Odd disc brakes on XK120 chassis

I picked up a parts XK120SE chassis this past weekend and I noticed it had these very interesting holes on the drums and then inside it has disc brakes! Has anyone ever seen something like this before? Any info is appreciated. Thanks!

That is…odd.

most unusual would be nice to see with drum off.

This would be done to mask a disc brake conversion so the car appears to have drum brakes still, but the vent holes belie the truth. Unnecessary unsprung weight IMO which is the worst kind.

Home-made machinery at a critical place on the chassis… It wouldn’t take me a minute to decide what to do here.

The disc must be tiny in order to fit the caliper inside the drum. I can’t imagine it’s an improvement.

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that is icky ! …

Are you sure? I don’t see a disc rotor.
That’s an ENV axle with the drum in the normal position.
I see a flange bolt head.
I think you are seeing what’s left of the wheel cylinder through that hole, attached to the backing plate.
I’ve read that putting holes in the drums was a common racing mod to improve brake cooling.

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Agreed. Most likely still complete – minus the shoes of course. I can see the lining face on the drum through the holes. I wonder if anything was done to keep the wheel cylinders from blowing seals upon accidental application of the brake pedal? Or maybe what was left of the car was so far gone it didn’t matter at that point? My '51 still has the ENV axle with drums, but wire hubs have since been fitted in lieu of the old disc wheels. Spent a lot of time rebuilding that axle and brakes.

yes the did put holes for coolie,and less weight as well…maybe not a fine idea for strength. then came finned aluminium

brake drums, Jaguar had the air scoops inside, with a screen, and a blank off plate…anyone have those? Now we see discs that are drilled, and slotted, to remove heat…a worse enemy than reduced surface area to the pad,.
Nick

Greetings All,

Chrysler Imperials had disc brakes that had a “dust cover” over them to keep their ornate wheels from getting dusted.

Have no idea of someone retrofitted these as I didn’t think XK120SE’s had discs?

Alex, how about pulling off that drum; I suspect someone removed the shoes and put the drum back on so the wheel would fit right for rolling.
Here is one with all the parts.
PICT0028


We’d love to see more pictures of anything else interesting on that chassis. Is the chassis number identifiable?
BTW drilling holes in the disc wheels was another trick with some racers.
I have the cooling scoops on my front brakes.

Lovell, correct that no 120 had discs as they did not become available until 1957. The '53 C Types for LeMans and all D Types had discs but they were not offered on 120 or 140.

Dollars to donuts I’m looking at the same cylinder we use on the MGA.

Its Lockheed with 1-1/8" diameter piston.
I just realized that in the original picture we are seeing the aluminum abutment piece peeking through the hole, opposite to the hydraulic cylinder.

that makes a lot more sense

Yes, even my Mini’s tiny discs and calipers wouldn’t fit inside a drum mounted in the normal position.

I’m sure I saw an article somewhere stating that drilling “speed holes” in the drums was to help dissipate heat buildup and was an old racer-hot rodder trick. (Edit: And Now I see Rob already mentioned this in the thread a day ago :blush:)

Funny enought there’s even an XK120 restoration article in the October XK Club magazine (image shown here without permission (Hope this is OK)) and a caption “sprucing up the drilled brake drums, an idea that was apparently taken from West Coast racer Walt Hansgen

Drilled drums were very common among ‘sporting’ cars here in the UK. I think there were two reasons: heat dissipation, and lightness. Whether it made much difference or not, I don’t know. I’ve seen it a lot in both cast iron and aluminium drums, including finned ones. I think it pre-dates Walt as well - I’ve seen it in thirties European cars too.