19 replies to this topic

[ValentinoRoddy]

Hello

I bought a mini project a couple months ago and its come with half a rear subframe because the previous guy has cut most of it off and just left it as a beam basically. Since he's cut off the rubber cone part I'll need to do a coil over conversion if I'm going to use it but I was wondering if it will work as the rear wheel won't have anything like an anti roll bar to connect them like all of the beam conversions you buy have.

Any thoughts on how a cut down rear subframe for a coilover conversion will affect handling or safety would be appreciated, will post a picture in a couple days because it's away getting sand blasted and paint right now so I don't have it. Cheers

[smudger068]

Hello,
Mine has been done like this. But my understanding of it is that you need a strong heal board. I have no rear ARB but could benefit from one though. Would be worth converting back to cones of you could. I'm sure more people will elaborate on this as I bought my already done.

Edited by smudger068, 27 October 2016 - 11:22 PM.

[ValentinoRoddy]

Thanks for that information glad to hear other people actually do have this modification!
The car back seat has been cut away and welded differently to a standard mini, it is a lot closer to where the rear subframe mounts onto the car so I reckon is strong and it's also got a full roll cage which definitely makes it more rigid. I've read into the benefits of coilovers over rubber cones and feel that coilovers are more what I want over the rubber cones so my main question now is,
Will this chopped up rear subframe that's been turned into a beam without an anti roll bar be any any good at handling compared to if I buy a beam and install coilovers?

[nicklouse]

 I was wondering if it will work as the rear wheel won't have anything like an anti roll bar to connect them like all of the beam conversions you buy have.

 

cant say I have ever seen one with the arms connected as a kit. they just have the arms bolted to a bean and away you go.

[nicklouse]

now onto the main issue. depending on how it has been done it will be either downright dangerous of half safe.

 

to mounting points on the subframe need some serious modification as the originals are unsuitable.

 

additional mounting points will also need to be added to the frame.

 

finally Coil springs seriously limit the usability of the car as they can not compensate for weight changes like the original rubbers did.

 

if a road car I would be replacing the subframe and going back to the original set up. if a track car I would be getting, or having made, a suitable beam.

[ValentinoRoddy]

Hello,
Been a while but I've finally got my rear beam back. That's for your previous reply thought I'd add a little more information about the car. Its being build with only speed in mind I'm not bothered about comfort at all. It's been converted to a metro turbo engine that's been modified ever more and has a straight cut gear box on it.

Added a picture of it hopefully it uploads and you can see it, there is 2 holes for bolts where the extra bits have been welded onto beam and these bolt directly to the floor of the car where the rear seats would be (the rear seats have been cut out and welded up in a slightly different way). The standard mounting points for each side have not been changed at all either.

Now that there is a picture up have you ever seen this fine before?

Attached Files

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[ValentinoRoddy]

There's another photo of the mounting point that have been welded onto the rear subframe

Attached Files

•  IMG_2239.JPG   36.87K   16 downloads

[nicklouse]

so it still has the original mounting system on the ends.

 

Daft.

[ValentinoRoddy]

Yeah it still has the standard pinion that slides into the end of the beam and is rubber mounted.

What is it that's wrong with that? I've been told that you should either have it all solid mounted metal to metal or all rubber mounted so I was going to change it all to solid mounted when putting it together which I thought would be strong enough

[tiger99]

The rule about all solid or all rubber, which people fail to apply to front subframes quite often, and suffer the consequences, is to prevent fatigue cracking, and is correct for almost any two items that are mounted together.

 

In this case it MUST be all solid, because the additional fixings are to stop rotation of the beam around its pins (not pinions!) in the trunnions.  The fixings are not spaced far enough apart radially to allow rubber because the way the loads are applied results in a torque on the beam which will try to rotate it, and you need widely spaced rubbers to keep the deflection within limits.

 

But in any case you are not improving the car in any way. You should retain a full subframe and rubber cone springs unless you are fully competent to design the correct load path reinforcements for anything that you are doing. I suggest reading today's other thread about coilovers to see why you are going to gain no benefit.

[nicklouse]

Yeah it still has the standard pinion that slides into the end of the beam and is rubber mounted.
What is it that's wrong with that? I've been told that you should either have it all solid mounted metal to metal or all rubber mounted so I was going to change it all to solid mounted when putting it together which I thought would be strong enough

Have you never looked at a rear coil over beam?

For example mine. The "beam" is solidly mounted to the original points and also to stiff point on the shell.

Your solid mounts seem to be in the flexy mid points of the panels.
It is going to move all over the place.

[Ethel]

The trunnions are fitted in fours, just the front pair creates an extra pivot so the beam will be nearly as free swinging as the arms. As the arms and springs were all contained in the subframe, the car would sit with the load going fairly equally straight down on each of the four corners. Coilovers put it all on to the dampers, but I doubt the instantaneous loads will be very much higher than they got with dampers alone. 

 

Minispares do an alloy beam, Huddersfield do a copy of the Speedex one (not with the best reviews) and there are plans on the Mini Midas forum for a real heavyweight that's not strictly Mini fitting, does give you some dimensions though.

 

Whether it'd benefit from an anti-roll bar is a separate issue really, the geometry will still be the same if your radius arms are. You'd need to look at centre of gravity and spring rates.

 

....like the arms Nick, are the fabricated from scratch?

[nicklouse]

The trunnions are fitted in fours, just the front pair creates an extra pivot so the beam will be nearly as free swinging as the arms. As the arms and springs were all contained in the subframe, the car would sit with the load going fairly equally straight down on each of the four corners. Coilovers put it all on to the dampers, but I doubt the instantaneous loads will be very much higher than they got with dampers alone. 
 
Minispares do an alloy beam, Huddersfield do a copy of the Speedex one (not with the best reviews) and there are plans on the Mini Midas forum for a real heavyweight that's not strictly Mini fitting, does give you some dimensions though.
 
....like the arms Nick, are the fabricated from scratch?

Metro, so to adjust the track.

[Ethel]

Mmm, must be a while, I didn't recognise them with the bump stop platform removed, How do you mount your coilovers? I take it the shocker turrets are much altered. .

[nicklouse]

Mmm, must be a while, I didn't recognise them with the bump stop platform removed, How do you mount your coilovers? I take it the shocker turrets are much altered. .

 as the Tro does not have shocks there is no pin for any shock to mount. and as I hated having to remove the shocks from the car to drop an arm or the frame the axels were drilled and threaded for a bolt fitting.

 

I have recently changed the axels, as the holes were formed while the axels were in the arms so not quite right, with Mini ones with pins removed and hole and thread added.

 

note it was a common conversion to swap the Tro axels out for Mini ones when deciding to fit shocks to Metros but I wanted the ease of using a bolt.