First off I must stress that I am by no means a qualified bicycle mechanic, I do have little very little experience with them. Secondly I cannot take full credit for this fix, the idea was given to me by a very very generous hubber who’d had offered to fix for me for free. KUDOS @BikeWhisperer and a close friend @gyro for the time Ok, then this is not an avid or shimano appreciation thread, nor an avid vs shimano thread. SYMTOMPS: Pull lever, and it does not return at all or very slow and spongy. If bike in open sun, levers lock up. POSSIBLE CAUSES: Dirt and grime build up in the lever cylinder, as well as on the piston. See below With the dirt and grime build up, when in heat the swelling cause the lockup and no return of lever. TOOLS NEEDED: 2mm Allen Key Star Screwdriver Isopropyl Alcohol Toilet roll/Roller towel Thin Nose Pliers 1 x 3000 grit Sand Paper 1 x 2000 grit Sand Paper 1 x 1000 grit Sand Paper This is from the shimano site, I will make reference to the number here in my photos as well For starters is always good to remove the lever completely off the brake line. Below is an image of a lever I had repaired and one that was going to get repaired, taken as is off the brake system Remove 8 in diagram above like below, there a tricky little rubber cover than can be removed with a thin small screwdriver or pin Push out 5 using the 2 allen key, this will separate the lever trigger from the rest of the lever Use the thin nose pliers to twist and remove the roller connector/part of the lever Using the star screwdriver, remove 6 Turn the lever upside down ie. reservoir facing down and use the screw driver to pop out the plastic roller fitting ..and finally we get to the problem child, this is just to show you how the piston is actually stuck in the cylinder Easiest way to remove the piston and spring is using the 2mm allen key This is your best friend keep on using it throughout the process, clean up all you bits you can, all the none plastic and rubber bits I let sit in the isopropyl alcohol for a few mins …so time for the fix the red blocks is whats needed to be sanded down using the 1000 then to 2000 then smoothen with the 3000, very very lightly and depending on your piston condition very very little too. PS: it may or may not be easier to remove the rubber seals, just be very careful when sanding around them what I do to test I push the spring in with the piston, and see if there’s a “spring” back in the piston by pushing in and out the cylinder And the final product! DISCLAIMER: I am not in any way affiliated to Shimano. I will not take any responsibility for any damage done to your lever or other parts when attempting this fix. I am not 100% sure of the repercussion sanding down the old dirt or grime build up, and will not be held responsible if it does fail. Our scholars tell us, that we have to go out to seek knowledge and whatever knowledge is learnt must be shared so it be beneficial for myself but humanity at large…
