Front End Shudder/Vibration During Braking

[Fourteener Rider]

I'm having an intermittent issue with my '08. Occasionally while braking the front end will vibrate or shudder. What do I mean by this? There is no side to side movement. The bars are rock solid. The best way I can describe is that the forces causing this are parallel to the direction of travel. It's like something is grabbing the bike and moving it front to back real fast, but it's all happening at the front axle or thereabouts. I'm pretty sure it's not happening at the steering head - don't ask me why, just the way it feels to me.

It only does this at low speeds (<15 mph) under moderate to light brake pressure. I have never had the problem at higher speeds or with heavy brake pressure. I'm 100% sure that it has occurred when using both brakes. I'm 70% sure it has occurred using front brake only. I've never had it occur when using only the rear brake.

The bike only has ~2600 miles on it. The tire is in good shape, no cupping, and I run it at the pressure recommended in the manual. I cannot predict nor replicate this phenomenon. So far it has not caused any safety issues but I would like to get it taken care of before it does. I would take it to the dealer (and yes, I have YES) but we all know how hard it is for them to address an intermittent problem.

I'm thinking one possibility is that the ABS system is starting to activate for some reason or is maybe on the verge of activating (but I don't recall feeling any backpressure on the brake lever like you do with a car foot pedal). Or maybe something with the linked braking system is not working correctly, like the proportioning valve.

I have searched the site several different ways but have not been able to find any similar reports. I'm wondering if anyone has had this problem or has seen a post on it. Thanks in advance for your help or advice.

 

[user 213]

There is no "on the verge of abs". It's either activated, or not. Have you checked to see if the rotors have play in them, front to back?

FWIW, with the linked brakes, you're never really applying only the front, or only the back. It's possible that you are feeling something to do with your very light pressure on the lever and the rear brake not fully engaging, but that's a WAG.

I say very light pressure because you're mentioning <15 mpg. Anything but very light pressure would have you stopped.

Any chance you just came off a heavier bike?

Have you ever bedded the brakes?

 

[buf2phx]

FWIW, with the linked brakes, you're never really applying only the front, or only the back. It's possible that you are feeling something to do with your very light pressure on the lever and the rear brake not fully engaging, but that's a WAG.

That's not entirely correct. The front brake lever applies only the front brakes. The rear brake pedal applies the rear,and two pistons of the R/F caliper.

Mike

 

[user 213]

That's not entirely correct. The front brake lever applies only the front brakes. The rear brake pedal applies the rear,and two pistons of the R/F caliper.Mike

Thanks buf2phx - I stand corrected. The footbrake pedal operates the rear brake and the lower two pistons on the right-side front calliper while the handlebar lever is responsible for the upper two pistons on the right and all four on the left.

 

[Sagebrush]

Mine has always had a bit of low speed front brake shudder, around 15 to 20 mph. I figure it's the abs trying to decide what too do so close to it's shut off point. It goes away if I add more pressure to the brake lever. Only happens with the front, won't happen when using both brakes at low speeds, so I use both brakes or the rear when speed is very low, no shudder.

 

[kaitsdad]

Just a suggestion - double check the torque on the front axle pinch bolts as well as the left side axle nut.

Just for grins.

 

[SLK50]

Ah Yeaaahh...This "grab and release" is normal and occurs with all disc brakes. If it occurs at a high enough frequency brakes "squeal". It's like rubbing a wet finger across smooth glass.

If it really bothers you, you could pull the brake pads and rough them up with sand paper or a file to break the glaze or try lightly sanding the discs to give them a new mating surface, then follow up with rebedding them.

This phenomenom is more prevelent with SS discs and the latest high friction brake pads, especially when they are hot.

 

[Foxhuntr]

My '07 has that too. I've chosen to ignore it. :blink:

 

[FJRScorpion]

My other bike does that and I temporarily cure if by wiping the disc with brake cleaner. Additionally, I try to keep other chemicals away from the disc and pad like wax and such. Also, I get the same result if I disassemble the rotor, rough up the pad with a file, then reset it... about 5 miles of no issue. Good Luck

 

[Anthony]

My ABS Vstrom did this until I added a forkbrace. Dunno if the same fix applies.

 

[flapsup]

My '06 does the same thing. Front brake only, relatively low speed, a very mild but pretty rapid pulsing that I can feel in the brake lever.

The feeling at the lever is the same as when the ABS is activated except I'm not trying to keep my eyeballs in my head. I like to do that about twice a month just to make sure it still works!

Discs and pads have been checked for glazing, scoring etc.. I'm on my third set of tires, different brands each time, and it still does it, so it's not tires, or the mileage on the tires, or the pinch bolts.

I just choose to ignore it.

 

[leo]

Mine shuttered at low speeds too when it was new. After changing from Brigs to Pirellis it hasan't shuttered since.