Motorhead Lawyer
It's entirely possible if it's an old vehicle with old tires that the cf might be lower than you'd think. I've been chasing my tail with a premature rear lockup issue on my '55 Stude for a while now; I've had the rear brake drums off a couple times and can see nothing wrong other than that the rear shoes haven't even worn in yet. Now I have the old tires from my Porsche on the front and some BFG T-As of unknown history on the rear (they came with the wheels.) The tires have lots of tread left and don't appear to be weather checked or cracked at all and yet I am getting rear lockup at something that my butt-ometer guesstimates at about 0.15-0.2G. (it's not as handwavy as you think; I do have some experience doing brake tests in instrumented vehicles so I have some vague idea of what various decels feel like, although it's been a while since I've been in an instrumented vehicle.) I cannot 100% confirm this without trying a new pair of tires on the rear, but I suspect that the fault is wholly with the tires as I have rebuilt all the wheel cylinders, replaced shoes front and rear, cleaned, inspected, and lubed where appropriate all hardware, replaced all hoses as well as the rear axle hard line, and replaced the master cylinder. If I had all four tires with a similar coefficient of friction it's entirely possible that I could slide for 500 feet without achieving "excessive" speed.
Now you might express doubts about the sanity of someone who would knowingly drive for any appreciable distance on tires like that (it would be difficult to do so for any length of time without being aware of the situation) and you'd be quite right to do so, but I'd be willing to bet that there are people out there that do such things...
nate
(and I have to buy NEW TIRES TOO? make it stop! pun not intended...)
