marina disc brake problem

[tomlucke]

Driving home yesterday I noticed a noise from the front nearside wheel.
When I got home I investigated to find the wheel wobbling worryingly on the stub axel.
I thought it must be the hub bearing but looking closer the 4 bolts attaching the calliper braket to the king pin had come loose.
Two questions:
Can I lift the calliper out of the way after unbolting it from the mounting bracket so that I don't need to bleed the system again?
How can I prevent this from happening again? I fitted the brakes several months ago and everything was bolted up tightly.

Also if the wheel had a lot of play I guess the hub bearing must be loose as well??
thanks

Tom

[philthehill]

You can remove the caliper and hang it up out of the way but make sure that you do not stretch or put pressure on the flexible pipe. You will need to remove the hub/disk assy to put a spanner on the four caliper bracket bolts but it would be better to replace the bolts/nuts. Be aware that those 3/8" bolts have reduced bolt head thickness. I would also advise that you check the serviceability of the hub bearings and caliper mounting brackets before refitting and replace if necessary. When adjusting the hub after assembly tighten the hub nut until there is no play and then slacken off. Tighten again but only finger tight. Install retaining washer and lock nut/split pin. You should be able to feel a small amount of free play at the tyre. Do not reduce endfloat or preload the bearings. If you have the special 'Top Hat Spacer fitted (to make up the difference in dia between the Minor and Marina stub) that should also be checked for seviceabilty. Whilst highly unlikley check that the stub axle has not come loose in the upright.

[simmitc]

When refitting the bolts, you can use locktite or similar.

[bmcecosse]

Caliper bracket bolts have nothing to do with wobbling wheel....something has gone awry with the bearings! These marina conversions are a real lash up, I would be changing back to standard drums urgently before you have a serious accident.

[philthehill]

bmcecosse
I totally agree that you regarding the wheel wobble (that is why I said in my post check the wheel bearings) but to say that the Marina/Minor disc brake conversion "are a real lash up" is a bit harsh! There are many Minors out there that have been converted and have had no problems. I have personally used the Marina conversion on my competition car and road car and have had no problems whatsoever. What I will say is that the conversion needs to be fitted correctly because as with all things if it is not fitted correctly problems will follow.

[bmcecosse]

In this case - the wheel bearings have gone wrong AND the caliperbracket has come loose. ... I think the evidence speaks for itself...

[philthehill]

I never presume anything until I have seen the evidence!

[bmcecosse]

Seriously though... Fitting bearings with 'sleeves' can't be right.

[philthehill]

I agree it is not the best way to fit bearings but not unheard of. As regards the Marina hub/Minor stub axle conversion - I am not aware of anything available commercially until Grumpy's brought out his Marina disk brake conversion and people wanted disc brakes on their Minors myself included even if it meant having to use the top hat bearing spacer sleeve. As you probably know CS Autoclassics went in a different direction by machining the Minor upright and fitting the Marina stub axle but that still reguired a sleeve to make up the difference between the internal diameter of the Minor and Marina hub seal. I have recently spoken with CS Autoclassics and their conversion is no longer available. Over the years I have used both types of conversion on my Minors. Currently I have Marina stub axles fitted to 8cwt uprights (not a CS Autoclassics conversion) so I can use original specification Marina bearings. The only difference between the Minor and Marina upright casting in the area of the stub axle is the larger diameter of the Marina hub oil seal seat. To assist in the longlevity of either conversion I have always ensured that both the oil seal sleeve/top hat bearing spacer sleeve were retained on the stub axle/upright with Loctite bearing lock. Before the Loctite set they were held in the press to ensure that they were retained in their working position.
I see that ESM now advertise a new hub as part of their Grumpy's style Marina brake conversion and for which they appear to have revised the diameters of the recesses in the hub for the bearings so facilitating the fitment of bearings without having to resort to a top hat bearing spacer sleeve which is a most sensible move. I have no experiance of the ESM hub/hub set up but no doubt someone will express an opinion.
If I have any concerns over Minor disc brake conversions it would be the extra loading placed on the standard Minor stub axle. The stopping power of current conversions seem to be immense!

[bmcecosse]

Good explanations there Phil - does sound like a much better way to go.

[philthehill]

Bmc
Thanks.
I was hoping that someone would come back to me with an opinion regarding the possibility of overloading the Minor stub axle to a point which if exceeded could lead to catastrophic failure - but as yet no takers.

[bmcecosse]

Oh I think it will be fine - never heard of one breaking or pulling out. Big wide wheels/tyres are the more likely cause of any such failure rather than brakes I imagine....

[IslipMinor]

I have considered going 'taper roller bearings', but have retained the standard angular contact bearings clamped to the spacer to give that little bit of added strength to the Minor stub axle.

The hubs are standard Midget, which run directly on the standard Minor stub axle, but the brakes are Metro vented discs, with Metro 4-pot calipers, Mintex 1155 pads and Yokohama A021R very sticky, when warmed up, tyres. The brakes are seriously good from 100+ mph on track days, lap after lap. I don't think a reasonably standard car is going to have problems with stub axle strength.

[philthehill]

Bmc & Richard
Many thanks for the replies.
I would agree that hard rolling braking (i.e. the wheel not approaching the point of locking up) encountered by lightly modified Minors should not cause the stub axle to become overloaded.

[rayofleamington]

If I have any concerns over Minor disc brake conversions it would be the extra loading placed on the standard Minor stub axle.

The braking loads are very small compared to forgetting to slow down for hitting speed bumps, pot holes and kerbs!
There are plenty of cases of broken wheel studs (mostly due to fatigue and/or over-tightening) , but I've never yet heard of a broken stub axle.