Leigh Harrison Brakes

I want to be sure to not give a wrong impression with regards to my changing from TSM brakes to the Leigh Harrison brakes.

Installing the TSM disk brakes on all four rears improved braking dramatically, both in effectiveness and smoothness without fade.

By the time I heard of Leigh's brakes I was well into the project so just carried on at the time. It gave me a taste of improved braking for my GMC so naturally I wanted to explorer further to assure I did all i could to take care of life and limb and also my GMC.

To summarize: 
Stock brakes are obviously adequate and were probably excellent at the time the GMC was being manufactured. 

TSM disk brakes on the rear are an excellent replacement and improvement at quite reasonable cost, especially if you find yourself having to replace rusty drums, etc.

HARRISON brakes by far outshine the original as well as the TSM's but do require a larger budget than either the original or TSM. Each of us has different desires, requirements and constraints. My comments are not meant as a recommendation for or against anything. This is simply: That's  what "I" did.

After reading raves about the Harrison brakes on GMCnet and also due to the fact that by now I had several of Leighs' other products (four bag suspension and serpentine belt) I decided to give 'em a try. I only replaced the front rears. The rear rears are still TSM disks. I also ordered Leighs' 80mm front calipers, the master cylinder and booster kit as well as the miro locking switch to be use as parking brake.

The Harrison brakes, at least the ones I got, have no provisions for a cable operated parking/emergency brake. By retaining the TSM disks on the rear rear I do have a cable operated parking/emergency brake, though how effective it is remains to be seen.

While really quite straight forward it did require a couple of phone calls. Unfortunately the documentation that accompanies the product is on the other end of the quality and substance scale. I can relate as we're in the same predicament with our software, concentrating on the quality of the product. Leigh's products are certainly A-number-One quality and once you have it together the shortcomings of documentation are quickly forgotten, though they can be frustrating at the time :-)

Couple of points re installation:
1) Master cylinder - fittings are reversed front to back. The front chamber is now the front wheel brakes and the rear chamber for the rear wheels. Original fittings are used. It's a tight fit, but it does fit.
2) Miro Lock - was not easy to make it fit. While some adapters and fittings were included, none were GMC specific.
3) Booster replacement was just plain miserable.

TSM rotor overlaid on LH rotor.

TSM and Harrison Rotors.

The Harrison Rotor came pre-installed. he does charge a hefty core charge to assure return of the old hubs. I put new bearings in as well.

      The brake hose is now fastened directly to the A-frame. A 1/4" hole is drilled.
  The original brake hose clamp is removed. A washer is used to maintain the original spacing.    The miro lock will be placed on the frame and piped in behind the proportioning valve.


New Master Cylinder, Booster and 80mm Front Calipers.


A new brakehose assembly is used. A new brake hose is used with the 80mm caliper. 
The grease nipple is used to maintain the front wheel bearing. Wheel bearing grease is applied with EXTREME CAUTION at 5-10 thousand mile intervals. A close-up of the zerk fitting for the front wheel bearing.


Leigh Harrison Disk Brakes - Front Rear

The Miro Lock. Hydraulic Parking Brake, electrically operated.

What was the outcome... was it all worthwhile? Will have to wait until first lengthy trip to be really sure but the first test-drive was very encouraging. Definitely rearranged contents of cupboards getting the pads seated. A very different pedal feel. Pedal movement applies brake. Very little pressure needed for normal braking. As of today (Jan 22/00) I still have to hook up the electrics for the miro lock and I also have to reseat the rear bearings, I.e. pre-load as per Timken website.

If you want more information regarding the disk brake kit or any other Leigh Harrison product, 
his phone number is: (703) 494-9914.

If you have questions regarding my rig, please email me directly or ask your questions 
and make your comments on GMCnet.

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This page was last updated
on Tuesday, August 22, 2000 05:10 PM