Emergency brake (e-brake, parking brake) systems in most cars are a purely mechanical system using a cable. In the passenger compartment the hand brake lever pulls two wires which have a direct cable link to a caliper on each of the rear wheels. The brake clicks because it ratchets and you press the button to release. Some cars have a foot-operated brake that are the same concept.
Basically all vehicles codes all over the world require a mechanical secondary brake to the main brake on the car and in general, manufacturers use the cable-driven approach because it’s simple and has proven itself over time. That said, many high-end car manufacturers now have electrical systems for this, but that basically just means there’s a serve which pulls the caliper. You can also buy emergency brake kits which are hydraulic, but these are not allowed in many jurisdictions for constructed vehicles. (The may be allowed for OEM, but I’m not sure)
Anyway, cable-driven e-brake it is. Reliable, proven, easy to adjust and maintain. But not that easy to install in my case. Here’s what I had to do to mount the caliper – cables have not arrived yet, so I’m holding off on the handle install until then.
4x M10 x 25mm bolts for calipers to brackets
12x M10 washers (4 for screws, 8 for spacing between caliper and bracket)
4x 1/4″ x 1″ bolts to mount bracket to upright
Step one: Align the bracket
Although I’m holding it slightly askew, the first step is to figure out where to align the bracket (in my hand) on the upright (what I’m holding it against). The picture doesn’t quite do it justice, because you actually need to do this with the caliper mounted to the bracket to see how high or low on the upright it needs to go. For horizontal alignment, align the two outermost edges nearest the rotor flush with each other. Mark the upper hole with a pen and remove bracket.
Yes, this is not really hard to drill with the upright mounted in place. Just takes some guts to do. The metal is actually quite soft to drill into.
Step two: Drill upper pilot hole
Using a small bit (less than 1/8″) to make sure I can hit the center, I drilled a pilot hole about 1/8″ deep. It’s much easier to center if you drill a small pilot first and then do the thicker bit on top of that hole.
Step 3: Finish drilling with tap bit and tap
Making sure to be absolutely perpendicular to the surface and drill a little over 1″ in. The bolt is 1″, you lose about 1/4-5/16″ via a washer and the bracket, but you need some space at the end of the tap tool since that has a tapered end. Once drilled, tap it. I used a wrench to get leverage and removed the tap 2-3 times to get the shavings out.
Step 4: Drill second hole
You’ll want to now mount the bracket hand tight with the first hole and align it against the upright edge. Then take a 1/4 drill bit and drill a starter hole directly through the lower bracket hole. This ensures you have a near-perfect aligned hole. Remove the bracket and finish drilling with the tap bit and then tap it.
Step five: Mount and done
With both holes tapped, let’s mount it up! I used a little loctite on all the bolts and did them hand tight with a 3/8″ drive ratchet. In the pic below I didn’t install the washers to space yet, but you’ll likely want to have 2 washers between the caliper and bracket on each bolt such that you don’t have to back the center lock nut off as much as the pic shows. Otherwise, the scary part is done!
I am missing the brake cables, so this is as far as I can get right now. Once I have those, I can route them and place the e-brake lever in the passenger compartment to actually make the brakes functional. Important part of the build since I live on a hill…
3 thoughts on “Mounting the emergency brake caliper”
Cripes…drilling the first hole is definitely the toughest. Question did all of the fasteners come with the “kit” or did you have to buy them seperately? If you did have to buy them are you buying aircraft quality or ?.
Keep us posted on your progress.
Yea, classic case of measure 18 times, cut/drill once.
No fasteners in the kit. Had the buy them all separately. I used grade 8 on the SAE bolts and grade 8.8 on metric, which is equivalent to grade 5 SAE, because that’s all the store had. I may upgrade to a stronger 10.9 metric bolt later (about similar to SAE grade 8).
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