Shimano J-Kit (easy hose joint system) explained

If you have ever opened a new set of Shimano brakes and found the lever and the caliper sitting in the box as two separate pieces, lever plugged with a yellow seal plug, hose sealed with a thin membrane, you might reasonably assume something is missing or that the brake has not been bled.

Nothing is wrong. What you have is a Shimano J-Kit, and it is one of the more confusing things in the box because Shimano barely explains it anywhere. We get this question often enough that we thought we would put together a quick post to clear it up.

What Is Shimano J-Kit?

J-Kit is not a different brake. The lever internals, the caliper, the pads and the power not different in any way. It simply refers to how the brake is packaged and shipped. Sometimes brakes arrives as one connected unit. J-Kit brakes arrive as two sealed halves:

• The caliper, with the hose already attached, filled with mineral oil, the connector insert (barb) already pressed into the free end of the hose and that end sealed with a thin membrane.

• The brake lever, also filled with mineral oil, with a seal plug in the hose connection port and the olive already installed inside it. A plastic lever stopper is fitted to keep the lever from being squeezed before it is connected.

Both halves are full of oil from the factory. The brake is pre-filled, it is simply not joined together yet. Shimano calls this J-Kit or the easy hose joint system. The reason it exists is modern frames. With a J-Kit you can feed the sealed hose through internal routing ports without dumping oil everywhere and needing to do a full bleed.

Connecting It

1. DO NOT squeeze the lever and do not remove the plastic lever stopper until the hose is connected. Do not push on the caliper pistons either. This is the single most common cause of trouble, because it moves oil and lets air in.
2. Mount the lever on the bar, mount the caliper, and route the hose into its final position.
3. Check the length. There is a witness mark on the hose. With the lever set to your riding position, that mark should line up with the edge of the flare nut. If it does, no cutting is needed.
4. Turn the lever so the hose connection port faces upward, then pull out the seal plug. Keep a clean rag handy, a little oil can seep out.
5. Push the hose into the port up to the witness mark, taking care not to snag the olive already sitting in there, then tighten the flare nut to 5 to 7 Nm.
6. Remove the lever stopper with small back and forth movements, without squeezing the lever.
7. With the pad spacer still in the caliper, squeeze the lever several times. It should go firm.

The First Lever Pull Feels Strange, and That Is Normal

Here is the part nobody warns you about. The hose end is sealed with a thin membrane on the connector insert (barb), it’s there to keep the oil in and the air out during shipping and instalation. It has to be broken through before oil can flow.

Sometimes it is pierced the moment the hose bottoms out in the lever. Often it is not, and the first pull or two feels light, vague or dead. Squeeze the lever firmly and it will break through and go solid. This is not a failed bleed and it is not a faulty brake.

Do You Need to Bleed It?

Usually not. If you connected the hose without squeezing the lever beforehand, the brake should come up firm and stay firm. If the lever stays soft after ten or so pulls, then it needs a standard funnel bleed with Shimano genuine mineral oil. Never use DOT fluid in a Shimano brake.