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Rodney Collins
United Kingdom
424 Posts |
 Posted - 09/05/2005 : 09:00:25
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Peter, I replaced the front bearings with taper bearings which are readily avaliable from the same sources, at very little extra cost.
Rodney |
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Peter Scott
United Kingdom
1240 Posts |
Posted - 09/05/2005 : 10:21:50
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Rodney
Good on yer'. I trust that they were Timken bearings. I worked for Timken for 38 years. I am just checking with my old colleagues how I can get a discount at the local bearing stockists for the rear hub bearings.
I have not had any problems with the front hubs (yet!). However I will consider tapered roller bearings when I need new ones on the front.
Peter |
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DickMorbey
United Kingdom
3678 Posts |
Posted - 09/05/2005 : 12:13:28
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A word of caution regarding the fitment of taper bearings to PA and Triple-M front hubs in general.
All the guidance I have received from knowledgeable members counsels that you do not use tapered bearings, but rely on the conventional set up. Evidently the Triple-M stub axles are just not designed to take the extra streeses and strains that tapered bearings impart.
Perhaps others with greater knowledge than me would care to comment?
Dick |
Edited by - DickMorbey on 09/05/2005 12:14:34 |
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Peter Green
United Kingdom
1682 Posts |
Posted - 09/05/2005 : 12:48:09
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I personally still use standard bearings in the front hubs of my Triple-M cars but if taper roller bearings are used they MUST, repeat MUST, be used with the correct length spacer between them. As Dick has mentioned our front hubs are not designed to take the added stresses of using taper bearings without a spacer being used.
Peter. |
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Peter Scott
United Kingdom
1240 Posts |
Posted - 09/05/2005 : 18:42:08
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The issue with tapered roller bearings, in wheel applications is that they must be set up with a small amount of end-float (typically 3-4thou). They must NOT have any preload otherwise they will fail quite quickly. When properly adjusted you will be able rock the wheel and clearly feel the play, up to 1/8" or more at the rim. You also have to explain this carefully to some MOT mechanics as there are a surprising number of them who do not understand how to set up TRBs.
Peter |
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Rodney Collins
United Kingdom
424 Posts |
Posted - 10/05/2005 : 08:54:09
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Now you all have me worried, I was recommended to fit taper bearings by Tom Dark. When I asked about the spacer inbetween he said just throw it away, it will only rattle around and is unnessary anyway! He fits them all the time.
Rodney |
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Peter Scott
United Kingdom
1240 Posts |
Posted - 10/05/2005 : 10:15:58
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Rodney
There are two reasons why a TRB fails, lack of lubrication or incorrect setting. The latter is the more prevelant as few people, including many qualified mechanics understand how they should be set. My enginnering friends at Timken, when asked how do you set a tapered wheel bearing, ask do you want to get through the MOT or do you want it to be right? They need a small amount of end play which as I said before results in you being able to rock the wheel, 1/8" or more at the rim. A small amount of preload dramatically reduces their life.
Having said that, a TRB of the size used in an MMM front wheel is grossly over engineered and properly set would be capable of taking much bigger loads than will ever be experienced in your PA. So people who use TRBs without the spacer may 'get away with it'. However, as Peter Green said, you should have a spacer and it should be shimmed to give say 2-4thou end-play.
I am very much a novice when it comes to MMM cars but after 38 years at Timken this is one subject which I do understand.
Peter |
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Peter Green
United Kingdom
1682 Posts |
Posted - 10/05/2005 : 10:46:36
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There is nothing wrong with using taper bearings but they must be used with a spacer on our cars. The original spacer will 'rattle around' as it is to short for use with taper bearings. The inner parts of the two taper bearings must be held apart (or together) by the correct length spacer when the nut is done up tight. The 3-4 thou end float that Copperhide mentions must not be obtained by leaving the spacer loose. The spacer must be sufficiently long to give the required end float when the nut is done up tight.
Peter. |
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Peter Scott
United Kingdom
1240 Posts |
Posted - 10/05/2005 : 11:47:40
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I agree with all of Peter Green's comments. An additional potential problem with omitting the spacer is that there is nothing to prevent the inner races from spinning on the axle.
Peter |
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Rodney Collins
United Kingdom
424 Posts |
Posted - 10/05/2005 : 18:54:35
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So how do you work out the size of spacer needed to hold the taper bearing at the correct position?
Rodney. |
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Peter Scott
United Kingdom
1240 Posts |
Posted - 11/05/2005 : 08:11:57
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Rodney
Never having stripped or worked on a front hub, I am not the person to answer your question. I guess that you will have to use trial and error. Starting too big and working your way down to the correct length.
The MGB was the first MG designed to use tapered wheel bearings, apart from the disc braked MGAs such as the Twincam. On the B the spacer is a few thou short of the required length and the final adjustment is made using shims. The shims are are made in three diferrent sizes (5,3 and 2 thou if my memory serves me correctly). They are 1" OD and 3/4" ID which is probably too samll for the MMM axle? I think that it is helpful to be able to make the final adjustments using shims rather than trying to get the spacer exactly the right length.
You really need someone with MMM experienced of TRBs to answer this question.
Peter |
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Rodney Collins
United Kingdom
424 Posts |
Posted - 11/05/2005 : 11:11:59
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Thanks Peter I am sure we will f=get more answers to the problem. Looks like I will be stripping the front down yet again. Still I was thinking of taking the back plates off to be painted.
Regards Rodney. |
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Peter Scott
United Kingdom
1240 Posts |
Posted - 11/05/2005 : 18:31:59
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Rodney
Well I am logging out for nine days as I am going on holiday. I hope that someone will by then have answered your question. I'm sure that the backplates will be much better repainted. They are in a very visible position.
Peter |
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