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Ari's answers: All about brakes

May 05, 2020

This edition of Ari's answers is all about brakes. So let's get right to the heart-stopping, show-stopping questions.

Editor's note: Ari's Instagram inbox is often full of technical questions and he replies to (almost) all of them. We publish a few of the answers here so others can benefit from the info. Got a question you'd like answered? Leave it in the comments section below or message him on Instagram at @arihenning211.

Triumph Tiger Explorer brakes
Out of all the manufacturers, Triumph’s brakes consistently offer some of the best feedback and feel, even with the additional of ABS plumbing and circuitry. Triumph photo.

I recently bought a Triumph with ABS and the front brake feels spongy unless I pump it up. This is the first bike I’ve had with ABS so I’m not sure if this is normal or not. — @mvigs86

ABS can make a brake system feel spongy, but that’s usually only on low-buck bikes, and it certainly shouldn’t be soft enough that you would need to pump the lever to get pressure. Of all the brands, Triumph actually does the best job of retaining a firm lever and excellent feedback with their ABS bikes. I attribute it in part to their extensive use of stiff, stainless-steel hoses (rubber flexes a bit, and ABS plumbing can add several feet of hose to the system) and quality fittings.

That’s all to say that your bike definitely shouldn’t have a soft lever. If it’s a new purchase, I’d take it back to the dealership and tell them to fix it. It might just need a bleed, but it could be a faulty component. It’s a safety issue, so they ought to handle it ASAP.

A (big) syringe and a length of hose is a useful method of bleeding brakes from the bottom up, which makes purging air easier. Photo by Ari Henning.

I rebuilt the brake calipers on my 2011 Concours as per one of your old YouTube videos and now I’m having trouble getting the front to hold pressure. I have bled the system and don’t think there’s any air. But the lever is soft unless I pump it up. — @okmotocru

Ugh. Been there! I’ve had to push several quarts of fluid through an empty system to get it fully bled. It’s especially challenging when you’ve removed a component like the calipers, master, or lines, since it introduces so much air. But if you don’t have pressure, there’s air in there somewhere, plain and simple.

Bubbles tend to cling to the inside of the hoses or hide in corners of the caliper, so it can be helpful to tap on the lines and calipers with a screwdriver handle to free them up. Another technique I like is to use a syringe and inject fluid from the caliper up to the master. Since air wants to rise, it pushes all the air up instead of trying to force it down against buoyancy. That trick has worked for me, but ultimately it’s just a PITA and you have to keep at it. Good luck!

I’m curious about new electronics on bikes. Are they really that good? What I trust least is lean-angle ABS. Can you really lean the bike over, hamfist the front brake, and expect not to crash? — @nathanbaeyens

You and me both, man! It’s hard to have faith in ABS during something as precarious as emergency braking while leaned over, but modern electronics are truly outstanding.

The introduction of the Inertial Measurement Unit (IMU) has enabled TC and ABS systems to factor lean angle, yaw, and various other parameters into their algorithms, making them extremely refined and also somewhat predictive. On top of that, modern ABS actuators like those produced by Bosch and Continental can adjust pressure up to 100 times per second, giving the system incredible control.

So you may hamfist the front brake while your knee is on the ground, but cornering ABS isn’t going to feed that much pressure to the calipers because it knows that a great deal of traction is already being spent resisting cornering forces. It’s doing what skilled and experienced riders do already, just at a rate that’s vastly quicker and more sensitive than any human could hope to accomplish.

A photo, since you asked. I kept these roached brake pads specifically for illustrative purposes, so I’m glad I finally got to use them! Photo by Ari Henning.

When should I change my brake pads? My bike has 18,000 miles and I still see some clearance. Please post photos for reference. — @theycalmepanda

Most brake pads have grooves molded into the friction material that serve as wear indicators, similar to the wear bars that are molded into the tread of your tires. When you’ve worn the pad down to the bottom of the grooves, usually when there’s about one millimeter of material left, it’s time to swap them out.