Question 1: Does a 914 rear caliper need fluid in it for the parking brake parts to work?

Background: I'm building a small (250cc Yamaha-based) trike and need a rear brake system that can be operated by a cable connected to the bike's foot pedal (no hydraulics). I remembered that a 914's parking brake is cable-actuated, so the plan is to hook the bike's foot pedal cable to the parking brake arm on a 914 rear brake caliper. (I'd mount the rotor directly to the Comet differential case so one brake will work both rear wheels - should be sufficient stopping power at the sub-freeway speeds the Yamaha can achieve.)

Question 2: Any reason it wouldn't work, or issues I need to deal with?

More into: If pictures help, I've documented the plan at http://www.carcentric.com/YamahaSR250Trike.htm

Thanks for any assistance,
M D "Doc" Nugent
Former owner of 914 Lite 2.5
http://home1.gte.net/nugentmd/914lite.htm

Welcome DOC Nugent..

You can use the 914 rear caliper without fluid (I would put some in them to keep the seals wet and cap it closed).


B

I'm not sure I would trust that little arm with my life though.

doesn't need fluid.

just be aware that the parking brake is pressing against only one disk surface. used as a service brake, that -may- be putting forces the disk wasn't designed to see, and differential heating may slowly turn the disk into a big Belleville washer...

the other issue is that the parking brake is kept in adjustment by application of the hydraulic brake. without that continuous adjustment force, you'll be needing to keep re-adjusting the inner pad location. venting clearance (inner pad) adjustment seems to be a weak-ish point of these calipers.

i'm sure it can be made to work, but those are the potential issues as i see 'em ...

Hey, this forum is FAST with the responses!

A few more data points (if they matter). Expected top speed is 45mph. Expected annual mileage is maybe 500 at the most. No racing.

Thanks for the initial input. I'll almost fill the caliper with DOT 4? (the kind that doesn't absorb water) to minimize internal rusting, and check frequently for weird wear and cupping of the rotor (unlikely, I think, given its use parameters). Anything else?

Is there a manual way to make the adjustments ArtechnikA mentioned? Would a simple pumping of compressed air into the (unused) hydraulic line occasionally do the needed adjustment?

M D "Doc" Nugent

...it'll probably still take forever to stop, even though the trike is lighter.

I like to think of the parking brake as a "gradual momentum reducer."

Doc, once again I will recommend Wilwood mechanical spot go-kart calipers.

--DD

when i blew my master cylinder going over the bay bridge, all i had was the parking brake. it did a pretty good job in slowing down my >2000 pound car and i was at least going 50 mph.
dependig on the weight of that "thing" you might get away with just the parking brake.
but why not mount a real braking system ????

Andy

Answers to questions:

1. "dependig on the weight" - It'll weigh under 750 lbs with me and my wife aboard.

2. "why not mount a real braking system?" - Cost and complexity . . . and cost (I still have a few 914 parts left, so they're "free").

Got your message, Dave. Still looking for the "no cash outlay" solution.

MDN