build diary

September 4, 2006: It wasn't a Seven, but the same principles apply.
Trust me, this is on topic! I spent the day recovering a Jeep. I live about 100 miles from Moab, and a friend's sister got into some trouble on Moab Rim. This trail is a fairly brutal one, given the highest rating available for trails in one of the more hard-core off-road spots around. It climbs 1000' in about a mile of ledges and steps, right along the edge of a cliff over a river. In some places, a mistake or mechanical failure is rewarded by a long fall then a big crunch noise.
This particular Jeep had experienced a total loss of brakes right near the top and had gone for a dramatic backwards ride down about 300' of a steep slope and ended a small ravine. The final drop was probably about 5' tall and the truck was literally flying by this point. No permanent damage was done to the occupants, but both spent some time in hospital. The driver got a concussion from an unpadded roll bar and it's lucky she didn't get worse. I went up to get the truck back down to the end of the trail and tow it home.
The failure had come when a brake line ruptured. It was a stainless steel line, but had been routed so the tires chafed on it. When the truck was being held on a slope by the brakes, the exposed interior line exploded and the front brakes lost pressure. A mechanical moron had replaced the rear axle with one that had disc brakes instead of the original drums, and the otherwise-unmodified master cylinder and proportioning valve didn't provide anywhere near enough pressure to the rear lines to even slow the truck on flat ground - never mind a steep rocky slope. The new disc brake calipers had a different cable attachment so the emergency brake cables weren't attached. In other words, the truck had one weak spot and managed to lose all braking capability due to both negligence and ignorance.
The moral? The owner and driver of the Jeep knew about the vulnerable front lines and the lack of an emergency brake system. The lack of rear brakes was a bit of a surprise, but it wasn't hard to figure out what was going on. In the process of bringing the Jeep home (very slowly, as we had to pass over some tough terrain while looking at the river far, far below), we came up with a catalog of weak spots in this truck that filled a page of notes.
How does this apply to Sevens? Well, off-roading and track use share a certain exposure to risk and reliance on mechanicals. It's more than foolish to go out with known weak spots in your vehicle, it's dangerous. If you're going to make major modifications or build your own car, make sure the components you're using will work together. If possible, test the modified parts to ensure they're working. And do not explore the limits of your talent and the vehicle's talent when there are known problems in major systems.
As for my Seven? Well, it's been quiet for the last week and a bit as I travelled back to Ottawa to clean out my old house and garage. But in the meantime I've learned some interesting things about the rear lower control arms. More on that in a couple of days.

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