Bleeding the brakes / ABS problems

If the brake lever can be pulled all the way to the handlebars and the brake has no or only weak effectiveness, there is usually air in the brake system. It needs to be bled.

As a DIY you can make yourself a cheap Universal venting set and carry out the deaeration yourself.

How do I bleed the air?

how that works, I've in a Quick guide compiled.

More links to «how-to» videos:

> Bleed the bike brake correctly – it's that easy > TEKTRO | TRP
> Replacing a bicycle brake lever – this is how it's done correctly > TEKTRO | TRP
> Tektro Service Videos (incl. brake piston service: oiling and mobilizing) > TEKTRO | TRP
> For more on the Stromer ABS, see also here in the chapter: BRAKES - 'ABS'
> See also here under Videos the tips from TRP.

> Which oil should be used?

ABS

Because of the more complex routing of the ABS lines, air can become trapped in the system and be difficult to remove.

Professionals use, among other things, special "brake bleeders" (vacuum pumps) 1 | 2) for quick and safe venting. This option is probably too expensive for the Stromer DIY.

Service instructions

Shimano also uses Blubrake's ABS module, but designates it as BS-AU 300. Shimano presents on its Website various instructions available. For example, there is a dealer operating manual «ABS Servicesoftware», which is used for basic setup and maintenanceEN | EN), as PDF here (EN | EN). To work with ABS, Blubrake's dedicated ABS service software and some external hardware are required, among other things (see System Requirements, p. 6). This is not an option for DIY.

The system's venting is described in the retailer's operating manual, «Antilock Braking System (ABS),» in the last chapter.EN | EN). See also chapter: BRAKES - 'ABS'

DIY alternative

If you’re just bleeding the brake system, you can hang the Stromer by its front wheel while bleeding it. For the passive method, leave it hanging vertically for 1–2 days. Occasionally squeeze the front brake lever. This causes the air bubbles in the system to collect in the brake lever’s reservoir, where they can then be removed. Sources: speedpedelecreview.com | electricbikereview.com

Problems

If the brake lever still doesn't work properly after bleeding, the entire brake system must be checked for leaks. Special attention should be paid to:

• the connections and bleed nipples on the brake callipers
• the brake line screw connections in the stem
• the brake lever oil reservoir
• the ABS unit in the top tube

Oil reservoirs

The oil reservoir in the brake lever can be a source of problems, although this is rarely the case. I am not aware of any service kits. If necessary, you can use a liquid sealant, e.g. K2 Siltec, or Round cord help.

ABS from Blubrake

With Blubrake ABS, the unit in the top tube must be checked for leaks in the event of oil loss. The focus here is particularly on the screw connections.

Brake lever: (as at May 2024)

In some forums (1 | 2to read that specifically for the ST5 ABS, ST5 Pinion (delivered from Jan. 2024), and ST7, the braking force of the front brake is decreasing and the pressure point is soft. The brake lever can practically be pulled to the handlebars.

Besides air in the system, a defective brake lever also appears to be the cause in individual cases. Bleeding the system doesn't solve the problem – the defective brake lever must be replaced.

In this context, one also reads about heavy wear of the brake pads. In extreme cases, they are said to after 600 until a few 1,000 km they are worn out. With this type of fault, it is recommended to check the piston reset. It should not look like this, as shown here.