No brakes when hitting a bump (ABS)?

Ryan_B

Ryan_B

Joined
Nov 17, 2020
Messages
59
Age
41
Location
Denton, TX
Bike
2016 Honda ST1300PA
I ride a 2016 ST1300 with ABS, has about 10k miles on it. Maintenance is kept up.

Curious if anyone else has experienced this. Only a slight pucker moment, as I was on a low traveled, no-outlet road with plenty of pavement left - so not an emergency, just concerning.

I was braking fairly aggressively while going downhill at ~30mph, and hit a bump. Well, more of a hump or a wave. I momentarily went airborne and when I touched down it was like I had zero brakes applied (I was on both the handle and the pedal, no pressure drop or anything). It was only long enough to register that my brakes must have failed and then they came back just as quick. It felt like forever but in reality it was probably less than a second. I can only assume that my ABS noticed stopped wheels and corrected for that. No actual lockup on the street and if ABS actuated, I did not hear or feel it.

This jogged a memory of my commute home from work, where there is a "wave" (drop-off) where two road types meet. It did the same thing there. Coming home, I just correct for that spot and don't hold my brakes going over it, but I forgot the "no brakes" sensation until now. Is this just how an ABS bike behaves or should I be more concerned?

Thanks!
Ryan
 
Never heard of this, but I'm pretty sure ABS works when the two wheels' speeds don't match and the speed of one goes suddenly down. If you go airborne while the brake(s) are applied, then the wheel(s) will slow/stop and I would expect the abs to momentarily turn on releasing the calipers. Sounds like your system is behaving normally, but I'm guessing here.
 
Sounds normal to me. If you’re on the brakes when the tire leaves the ground it’ll immediately lock. The ABS interprets this as a skid and backs off the brake pressure. When the tire again touches the pavement while you’re still on the brakes, the system will sense the wheel rotating and allow brake application again. There’s probably a slight split second delay before system reacts.

Without the ABS the wheel would remain locked when it returns to the ground. Seems like it’d be safer to for the wheel to rotate at that point than to be locked. Possible low side crash?
 
Okay, first bike with ABS and linked brakes, so I didn't know if this was normal. Sounds like it is, and makes sense.

There is no denying how fast these bikes can stop. It has saved me at least once when a car pulled out in front of me.

Ryan
 
wjbertrand said:
Sounds normal to me. If you’re on the brakes when the tire leaves the ground it’ll immediately lock. The ABS interprets this as a skid and backs off the brake pressure. When the tire again touches the pavement while you’re still on the brakes, the system will sense the wheel rotating and allow brake application again. There’s probably a slight split second delay before system reacts.

Without the ABS the wheel would remain locked when it returns to the ground. Seems like it’d be safer to for the wheel to rotate at that point than to be locked. Possible low side crash?
Click to expand...
perfect explanation. My last bike did not have abs and in that same situation you could hear a quick rear tire squeal as it hit the ground. Because the rear brake was not fully applied the tire would continue to spin once in contact with the pavement, no chance of a crash. :thumb:
 
You should still feel that 'ratchet' effect on your brake lever as the electric motor cycles the cam that removes the pressure and reapplies it in rapid succession if ABS is active. That continues until the ABS system recognises that both wheels are turning again.

One other possibility is that with your brakes applied, your front wheel hits a bump - there is a twisting effect in the front wheel and disc which will nudge the pistons in slightly. (No I'm not convinced either, but apparently that sort of thing happens on the race track, when the front wheel lifs and drops back to the ground) The first application of the brakes after that meets with no resistance. ??
 
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