Wobble/shaking when braking?

[qfo]

So when I brake with my bike I can feel the front shaking, but I don't feel any play in the lever as if the discs would be warped. At very slow speed when braking it feels like something is pulling me back, then letting go, then pulling back again with every rotation of the wheel. Has any of you experienced this before? Also I freed up the discs bobbins

[AMCQ46]

this sounds like disk runout.............can you get a clock gauge to measure them?

[Jonesey]

Sounds like you're warped to me, and you might have an out of shape disc too.
Chris.

[Stephan]

2 options: disc runout, but I expect this would kick to the lever. If it is ok, then clean the brake pistons. If it doesn´t help, change all piston seals and dust seals.

edit: bad piston seals you notice only in higher speeds, if it is wobbling in lower speeds, it could be maybe warp as mentioned above - I don´t know how to say in english when disc is somewhere thinner ...

[Stratman]

I think you are warped too, but could be a sticking piston.

[seb421]

I would either say warped discs or wheel bearings on the front

Sent from the Millennium Falcon via Carrier Pigeon

[tony.mon]

Also check the steering head bearings and feel for play in the fork slider bearings, by having a mate lift the front wheel off the ground by pulling the bike over on the sidestand, then you can pull the forks back and forth to feel for any play. Not too hard, if you pull it forward off the sidestand it'll probably fall over.

But I'd expect warped discs.

[qfo]

I suspected the discs to be warped too, so i bought used discs from another vtr owner and i had the EXACTLY same wobble. No sticking pistons either, they all get in and out freely. No play in steering head bearings either. If the discs are warped isnt the lever supposed to be moving more or less, due to the pistons being pushed back in? The kind of wobble i have is as if the brakes are catching on the disc, then letting go, then catching again, as if something is pulling me back...how much play are floating discs supposed to have? I've seen a video on youtube of an aprilia bike with floating discs and they could move atleast 3/8th of an inch in the bobbins and the guy says he has no problem with them. I don't have that much play in mine, but when i move them back and forth i'd say they move about 1/16th of an inch which i think is normal? That is after i freed up the bobbins, before there was no play at all. I've tried the most common things people talk about and haven't felt even a minor change in the feel of the wobble...my next concern would be the rim, where the disc mounts? I thought of maybe removing the rotors one by one to see which one is worse and then inspect it closer than i already have

[seb421]

Have you had a look at the wheel bearings?

Sent from the Bat Cave via Cup and String

[qfo]

I replaced them when I got the bike due to a noise that I had around 120km/h but it turned out to be the helmet -.- I installed original bearings from honda + seals...but I just don't get why a bearing would do that? The problem I experience is only when braking...

[tony.mon]

Did you pay to have the wheel balanced when you last had tyres put on?
If so, are there any sticky patches on the front rim where a weight might have come off?
Try getting the front wheel and tyre dynamically balanced.

[qfo]

Tire is relatively new so i had it dinamicaly balanced not too long ago. But if it was the balance it would shake at certain speeds, no matter if im braking or not, or am i wrong?

[tony.mon]

Tire is relatively new so i had it dinamicaly balanced not too long ago. But if it was the balance it would shake at certain speeds, no matter if im braking or not, or am i wrong?

It is usually worse at some speeds than others if the balance is out, but tbh it shouldn't only be when braking.

Still inclined to suspect the discs.

Secondhand discs can be warped as well, of course.
Can you just lift the front a measure the runout with a dti?

[seb421]

I have had the same, bearings are cheap just do them again and fingers crossed that's it
When your on the bike riding with a fooked front bearing you might not notice anything until you apply The front brake a which point all the load is being shoved onto those bearings which can make the wheel distort and move shake under braking possibly giving you the sensation you are feeling,
and the sensation you are feeling is not called the quickening lol

Don't loose your head, there can be only one!

Sent from the Bat Cave via Cup and String

[VTRDark]

Did you check the steering head bearing's? It won't cost anything to check and rule it out. And check to see if the discs are warped. Get the wheel off the ground, one way or another, and if you havent a tool, do a visual check. Just spin the wheel and look straight on at it. If it's that bad you should be able to see it. Also while the wheel is off the ground, you should be able to check the wheel bearing for any movement.

(:-})