Yes, a bleed really is the cure BUT not just any old bleed will do. You need to know what causes the wandering before you start the procedure.
Modern Shimano disc brakes can suffer from what is commonly known as wandering bite point. This is where, upon first squeeze of the brake lever (usually the rear brake), the brake lever pulls too far to the handlebar and only subsequent squeezes of the brake lever get the brake lever biting where you originally wanted it to ie. further away from the handlebar.
Wandering bite point is at the very least incredibly annoying and can really detract from the control and joy of just riding your mountain bike.
But don’t junk those Shimano disc brakes just yet! When they work, Shimano brakes are arguably the best feeling brake out there. Which is what makes the whole wandering bite pint thing so flipping irritating.
Honestly, when I cured my rear Shimano Deore M6100 disc brake of its wandering bite point, the whole bike became so much nicer to ride.
So what causes this wandering bite point? Based from my experience, the wandering issue started when Shimano moved the position of the bleed nipple on the caliper. It’s nothing to do with ServoWave at the lever end or anything like that. The wandering is caused by miniscule bit(s) of trapped air in the caliper.
To stop the wandering bite point, you have to fully rid the caliper of air. And I mean fully.
This is not as straightforward as it might sound. As you may well already know (you’ve landed on this page for a reason after all), a regular brake bleed doesn’t cure the wandering issue.
There are actually two bleed methods that work. Jason March (World Cup race mechanic) method in the video above, and the significantly more-involved ‘official’ method detailed below.
I’d strongly recommend Jason Marsh’s method. It requires a bit more tidying-up afterwards (the caliper gets covered in waste mineral oil basically) but that is a price well worth paying for the faff saved elsewhere and the more consistent end result.
Key things that are easy to miss with Jason Marsh’s method
I remember this video coming out a couple of years ago and I failed to heed all of its wisdom due to me rush-watching the video.
- Get a big enough rag to deal with the mineral oil that comes out (kitchen roll won’t cut it).
- Remove brake pads.
- Remove the caliper from the frame before you start anything (just have the caliper dangling in the air a bit away from your chainstay).
- I’d also recommend removing the rear wheel from the bike until its time to remount the caliper on to the bike (to ensure you don’t get any mineral oil on the rotor).
- Remove the entire bleed nipple assembly from the caliper.
- Spend as long as possible manipulating, rotating and tapping the caliper around in all planes to get all that pesky trapped air outta there. It is this aspect that is key to the whole method.
Below is our earlier video explaining the official bleed method if, for some reason, you don’t get on with Jason Marsh’s method.
NB: the small but crucial thing here is to use a proper Tube Holder tool (a small black plastic thingy that holds the tubing on to the caliper bleed nipple). Without it you won’t be able to manipulate the rear caliper sufficiently without the tube coming off and peeing all over you and the floor etc.
Official method: you will need
- Mineral oil
- Bleeding bucket (AKA Shimano SM-DISC)
- Tube holder
- Receptacle for old fluid (I use a sandwich bag zip-tied on to the end of the tubing)
- Bleed block
- 7mm spanner (ideally a ring spanner)
Warning: Mineral oil isn’t half as evil as Dot fluid, but gloves and eye protection are strongly recommended.
The brakes use mineral oil, which isn’t hygroscopic like the Dot fluid used by many other brands, so Shimano recommends replacing the fluid in its brakes when it becomes discoloured, rather than on a purely annual basis.