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Brake Modifications - A Cautionary Tale

There has been much discussion of brake mods like vented brakes, metal pads, 100 pads and the like on this list and I've always been uneasy about it. I have an extensive background in vehicle design and have made a few comments over the years on these threads of a cautionary nature.

Your situation is a perfect example of why brakes should not be altered casually simply because the parts are available. A vehicle's brake system is one of the most rigorously researched, designed and assembled aspects of its creation. For some reason, the 80's brakes have gotten a bad name here on the list and it has become part of Land Cruiser lore. Personally, I feel the stock brakes are magnificent and highly effective and this lore is the result of poor maintenance or other mods. Mine stop the unladen vehicle powerfully and with authority, and when I'm towing my boat there is no question these large 4 wheel discs are up to the task - even during the worst scenario I can imagine which happened last summer. While towing on a heavily crowned road a deer ran all the way across a field just to jump in front of me. I saw him coming for over 10 seconds and stayed on the gas thinking there was no way he would catch us while my wife and I watched. He suddenly picked up speed and practically threw himself in front of me -literally running an eighth of a mile nearly parallel to the road to do so. I hammered the brakes from 65 to 30 and everything not nailed down ended up on the floor or against the seatbacks. No drama.

In short, I feel an 80 series with stock pads, properly bled brakes, antisieze on the pad locating pins, a properly adjusted LSPV valve and stock tires is a vehicle that can stop with authority.

Putting larger surface area pads (100s) up front reduces the PSI you are applying to the rotors. Total force is the same, but PSI is critical in converting forward vehicle motion into heat (that after all, is all that brakes do). The critical interface of pad and rotor was carefully taken into consideration when Toyota designed the pads size, shape and material composition. Using a modified pad off another vehicle similar only by the badge on its fender is ill advised. Ditto purchasing aftermarket pads with an unknown composition that was certainly not tailored to the Land Cruiser but simply spit out of a factory for every US vehicle. Ditto putting slotted or drilled rotors on it.

The conversion of forward motion into heat is a simple task, but the efficiency of that task can be dramatically changed with relatively small modifications. I know I will catch some flak for this post as there are a lot of people who've modified their 80 brakes. And it is difficult to admit that you've done something that may have decreased your vehicle's performance under certain conditions, or ignore a challenge like mine to the veracity of your modification. Putting metal matrix racing pads that don't stop well until they're warmed up on a street vehicle borders on insanity to me, for instance! Panic stops are called that for a reason - completely unexpected.

Additionally, "My truck stops so much better now" and objective measured reality may not coincide. You might have said the same thing if you'd put fresh stock pads on to replace the braking deficiency of the worn out pads that caused you to make the change in the first place. And was this opinion based on an untrained sample of one person's behind, or painstaking track testing with high speed photography under the track surface, radio transmitting temperature senders embedded in the rotors, and $100,000 worth of computers and sensing equipment on board? I've personally spent track time on brake projects where different pad compositions being considered by the manufacturer were tested and can tell you the odds of tossing a set of randomly designed pads on a vehicle and improving its braking are astronomically against you. You may achieve better hot braking for the first 20mph of deceleration, but the last 30mph will be 25% longer. Or the opposite. Or they may be inordinately grabby when cold, but fade briefly before coming back to full strength. There are all kinds of brake performance nuances that happen which drivers are completely unaware of. Aftermarket pads may be intentionally "grabby" when first applied to give the proud owner the "feeling" he's improved something. In instrumented testing, these brakes may fade midstop and produce a 7% longer stopping distance.

My point here is that it is flawed thinking to assume that we can do a better job with the brakes than Toyota did. Absolutely flawed.

As to your case specifically JJG, I'll assume all is well with your braking system. If that's the case, then you've got pads on your truck that are not generating the proper amount of friction, not transferring the heat thus generated at the proper rate, the wrong size for the caliper piston's designed pressure, contact the rotor before the nonlinear pressure in the brake system reaches the peak pressure (too thick), or a combination of these and a dozen other issues I won't go into. Or, you could simply have oil on the rotors - hit em with a can of brake cleaner.

This turned into a bit of a rant, but this topic has been a pet peeve of mine for years and I guess I finally snapped today <grin>. Seriously, brake mods should not be conducted as casually as experimenting with a different oil filter brand. The brakes on your Land Cruiser are a complete system and minor changes to any part can dramatically degrade its performance as a whole.
I'd be willing to bet a case of #6 that the best stopping 80 is one whose system is in good working order with a set of stock pads on it.

Doug M

Yankee Toys
Land Cruiser Association