Manual caliper adjustment

[Wilson_Engine_Shop]

I finally got some new brake pucks for the murray I got but the kart still doesn't want to stop. I can still move the kart with my foot all the way down on the brake pedal which I know isnt right.

I cant find any way to adjust these calipers, I tried earlier today with no success. Should I buy a new manual caliper that is adjustable? Brakes are really important to me and they don't work very well. I'm pretty sure I should be able to lock the 18" tires up if adjusted correctly

I figured out why my other murray was bent up when i got it. The brakes don't work well on it either, it did not want to stop from 25mph very well

 

[itsid]

first make sure the caliper is able to float in it's bracket
(the slightly rusted part in the pic the caliper is attached to)

the caliper can ONLY do it's work if it is allowed to move laterally inside the bracket
so that both pucks actually get into contact with the fixed brake disc.
that's the most commmon failure for single side actuated calipers like yours
they seize in their bracket when not properly maintained.
Once that's done,
allow for some play between the puck and the disc
(not much is needed but a mm on each side should be eyeballed in)
And then all you need to do is to adjust the lever such that it can easily be pulled
usually with a brake rod..
and most of all without that spring you got in there for a connection
in case you need a better bite, but I guess just fixing the caliper bracket
(derust, light grease) will do the trick already

'sid

 

[Wilson_Engine_Shop]

I cleaned the caliper and the surface where the caliper floats, greased it and it moves freely. Both karts came with the spring there, i dont have anything to replace it. The brake pedal pulls the rod as far as it can possibly go (i cant move it anymore by hand) but it still doesnt clamp enough.

 

[mckutzy]

I would say(with the added above advice, of course) Disassemble, clean, de-rust all parts.
First note the location of the actuation lever, and it constituent parts, in relation of how it is mounted...
This is fundamentally required to re assemble correctly, with your style caliper pictured( the other is a slightly different style)...

After disassembly, lubricate the internal lever pivot point, actuating lever cam, Piston(may look like a bullet and the ways of the caliper bracket( a little on the groove of the caliper wont hurt aswell)...
Once this is done, but away from the kart....Sand with a med-fine grit paper on the disc. a flapwheel or the like is fine... This will resurface the disc.
After re mounting the caliper to the kart and lubricating the ways on the bracket, a good idea is to sand the pads.
A method is to put a piece of sand paper on the disc face and work the axle back and forth to break the gaze off of the pucks... you only really need to clamp with hand pressure.
Do both pucks... If able check again where it is clamping on the disc to the pads...
At this point also, youll notice if and how much out of true the disc when spun...

Dont breath the dust, its bad, as all brake dusts are... Might be asbestos, who knows these days..
Clean disc and pads with a brake cleaner(WEAR SAFETY GLASSES, you can go blind if you get this in your eyes), to remove the finger oils... Dont hose down the caliper as this may wash off the lubricant, just clean the pads.....
Reassemble, test fit unpowered, like a push test.. then do a few low powered test stops in a safe flat un-populated area....
If confident good to go, go for a lower speed ride. Adjust if necessary...
I do basically this on my brakes of my bikes.

 

[Wilson_Engine_Shop]

Ive already disassembled, cleaned, lubed and reassembled the caliper. The kart can still be pushed fairly easily with the pedal all the way down and brake fully engaged. My pads are brand new (I got them yesterday). It doesn't make any sense to me to sand brand new pads. I cant find any way to adjust this style of caliper either. The rotor is as rust free as i can get it

 

[Hellion]

Remove that spring!

Should be a solid/rigid linkage from brake pedal to brake.

If your brake disc is rusted or pitted, you might need to 'dress it' or otherwise surface it so the surface is uniform. A flap sanding disc (medium grit, etc) would work.

EDIT--I think too much like Sid (I'm saying the same things) but he did say to sand the brake disc, not the pads. I can tell the edge is rusty and most karts are left outside to rust so the brake discs get pretty much ruined....

EDIT X2--fairly certain your outer adjusting nut needs to be screwed in a bit. Perhaps this video will shine some light on the issue:

https://www.youtube.com/watch?v=QA_VvKEUpK0

 

[Wilson_Engine_Shop]

Okay i'll dress the rotor some more when I can. What should I use to replace the spring? I don't have anything "readily available". All i have is a drill and some wire wheels, i don't have a flap disk or a angle grinder to put it on

 

[Hellion]

I added a video you may not have seen. I write fast, hit "post reply" and often add more info via the edit function.

You said your rotor is rust free. It's probably fine but I can only guess since there's no pics. If you can adjust the caliper per the video, your spring linkage might be okay as-is.

