Front wheel "kick" when disc brake applied

[Globalti]

Well as long as you can avoid catching a finger in the spokes, a shock stress test like that might reveal something loose. The deceleration will be so instant that you'll be able to feel any looseness as a bang through the forks and feeling carefully with your hands might enable you to locate the problem.

 

[stuarttunstall]

I did pull and try to move all the spoke and they seem OK to me... I rode the bike for about 6 miles after I first noticed the "kick/ movement" in the wheel and it was still as smooth and quite as ever, no noise or bangs etc... maybe the deflection I am seeing is normal under heavy braking... it is not a massive move in the wheel but as I have mudguards fitted which are straight you can see it come to the left slightly

As I said earlier I have tried to move the wheel by hand and it seems solid, or at least I could not see or feel anything, spin the wheel and that seems true and smooth,

I have emailed the store to go Friday afternoon or early Saturday just to be safe..

 

[rogerzilla]

I've found front forks can twist a lot with disc brakes. It's hard to make one stiff enough without also making it rather heavy.

 

[stuarttunstall]

I've found front forks can twist a lot with disc brakes. It's hard to make one stiff enough without also making it rather heavy.

It may be... it could have always done it but for some reason I noticed it today... no harm in getting it checked

 

[Ian H]

If you have cup and cone bearings, and you say you finger-tightened a cone-nut, there's your problem. The bearings need proper adjustment.

 

[Levo-Lon]

As above, and make sure the qr is tight after refit

 

[Globalti]

Oh it's got cup & cone bearings? I missed that. They need to be checked carefully and any play adjusted out using two cone spanners then the locknut tightened down hard. A certain amount of mechanical skill is needed to get this right.

A tiny amount of play in the bearings will allow several mm of movement at the rim.

 

[fossyant]

This is the third time recently where folk have had issues with QR's and discs - wheels shifting.

You need to change the QR for either a Shimano or Campag QR with the internal cam.

Both times I've sent a spare QR to the individuals and it's fixed the issue. What width are your drop outs ? I may have 1 black 100mm Shimano QR left, and I have a few silver ones.

The aftermarket QR's aren't a patch on OEM, especially external cams.

It's why MTB's have through axels now - too much breaking force - and for suspension rigidity too.

 

[stuarttunstall]

Thanks for all the replies, I do appreciate it... I am going to get it to the store the weekend and get it checked just to be safe, may be nothing but you never know

The bike has suspension forks so I would have to measure the QR

 

[stuarttunstall]

Store just replied to my email... going in Friday or Saturday just waiting for him to confirm...

Does agree that it sound like the hub needs setting up correctly ...

What would make this happen after 600 miles of use? is hub bearing adjustment a normal thing that needs doing now and again?

 

[Levo-Lon]

Store just replied to my email... going in Friday or Saturday just waiting for him to confirm...

Does agree that it sound like the hub needs setting up correctly ...

What would make this happen after 600 miles of use? is hub bearing adjustment a normal thing that needs doing now and again?

Routine maintenance, its easy once you've done it.. All about getting the right tension in the bearings.
You set them just as the play stops like headset bearings.
No play but spin freely is the correct setting.

 

[stuarttunstall]

So normal routine stuff? I suppose the country lanes I an using are not the best with rough road surfaces in places could shake them loose lol ...

 

[andrew_s]

fossyant has it.

A disc brake will force the disc side of the axle downwards on braking, with a force that can be up to double your body weight, if you brake hard enough.
Weak QRs can't cope, and that side of the axle gets pushed down, moving the top of the wheel to the left, until the lawyer lips stop it. You stop braking, and your weight pushes the axle back to the top of the dropout slot.

To stop the movement, you need a strong QR, done up as tightly as you can reasonably get it. That means a Shimano/Campag style internal cam QR, or an allen key skewer (what you might call a slow release skewer).
What's more, if you ignore it for long enough, the repeated up and down movement can loosen the skewer enough that the wheel comes out of the forks, which is fairly obviously not good (I've seen it happen).

Many modern bikes side-step the issue by either using a thru-axle, or by having forward-pointing dropouts so that the axle is forced against the side of the dropout slot rather than out of the end. The real solution would be to put the caliper on the front of the RH fork blade, so the axle gets forced upwards, but only Cotic have ever done that, as far as I know.

 

[Ian H]

It doesn't sound as if that's what is happening here.

 

[andrew_s]

The OP mentioned a not very tight QR, as well as loose bearings.

It amounts to the same thing anyway, even if it's loose bearings moving rather than the QR in the dropout.
There's still your body weight holding the axle against the top side of the bearing to be overcome before you see any movement at the rim.