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Rear Brake Rotors

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It would be interesting if anyone had the part numbers for the rear disc brakes on the MM model. I know they were Girling, but beyond that, can't say. Then a cross reference to other cars using those discs might help out a lot. Anyone have a BMC parts list for the BN4 series?
 
Greg -

The part number in question is: AH8462. This kit included the the calipers, hand brake levers and rotors.

Dougie
 
Hi guys,

I thought I'd chime in to confuse or clarify a lttle more as this is of particular interest to me. H8462 is the part number for the rear disc kit in a 1964 Holly Wood Sports car catalog that I have, this would indicate it was for the 3000 and was probably the Girling units. I have a Hambro parts list from '58 that lists H8249 as the 4 wheel Disc kit for the 100/6 or MM which was the earlier Dunlop units. I can take some measurements on the rear discs that I have that were part of the MM Hambro kit if anyone is interested.

Barry
 
Not that I am going to act on any of this right away, but it would be interesting to know the part numbers for the components. I.E. the calipers and rotors. It might be possible to reference that to a current Brembo rotor for instance. Barry, if you feel adventurous, getting those dimensions would be cool, but as I said, I won't be tackling brakes anytime soon. Maybe someone else needs the info in a more immediate fashion. Thanks.
 
Hello Barryp,

I am interested in any measurements you can supply. I already have the stud PCD and diameter for obvious reasons. Thank you in advance,

Best regards,

bundyrum.
 
Same for me, any further dimensions that everyone can contribute to help nail down an alternative Disc source would be appreciated. I'm part way thru a full restoration. Thanks for everyones efforts so far
 
Ok here is what I got for those that are interested.

Diameter: 11.875"
Thickness: .400"
Hat height from back of disk to front (outboard) face of hat: 2.330"
Thickness at hub face: .458"
Hat OD: 6.625"

Interesting that the Rear Diameter was larger than the fronts, would lead me to believe that these were originally made for something else (Jag 150 maybe). These were bought in early '59 from Hambro as the MM option with Dunlop calipers.



Barry
 

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Great photo Barryp. I assume the Caliper Pistons are Dunlop & was wondering what size is engraved on your Piston Casting & if they use round or square pads.
I have a set of Dunlop Calipers with round pads & the rears look very similar to yours. I also have a set of the XJ6 rear calipers. The Dunlops are much lighter & a smaller pad area, so I'm thinking their a better match for the typical frt setup
 
Hello Barryp,

Thank you for those measurements. As mwagon says what are the piston size. I don't think it's engraved on the outside of the caliper so much as it was cast as part of each of the piston housings where the bleed nipple screws into.

It is quite normal for rear discs to be larger than front ones even today.

The reason the Dunlop pads are smaller is because that's what they made because they didn't know any different. Don't forget this was early days for disc brakes on cars. We grew from what you have there.

I know of a 100/6 in Australia that has the 4 wheel Dunlop discs and they were fitted at the factory, they weren't an option fitted by a dealer.

I've noticed a few people here on the forum using the MM designation when referring to the 100/6 with 4 wheel disc brakes. Where does this designation come from?

Hello mwagon,

My suggestion to you is to use the XJ6 calipers because the piston seal design is going to be far superior to the Dunlop ones. Apart from which rebuild kits and pads are going to be easier to find. You could sell the Dunlop ones to finance the new parts you need for the rest of the car. No I don't want to buy them for the reason I said above.


I just had an e-mail from AH Spares in the UK today and they say that with their new rear caliper brackets there is "NO NEED TO GRIND THE AXLE HOUSING". yes it was in capitals and quite obviously a jab at some other parts supply place over there.

Best regards,

bundyrum.
 
Piston sizes are 2 1/8" frt and 1 5/8" Rr, and yes it is cast into the piston housing as is the the word "Dunlop". Pads are square and appear to be the same front and rear, and are small by todays standards. MM stands for Millia Miglia, Dougie can give you a better history lesson than I can.

