chopping a rear subby into a beam axle
Turbo Mini Forums

Has anyone on here done this conversion? I quite fancy having a bash at it on my new project.

Got a pair of coilovers on the way and a spare rear subby so i might have a crack at chopping one down and strengthening it a bit. Just thought i'd ask and see if anyones got any tips or pitfalls to watch out for.

Cheers, Nick :)

go for it

I doubt it needs extra bracing or anything... its rock hard as is!

Alex

AlexF

my experience with beam axels is they need to be spot on perfect.... willl you be keeping radius arms, or going full hog on the rear end...my advice would be if it is for off road you will not want independant susp on the rear (your car will be on its roof at the first bend) if it is for road / circuit then cool.......the conversion seems like a lot of work, bearing in mind you can get purpose made replacements quite cheap

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MikeRace, Mini13

yeah its only going to be a road/drag strip blaster. just trying to keep the weight down as much as possible. keeping the radius arms but using coilovers which ive picked up for £30 and i'm getting a spare rear subby off a mate too.

£125ish for a steel beam aint cheap when you're only on minimum wage dude wouldnt mind one of the minispares alloy ones though!

Edited by Nick on 26th Dec, 2005.

bud you need to weigh up the cost of damage to the shell when your cut subby fails and the wheels come throught the floor pan, i personally would run standard until u save up 4 the pucker stuff just my opinion dude thats what i would do

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MikeRace, Mini13

i've spoke to a chap on 16V mini forum who's running a chopped rear subby and he's had no issues at all with it. i cant see how it would fail being chopped down than if it was complete.

here's a pic of the chaps cut down jobby

Edited by Nick on 27th Dec, 2005.

are there any disadvantages to a beam at all? i can onlysee advamtages so far, am i missing something?

thanks, Dan

less protection in a rear end shunt for a start i guess.

you need to run coilovers which arent cheap most of the time, plus the strengthening of the shock mounts needed for coilovers.

seems a small price to pay:) thanks!!

Dan

ive critised my handling at the rear since fitting a beam in the past...

however after setting it up correctly it seems to be just as good as cones (ie didnt see any differnce round combe or on the road to my friends mini)

I like the idea so crack on with it Budd and try and get a before and after weight for us.

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Hi,
What's going to stop the rear most end of your beam flapping about, as the whole lot is mounted on 2 rubber mounts that will rotate?
Cheers,
Gavin. :)

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Bat what the heck are you smoking buddy because i want some. LOL :)

Two things are infinite: the universe and human stupidity; and I'm not sure about the the universe.

I understand what he means. Keeping the standard subframe outer mounts, they have the trunnion mountings with rubber bushes. So with no rear-facing members any more, what is to stop the remaining front x member turning axially on the trunnions?

the idea is to not use the pins, bushes and trunions - and instead weld a couple of pieces of angle onto the ends of the front x-member of your 'beam'.
This can then be bolted securely to the rear toe-board.

If course - do this and also cut out your boot floor, and you have very little 'shear' across an area where there was once plenty... Might be an issue - might not. Up to each to decide for themselves.

I reckon another 'support' in the middle of the beam wouldn't go amiss - tying the centre right to the tunnel in the shell - belt and braces and all that...

Edited by turbodave16v on 27th Dec, 2005.

just had athought while rreadsing this and iirc when i changed my srear subframe the heavest things were the arm and the frame itsself waighed so little so now i dont see an advantage apart from more work unless you are down to the last few pounds your trying to save? it looks lik ei would save more by going to the toilet before i get into the car. am i wrong? lol

Dan

i was looking at doing this a while ago, but didnt due to not having the coil overs at the time....

is definately something i will be doing in the future, i had always planned to ditch the existing mounts, as td says, and also to fix it in two more places, using bolts and large spreader plates. imho this should suffice to replace the strength lost when cutting the rst away....

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I have run with no rear subframe for 4 years. As Dave says you need to do away with the rubber mounts and weld brackets to the remains of the subframe. You also should weld on some more brackets that bolt to the body as near to the inner most mounting points of the radius arms otherwise the beam will flex resulting in variable toe angles and possibly metal fatigue. The beam I made from alloy really made a positive improvement to my Sprints handling and an excellent weight saving.
Paul

I seriously doubt it!

yeah the plan is to get it bolted into place with the stock mounts, then i can pack it out from the heelboard cos i dont think it sits flush against it does it? Then get at least another 2 fixing points where its been packed out.

Its all hypothetical at the minute as i haven't picked up the subby or coilovers yet. but i should have finished the deseaming by the time i get em so i can crack on with fitting it up and seeing whats what.

ihmo you are wasting your time if you were auto crossing or rally crossing i would say go for it as it would be a neccessity however for the work you will put in for the amount of weight lost why bother when it comes to getting weight down where do you draw the line ? removing all glass having mesh ? fibreglass roof (popular with auto x)

i would rather have a smaller fuel cell to compensate easier than welding bits onto ya motor.......just my opinion, each to their own and all that :) good luck either way sure everyone will help u whatever decision !

Richie

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