Properly adjusted, these brakes are pretty effective and can lock up the wheels nice and tight.


EDIT--otherwise, most hardware stores (Lowe's, Ho Depot, TSC) usually sell 1/4" steel rod. That's what I'd use to fabricate (if needed) a new brake rod.

 

[Wilson_Engine_Shop]

Thats the same video i watched earlier today. The caliper in that video is the one i want to switch to. Its much easier to adjust than mine(which i dont think is adjustable). The good hardware stores that you mentioned are around an hour away from me. I have an Orschelins Farm & Home, Ace Hardware and Fastenal. Thats about it for hardware stores close to me

 

[Hellion]

Okay Ace then. Ace probably has the rod you need, if you need it. Sorry I forgot to add that very crucial "etc." There's always mail order--unless you live in Antarctica...

That style of caliper should be adjustable too. I mean, why wouldn't it be? It might be seized from rust or corrosion.

 

[Karttekk]

"EDIT X2--fairly certain your outer adjusting nut needs to be screwed in a bit. Perhaps this video will shine some light on the issue:"

This is important. Loosen the lock nut on the bolt going into the caliper, turn it in until the brake pad in front of it contacts the rotor then back off the bolt a quarter turn or so. Tighten the lock nut. This way you're moving the outboard pad I guess it is closer to the rotor for a higher pedal and more effective braking.

 

[Wilson_Engine_Shop]

That doesn't look like my caliper. Mine has a jamnut, no adjusting screw and a little bolt that holds the arm on the caliper. Also, my caliper has a spring on it that pulls the arm back to resting positon. If i loosen the jamnut I wont get full travel out of it, the spring binds at full engagement as it is now. If i remove the spring from the caliper, it wont retract the pads at all

---------- Post added at 08:20 PM ---------- Previous post was at 08:18 PM ----------

If I replace the spring with a rod, do I remove the adjustment on the brake rod itself?

 

[Wilson_Engine_Shop]

This is what my caliper arm looks like

 

[itsid]

hm too skinny disc is indeed the only other thing I could think of..
and if that caliper is out of adjustment rrange.. it might be time to replace the disc itself

should be 1/8" thick in 10" in diameter
(that is the Comet caliper, right?)

Anyways, the large "nut thingy" is in fact a barrel for adjustment
Check the manual for proper adjustment
in the attached manual (pages 4 ff)

'sid

PS check if ramp block and actuator are worn out or installed incorrectly perhaps..
I doubt it tbh but it's still worth checking

 

[Hellion]

I'd put that document in the FAQ if it's not there already.

 

[Wilson_Engine_Shop]

Yes its a Comet caliper. My rotor is only 7-3/4" in Diameter, its an odd size. I dont know how thick it is

 

[mckutzy]

No... I said sand new pads aswell.... It has worked for me.....
With that being said.. its to help mate it to the conform of the disc, to help bed in... The disc aswell, but to break the glaze off and to freshen the surface if it has been polished or rusted..

 

[Wilson_Engine_Shop]

So I replaced the brake spring with some solid linkage that I found laying around and adjusted the linkage so the pads ALMOST touch the rotor. The tires will now skid when the kart is pushed forward and the brake is fully engaged just before the pedal stop. It would never skid tires before so I think the brakes will stop much better now.

The caliper adjustment nut was already as far in as it could go so the spring was the issue, plus the tension rod attached to the spring wasnt adjusted right anyway. The linkage is just a test for now, I wont be keeping it on long

I dressed and measured the rotors on both Murrays and their thickness measured .135 which is just over a 1/8"

 

[Hellion]

Hey, thanks for the follow up and the extra pics.

Might have been a factory setup, but that extra threaded adjuster section added to the brake rod (plus the spring) looks semi ghetto-rigged. Just in photo #1 it shows some 'floppyness', 'off' angles and slack in the linkage. Like someone wanted extra adjustability in the brake linkage just to complicate matters. A nice, straight actuating rod is what you want, even though the caliper and disk are fixed in place.

The adjustment is usually in the caliper itself. Your mileage may vary though.


Documentation is scarce for the Murray karts and there are no known manuals or exploded parts lists out there in cyberspace. If I had a Murray, I'd love to know what was factory original and what was a Bubba-mod...

 

[Karttekk]

Glad to see you got it working. The first step is to have the pads close to the rotor without dragging, making sure the caliper slides freely and making sure there are no rods or levers or anything putting pressure on the caliper when you adjust them. Once the pads are set right then go ahead and adjust pedal travel, check spring tension, brake operation with the drive wheels off the ground then road test. Good work!