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Brake problems with older Toyotas?

February 05, 2010

Looks like Toyota is headed for a software fix for the Prius brakes. Weirdly enough, I feel like I have a personal intersection with Toyota's alleged ABS brake difficulty.


I own a 1997 Toyota 4-runner. Several times in the life of that car I have experience a complete loss of braking - always when braking while riding over significant bumps. The first time it happened was weird… but not overly terrifying. I quickly assumed the failure was being caused by "resonance" or the unhappy combination of the ABS choosing to brake when a wheel was virtually mid-air and then releasing just as the wheel hit the ground as the wheels bounced over the bumps. If this explanation is right it could and perhaps should have been solved by tuning the ABS braking frequency to ensure that the natural frequency of the suspension could never match the ABS braking rate.


Perhaps this explanation is naïve or just plain wrong. Regardless I am left to wonder if my 1997 car suffers from the same flaws as the 2010 Toyotas. Is it possible that these cars share the same basic control strategies and algorithms even after all these years??? If so this highlights a weakness of platform engineering and presenting a pretty damning portrait of their ability to spot and eradicate problems. I've never experienced this phenomena on any other car I've ever driven. Alternately perhaps it's the same engineering team making the same mistakes year after year. It is ironic that as an engineer I simply wrote this off to a freak combination of speed, bumps and possibly a sloppy - but not criminal - job of engineering. The brakes on the 4-runner have always been pretty marginal and even need to be pumped a few times in very cold weather before they'll work. Like many engineers I think I'm perhaps too tolerant of design related issues.