8 replies to this topic

[catch_me]

Hello,

 

I was wondering what the opinion would be on the rear subframe I should choose for a pup build I am working on. Currently I am going to replace both the front and rear subframes, as the originals are pretty rough. that being said, I will be doing a pretty custom build, and will be using 13" or similar sized wheels. I noticed that the 1996+ rear frame was supposedly reinforced as the sport pack option gave 13" wheels so they needed to reinforce the subframe. Just wondering if this is the route I should be going then, replacing my 1976-90 rear sub frame with a 1996+ subframe instead as it will be stronger.

 

Looking for thoughts on this, especially from those who have done custom minis.

 

Thanks!

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[nicklouse]

Just get any. The main changes were the exhaust hangers and the addition of some metal discs to the cone seats that bent the radius arm pins on the sports pack cars.

[Cooperman]

Until it corrodes, the basic Mini rear sub-frame is very strong.

Even on rally cars there is no need to add additional welding or strengthening.

For really hard use the only weak point I have found are the radius arm outer retention brackets. Over time and after a lot of abuse on rough roads, the flange of the bracket can start to split. The solution is to weld a triangular piece of 4 mm thick steel onto the top corner which cures the problem.

[pete l]

"addition of some metal discs to the cone seats that bent the radius arm pins on the sports pack cars"

 

Can you explain further ? 

[mab01uk]

REAR SUBFRAME " SPORTSPACK " STRENGTHENED

"Fitted to the sportspack twin point injection cars from 1996 on as they required stiffening up for the 13" wheel option. See MS45LATE for E coated version which gives a better finish and longevity
The cone spring platform had 2 extra bracktets either side to act as reinforcements and the platform hole has a bottoming out metal plug fitted."

http://www.minispare.../KHB100590.aspx

Edited by mab01uk, 26 June 2024 - 06:00 PM.

[pete l]

I'm putting wide wheels on mine, do I need to strenthen my rear subframe ?

 

I don't understand why wider wheels need the rubber cone supports strenthening !

[mab01uk]

Long before the MPi Minis were launched wide 13" wheels were being fitted to older Minis without any need to strengthen the rear subframe under normal road conditions. As others have said even race and rally Minis rarely needed the rear subframe strengthened for most competition use.

 

However a car manufacturer like Rover has to take all extremes of use into account in world export markets during development of a new car or model. This often results in small variations made to existing parts to meet and pass the new test specs and requirements specified by the EU, Japan, USA, etc.

 

The rubber cone supports may have needed strengthening to pass 'extreme' test conditions because the 6 x 13" Sportpack Mini wheels and 175/50 tyres are a lot heavier than the previous 10" and 12" wheels the subframe was originally designed around and a metal plug was also fitted to stop bottoming out of the suspension cones with the larger heavier wheel assembly. Uprated shock absorbers/dampers were also factory fitted on Sportpack Minis to better control the heavier wide wheel/tyres.

The MPi Mini steering rack lock was also restricted to prevent tyre rubbing on full lock, again of course a car manufacturer has to do that but most Mini enthusiasts don't when modifiying an older Mini even if they should...

Edited by mab01uk, 27 June 2024 - 08:54 AM.

[stuart bowes]

That's interesting, mine is an '88 and the subframe has a metal plug in the rear cone seat, I was wondering what that was about because I thought there was usually a hole through there that you could use to get the cone compressor through when fitting

 

there was also evidence of repair to the back of the boot floor which I supected was a rear ender at some point

 

now I'm wondering if they swapped in a new / 2nd hand subframe at the same time which might go some way to explain the pretty reasonable condition it was in

[mab01uk]

The 'curious metal cone shape' on the original dry rear subframes acts as a variable spring platform and is mentioned by Keith Calver in link below when explaining what can happen if you use a Hydrolastic rear subframe when converting to dry rubber cone suspension.

 

Suspension - Converting from wet to dry.

Bringing up the rear. 

"Again, as with the front, the hydro rear ‘frame can be modded to take the rubber springs. Same mods, but very, very much easier. However I don’t advise this unless the Min’s used solely for normal road use, carrying two people in the front, minimal luggage, and totally standard wheels/tyres and standard ride height only. Why? because that curious metal cone shape on the dry type acts as a variable spring platform - progressively increasing the spring rate as more load is applied. Carrying more load than the minimal amount mentioned above will have the tyres bashing the wheel arches. Trust me in this, that’s all the explanation you’re going to get, as it’s a bit complicated (not enough room here for full dissertation)."

https://www.calverst...rom-wet-to-dry/

 

Edited by mab01uk, 27 June 2024 - 11:24 AM.