Unsprung weight

[RobThomas]

Has anyone ever weighed drum brakes Vs disc brakes? I was wondering if there was any significant difference or if it wasn't worth worrying about.

Ta.

Rob

[philthehill]

Rob
When I fitted disc brakes to my Minor I did weigh the disc brake components of different marques and found the Marina was the lightest so that is why there are Marina disc brakes fitted.

The Marina disc brake set up was very much lighter than the Riley 1.5 front bakes fitted at one time to the Minor. The original 7" drum brake set up was very much lighter than the Riley 1.5 front brakes.

Normally un-sprung weight is not a consideration on an ex factory spec car but when the un-sprung weight is increased it can play havoc with the damping which may require stronger dampers to be fitted.
It can also have a detrimental effect on the suspension bushes.
In-sprung weight needs to be as low as possible both front and back of the vehicle.
Phil

[RobThomas]

Thanks, Phil. I now have the necessary parts here to fit MGB hubs direct to the uprights without having to add any sleeves within the bearings. The new spindle (?) is much beefier. I can now use any of the MGB/MGA/Magnette/MO/4-44 brake parts since they all fit each other.
I tried the Wolseley 4/44 drums today and they fit nicely but are heavier than I expected for 9-inch brakes but match the 9-inch rears and are cosmetically identical to the early Lowlight drums, if a little bigger. All MGB parts would end up cheaper if they were no heavier, especially if there are any alloy calipers to look at. Any thoughts on that?

[RobThomas]

Does anyone have an early (Lowlight-ish) front brake drum that they could weigh for me???

[philthehill]

Rob
You mention new spindle.
What new (hub) spindle have you had fitted?
I have had Marina front hub spindles fitted to my Minor uprights which removes the need for sleeves for the bearings.

If it means you can reduce the un-sprung weight by fitting alloy calipers that is the way to go.
Phil

[RobThomas]

Phil. It is a copy of the MGB spindle profile that runs through the same hole as the Minor one but also has a nut at the back to keep it in as well as friction and loses the circlip. I wanted to go for the 4.5 inch PCD to utilise a certain wheel option but was reluctant to try modding Marina hubs out to 4.5 inch or to pay the premium for original 575 Van ones. This way I also get flexibility with other BMC parts-bin components. I quite enjoy the challenge of seeing if something can be made to fit rather than taking the easy (sensible) route. The kit I now have could also have been made by anyone back in 1949.

Does anyone have an early (Lowlight-ish) front brake drum that they could weigh for me???

[philthehill]

Rob
If the stubs are a copy of the MGB spindle profile have they been case hardened?
The Marina stub axles are case hardened.
Phil

[RobThomas]

Yes, they have.

[les]

When changing to discs, different drums or even wheels/tyres, is this really an issue? Maybe in motorsport.

[ianmack]

No issue at all for those of us who just pootle around country lanes. Motor sport is a whole different ball game

[philthehill]

It is important that the stub axle is made from the right grade steel and surfaced hardened even when not used in motorsport.
The surface hardening gives an additional layer of strength and helps reduce bearing race rotational/skid wear of the stub axle.

As an aside:-
Whilst the Marina stub axle is slightly larger in diameter than the Minor stub axle the physical dimensions of both the Marina and Minor steering swivels in the area of the stub axle hole are the same.
The other major differences between the two steering swivels is that the bottom swivel/trunnion threads of the Marina are of a larger diameter and the top joint of the Marina swivel is formed as a ball joint similar to the Mini.
There is a body of thought that the bearing spacer fitted to the Minor hub provides additional strength to the stub axle. If that is correct and the bearing type is changed with the spacer being discarded the strength of the stub axle may be reduced and/or compromised.
To ensure that there was no possibility of a reduction to the strength of the stub axle assy when taper roller bearings are used I had the Minor swivel stub axle hole machined to the same dimensions as the Marina and fitted Marina stub axles.
It has to be remembered that parts cannot be changed or modified in isolation as invariably it has an impact somewhere else.
Phil

[RobThomas]

I didn't know that the Marina used a larger bottom trunnion thread. Do you happen to know the size, Phil? It might be that it will fit the MO leg if it is jsut a gnats below 13/16.

[philthehill]

Rob
Unfortunately I have got rid of the NOS Marina bottom trunnions/swivels I had on the shelf so are unable to give you a definitive O.D. measurement of the threads.
There may be someone on here who can though.
The swivel thread centre to the trunnion pin centre is greater so if it did fit the negative camber will be increased.
Here is a link to a Marina bottom trunnion:-
https://www.ebay.co.uk/itm/MORRIS-MARIN ... Sw3Z9auB2K
As can be seen the swivel threads are further away from the trunnion pivot pin therefore the Marina swivel does not need a relieved centre to the bottom swivel threads as has the Minor to allow the trunnion pin to pass through.
Interesting thread here re bottom trunnions:-
https://www.mmoc.org.uk/Messageboard/vi ... hp?t=19385

Phil

[IslipMinor]

Phil,

The same principle of using a clamped spacer between the bearing was used on the MGB as well. They have taper roller bearings, and use shims to achieve the required running clearance.