I’ve been putting off doing anything with the car for a few weeks since I’ve had other plans and some work travel keeping me occupied. Finally, I had a day to myself so decided to investigate the brake noise. As I’ve reported before, I had some odd scraping noise when coming to a stop, almost like the pads weren’t seated properly. That was both a correct and incorrect statement as I’ll explain…
First up was to re-route the handbrake cable. Prior, I’d zip tied it to the fuel line as depicted in the Caterham build manual. After reading a bit on Blatchat and USA7s it was determined that’s a bad idea; it puts strain on the fuel line and causes premature wear. The better approach is to run a zip tie, or two, off the rear support bar of the diff carrier and then suspend it over the axle. I got the idea from Daniel French’s blog and one of the pictures he had posted during his build.
To change it, I just popped off the wooden boot floor, ran two zip ties, then cut the other one off the fuel line. Relatively straight forward and easy to fix. It’s also got much better clearance from the DeDion tube as well than the way it’s shown in the manual. Note, the angle of the picture makes it look like the cable is against the fuel tank, it’s really not.
Next up was investigating the brakes since I had the car on jack stands, the wheel off, and the boot floor out. To start with I poked around to see if any bolts were loose and found none that looked obviously loose or missing. I then re-enacted the wheel movement by spinning the hub with my hands slowly to watch for any movement or play. Unfortunately, I couldn’t get quite enough speed going so put one wheel back on and spun that which worked much better. As I was spinning the wheel I happened to notice a double clunk coming from under the car. Maybe the issue wasn’t the brakes after all but something else?
I then climbed under the car and tried to repeat the same processes, but couldn’t quite get the wheel spinning with me under the car and trying to watch everything at the same time. So I started hollering for Kim from the garage- she came rushing down, no doubt expecting me to be pinned under the car slowly being crushed to death – only to find me too lazy to climb out from under the car. I explained I needed her to spin the wheel while I watched everything and we set off doing it.
Within 5 seconds I saw what was happening. The wheels would spin then when stopped the differential would clunk from the play in the gears. That’s completely normal for a small bit of play. The second clunk, however, was not. That was the brake caliper moving about 3-4mm from the torque applied against the brake disc suddenly shifting. Inspecting closer I found the culprit – the bolts holding the brake caliper to the DeDion ears were finger tight but would only appear that way when there was no load on the wheel or brakes.
I then grabbed the socket and torque wrench, tightened them up to spec, marked with the paint pen, and tried it again. No more double clunk, just the expected slop in the differential. Problem solved.