Brake conversion

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Rust bucket
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Brake conversion

Postby Rust bucket » Tue Feb 12, 2019 11:45 am

Almost given up on looking for Wolseley 1500 front brakes, did buy a new pair of Midget 8.4 solid discs which were being sold off cheap, just in case I went for a disc brake setup instead.
Would Midget discs be almost the same as Marina apart front the pcd, solid type Marina caliper bracket also looks stronger than J type.

paul 300358
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Re: Brake conversion

Postby paul 300358 » Tue Feb 12, 2019 1:01 pm

I have just swapped mine to midget disks, dead easy. you need the hubs which fit the same as the standard, the pcd is also the same. you then need a pair of calipers. you use the minor brake hoses. Can you fabricate a pair of the brackets?
untitled.png
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This drawing was supplied by Richard (IslipMinor) and it is spot on. Have a look at viewtopic.php?f=4&t=59468&p=550924&hili ... ke#p550924.

You will also need 4 X 5/16 bolts to bolt the caliper to the bracket, 6 off 8mm dome headed 30mm long bolts and 18 off 8mm washers (spacers) to fit the brackets. Everything is availible new.

philthehill
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Re: Brake conversion

Postby philthehill » Tue Feb 12, 2019 1:02 pm

The Marina/Ital disc brakes are larger at 9" dia.

The Marina/Ital caliper mounts are a straight bolt on item but they are handed R & L.

The Marina/Ital brake set up is the easiest kit to fit especially as the ESM hubs are available to mount the Marina/Ital disk onto and also without having to use the Top Hat spacer.

Below is a view of the Marina/Ital disc set up on my Minor
img188.jpg
img188.jpg (677.97 KiB) Viewed 853 times


pgp001
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Re: Brake conversion

Postby pgp001 » Tue Feb 12, 2019 1:21 pm

Phil

That tie bar mounting looks to be a home brew, what's the story behind that one ?

Phil

Rust bucket
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Re: Brake conversion

Postby Rust bucket » Tue Feb 12, 2019 2:11 pm

If I did go for this mod I was thinking Ford caliper, Fiesta or Ka etc.. yes I could make up a bracket but would sooner buy some, would the bracket be the same the J type I doubt. If making some I guess with adjustmenst to the caliper bolt holes would be needed, the Ford calipers look to be cheaper and better pad area than the Midget calipers.

philthehill
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Re: Brake conversion

Postby philthehill » Tue Feb 12, 2019 2:50 pm

pgp101

The home brew item is the end of the anti-roll bar which is a period item purchased many years ago and unfortunately no longer available.

----------------------------------------------------------------------------------------------------------

The Ford Caliper is fully floating against the fixed calipers of the Marina/Ital and Midget.

The ford disc brake set up is heavier (I have weighed both of the complete assys) than the Marina/Ital set up so more un-sprung weight which is what I do not want.

The advantage of the Marina/Ital set up is that all parts are available either new or S/H so the cost can be adjusted dependent upon the use of new or S/H parts. No fabrication of brackets etc required - a straight bolt on modification.

The Marina/Ital disc brake set up gives more than adequate stopping power even without a servo.

I also had the Marina/Ital disc brake set up on my Ser2 and was very pleased with the conversion and that was also driven hard.

As you can most likely tell already my vote goes for the Marina/Ital disc brake set up and it is also cheaper with all new parts than the Ford disc brake kit.

Phil


Rust bucket
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Re: Brake conversion

Postby Rust bucket » Tue Feb 12, 2019 3:39 pm

Thanks Phil.
So could I use a bit of mixed bag, IE: Midget hubs and 8.4 discs with a good used Marina / Midget caliper and a new Grumpy bracket from ESM. Just trying to get the best stopping power and value using a mix of used and new parts. I have a remote servo in store, so if it's needed, so be it.

