Vibration when using front brake

[Mick54]

Hi folks,any thoughts on the following problem thats just recently started .
After heading down steep hill,applying the front brake gradually,the bike vibrates excessively to the point of not being able to hold on.

First thought i had a puncture but after releasing the brake it stopped and had to slow down using the rear .

It has happened three times on the same hill but doesn't appear to happen anywhere else.

Nothing is loose on the front end and bike is approx 4 months old with disc brakes

Any feedback appreciated

 

[vickster]

Warped rotor?

 

[C R]

Is it the hill or the speed? Can you get to the same speed somewhere else to see if the vibration happens?

 

[fossyant]

Could also be contaminated pads and disc.

 

[Oldhippy]

Something like that happened to me and it turned out to be the pads not being fitted correctly.

 

[Cycleops]

The first thing to do is check the bolts holding the discs are tight or if it’s a centre lock that’s secure. After that spin the wheel and see If the disc runs true. If it’s only just started could be something has worked loose or the disc have taken a knock. Check the pads too, any oily stuff? Could be leaking fluid but you didn’t say if hydraulic or cable, but my money would be on the discs.
If you bought it locally run it back there. Alternatively don’t go down that hill .

 

[Tenacious Sloth]

Just to throw something else into the mix, check your steering head bearings.

With the bike stationary and the front brake hard on - rock the bike fore and aft. You should be able to feel any play in the bearings.

 

[Mick54]

Just to throw something else into the mix, check your steering head bearings.

With the bike stationary and the front brake hard on - rock the bike fore and aft. You should be able to feel any play in the bearings.

Yeah cheers,i checked that and all appears to have no movement 👍

 

[Mick54]

Warped rotor?

Not sure but hopefully not,but something i,ll check out

 

[Mick54]

Is it the hill or the speed? Can you get to the same speed somewhere else to see if the vibration happens?

Very good question and its something i,ll have to investigate,i can't recall it happening on any other hill but after the recent event it something i,ll have to be get my finger out and pinpoint the problem as its very dangerous

 

[si_c]

Caliper isn't aligned properly or the rotor is warped. Could be contaminated pads, but unlikely.

 

[Sharky]

Does this describe it?

https://cyclingtips.com/2020/07/bicycle-speed-wobbles-how-they-start-and-how-to-stop-them/

 

[mustang1]

Does the wobble occur when you apply the brakes beyond a certain pressure?
Like the others mentioned, it sounds like warped disks or brake pads not held in place firmly.

 

[Mick54]

Does this describe it?

https://cyclingtips.com/2020/07/bicycle-speed-wobbles-how-they-start-and-how-to-stop-them/

Absolutely bang on i would say..thanks

 

[si_c]

Absolutely bang on i would say..thanks

That doesn't describe something that happens when braking, rather a shimmy which occurs when coasting.