Brake assistance desperately needed.

[Trip..]

Hey guys I need some help diagnosing the brakes on Kermit.


My brakes are only working about 40% of the time. I won't come to you guys with something simple like servo throw or dead battery issues. The problem is when I hit the brakes while the car sits on the stand they work 100% When I push the car around on the ground, they are 100% ...But when the engine is running, they either work perfectly or not at all!


The brake discs are perfect, the brake calipers appear to be in working order, the rod that delivers the servo's command is working properly, the servo obviously works, I wouldn't come to you guys with something that simple. I do notice the vertical rod that rides in the brass bushing in the bottom of the chassis does rise up from time to time. Could this be the culprit?


Here are some pics.














The linkage is slightly bent to clear the mounting screws for the throttle servo, I am the one that did this and the brakes were failing before the addition of this servo and linkage modification. In fact, the brakes have been like this since I took it out of the box and since I don't believe in sending shit back for warranty, this problem is on me.


Before it's asked, yes the servo travels to it's extent every time I hit the brakes, the servo travel is the same whether the brakes are working properly or not. The Tygon fuel line is not sliding through the eyelet on the brake lever, it gets squished up even when the brakes are malfunctioning..


When the brakes fail, I can pick up the car and rev the throttle and then the brakes will work again, usually.


Like I said, this is not a simple "Gee my brakes don't work" I wouldn't bother you guys with that rubbish.. I haven't had the braking system completely disassembled yet, so I can't say for sure what is malfunctioning.


Any educated guesses?


Thanks for your time guys,


Trip..

 

[cordy]

Is the brake cam alinged with the flat spot? The reason I ask is becuz when I was putting in my lightened gear plate on my xb, my brake cam wasnt alinged and my brakes wher messed up,put it back the way it was suposed to be and they worked fine. Your probably right with it not comming up cuz thats the only thing that moves to put pressure on the pads and disks .Just food for thought.

 

[Trip..]

Yes, good point! The flat spot is pressing against the first brake caliper/pad.

 

[cordy]

The only other thing I can think of are the two alignment pins seated properly into the gear plate?cuz if thier not they could be shifting the plates and pads.The other thing is your center diff mount the one by the brake pads, are the chassiss screws tight? Cuz if thier loose it may be shifting under load and moving the alingment of the pads and disks.

 

[andyken]

Check the set screws for the brake, on the center diff mount.

If they are too loose the pads will bind.

Also the shaft they mount to can wear.

 

[GTS 666]

Agree check your set screws that are located in the centre layshft bearing carrier. You can get alot of brake adjustment with these screws. Can be a pain to get a tool on though.

 

[Deluge]

Agreed. The set screws probably need to be adjusted.

Here's a visual. The red circles show where the screws are at, obviously.

 

[Trip..]

Thanks guys, I'll check em out.

 

[Deluge]

No problemo. Keep us updated!

 

[cordy]

Yes thanks I never knew they wher there.

 

[Trip..]

*Problem solved*

The gear wasn't shimmed properly on the layshaft, so it was wearing poorly on the center drive gear. Because the gear was pushed in too far the brake pads were slipping off the brake square. Make sense? Look at the pic posted by Deluge (Thanks Deluge btw) The gear on the end (right side of pic) wasn't shimmed properly and was flopping in and out of the motor mount. That was causing the brake disc to fall off the brake square. So even though the brake lever was doing it's job, there was nothing for it to push up against because the brake disc wasn't seated on the square.

Those set screws must be screwed in to the make the proper backlash, this took me a few times to get right and I had to disassemble and reassemble a few times to get them perfect.

While I was in there playing I also changed the clutch spring to the 9500 ddm spring, it revs a little higher than I was expecting, but it works well. I have the Nutech 8k spring in my Marder, but this revs much, much higher before engagement. I think the Nutech spring is a little optimistic on the 8k engagement.

While I was putting it back together, I shattered the stock plastic transmission mount. I shattered it like glass! Whatta piece of shit! I guess it's time for the 7075 parts!

The brakes are now 100% as they should be. This thing is a blast to drive around in the grass, I did manage to flip it over once, but it was right back on it's wheels. Usually when I get into a tight turn, it just blasts the front tires and thatches my lawn with a big pile of dead grass flying 2 feet in the air.

Other bad thing is now I have a bent wheel shaft, wheel flops around and looks janky! Got any suggestions?

 

[Guest]

Other bad thing is now I have a bent wheel shaft, wheel flops around and looks janky! Got any suggestions?

The 10mm threads to start. Then a set of Baja adapters on top. I've never bent one with adapters.

 

[Guest]

Good to hear you have resolved the brake mystery.

 

[Trip..]

It was just assembly issues.

I'll get a set of adapters as soon as I kill the stock tires .So far even with beating them on the street, they seem to be holding up very well, so are the foams.

 

[Guest]

I think I got about 4-5 tanks before mine went south.

 

[Trip..]

I'm on my 3rd... Motor should be starting to loosen-up, I do believe.

 

[Deluge]

*Problem solved* The gear wasn't shimmed properly on the layshaft, so it was wearing poorly on the center drive gear. Because the gear was pushed in too far the brake pads were slipping off the brake square. Make sense? Look at the pic posted by Deluge (Thanks Deluge btw) The gear on the end (right side of pic) wasn't shimmed properly and was flopping in and out of the motor mount. That was causing the brake disc to fall off the brake square. So even though the brake lever was doing it's job, there was nothing for it to push up against because the brake disc wasn't seated on the square.

Those set screws must be screwed in to the make the proper backlash, this took me a few times to get right and I had to disassemble and reassemble a few times to get them perfect.

While I was in there playing I also changed the clutch spring to the 9500 ddm spring, it revs a little higher than I was expecting, but it works well. I have the Nutech 8k spring in my Marder, but this revs much, much higher before engagement. I think the Nutech spring is a little optimistic on the 8k engagement.

While I was putting it back together, I shattered the stock plastic transmission mount. I shattered it like glass! Whatta piece of shit! I guess it's time for the 7075 parts!

The brakes are now 100% as they should be. This thing is a blast to drive around in the grass, I did manage to flip it over once, but it was right back on it's wheels. Usually when I get into a tight turn, it just blasts the front tires and thatches my lawn with a big pile of dead grass flying 2 feet in the air.

Other bad thing is now I have a bent wheel shaft, wheel flops around and looks janky! Got any suggestions?

Anytime, dude! Glad you got it sorted.

Bent wheel shaft? Do you have the 6mm axles? Cause that's pretty common with them. They either bend, or completely snap off.

 

[Guest]

I'm on my 3rd... Motor should be starting to loosen-up, I do believe.

About the 5th tank is when they seem to wake up.

 

[Trip..]

Yeah I forgot the tanks are half the size of the FG tanks, so three FG tanks or 5 Redcat tanks.

 

[Deluge]

The X Series tanks are a bit undersized.