Biggles1957
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Re: Brake conversion

Postby Biggles1957 » Tue Feb 12, 2019 4:51 pm

I put Wolseley's on my traveller - dead easy, brilliant brakes with the added bonus that the back plate stops the king pin dropping off if it fails! Haha! As you say, rare as hen's teeth but I know that Richard at Minorparts of Oxford was advertising a set at a very reasonable price the other day.
Regards,
Bob

Rust bucket
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Re: Brake conversion

Postby Rust bucket » Tue Feb 12, 2019 4:58 pm

Biggles1957 wrote:
Tue Feb 12, 2019 4:51 pm
I put Wolseley's on my traveller - dead easy, brilliant brakes with the added bonus that the back plate stops the king pin dropping off if it fails! Haha! As you say, rare as hen's teeth but I know that Richard at Minorparts of Oxford was advertising a set at a very reasonable price the other day.
Regards,
Bob
Yes I know about the Minorparts bits, good price too . I missed them by about a day :x

philthehill
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Re: Brake conversion

Postby philthehill » Tue Feb 12, 2019 5:21 pm

Rust bucket

I would not recommend that you mix and match Marina/Ital and Midget disc brake parts.

You have to use one system or the other.

The Marina/Ital disc brake set up is good value for money. Even better if you can get good S/H disc brake parts.


ManyMinors
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Re: Brake conversion

Postby ManyMinors » Wed Feb 13, 2019 7:28 am

Having driven Minors fitted with both the Midget and Marina disc conversions, I would say that the Marina brakes are much superior to the Midget. The Midget brake discs are very small - after all, they were designed to slow down a very small light car in the early 1960s. If I were going to the trouble of fitting disc brakes I would go for the Marina kit. As Phil says, a servo isn't really necessary. Originally the Marina did without one - as did the Midget of course along with the BMC 1100/1300, MGB etc....

philthehill
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Re: Brake conversion

Postby philthehill » Wed Feb 13, 2019 8:23 am

The drawing above specifies the holes in imperial measurement therefore metric bolts/fastenings should not be used; and those bolts/fastenings should be fitted bolts and of a high tensile strength.

The brake fastenings on the MG Midget/Sprite, the Marina/Ital and Minor are all imperial and therefore imperial fastenings must be used.


Rust bucket
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Re: Brake conversion

Postby Rust bucket » Wed Feb 13, 2019 8:50 am

Safety first I wouldn't forse any fixings, yes they are all imperial. Some early Midget disc sizes are 7.5" I believe, the new pair I've just bought cheap are are 8.4" diameter. Marina disc's are 9", so it's the extra leverage of .6" combined with a bit better caliper which makes it superior to the midget items I suppose.

paul 300358
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Re: Brake conversion

Postby paul 300358 » Wed Feb 13, 2019 9:14 am

I suppose that you could use a 5/16 bolt instead of the M8, but the M8 is a better fit. When you convert 21/64s to metric it's 8.33mm a 5/16 is 7.9mm.

mobylette
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Re: Brake conversion

Postby mobylette » Wed Feb 13, 2019 9:27 am

Someone here selling Wolseley brake set:

https://www.morrisminorowners.co.uk/vie ... =1&t=12893

philthehill
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Re: Brake conversion

Postby philthehill » Wed Feb 13, 2019 10:01 am

All of the original fit imperial bolts holding the brake parts together are fitted i.e. their unthreaded shoulders fit the hole snugly with no slackness.

The bolts holding the Marina/Ital caliper mounting brackets to the swivel are fitted and have reduced depth heads to fit between the bracket and hub. Also the bolts holding the caliper to the bracket are fitted.

The bolts/holes which hold the Minor back plate to the swivel (5/16") have to be drilled out to 3/8" to accommodate the Marina/Ital mounting bracket mounting bolts.

I would not be happy with the use of only three 5/16" or M8 bolts to mount the caliper mounting bracket (even though it states/shows qty 3. 5/16" in the drawing above - the Midget caliper is bolted directly to the MG stub axle with 7/16" bolts - it does not have a separate mounting bracket) - I would suggest that there should be at least qty 4 bolts of 3/8" diameter fitted and be of the correct tensile strength and the bracket be of a full circle when fitted to the Minor as per the Marina/Ital type.

When the Marina/Ital discs were fitted to the swivel (which is basically the same as the Minor) the mounting bolt dia of the bracket was increased to 3/8" fitted. The Minor swivel in the area of the brake mounting boss is the same and can safely accommodate 3/8" fitted bolts

Bolts with a shoulder diameter of the thread should not be used - only fitted bolts with the correct dia/length of shoulder should be used.

Fitted bolts alleviate any rotational movement of the brake parts which could lead to shearing of the fastenings.


