Matco brakes & mechanical advantage

[JorgeEC-YUQ]

Hello guys,

I have a Kitfox III with MC-4 master cylinders and double pucks and I've been struggling with poor braking since I install them ...

After purging the system several times, making sure the pucks move without restrictions and the pads are in contact with the rotor, modifying the pedals was the only option left. I thought the geometry was right this time, but it wasn't apparently ...

Was anybody able to get the right pedal geometry and the required mechanical advantage (2'5 to 1 or close)? Did anybody try the Matco intensifier sleeves?

Hope any of you can help!
Cheers,
Jorge

[Av8r_Sed]

Hi Jorge,
You need to move the brake cylinder attach lever arm down close to the pedal pivot point. Your mechanical advantage in the current configuration is less than 1.

Reference the MATCO drawing: http://matcomfg.com/pdf/brake4.pdf?Iit=3575&Ict=21

[JorgeEC-YUQ]

Thanks for your reply Paul.

That would be the ideal position indeed. The problem I see by attaching the lever there is that the actuator from the master cylinder is too long (where the clevis is attached). Won't that make my pedals to move backwards (opposite from the firewall) in a extreme position?

I guess it could be adjusted by cutting and making a new thread but sounds like a mission.

According to the diagrams, some source of fork arrangement could be done , any experience on that? Could you send me a picture of your pedals?

Thanks again and merry Christmas!

Jorge

[Dave S]

Jorge,

While I have a different model Kitfox, the old bankrupt skystar company had sent me the wrong master cylinders with my kit......what I discovered is if a person calls up Matco, they can solve just about any problem with this stuff.....for instance, they have several versions of the MC-4 (which have addittional part # designations) and the variations incude different length piston rods as well as different length bodies - I believe they even have a short version of the master cylinder. Matco is also very knowlegeable about applications such as specific Kitfox
models and what works. If you get stuck, might be worth a call or google-up for Matco - explain what you neeed to solve and see if they have a frugal solution. I found them to be very intelligent and helpful.

Sincerely,

Dave S

[jrevens]

Hi Jorge,

Are your brake lines 1/4" or 3/16" o.d.? It's just a thought, & I know it's not your main problem, but 1/4" plastic lines will give a more "mushy" feel & require more pedal pressure than the smaller 3/16" or 1/8" lines.

[JorgeEC-YUQ]

Hi Jhon,

yes, I believe they are 1/4". It seems to be the common size around my place ...

[herman pahls]

When I installed 29" tall tires on my model 4 Kitfox, I was not able to hold 3000 RPM with a 912ULS to do a run up.
The master cylinders were 5/8" bore with Matco external caliper brakes versus the internal caliper brakes that normally come on a model 4.
I called Matco and they told me to do a pressure test before they would determine a fix.
I ordered a 1000 psi gauge from Amazon and with firm braking pressure the gauge read 425 PSI.
I ordered Matco Sleeved down master cylinders ( 1/2" bore) and the pressure exceeded 600.
I can now easily hold 5000 RPM and have plenty of braking to nose over the airplane at any time while landing.

[JorgeEC-YUQ]

Hi Herman,

I bought that kit but I failed to install it ...I am a horrible mechanic I know!
Somehow the sleeve wouldn't slide in the master cylinder anymore after I cut it. Seems like it got deformed or something and I was afraid it could get stuck inside being to long and needing more trimming.

So finally decided to go without it for the time being hoping the new pedal set up and double pucks would work ... but it didn't :D

How did you removed the extra material, did you cut it or filed it? Maybe some pics?

Thanks!
Jorge


When I installed 29" tall tires on my model 4 Kitfox, I was not able to hold 3000 RPM with a 912ULS to do a run up.
The master cylinders were 5/8" bore with Matco external caliper brakes versus the internal caliper brakes that normally come on a model 4.
I called Matco and they told me to do a pressure test before they would determine a fix.
I ordered a 1000 psi gauge from Amazon and with firm braking pressure the gauge read 425 PSI.
I ordered Matco Sleeved down master cylinders ( 1/2" bore) and the pressure exceeded 600.
I can now easily hold 5000 RPM and have plenty of braking to nose over the airplane at any time while landing.

[Monocock]

I recently bought new master cylinders from Matco for my Mk3. They are the ones with inbuilt reservoirs and I also had to cut down the threaded section to get a good fit. I can hold at 6000 rpm (582) with 21 inch wheels before it starts to slip.

Let me know if you want my part number.

[herman pahls]

I purchased the Cylinders from Matco with the sleeves already installed.

[JorgeEC-YUQ]

Hi everyone,

I made some achievements with my matco brakes setup and I would like to share with you some pics :D

I tried the lateral fork arrangement as described in matco instruction's and the thing is finally braking "satisfactory" allthought I still have the issue when pivoting in one wheel (since moving the pedal foward it losses the mechanical advantage). One can manage with a bit of power ... Somehow.

Still far from perfect but I believe I can get it better. Will keep you posted.