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Rear Radius Arm

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#1 Karlhall230


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Posted 06 June 2020 - 02:09 PM

Hi, I’m new to the forum but not that new to minis, having owned my current car for about 12 years it has been off the road for about ten of them. Having some spare time recently I have decided to start to restore it. There is a lot of welding to do so the first thing I have done is remove the rear subframe. I thought while it is off I would take the time to overhaul the rear suspension. On inspection of the rear radius arms the bearings and bushes are completely shot with one of the bushes being completely worn away on one side. I have a couple of questions, first one being at what point is the radius arm considered scrap from excessive wear? The next being is it more economical to invest in the tools to recondition them yourself or to buy reconditioned units from Minispares.com, I already have the overhaul kit with fresh bearings, bushes and pins etc. Cheers

#2 kit352


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Posted 07 June 2020 - 05:51 AM

I would buy the tools to refresh it yourself seeing as you already have the parts.

As for when the arms are too far gone to redo it going to take some inspection work. I would say if the bushes have worn through to the actual radius arm then that one may be too far gone depending on the damage.

#3 nicklouse


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Posted 07 June 2020 - 08:36 AM

Send it away for reconditioning (exchange) very few people have the correct kit to correctly ream the bush. A single hand reamer will not accurately work as they have no means of locating in the bearing to make sure of correct alignment.

#4 northernboy


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Posted 28 June 2020 - 08:13 PM

I have recently had the same issue - I had two radius arms that looked well past their sell by date. However, after a good clean, the actual arms were OK but they did require new bearings, bushes and pins. Replacing the arms from a reputable supplier is one option with a guarantee they will be ready to fit and provide good service but this comes at a price. The second option is to renovate. To do this yourself without a big struggle you will need suitable tools.
I bought a kit that included a drift, a reamer and two new bearing / pin kits for around £85 and it has been very successful but you have to follow the guide.
They also do an advanced kit that has an alignment attachment but this is a bit more expensive but does solve the alignment issue as mentioned in the previous post.
The first problem is removing the old bearings. Knocking them out with an old screwdriver or long rod is unlikely to work as there is not much to hit and they may well be very tight. 
There are now internal bearing pullers available that you insert into the bearing , expand up and then pull out the bearings. I have not tried these but guess if the tool is good enough should work fine. I chose to use a purpose built drift in the kit.
The drift is simply a steel rod that that has been machined to slide into the bearings exactly and they are hammered out. It is simple and it works. You place the arm on a block of wood, roller bearing down then insert the drift into the brass bearing and hammer away. The drift pushes the brass bearing through the arm and eventually starts to push out the roller bearing. You obviously need to ensure the needle bearing can be pushed out so arrange the block of wood to allow this. Once done, continue to push the drift all the way through the arm until completely out. You will then have to use some nose pliers to extract the old plastic sleeve.
The arm can then be thoroughly cleaned and inspected - you will find a lot of old grease in the arm try to get as much out as you can.
Replacing the bearings is easier but requires care to ensure they fit correctly.
Firstly, insert the new plastic sleve then push in the needle bearing using a bench press or soft faced hammer to ensure the bearing is not damaged. Constantly check the bearing goes in straight or it will jam and can be damaged. The brass bearing can then be pressed or knocked in again ensuring it goes in straight.  To ensure grease can move around the bearings freely, it is best to knock these in a mm or so down from the edge of the arm. The brass bearing is relatively soft so you may find the end that gets slightly damaged if hammered in. This should not be too much of an issue unless seriously damaged as the brass bearing must now be reamed out to fit the new pin and the reaming process should remove any burred metal.
To ensure the brass bearing is reamed out correctly it is essential the process is done with care and time is taken to check regularly the reaming process.
The reamer is initially set to the same internal diameter at the brass bearing and then slowly wound down to expand the reamer and ream out the bearing to the correct size. Lubricate well and ream out only a little at a time and keep checking with the new pin pushed in from the roller bearing end. 
The new pin should snugly fit the brass bearing with very little sideways movement and when also inserted through the roller bearing should slide in and out with minimal sideways movement and rotate freely. Once you are happy the new pin fits, thoroughly clean out before final assembly. Remember to lubricate as you assemble and re pack with grease once assembled using the grease nipple.
Cost wise, the complete kit of bearings and tools is around the same price as one of the lower priced re conditioned arms so if you have more than one arm to re condition the kit is well worth a try.
Remember you have to take your time and follow the instructions. If you make a mess and damage a new bearing or ream out too much, then new bearings are relatively cheap and you can try again as you will still have the tools :)
If you are not confident to do all this, then plump for new/ re conditioned and job done. 