I've been on a quest for about two years to find info on the MM's fitted with the four wheel discs either factory or dealer installed, and have found very little infomation as there doesn't appear to be many of them or even people that have seen one. Given the rarity of these I sent the calipers to White Post for refurbishing, expensive but they're nice.


Barry
 
The Mille Miglia moniker was initially attached to cars with the then new twelve port cylinder head (6 in/6 out).

I have a couple of old road tests from magazines calling the "new" car a 100/6 Mille Miglia. The MM designation was used on both 2 & 4 seaters; drum or disc brakes didn't appear to be a factor.
 
Randy that's correct the MM did refer to the new 12 port cylinder head version of the 100-Six that was introduced after it's success in the 1957 Mille Miglia. There was also a dealer "performance" package offered at that same time which included among other items 4-wheel disc brakes. I do have a lot of period articles and correspondence on this topic, but Derek Job's site on the 100-Six has most of this information presented neat and clear. https://www.healeysix.net/100sixmm.htm

Dougie
 
Not to be flip, but why all this effort to find arcane or high priced brake hardware to convert the rear of your Healey to disc brakes? I'm all in favor of originality, but is seems the rear disc conversion is not anything that came on your cars in the first place, so whatever you put on will be non original. Why not just buy some brand new, inexpensive American stuff off the shelf?
 
Hi Bill,
That is exactly the point about getting part numbers to cross reference. Or measurements that can be looked up. Though I was on Brembo's site last night and their PDF's don't lend themselves to searches very well.
 
I sell solid rotors for the rear disc brake conversion using the Jaguar XJS calipers. They are $175 apiece.
Other options are Denis Welch rotors at 145 pounds each, which is approximately $207 and that does not include shipping from the UK.
Another option is the Jaguar MK IX rear rotor that is available from XKs Unlimited, www.xks.com, (here in the US) for the princely sum of $370.00 apiece.
Some years ago, I checked out the Range Rover option and my recollection is that the rotor was just too massive and needed too much machining.
My rotors are OEM quality material for a German brand that has been machined to fit our application.
I also sell the caliper brackets for $140.
 
Hello fellows,
While I do recall that a Range Rover rotor will work, I will defer to Richard. Although I think I have some info somewhere in all of my Healey files, I cannot seem to locate it. I apologize for not coming through on this one. I will continue to research. As I said previously, the rotors I have on my car now came with my conversion kit from Cape International.

Lin
 
Thanks Richard, I couldn't remember if you got your rear rotors worked out. I know you had been working on a larger replacement for the front as well.

BTW - Here's Richard's brakes at work, my florida green Healey and me are the 1st car out, Dave Phillips, red57 is right in front of Richard :
https://www.youtube.com/watch?v=2IEuEvVn1PI

Oh, and legal Bill............................ some Healey owners use their cars as DMH had intended, beyond being a trail queen and concours ribbon winner.


Dougie
 
Well, as I said back on page two, the Healey Marque magazine had a how-to some time ago using Camaro rotors and calipers. You can get those new at the local Pep Boys. Why not just use that?
 
Hello Dougie,

Thanks for the Healey six link, it took some time to read it all but now I can see what you're all talking about.

It actually said that 40 cars were produced with the 4 wheel disc brakes which ties in with what I was told.

It is interesting that nobody has been able to identify if the rear discs actually fit some other vehicle in production at the time.

Also nobody is saying which vehicle they get their discs off to fit them onto a Healey.

Yes, Legal Bill, we could fit Camaro discs but as yet we don't even know which month/year the article appeared in the Healey magazine.

I've also seen reference to 1985 Cadillac rear discs fitted to the rear but that's all.

I remember seeing ventilated Chrysler discs fitted to the rear of a Healey in Australia many years ago but that's all I can say because I never inquired about the finer details.

As with a lot of posts the plot thickens.

Best regards to all,

bundyrum.
 
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