Air Leak At the Brake O-ring
 

I am working on a Cermark F 16 and have a leak at the oring on the brakes.. When you apply the brake you can hear the air escaping around the oring excessively. What is the fix for this? Do I need to replace the oring? Thanks in advance.

Coat the o-ring with silicone grease and reinstall it.

Maybe you have a unique design. ??? But, typically, if the brake is leaking air, the O-rings on the brake's pistons need replacing/lube. The band around the axle that rubs on the drum does not hold back the air. It holds back the pistons and when the pistons are pressured out, the band rubs on the drum. Maybe you have something different. ?

Same problem on my 2m MB339 brakes, loosing air.

Well greased with silicon grease, quite mobile on their aluminium discs...but when applying air pressure - without wheels - I see the O-ring expanding a little bit but a lot of air pressure escaping from O-ring sides. Installing the wheels, same thing, no braking forse at all, lot of air escaping form O-ring sides...

All new, never used still.

Maybe worth to change the O-Ring ??

Thank you

Remove the o-ring and make sure that the grove is well coated with silicone grease. If that doesn't work then replace the o-rings.

Thank you for the suggestion! I'll give it a try.

...Question : best method to remove the rings without risking to dent the aluminium discs o-ring housings ?

...removed one O-ring, very dry I think...and it broke in fact...

I use a small wood dowel, not much bigger than a toothpick. Sand one end to look like a flat tip screwdriver. It needs to be a hard wood to be strong enough. If the o-rings are dry and stiff then that's your problem. Replace them.

Hi,
I used a wood piece in fact. I think that my problems comes from O-rings too stiff and dry indeed.
They too easily broke while bending or applying some reduced tension in my hands...see below.
I see diameter of 35mm, 5mm thickness...same measure or maybe 1mm wider just to test, in case they exist ?
http://www.rcuniverse.com/forum/atta...mentid=2193042

Denis

Same size, just new and soft. As said speak to C&C

Dave

Hi,
just to let you know that C&C Models was so kind to send me couple of new brakes disks + Orings : perfect now !

I think my problem were mainly due to dry/old Orings + potentially some dents in the brakes aluminium disks maybe helping loosing too much air while on pressure.

Nice that you got it fix :) when I first read the thread title, dry O rings was my first thoughts.

The O rings that are used on some of our retracts will get dry in time, used or new without use, as suggested by Joe lubrication is the key to keep them nice and elastic.

When I get a new set of retracts I inject Teflon fluid in them, if you do that the retracts will give you more cycles per air tank, refreshing the O rings on your retracts should be done at least once a season, specially where is colder.

The Teflon fluid that I use is comes from the RC car section of my LHS or you could order on line, get a midium thickness bottle and a plastic syringe to inject it into the struts.

http://www3.towerhobbies.com/cgi-bin...&I=LX3305&P=ML



http://www.rcuniverse.com/forum/atta...mentid=2195595

Excellent, thank you !

Can anyone direct me where to get some o-rings for my FB Velox they are 20mm with a 5mm cross section... Also what durometer do I need .. Is A70 ok?


Thanks

McMastercar or your local auto parts store should have something.

You can also try " O ring Store " on the internet.
I had good luck ordering from them.