20 replies to this topic

[Cerberus]

I'd like to solid mount my front subframe as I'm pretty sure the rubber mounts are due for a change, and having seen how much movement is in them, solid seems the way to go, especially after everything I've seen/read on here about them.

 

Now, the toe board reinforcing plates.  Can I just use a large plate, not weld it in, so it's basically like a big washer.  In my mind, I can't see there being any difference, as when it's all bolted up, the plate will produce the same results as if it was welded, but without the hassle of having to do some welding.

 

I'm presuming they go on the inside of the body, is this correct?

 

 

Cheers

[cradley-heathen]

i agree with the idea of fitting solid subframe mounts, i have always used them on all my minis, however some will tell you thay are unnecessary and/or harsh on a road car.

 

personally i found i could barely tell the difference in noise/vibrations transmitted into the car, and done forget early minis have solid mounted subframes anyway.

 

as for the reinforcing plates, i have never put them in any of my minis, and i can weld! however i have always had minis with good solid shells. i have seen the area in that area in the bulkhead crack, but only on cars with knackered rubber mounts, never on a solid mounted car.

[Cooperman]

As above, check the floor in the area of mounting and see if it is split or cracked. If it is not, then go ahead and simply fit the solid mounts.

If there is any sign of cracking then add a 1.5 mm/16SWG steel sheet reinforcement about 6" x 6". You could bolt this in with a series of small bolts in a pattern around the edge. Maybe 10 small bolts of M5 size would be ideal, then bolt the mounting on.

[cradley-heathen]

i was going to suggest a series of bolts.

 

where abouts are you in the country?

[tiger99]

It is much less likely to crack in that region if the front mounts are properly supported, i.e. inner and outer STEEL wings, welded in place to normal spec. I know that some misguided people claim that the front mounts are only there to support the body, but any engineer will know at a glance that they actually carry considerable dynamic loads. However, there is a risk of flexing at the toeboard allowing excessive inner wing loading, and they crack vertically just ahead of the subframe towers, a tedious repair becuase the front has to be "persuaded" downwards to close up the cracks before welding.

 

To avoid problems, I would just fit the reinforcing plates, but they do need to be welded. It is not a BIG welding job, making up the plates and preparing it can be done at home, and a professional will only take a few minutes to run the MIG around them. Don't forget the rust precautions, inside and outside, afterwards.

 

You could, at a pinch, use about 20 M5 or 3/16" grade 8.8 set screws around the edges of the plates, and a few inside too, with washers underneath, but it would be ugly, maybe cause bumps under the carpet, and probably cause serious difficulties at MOT time, because it would seem to be a repair, and bolted repairs are just not allowed.

 

Edit: As I was writing, I was beaten to it, twice, and we seem to agree that bolting is possible.

Edited by tiger99, 03 April 2014 - 08:00 PM.

[cal844]

BOLTING IS NOT POSSIBLE!! Id expect the car to fail the MOT with bolted floor reinforcement!

Edited by cal844, 03 April 2014 - 08:07 PM.

[tiger99]

I did suggest that, but as it is a REINFORCEMENT, not a RUST REPAIR, what do the MOT rules actually say? Just curious, because I think we don't really know, and will not, until someone gets one MOT'd. Is it possible to sell, as an aftermarket accessory, a solid mount with a much larger base area, to be bolted through a backing plate? Would that pass? And why can't we buy mounts like that, complete with drilling template? It isn't rocket science.

[Cerberus]

I'm pretty confident that my shell is good and strong in that area.

I'll have to have a good look around and then decide what to do.

 

 

What's the reasoning behind the plate having to be welded or bolted on with a series of bolts?  I presume all the plate is doing is acting as a spreader, to spread the load of the mount over a slightly larger area (although I suppose the load is the same whether it's rubber/poly/solid), so once the mount is bolted to the floor, with a plate on the back, it's all the same.  I can understand welding if the floor was cracked.

 

 

I've got one other issue that I'll be looking at too, so money may need to go towards that rather than solid mounts.

 

 

Thanks for the answers/help.

[Dan]

The doubler will only reinforce the area if the two panels can't slide over each other. Think about what happens when the two panels flex against each other. Weld the edges and nothing can slide so if they are going to flex they have to do it as one.

[A-Cell]

....or just restore it as production, by fitting new standard mountings. Less hassle all round. No welding of plates, no risk of failing MoT with bolted in repair plates. Moreover the original production was proven to have structural integrity by extensive vehicle tests including Pave testing, crash testing, extensive durability tests, etc.

[tiger99]

Been thinking about this some more. The mounts are an easy enough shape to make, from 2 pieces of steel, and a single line of weld, which can be MMA (arc) or MIG, as the thickness is considerable.

 

So, if we make a complete new mount on which the toeboard plate is maybe 2 or 3 times the size of the existing one, and an internal plate, both drilled to the same pattern, we have in effect fitted an upgraded mount, not a repair panel, so it should be ok for the MOT.

[tiger99]

A-Cell, the ORIGINAL design was very well proved, round and round the Chalgrove aerodrome perimeter, after the subfremes were introduced to deal with the fatigue cracking experienced in the subframe-less orange box prototypes.However, I do not believe that the rubber mount design was ever "properly" tested, because I had two Minis, one from new, with that abominable arrangement, and within 10k miles of very normal use, mainly motorway cruising, they both broke one or both mounts. Replacements did not last long either, and there is a serious design error because the toeboard mounts, which structurally are important, are not safety through-bolted. In short, I think that a complete idiot designed that arrangement, which is just about as bad as bad can be. I was forever changing mounts, until I twigged that they were also the cause of bad handling, and made my own solid mounts, before such things were commercially available.

 

I suspect that it was the well-known problem of having to test to some standard or other, however the test did not bear much resemblance to real life usage. A bit like the combined cycle MPG test on modern cars, which is never, ever approached by disappointed owners in normal driving, because it is purely a government-dictated standard test with no relation to reality. BMW on certain models tested their structure to some standard, probably TUV, and the rear suspension mounts turned out to have serious fatigue problems, again because the test cycle bore no relation to reality. I strongly suspect that the testing applied to the squidgy-subframed Mini similarly bore no relation to actual usage. Crashworthiness will have improved, because the mount will fail in a severe frontal impact, allowing the subframe leg to deflect down and back under the floor, where the solid design used to make the floor crumple, trapping the drivers feet. (Seen umpteen crash test dummies trapped in Minis at TRRL.)

 

I have looked at a few Minis belonging to other people, and in most cases I found that one or both toeboard mounts were broken, and in many of these cases the dreaded inner wing cracking had started. That problem was never seen on Issigonis' design.

[Steve8274]

I am considering this upgrade on my car. Has anybody got any photos of their reinforcements they have added. Never seen one so want to make sure I do it right
Thanks

[Carlos W]

When I did mine I seam welded around the edge as well as plug welding in the middle. I can't see how this could be done with nuts and bolts. You wouldn't be able to get the mount on

[tiger99]

I don't understand. The mount should still go on, because none of the nuts and bolts would be within the area of the mount itself.