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Bottom Arms - Handed?


Best Answer Cooperman , 22 April 2019 - 10:37 PM

The tapered hole is very obvious and there is little chance of getting it wrong.

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#1 jonsharman

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Posted 22 April 2019 - 04:32 PM

Evening Everyone,

 

After pulling off all the new parts I bought from the now-written-off Mini Auto I'm in the process of ascertaining what I have and what I might need for the new project.  Today I was building up a new front subframe and as I started to put the bottom arms back in I noticed 2 x 21A1881 and not 1 x 21A1879 & 1 x 21A1881!   O_O  This fact does also mean that the previous car had potentially the wrong arm fitted on one side as, when they were new, I used the part number on the box to identify R/H and L/H and fitted them to that subframe based on said fact as I remember laying everything out on each side in the boxes they came in - top, bottom, etc.

 

Question is does this matter?  My head says yes of course it does otherwise the instructions would just say 'fit it the opposite way around'!  However the frustration in me - and now being potentially £45 out of pocket -  says I hope not!  Given they are used, albeit only very slightly, and nearly 12 months old I won't be able to send one of them back now.   :mmkay:   

 

Thoughts?  Deal with the fact I should have noticed first time around and get the right parts?



#2 Artstu

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Posted 22 April 2019 - 04:44 PM

Think about the ball joint tapered hole.



#3 Tupers

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Posted 22 April 2019 - 04:45 PM

They are sided because of the tapered hole for the lower ball joint is machined in from different sides depending on it it’s a LH or RH arm.

You cannot physically run a car with the arms on the wrong sides as the ball joints simply won’t seat in the tapered hole if it’s pointing up instead of down.

Check which way your tapers are pointing the bigger end should point up. I must admit I’ve never looked at the part numbers but I would have thought they’d use the same casting and fixture them in the opposite directions for machining.

#4 jonsharman

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Posted 22 April 2019 - 05:44 PM

Thanks for that - it hadn't occurred to me that there would be a taper. I'll check each arm and see what I need to do from there!

#5 richmondclassicsnorthwales

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Posted 22 April 2019 - 06:18 PM

Hi Johnathan

 

I have some lower arms if you do have some odds, so let me know what you want if need me



#6 Spider

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Posted 22 April 2019 - 06:28 PM

If the numbers you found were forged in to the arms, confusing as this is, they are not part numbers but blank forging numbers.

 

Both arms are machined from the same forging, but, as the other guys have said, there is a Right and Left.



#7 dodge44

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Posted 22 April 2019 - 06:31 PM

The numbers 21A1879 and 21A1881 are on both sides as the same forging was used for both sides. Because the only difference is the tapered ball joint hole I wonder if the original idea was one number (as appropriate) would be ground off once the machining was complete but manufacturing economies understandibly knocked this element off the job sheet?



#8 Adam Johnson

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Posted 22 April 2019 - 09:25 PM

Are the adjustable kind similarly left and right handed?

#9 DeadSquare

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Posted 22 April 2019 - 09:40 PM

Are the adjustable kind similarly left and right handed?

 

Yes.



#10 Adam Johnson

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Posted 22 April 2019 - 09:53 PM

Are they identified as such or do you just need to look at the tapering on the hole. I have changed one side and am due to change the other. It’s a 50:50 if I have gotten it right. They good news is I have not tighten anything so I can salvage my potential mistake.

#11 Cooperman

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Posted 22 April 2019 - 10:37 PM   Best Answer

The tapered hole is very obvious and there is little chance of getting it wrong.



#12 jonsharman

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Posted 23 April 2019 - 05:33 PM

Evening All,

 

Think about the ball joint tapered hole.

 

Being a bit of a novice I did not even consider this but of course it makes sense now I think about it!  Now that I have had another look it is - as they say - as plain as day that there is a taper in the hole and the arms taper in opposite directions thus giving them their hand.  I guess it was worth a check rather than charging in without another thought as there would have been a 50 / 50 chance the hubs would go back in ...  O_O

 

Had I had a proper inspection on Monday afternoon rather than my obvious man-look i would have noticed both part numbers are actually cast into the arm though that would have probably raised more questions for me than it answered!  Thank you for all the help - I suspect it won't be too long before I'm back ...  ;D


 



#13 Cooperman

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Posted 23 April 2019 - 06:14 PM

Never be afraid to ask a question. There is no such thing as a silly question if you don't know the answer. We all ask questions of each other.

Feel free to ask anything Mini-related. We are here to help keep our little classic cars going.



#14 Adam Johnson

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Posted 23 April 2019 - 07:54 PM

You would be surprised how much of a mistake one can make given the apparently modest ‘chance of getting it wrong’...

Thanks to you guys, if the idiot with the wrench had tried to put the arms on the wrong way round, the error of his ways have been spelt out before the torque wrench was used in anger.

#15 Ethel

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Posted 23 April 2019 - 09:32 PM

You wouldn't get even close to inserting the ball joint taper if you had an arm upside down. So don't worry if you got one side back together.

But there are brownie points for fitting the tie rod arm bolt from the top before fitting the ball joint.




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