on whether welding is allowed, only I don't want to take the trouble repairing, preping, painting, refitting etc for it to fail when I come to MOT it.

[Tupers]

Yes you can weld the subframe.

[Shifty]

I've never had a welded frame fail the ticket.

[waddle]

i read somewere wellding repairs, to a subframe is a mot fail, i cant see how it can be though,because you can weld a sill so wyh not a subby? weather the man spots it or not is another thing, so it to a good standard and flat it back, then hell never be able to tel, dont make it obvius with a big plate and lits of underseal or the MOTer might investigate!

[lrostoke]

If you patch the repair section in so its flush, any weld can be ground back flat..painted over nobody would know anyway.

[tiger99]

Yes, you need to do a proper job, and make it invisible. If the tester sees the repair, it is a clear fail under current regulations. Welding suspension and subframes is not allowed, however as we all know, all subframes and some suspension parts (on a Mini, only front tie rods, but also very early rear radius arms) were fabricated by welding.

Remember that the side members of the subframe, the usual things to rust, do carry very high tensile loads as you go over bumps, due to the 5 to 1 lever ratio of the radius arm, while the main crossmember does carry a fair bit of bending load. Many years ago, subframe failures were commonplace, and it was almost always a side member that failed. You do need high quality welding, definitely not gassless. Thinning of the lower side of the side members, or patches badly welded in at the low point, where wet mud collects, is not good.

You also need to weld most non-genuine subframes before fitting, because the (Chinese?) manufacturers have usually skimped on the spot welds, and they are known to be fewer than Rover's design calculations said were necessary for safety. A neat, tidy seam weld around the main joints is unlikely to be spotted by the MOT tester, who would not know whether it was original or not once it is painted.

[miniyellowmini]

Cheers for the replies guys.

Looks like butt welding in a repair then grinding flush is the way to go then. One of the holes is on the top of the frame where it joins the main crossmember, so wont be visible anyway. I think this area may have been where it was originally spotwelded and the other is in the same place but on the bottom on the opposite side of the crossmember. The rest of the frame is solid with no thin or weak points from what I can tell, it is genuine (stamped MOWOG) I will try to put a photo up later.

It's not like it's failed the MOT and I'm taking it back to be retested so the tester will know it's the same frame so it's obvious it's been repaired. So as long as I make it invisible I reckon I should be ok. I'll be giving it a good paint with POR15 as I don't want to it rust, but don't plan on over doing it on paint and underseal so hopefully it wont draw too much attention to it.

[JonnyBMX]

the MOT tester actually failed my subframe on the grounds of a small hole, he told me to weld it up and take it back, boat 30 mins work all in all and i was back in buisiness with a full ticket, so sure its tottally fine to weld them, you can even get hold of plates for them.

[tiger99]

Well, that is up to the MOT tester, and I would not rely on it. However I would point out that the so-called subframe repair plates are an abomination which are used by bodgers and incompetents to make rotten subframes look good for the MOT, and generally do not restore the lost strength, because they are rarely welded properly. In any case, like oversills, they greatly accelerate corrosion.

[Shifty]

The price of new frames now makes a welded repair very attractive indeed.

[miniyellowmini]

The price of new frames now makes a welded repair very attractive indeed.

It certainly does. £350+ for a new heritage was the cheapest I could find! I'm very pleased with my second hand one cost me just £40 and once the small bit of welding is done and painted it will be as good as new



Where it needs the patch

[minimissionary]

Get it sand blasted. Best £30 I've ever spent. Paint stuck to it like poo on a blanket

[miniyellowmini]

Get it sand blasted. Best £30 I've ever spent. Paint stuck to it like poo on a blanket

Good idea, thanks Will look into that and get some prices.

[tiger99]

That subframe already has had some seam welding done, if I am not mistaken. Good idea to do that anyway.

I am slightly concerned about repairing that area, where the side member overlaps the crossmember, because there will be rust between the surfaces, and some unknown about of thinning. I would suggest that the overlap needs to be completely removed, and a bit beyond, to clean it up properly, and a larger patch than envisaged will then be required. It will not actually take much longer to do. Seam weld right across the width of the side member, and be sure to plug weld where the spots were, and seam around the end again.

The metal should be thick enough to weld easily, if it is clean.

[1984mini25]

The price of new frames now makes a welded repair very attractive indeed.

The non-genuine one on the 25 has lasted 7 years and picked up another new one at mitp for 160. I know about the crap of non-genuine frames, but comparing this new one and the old the new does seam to be welded better. Besides, whats better a rotten genuine frame or a solid non-genuine one?

Plus I personally can't see the hype in powder coating a rear subframe thinking it won't rot, it will. The only way to stop the dreaded rot is to fill all the nooks, crannies and box sections with waxoil, Something powder coating never will.