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MG MGA - Front Wheel Bearings

Has anyone got any experience of changing the front wheel bearings to taper roller, or indeed any comments on whether it is necessary (for a race car!)

Colin
Colin Parkinson

Colin,

Don't do it. I did it when I was young and foolish (I am now old and foolish).
The MGA design uses that spacer tube to add strength to a lightly constructed stub axle.
It is extemely dangerous to remove that tube when using tapered roller bearings.
Note that the mga twin cam, which has tapered roller front bearings, has that spacer tube still fitted by the factory.
The Twin Cam uses the spacer and shims to set the tapered roller running clearance, the stub axle nut is still tightened down fully.
If you must use tapered roller bearings set it up like the Twin Cam. I would keep the ball bearings as they have a lower rolling resistance.

Mick
Mick Anderson

I converted our TD to tapered roller bearings years ago, but retained the inner spacer, setting the distance between the bearing races with shims as is done with the MGBs. Just take you present bearings to a bearing supply house and they can match tapered roller bearings to be used. You may have to polish the stub axle a bit to get the inner races to slide on and off easily, but from there it is very easy. Once done, removing the hub is a snap. Good luck - Dave
David DuBois

David -

Were the replacement taper bearings the same over all width as the ball bearings?

I ask because the conversion on the midget to (the wider overall) tapered rollers requires the recess in each end of the hub to be machined deeper.

Mick -

I agree that as long as the spacer tube is used and appropriate machining carried out to accomodate the tapered roller bearings, (which may be wider overall) I dont see a problem with stub axle stiffness.
However - I also wonder if the change is actually necessary.

Cheers
ian F



Ian Fraser

Ian - In the case of the TD, the bearing width was the same within .020" to 0.030", which was taken up with shims. As to whether or not it was a necessary change, I have always been told that the tapered roller bearings are stronger in the lateral direction than ball bearings. To me the biggest advantage though, is that I no longer need a hub puller to remove the front drums and hubs. Cheers - Dave
David DuBois

David,

There are several advantages with tapered rollers:
1. They can take higher lateral forces.
2. The hub is much easier to remove.
3. The hub can be removed to grease the bearings as often as you like without the bearings becoming loose in the hub. This can make a ball bearing hub useless.
4. They are adjustable by shimming.

The only downside is that tapered rollers have a greater rolling resistance.
To explain that you need to have an engineering knowledge of resolving a force into component vector forces. But to put it simply, when the weight of the car is vertically straight down (rolling or driving) there is a continuous sideways load on the tapered rollers. This does not occur with ball bearings. A "wedge" effect.

Mick
Mick Anderson

Hi Mick

I can see what you are getting at, but can't see how this force adds to the rolling resistance.

For an example, if the inner bearing is directly above the centre of the tyre contact patch, then the radial load on the that bearing can be resolved into two components, one of which is an axial force in the same direction as the 'pointy' end of the inner cone, ie towards the outer bearing.

This force is taken by the outer bearing as an axial load through the rollers in that bearing.

All loads are taken by the rollers, there is no friction loads anywhere.

If there is an increase in rolling resistance, is it produced by something other than this axial force?

Cheers
Ian F



Ian Fraser

Colin,

Dou yourself a favor and switch to MGB front kingpins, taper bearings/hubs, shocks etc. The screw type kingpins on the MGA are known as a week point under the extra load *Snap* found while racing.

I did this conversion while building my MKII for racing. It is not difficult.

For details go to http://www.mgbmga.com/ and look in the tech files.

Good luck and enjoy racing your MGA!

John
John

John, thanks for that info. I must be dumb as I cannot find an article on the conversion you suggest. Do you have a ref no for it. Actually I am not sure I could go that route, as the car is to FIA spec, so only homologated parts can be fitted. But may be useful for non FIA events with the 1950 engine!!
By the way, what a set of interesting articles!! Would recomend!

To everyone else that has replied - many thanks for all the info

Colin
Colin Parkinson

Hi Ian,

I will email you offline for a discussion on resloving a force into its components. Too boring for a BBS.
Just an observation from when I fitted tapered rollers to my MGA 1500 in 1959 (foolishly without the spacer tube).
Outside of my house I had a gently sloping road that then became flat for a long distance, traffic was a couple of cars a day.
I let the car roll on the slope and then waited for it to stop on the level part. I was surprised how much further it rolled with the ball bearings.
I would have changed the tapered bearings back to ball bearings, but I had already taken metal off the stub axle to make the tapered rollers a sliding fit. When someone wiser than I told me that the stub axle would break, I used the spacer tube and shim system of the tapered bearings of the just released MGA Twin Cam.

Mick


Mick Anderson

This thread was discussed between 08/07/2005 and 10/07/2005

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This thread is from the archive. The Live MG MGA BBS is active now.