Edited by northernboy, 28 June 2020 - 08:26 PM.

#5 MiniMadRacer


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Posted 28 June 2020 - 09:17 PM

Thats an interesting piece of kit

#6 mab01uk


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Posted 01 July 2020 - 07:04 PM

You may have to register on the Mk1 forum to read original post:-  

Ultra-simple tools to remove rear arm bearing, bush & tube



Disassemble the arm to the point where you have the pivot shaft removed. It helps to remove as much excess grease that's hanging around, especially inside the bore behind the needle bearing. Just use your finger and a rag and get the bulk of the grease out.

Making the needle bearing removal tool:

1. Take a 12mm flat/thick washer (13mm ID X 24mm OD X 2.5mm thick, DIN125 or similar, 8.8 or 10.9)

2. Cut it in half so you end up with 2 half moons. Deburr the sharp edges where you cut.

3. On a flat surface, position them back together as if they'd never been cut, and tape them together using 1 piece of masking tape, on one side only. Trim any overhanging masking tape from the hole and the outside diameter. You should now have a "hinging" washer


Removing the needle bearing from the arm:

4. Put the washer on your middle finger so that it "tent's" over the end of your finger. You may drop it a few times until you get the hang of it but persevere.

5. Summon your inner proctologist and feed the tented washer into the needle bearing and just a little bit further until you can drop it onto the inner end of the needle bearing and have it unfold on the top of the bearing. Again it may take a few attempts but it won't be long till you can do it blindfolded. Here's a photo of the concept using a loose bearing to demonstrate.

6. Keep your assembly in a vertical position with the bushing end up and the needle bearing end down so the washer doesn't fall out of position. Feed a pivot shaft through the bushing end until it seats on the folding washer. You can now tap the needle bearing out without any drama or expensive special tools and the needle bearing will likely be undamaged. (If you're using a good shaft, make sure you protect the threads before hammering)


Making the Bushing removal tool: (material used is fairly common in US but I'm not sure how available it is elsewhere and may take some searching or substituting to find something suitable)

Cut a piece of 1/2" steel water or gas pipe to approx 12" length. (1/2" pipe is actually .840" OD). Ideally, use a pipe cutter to make the cut because the 1/2" pipe is slightly undersize for what is needed and a pipe cutter tends to displace material adjacent to the cut outward, kind of like knurling, which effectively enlarges the diameter several thousandth's and that will help the fit. It also insures you have a perpendicular cut. If that's not possible, you can hammer tap on the end of the pipe in a circular pattern several times which will tend to flare it slightly. The object is to have a snug slip fit with the inside diameter of the grease tube so you maximize the contact area with the bushing. If you go overboard just grab some sandpaper or a file and dress the diameter down a little. After many removals you may have to lightly dress the pipe end back to perfect size because it will tend to flare with use.

Removing Bushing:
Just slide the sized end of the pipe down the grease tube and beat on the other end to drive the bushing out. I've found it's better to use the heaviest sledge hammer, that way you won''t have to take big swings. Let the weight of the hammer do the work.

Making Grease tube removal tool: (The material I used is commonly available in the US and may take searching or substituting to find elsewhere)
Cut a piece of 3/4" EMT conduit (Electrical Mechanical Tubing) also known as Thinwall to approx 12" length.

Removing Metal Grease Tube:
In most cases the Grease tube will fall right out, but occasionally you'll find a tight one. The 3/4" EMT is just the right size to drive the tight one's out without damage.


PS I don't know if any of these removal tools work with the plastic style sleeve, because I've never done one.

Edited by mab01uk, 01 July 2020 - 07:11 PM.

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