Disk brake conversion complete

I have completed the install of a Wilwood-based disk brake conversion kit on my Wife’s treasured 120 FHC.

I also replaced an upper ball joint and the ball joint, tie rod end, bump stop and shock absorber rubber bushings. The split pin at the bottom of the shock was really a challenge!! Put a re-build kit in the master cylinder as well. Pressing the bearing retainers into the hub could have presented a problem as not many of the local automotive machine shops have the capability any longer. Front wheels balanced, too.

I took me about 20 hours over a ten-day period. I am sure any of you could have done it in less time, but I am 85 years and do not move so quickly any more, especially during the up and down.

The parts all came from Moss Motors/XKS Unlimited.

The brakes are a great improvement over the drums, however one of the drum brake linings was fluid-soaked so I can’t say how the disks compare to a well maintained drum setup. I made the change because a cylinder leak and soaked linings had become about an annual thing. They do require a strong leg as previously-predicted here.

My Wife loves the car. I had installed an E-Type full synchro box many years ago which made the car much easier to drive but she was avoiding it because of the brakes. I think she will enjoy it again with trustworthy brakes.

Thanks to all for your comments and advice.


I’ve got the same kit for my 120. The mountains in this area are quite hard on drums. Many club members complain of brake fade on our drives regardless of the model.

I’ve locked up the wheels on my TD, but not when they’re hot.

I’m finding things more difficult in the garage and I’m only 65! It’s just great to hear you are still this active at your slightly more advanced age.
I like the disc brake conversion, I put one on my 120 also.
Best regards
Phil D.

Doubt it: I think you’ll still need a booster, unless you look forward to your left leg looking like Bruce Banner’s forearm…:stuck_out_tongue_winking_eye:

Pedal effort depends on several factors. For each of them you trade pedal travel for pedal effort. If you increase the number of pots in the calipers, you decrease pedal effort correspondingly. But more pots means more fluid displacement which means more pedal travel. You can also use a smaller bore master cylinder, but a smaller bore means more pedal travel as well. The only “free lunch” mechanism that I know of to decrease pedal effort is to go with a larger rotor diameter, which gives a greater braking lever arm and hence more mechanical advantage with no impact on pedal travel. Rotor diameter is, of course, limited by the wheel size.

On my Cobra, I had Wilwood 6-pots on the front and 4-pots on the rear, both on 14" rotors and both using 7/8" master cylinders with a balance bar. Pedal effort was very comfortable - even my wife could drive it fairly easily - and pedal travel was not excessive.

However, that was on a 2200lb car with 14" rotors. On a car that weighs over 500lbs - 1000lbs more and can only accommodate 12" rotors, I suspect things will be different. It may be possible to use smaller bore master cylinder(s) to make up the difference, and a lot will depend on how comfortable the drivers are with a heavier brake pedal.


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Kenetic energy has to be turned into another kind of energy in order to stop a car. The faster you can generate heat, the faster you can decelerate. Simple physics. Disc bakes generate heat faster than drums, and even though both systems will generate the same amount of heat to stop the same car, discs generate heat more quickly.

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More fun to watch, too!

Remember: they stuff all this inside 13" rims!

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Yikes. I have a few hills near my house…

Hmmmm. I own a GoPro…

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I would say more specifically that disc brake rotors are more able to shed the generated heat to the surrounding environment. In essence, they are better heat exchangers. You can generate big friction numbers with twin leading shoe drums, but you can’t shed the heat as fat as it is generated. A large percentage of the available surface area is occupied by the brake shoes and airflow inside the drum is poor. On disc brakes, much less of the surface area obscured by the pads and disc is much more exposed to the airstream. If you have vented rotors, you can move even more air, greatly enhancing the heat transfer ability. Also, when drums get hot, they grow radially, forcing the friction surface away from the shoes, so the pedal goes soft. When disc brake rotors get hot, the radial expansion is of no consequence and any transverse expansion only tightens things up, so the pedal stays firm.


In addition to getting bell-mouthed: cleverly, Auburn and others had composite drums: the very substantial “band” was riveted to a stamped, thick hub section.

They actually worked pretty well, and were (relatively) fade resistant.

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From a camera in the wheel well

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That is too cool.

Actually very very hot :fire:
I need to get a camera inside my (XJR) wheel well when I do a track day to see what the disc gets up to, I know they are blue when I have done my cool down lap.

Oh, you’ll see red… :heart_eyes:

As I remarked, last time I saw this video was not so much amazed at the brake disc, but rather at the amount of lateral deflection in the slick.

That’s partly why slicks generally run low pressures: on my Datsun (F/R), it was 16/12 psi, on shorter tracks, 20/16, longer ones. The sidewalls are designed to do that, and keep the tread on the ground.

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