Rust bucket
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Re: Brake conversion

Postby Rust bucket » Wed Feb 13, 2019 11:31 am

mobylette wrote:
Wed Feb 13, 2019 9:27 am
Someone here selling Wolseley brake set:

https://www.morrisminorowners.co.uk/vie ... =1&t=12893
Thanks for the tip but I haven't been on this site for a long time, forgotten the user name and when I type in my email twice which hasn't changed, just say's dosen't recognise it. Go to register and say's this email is in use?!

IslipMinor
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Re: Brake conversion

Postby IslipMinor » Wed Feb 13, 2019 12:14 pm

The Midget discs were always 8.4" diameter, it was some early Mini front discs that were 7.5".

As far as perceived braking efficiency, there is actually only a very small difference in the pressure pedal required for Midget and Marina discs, assuming the only change is the caliper and disc. It is actually the Marina that is the very small amount higher!

The reason is that although the Marina discs are larger diameter - 9.0" vs 8.4", the caliper pistons are smaller - 1.89" vs 2.00", which results in 11% less piston area vs 9% increase in pad radius, so overall very slightly less braking effort for the same pedal pressure.

There is a very good braking system design paper, based around the Minor, and written by the Design Manager of AP Lockheed, which explains in great detail how a braking system works, and the calculations required to understand the results. I have constructed an Excel model incorporating the AP design principles, and the output provides full details of the braking forces, brake balance front/rear, pedal pressure, servo effects, etc.

If anyone would like a copy of the original design paper and/or the Excel spreadsheet, please let me know your email address and I will forward them to you.

The table below shows the front/rear brake balance and un-servoed pedal pressure to achieve 1g retardation for many of the likely BMC/BL brake component combinations fitted to a Minor- I do not have any details on Ford caliper/disc dimensions.
Minor Brake Setup Summaries v3.jpg
Minor Brake Setup Summaries v3.jpg (119.57 KiB) Viewed 702 times
The combination shaded in pink/red is the standard set-up for the 803/948 Minor with 7" front brakes, the blue is the 1098 Minor with 8" front brakes and the green is the set-up we have with 4-pot Metro calipers. These have virtually the same total piston area as the 2-pot Midget calipers.

One thing that comes out of the summary is how many combinations result in the rear braking effort being >30%, including the original 7" front brake set-up. 30% is seen as maximum for the rear proportion to minimise the chance of rear lock-up under heavy braking.

There are many suggestions of what the maximum brake pedal force should be, but 100 lbf is seen as a maximum for the 'average' sized driver to achieve a 'controlled' 1g braking retardation (dry road, good tyres etc.). Interestingly much less than 40 lbf for 1g is seen to give poor control, as the brakes are 'too sensitive' or 'over light'.
Last edited by IslipMinor on Wed Feb 13, 2019 12:35 pm, edited 1 time in total.
Richard



IslipMinor
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Re: Brake conversion

Postby IslipMinor » Wed Feb 13, 2019 12:33 pm

Picking up on the Imperial/Metric comments.

The original design of both the Minor (excl MM) and Midget is wholly imperial, which is why the 'J' bracket was designed with imperial dimensions. The Midget caliper is attached with 7/16" bolts, and the 'J' bracket with 5/16" bolts, the same as the drum braked back plate.

The 21/64" holes in the 'J' are for 'clearance' and since 8mm is virtually the same size as 5/16", there is no reason why 8mm could not be used for the 'J' bracket (I use M8 button-head socket setscrews for ours), BUT the Midget caliper bolts MUST be 7/16".

We have had the 3-bolt 'J' brackets fitted for >20 years, with a servo, race spec Mintex 1155 pads, Metro vented discs and 4-pot calipers, lots of track days with some serious braking demands, and no problems with the brackets or their fixings at all in the 60,000+ miles since they were fitted. The only problems we have had on track days is when someone assumes they will out-brake us, and goes off as a result (it has happened a number of times). One organisation now, as part of the initial briefing, gives the advice not to try to out-brake the Minor!
Richard



philthehill
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Re: Brake conversion

Postby philthehill » Wed Feb 13, 2019 1:05 pm

Richard
Many thanks for the data and explanation.

Whilst you have had no problems I am still concerned that the three 5/16" 'J' bracket bolts are considerably smaller than the 7/16" bolts used for securing the caliper direct to the stub axle which a quite a solid lump.

Phil



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